vol. 74/mar. 1996 mitsubishi electric · vol. 74/mar. 1996 mitsubishi electric advance a quarterly...

MITSUBISHIELECTRIC

Environmentally Friendly Manufacturing Systems

VOL. 74/MAR. 1996

MITSUBISHI ELECTRIC

TECHNICAL REPORTS

OVEROVEROVEROVEROVERVIEWVIEWVIEWVIEWVIEWEnvironmental Preservation & Manufacturing Systems .......................... 1by Takashi Mitsuhashi

Mitsubishi Electric’s Commitment to GlobalEnvironmental Problems ............................................................................ 2by Dr. Toshio Ito and Eiki Jidai

Satellite Technology for Environmental Observation .............................. 8by Tsutomu Iwahashi and Hirokazu Tanaka

Ventilation and Air-Conditioning System Design forthe New Astram Metro Line in Hiroshima ............................................... 11by Shigenobu Horita, Tsutomu Kayama and Toshifumi Nakamura

Environmental Assessment of Gas-InsulatedPower-Distribution Transformers ............................................................ 15by Kiyoshi Sakai and Satoru Hoshino

The Application of Sound-Absorbent Plastic toAcoustic Paneling ..................................................................................... 18by Katsuhisa Ootsuta and Dr. Shuichi Tani

A Highly Sensitive Atmospheric NOX Sensor ......................................... 21

by Dr. Yoshio Hanazato and Saori Kimura

R&D PROGRESS REPORTAdvanced Ozone Water-Treatment Technology ..................................... 24by Dr. Junji Hirotsuji, Yoshitaka Kawaai and Tetsuya Tamura

NEW TECHNOLOGIES........................................................................ 29

NEW PRODUCTS ................................................................................. 30

MITSUBISHI ELECTRIC OVERSEAS NETWORK

Mitsubishi Electric Advance is publishedquarterly (in March, June, September, andDecember) by Mitsubishi Electric Corporation.Copyright © 1996 by Mitsubishi ElectricCorporation; all rights reserved.Printed in Japan.

CONTENTSCONTENTSCONTENTSCONTENTSCONTENTS

Editorial Advisors

Editor-in-Chief

Toshinori Kuroda

Jozo NagataHiroyuki NagataSatoru IsodaTsuyoshi UesugiMasao HatayaYoshio NakaiHiroshi ShimomuraHiroaki KawachiAkihiko NaitoNobuo YamamotoToshikazu SaidaHiroshi Tottori

Fumiya Taniguro

Toshinori KurodaPlanning and Administration Dept.Corporate Engineering, Manufacturing &Information SystemsMitsubishi Electric Corporation2-3-3 MarunouchiChiyoda-ku, Tokyo 100, JapanFax 03-3218-2465

Tsuyoshi UesugiStrategic Marketing Dept.Global Operations GroupMitsubishi Electric Corporation2-2-3 MarunouchiChiyoda-ku, Tokyo 100, JapanFax 03-3218-3597

Orders:Four issues: ¥6,000(postage and tax not included)Ohm-sha Co., Ltd.1 Kanda Nishiki-cho 3-chomeChiyoda-ku, Tokyo 101, Japan

Vol. 74 Feature Articles Editor

Editorial Inquiries

Product Inquiries

The cover for our special edition onenvironmentally friendly manufacturingsystems is a collage of some of the productsand technologies introduced in the followingpages. Recent award-winning advancesbring benefits that serve both modernbuildings like the Landmark TowerYokohama and rare butterflies in tropicalrain forests.Environmentally Friendly Manufacturing Systems

●Vol. 74/Mar. 1996 Mitsubishi Electric ADVANCE

A Quarterly Survey of New Products, Systems, and Technology

TECHNICAL REPORTS

OVERVIEWEnvironmental Preservation &

Manufacturing Systems

by Takashi Mitsuhashi*

I

is one of the ironies of modern, information-oriented society that the

Mitsubishi Electric Corporation and its associated group of companies,including affiliates and subsidiaries in over 30 nations, are currentlyintroducing and implementing a variety of measures to ensure that all

manufacturing systems are fully consistent with the requirements of environmentalprotection.

The main thrust of corporate environmental policy is to ensure conformity with theinternational environmental standards being advocated by the International Standard-ization Organization (ISO) based on international agreement and cooperation. Anenvironmental management system has already been created that covers all groupcompanies and is being implemented at each and every manufacturing site. Anotherimportant thrust is the performing of environmental-impact assessments for all prod-ucts. The concept of “design for environment (DFE)” has already been applied to allhome electrical appliances, and is currently being applied to other product groups. In thisarea, we have been cooperating with Daimler-Benz since 1994, with the result thatinnovative concepts are being applied to the entire production system, from materialsprocurement to the disposal of scrapped products. Again, in 1995, research and develop-ment throughout the organization underwent major revision, integrating and expandingenvironmentally related fundamental research and development. This has enabled us toenter new environmentally oriented areas of business and to create a structure gearedtowards greater contributions to the “recycling society” of tomorrow.

Mitsubishi Electric’s corporate slogan is “Technology for Life,” and the corporation iscommitted to a leadership role in the cooperation and international solidarity essentialto ensure an enriched—rather than an impoverished—environment for the six billioninhabitants of the world in the 21st century. As the world becomes ever more informa-tion oriented, our highest priority will be on establishing manufacturing systems thattake proper account of the environment. ❑

*Takashi Mitsuhashi (Managing Director) is with Corporate Engineering, Manufacturing & InformationSystems.

March 1996 · 1

TECHNICAL REPORTS

*Dr. Toshio Ito (Senior Managing Director) is with Corporate Research & Development and Eiki Jidai with theEnvironmental Protection Department.

It is incumbent on enterprise, as a whole, tominimize the waste streams generated bymanufacturing processes. Wastes and inefficien-cies are costly to manufacturers for the samereasons that they exacerbate global environmen-tal problems.

We must first recognize that supply and de-mand economics which exclude recycling is-sues are fundamentally flawed. It is mistaken

to consider a transaction completed when a prod-uct is sold and consumed, as though the usedproduct somehow disappears from the face ofthe earth. The resources consumed duringmanufacture, the packaging materials and thediscarded merchandise all continue to affect theenvironment as well as the activities of livingorganisms.

To incorporate environmental considerationsinto our economic framework will require thatcorporations cooperate with government andnongovernmental organizations worldwide.

With manufacturing operations in more than30 countries, Mitsubishi Electric has an espe-cially important obligation to promote globalenvironmental protection efforts. In 1991,Mitsubishi Electric adopted a global environ-mental charter and established clear targets toguide activities of some 110,000 employees inabout 100 corporate organizations worldwide to-ward sustainable manufacturing practices.

Measures to Avoid Ozone DepletionIt is imperative that the release of ozone-deplet-ing compounds be halted as soon as possible sothat stratospheric ozone can continue its life-sustaining function of shielding living organ-isms from ultraviolet radiation. MitsubishiElectric formed a committee on eliminating useof ozone-depleting chemicals, and initiated acompany-wide technological development effortthat has ended in-house use of these compoundsin 1995, four years ahead of the schedule speci-

Mitsubishi Electric�s Commitment toGlobal Environmental Problems

by Dr. Toshio Ito and Eiki Jidai*

Fig. 1 A CFC-free refrigerator and a cut-away view of the rotary compressor it uses.

2 · Mitsubishi Electric ADVANCE

TECHNICAL REPORTS

fied by the Montreal Protocol. The following sec-tions detail some of the steps we have taken.

CFC-Free RefrigeratorsTwo chlorofluorocarbons (CFCs) designated forphasing out under the Montreal Protocol werewidely used in refrigerator manufacture—CFC-12 as a refrigerant and CFC-11 as a foaming agentfor thermal insulation. Mitsubishi Electric hasalready developed technologies using the ap-proved alternatives, HFC-134a and HCFC-141b.Sale of refrigerators using these compounds be-gan late in 1993. Ozone-friendly refrigerators inpopular sizes over 400 liters were launched thenext spring. By June 1995, the corporation’s en-tire product line had made the transition to CFC-free technologies.

In an important technological coup, Mitsu-bishi Electric became the first company to mass-produce refrigeration equipment using a rotarycompressor with HFC-134a refrigerant and anon-soluble lubricant. Fig. 1 shows a cut-awayview of this compressor. The U.S. Environmen-tal Protection Agency awarded the corporationthe 1994 EPA Stratospheric Ozone ProtectionAward for this contribution to worldwide envi-ronmental preservation (Fig. 2).

Manufacturing Processes Free of Ozone-Depleting MaterialsDue to their outstanding solvent properties, themanufacturing industry had used CFCs andtrichloroethane (TCE) extensively in a wide va-

riety of manufacturing processes. WithinMitsubishi Electric, these solvents had been re-lied on heavily in semiconductor production andmachine parts manufacture. The corporation hasnow modified its manufacturing processes toeither use alternative solvents or eliminate sol-vent washing requirements completely.

A typical example is the tanks MitsubishiElectric produces for its free-standing oil heat-ers. A TCE wash is generally required to removecutting oil used to facilitate the forming pro-cess. The corporation has eliminated the oil andwashing requirements by using a lubricant-coated steel sheet (Fig. 3). The process reducesthe waste stream, lowers manufacturing costsand saves space on the factory floor. As this ex-ample shows, environmental protection requiresinterventions at both process and design levels.

Measures to Avoid Environmental PollutionEnvironmental pollution results when humanactivities exceed the earth’s natural self-cleans-ing functions. Mitsubishi Electric has succeededin reducing its waste stream by 30% since 1991by adopting new recycling technologies and in-stalling incinerators at its factory sites. Furtherreductions in the waste will require careful plan-ning in the design and manufacture of each prod-uct.

Mitsubishi Electric has already begun analyz-ing the environmental impact of new products—a procedure called life-cycle assessment—for

Fig. 2 The EPA Stratospheric Ozone ProtectionAward.

Fig. 3 Kerosene fan heater and tank formed fromlubricant-coated steel sheet.

March 1996 · 3

TECHNICAL REPORTS

Fig. 4 Packaging for color TVs made fromrecycled styrofoam.

which in-house standards have been developed.Products are designed with their ultimate dis-posal in mind: they must be easily disassembled,and the mass and volume of both product andpackaging reduced. In September 1994, Mitsu-bishi Electric and the Daimler Benz Group be-gan joint development of product design toolsthat will facilitate disassembly.

Many of Mitsubishi Electric’s products havebeen designed to satisfy product assessment re-quirements. Motor and compressor componentsare designed for easy disassembly. Air- condi-tioners use fewer electrical components, andheat-exchanger mass and volume have been re-duced by 30%. Recyclable plastics are now usedto manufacture washing machine bases, refrig-erator evaporation trays, television rear panels,vacuum cleaner components and the ducting forfree-standing oil heaters.

Packing materials use wood and styrofoammore sparingly, and styrofoam recycling tech-nology is being developed. Styrofoam packag-ing materials for TVs now include 50% recycledcontent (Fig. 4).

Measures to Reduce the Greenhouse EffectHigher concentrations of carbon dioxide (CO2)in the atmosphere cause a greenhouse effect andmay be responsible for climatic disturbances.

The solution is to reduce CO2 production byconsuming less energy.

All sectors of Japanese industry are workingto achieve the government’s target of stabiliz-ing the per-person CO2 emissions at the 1990level by the year 2000. Mitsubishi Electric fac-tories are taking steps to reduce the power con-sumption of boilers and air-conditioningsystems for clean-room facilities. The construc-tion industry is designing energy-saving tech-nologies for apartment and office buildings thatwill also contribute to reduced greenhouse emis-sions.

Energy savings in stand-alone electronic prod-ucts and systems requires a reduction in powerand fuel consumed in manufacture, operationand disposal. This is something Mitsubishi Elec-tric has worked on since the 1973 oil crisis. Fig.5 shows year-on-year improvement in the en-ergy-efficiency of Mitsubishi-built refrigerators.Improvements in compressor design and insu-lation efficiency have lowered power consump-tion, while better control electronics and sensorshave made it possible to develop new, more en-ergy-efficient refrigeration cycles. Similar en-ergy savings can be seen in Mitsubishi Electric’sair-conditioners and most other current prod-ucts.

Measures to Preserve GreeneryProtecting verdant open spaces is vital to sus-taining natural cycles since plants and trees

Monthly powerconsumption(kWh)

90

0.22

66

0.16

41

0.10

38

0.09

Year1978 1982 1991 1993

Power consumptionper liter capacity (W)

Fig. 5. The increasing efficiency of Mitsubishirefrigerators. (Figures based on 428-litermodels.)


TECHNICAL REPORTS

consume CO2 and liberate oxygen in the pro-cess of using solar energy to produce starch. Thedevelopment of rural and suburban open spacesshould be restricted. Mitsubishi Electric believesthat high-rise development in built-up urbanareas is the most suitable means ofaccommodating society’s needs for additionalresidential and industrial floor space. The cor-poration is devoting considerable resources to-ward development of elevator, escalator andair-conditioning technology for high-rise build-ings. The 70-story, 286m Landmark TowerYokohama building showcases the corporation’slatest offerings, including a high-speed passen-ger elevator that reaches speeds of 760m/min(Fig. 6).

Monitoring the EnvironmentMitsubishi Electric has developed an earth ob-servation satellite with a highly accurate radarsystem that can monitor environmental condi-tions on the earth’s surface under all weatherconditions. Mitsubishi Electric is supplying aneven more sophisticated radar system for use inADEOS, an advanced earth observation satel-lite scheduled for launch in 1996. With the ra-

dar, ADEOS will be able to see pollution on theland and ocean surfaces, and measure depletionof the ozone layer. We expect it to make a largecontribution to global environmental protection.

Establishing an Environmental ManagementSystemMany enterprises in Japan are setting up in-house environmental monitoring and manage-ment organizations that operate independentlyof their manufacturing activities. Companieshave established in-house environmental stan-dards, trained inspectors and are conductingenvironmental audits on a regular basis. Multi-national corporations are targeting the samestandards of environmental protection at theiroffshore manufacturing facilities that they ad-here to at domestic plants.

Mitsubishi Electric is taking similar steps. Thecorporation has issued company-wide environ-mental regulations and is taking a com-prehensive and organized approach towardenvironmental management. Corporate regula-tions have been updated with organizationalchanges and a new system of checks and bal-ances to promote transparent management prac-tices.

Routine OperationsMitsubishi Electric is also promoting environ-mentally friendly activities in day-to-day work.These goals include high-yield, zero-defect pro-duction, high productivity, efficient use of en-ergy, reduction of inventory levels, and a cleanand well-organized workplace.

We believe that this level of employee com-mitment at Mitsubishi Electric companies andaffiliates worldwide is essential to avoiding en-vironmental accidents. It will also contributeto smaller waste streams and higher levels ofrecycling both at the workplace and in societyas a whole.

Joint Activities with Other CorporationsMany manufacturing companies already evalu-ate environmental impact during the design ofnew products, and the International Standard-

Fig. 6 Landmark Tower Yokohama.

March 1996 · 5

TECHNICAL REPORTS

ization Organization (ISO) is investigating stan-dards for life-cycle assessment. To be effective,such measures will obviously need to be imple-mented at an industry-wide and global level.

Last year, Japan’s Ministry of InternationalTrade and Industry used life-cycle assessmentdata from companies in 15 industries to formu-late goals for future manufacturing environ-ments. We can anticipate greater internationalcooperation on environmental issues betweencompanies in similar industrial sectors, as wellas increasing cooperation between diverse in-dustries.

Cooperation Between Local and CentralGovernments, Industries and ConsumersA citizens’ mandate is needed to fairly distrib-ute the costs of environmental protection. In-dustries as well as governments have an obliga-tion to inform consumers regarding these issues.

Fig. 7 A model of Japan Earth Resources Satellite.

Beginning in March 1994, Japanese manufac-turers were formally obligated to collect andwhere possible recycle large appliances includ-ing televisions with screen sizes of 25 inchesand above and refrigerators with capacities over250 liters. This replaced an inconsistent hodge-podge of local directives.

For manufacturers to establish a nationalused-appliance collection system, central gov-ernment must lead the nation to a consensuson environmental policy satisfactory to con-sumers, manufacturers and local government.The nation is currently debating policies suchas restricting use of paper wastes in landfills,compulsory manufacturer recovery and disposalof used appliances, and recovery of CFCs fromused refrigerators and air-conditioners. InNovember 1994, the Electrical ApplianceManufacturers Association set up a discardedappliance reprocessing center to support local-


TECHNICAL REPORTS

government efforts to recover used appliances.We feel that cooperative efforts of this kind willencourage manufacturers to take the lead indeveloping the technologies suitable to addressthese issues.

Important characteristics of environmentalproblems are that they transcend national bor-ders, and they develop over a long period of timefrom the interaction of a multitude of factors.Actions we take now will bring visible effectsin the 21st century. This is why every sector ofindustry must make environmental plans atleast five to ten years in advance. Companiesmust question whether their practices are sus-tainable, and make medium- to long-range im-provement plans. Economic constraints shouldnot limit corporate investment in R&D, newtechnologies and public education aimed at pro-tecting the environment, since this is an invest-ment in the future of humanity.

One of the authors travels regularly to thetropical jungles of Southeast Asia to observe themany species of butterflies. Southeast Asia,South America and Africa are treasure troves ofbutterfly species. The Malay Peninsula alonehas twice as many species as the entire Eur-asian continent north of the Himalayas. A fa-vorite of this author is the genus Theclinae (Fig.8), which are colored in iridescent purples andgreens. The gossamer construction that givesbutterflies their beauty also makes them a sen-

Fig. 8 A photo of the Theclinae species found inthe Malay Peninsula.

sitive indicator of global environmental health.The yearly decline we observe in their numberssignals us that current environmental issues areserious and demand our immediate attention.❑

March 1996 · 7

TECHNICAL REPORTS

etation, distribution of water and its dynamics,the composition of the atmosphere, and the oc-currence of volcanic eruptions (Fig. 1).

The ADEOS SatelliteJapan’s National Space Development Agency(NASDA) contracted Mitsubishi Electric as sys-tem integrator for NASDA’s Advanced Earth Ob-servation Satellite (ADEOS, Fig. 2). Thecorporation is overseeing the entire developmentof the satellite, which is planned for launch in1996. ADEOS is designed specifically to collectenvironmental data that will be made availableto researchers worldwide.

Remote-Sensing InstrumentsThe following sections introduce remote-sensing instruments developed by MitsubishiElectric for ADEOS and other satellites.

ADVANCED VISIBLE AND NEAR-INFRARED RADIO-METER (AVNIR). AVNIR has high-resolutionpassive optical sensors that can monitor thestate of vegetation and other ground cover, andthe color of coastal waters. These sensors canresolve features as small as 8m in panchromaticmode and 16m in the multiband mode. AVNIR’spointing mechanism can direct the sensors asfar as ±40° left and right to scan a designated80km swath (Fig. 3).

Satellite Technology forEnvironmental Observation

by Tsutomu Iwahashi and Hirokazu Tanaka*

Over the past half century, we have witnessedlarge-scale changes in the earth’s environ-ment—desertification, decimation of tropicalrainforests, acid rain, depletion of the ozone layerand increased emission of greenhouse gases.Images and numerical data provided by remote-sensing satellites help researchers to betterunderstand these phenomena. This report ad-dresses the state of the art in this environmen-tally important technology.

Introduction to Remote-Sensing TechnologyEarth observation satellites are placed in rela-tively low orbits below 1,000km. The orbit isdesigned to allow the satellite to scan the earth’sentire surface over periods of days to weeks.

Surface phenomena are imaged using radia-tion in the visible spectrum, the near or ther-mal infrared region, or the microwave (radar)band. This radiation may be emitted, reflectedor scattered by the surface under observation.

The concentration of various substances inthe atmosphere is measured by using specificwavelengths at which these substances absorbradiation. The concentration of ozone, for ex-ample, is measured using wavelengths in theultraviolet and far-infrared bands.

Using data collected by various sensors, re-searchers can monitor the state of surface veg-

*Tsutomu Iwahashi and Hirokazu Tanaka are with the Kamakura Works.

Fig. 1 The basic concepts of remote-sensingsatellite technology.

Earth observing satellite

Flooding

Ocean temperature

Observation

Orbital travel

IcebergsDesertification

CloudsVolcanicactivity

Snow pack

Pollutedlakes andwaterways

Rainfall

Ozone layerGreenhouse-effect meterology

Fig. 2 Illustration of ADEOS (Courtesy ofNASDA).


Water content invegetation and soil

TECHNICAL REPORTS

ADVANCED MICROWAVE SCANNING RADIOMETER

(AMSR). Under development for ADEOS-II’slaunch in 1999, AMSR uses a passive sensor thatdetects thermal emissions from land or oceansurfaces in the microwave band. The data itcollects can be applied to monitor a wide vari-ety of phenomena, including ocean surface tem-perature and salt concentration, icebergs, oilslicks, water vapor content and precipitation.Fig. 4 shows the scanning geometry.

SYNTHETIC APERTURE RADAR (SAR). This activeelectromagnetic sensing technology derives pre-cise images from the coherence of radio signalsreflected by the ground. A recent subject of worldattention is the ability to generate topographicdata by combining holographic data collectedfor the same area from two separate orbits. SAR

has the advantage of functioning irrespective ofweather and daylight conditions. Fig. 5 shows aphotograph of the SAR antenna carried by JapanEarth Resources Satellite 1 (JERS-1).

Data ProcessingNASDA’s Earth Observation Center collects,stores and processes remote-sensing databeamed down by satellites. The data needs tobe “massaged” to compensate for various formsof distortion that arise due to the wobbling ofthe satellite, sensor idiosyncrasies and otherfactors. Once these errors are adjusted, numeri-cal data can be used to monitor changes overtime or converted to images. Sometimes, satel-lite data is combined with other geographicaldata or maps to produce special-purpose images.Figs. 6 and 7 show the region around Mt.Pinatubo before and after its recent eruption,showing the destructive effect on vegetationcaused by lava flows and cinders. The photoswere taken by MESSR, a near-infrared radio-meter carried on Marine Observation Satellite1 (MOS-1).

Several factors have brought about an enor-mous increase in the volume of remote-sens-ing data available for processing: sensorresolution is increasing, new satellites are ca-pable of carrying multiple sensors and geosta-tionary satellites are being used to relay data sothat signals can be monitored even when thesatellites move outside the line-of-sight of avail-able earth stations. At the same time, dramatic

Fig. 5 The SAR antenna for JERS-1.

OpticsHood

Point range (±40°)

Scanning range; 5.7°

80kmDirection of satellitetravel

Resolution: 16m in multibandmode, 8m in panchromatic mode

Altitude: 800km

Sun aligment sensor

Fig. 3 Scanning geometry of the AVNIR sensor.

Altitude: 800km

55°61°

55°55°

61°

Fig. 4 Conical scanning geometry of the AMSRsensor.

March 1996 · 9

TECHNICAL REPORTS

Sensors

Wider range of spectra

Special-purpose sensors for specific wavebands

More all-weather sensors

Improved spatial resolution

Observation

More frequent observations

Realtime observation using multiple satellites

Long-term monitoring program for greenhouse gases

Forecasting of short-term and local phenomena

Ocean pollutant monitoring for oil and suspended solids

Use of multiple sensors in combination

Data

Frequent distribution of realtime data

Information resources to support regional planning

Earth stations for rural municipalities to support localmonitoring applications

Regular telecasts of global atmospheric, forestry and watervapor data

advances in computing power have made it pos-sible to move the processing from mainframesto workstations—which is now the general prac-tice even in large data-processing centers. These

developments suggest that amateurs and stu-dents will have much wider acccess to satelliteremote-sensing data in the future.

Table 1 lists priorities for the future deploy-ment of remote-sensing systems, their use inearth observation and their application to real-world problems.

There is still much to be learned about currentenvironmental problems, and internationalenvironmental monitoring and protection or-ganizations will surely be needed to solve them.Mitsubishi Electric’s involvement in the fur-ther development of satellite remote-sensingtechnologies will continue to contribute to abetter understanding of our planet and its envi-ronment. ❑

Table 1 Plans for Development of Remote-SensingSatellite Systems for EnvironmentalObservation


Fig. 6 The Mt. Pinatubo region in November1989 (Courtesy of NASDA).

Fig. 7 The Mt. Pinatubo region in July 1990(Courtesy of NASDA).

TECHNICAL REPORTS

Purpose Evaluation item Location Conditions Simulation

Tunnels, stations Routine Calculate airflows in tunnels and stations with

Design ventilationventilation fans operating

equipment andStatic ventilation Platforms, stairways Track fire Calculate airflows at platform and stairways with train

establish procedureson fire at platform and emergency exhaust fans running

for routine andTunnels Tunnel fire Calculate airflows in tunnels with a train on fire stopped

emergency operationin a tunnel and emergency exhaust fans running

Calculate changing airflows and velocities in tunnelsDynamic ventilation Tunnels, stations Routine and stations under normal train operation schedule

with ventilation fans operating

Design ventilation Temperature andCalculate station and tunnel temperatures and

equipment humidityTunnels, stations Routine humidities under normal train operation schedule with

station air-conditioning and ventilation fans operating

Design air-Calculate cooling loads required to maintain a specific

conditioning Air-conditioning load Stations Summer

temperature in tunnels and stations under normal equipment

train operation schedule with station air-conditioning and ventilation fans operating

Design airflow paths Station exits, Two trains arrive,Calculate the strongest winds that occur when two

for station building Train wind platform stairways, or leave, simul- trains arrive or leave a station simultaneouslyand cooling tower ends of platforms taneously

Table 1 Simulation of Emergency Ventilation Systems for Underground Rapid-Transit Facilities

Ventilation and Air-ConditioningSystem Design for the New Astram

Metro Line in Hiroshimaby Shigenobu Horita, Tsutomu Kayama and Toshifumi Nakamura*

of airflow, power dissipation, thermal transferand thermal storage. These elements can inter-act in unexpected ways, and must be understoodif we are to design efficient ventilation and cool-ing systems. This knowledge is also essential toplan for emergencies such as an undergroundfire when exhaust fans must extract smoke andfumes from the platform and the stopped train.

Computer simulations of airflow and thermaleffects offer engineers a way to model and pre-dict system behavior under various circum-stances. Mitsubishi Electric used the provenSubway Environmental Simulation (SES) soft-ware developed by the U.S. Department ofTransportation to assist the design of emergencyequipment and operational procedures for thesesituations.

To use SES, we first represent the tunnels,platforms, stairways and passages as a networkof pipes through which pressurized air can flow.Calculations can then be made as to how suchfactors as forced-air ventilation, winds causedby the passage of trains, heat dissipation bytrains, temperature, humidity and the thermaltransmission of walls affect each other and thestation environment. Finally, how the various

*Shigenobu Horita and Toshifumi Nakamura are with the Nagasaki Works and Tsutomu Kayama is with theTransportation Systems Marketing Division.

March 1996 · 11

Integrated design of subway station ventilation,air-conditioning and emergency equipmentoffers the greatest performance and safety withthe minimum construction and operating costs.This article describes the use of simulationtechnology in the design of ventilation, air-conditioning and emergency equipment for un-derground stations in a new rapid-transit systemin Hiroshima.

Underground Environment of Rapid-TransitSystem and its Simulation by ComputerThe new Astram metro line runs 18.4km fromKoiki Park on the northwest to the city centerwhere the last three stations, Hondori,Kenchomae and Shirokita, are underground. Thetrain makes 21 stops, and the travel time fromterminal to terminal is 37 minutes. The line isthe first operational new-generation rapid-transit system in Japan to employ undergroundstations, and the first to use an enclosed plat-form with screened doorways, which lowers air-conditioning costs and improves safety.

The underground environment consists of tun-nels, stations, trains and surrounding under-ground passages, each having unique properties

Roger Williams

Roger Williams

Roger Williams

TECHNICAL REPORTS

number of trains, and ventilation and coolingrates affect airflow volumes, velocities, tempera-tures and humidity can be determined. Table 1lists categories of emergency equipment and thecontent of simulation operations.

The Design of Emergency VentilationEquipmentFig. 1 shows a ventilation network model usedto determine the airflows at Kenchomae Sta-tion. The model includes the two adjoining sta-tions and the tunnels that link them together.

We designed the exhaust fans to operate inseven emergency ventilation modes, each in-tended to clear smoke from a specific area. Wethen simulated their operation to determine theequilibrium airflow volumes and velocities. Wealso performed three-dimensional computa-tional fluid dynamics (CFD) of specific locationsand made measurements on small-scale mod-els to determine the airflow resistance of theplatform doorways and evaluate the pressureeffects of the exhaust fans.

The thickness and the direction of the arrows

in Fig. 1b indicate the magnitude and directionof the airflows predicted with a train stopped atKenchomae Station and fans TF-3, TF-5 and TF-6 operating.

We used simulations to verify that all sevenemergency ventilation modes would create therequired airflows and that the exhaust fans pro-vide adequate capacity.


To street

Concourse

Platfor m Doorways

1

2

3

4

a

b

1 2 3 4 5 6

TF-1

Hondori Station

TF-2 TF-3 TF-4 TF-5Light access

TF-6

Tunnelopenings

Shirokita stationKenchomae station

5406m3/min

1 42 3

a b

1 2 3 4 5 6

a) Airways through Kenchomae Station

b) Calculated airflows during a track fire at Kenchomae Station

Fig. 1 Modeling and simulation.

Fig. 2 The configuration of the environmentalcontrol system.

KENCHOMAESTATION

HONDORISTATION

SHIROKITASTATION

CRT CRT CRT PRTPRT PRTPRT

OPSOPSOPS

DMP DMP DMPCNS CNS CNS

MCC MCC MCC MCC

KeyOPS: Operator station DMP: Damper control boardCNS: Control station PRT: Printer

Roger Williams

Roger Williams

TECHNICAL REPORTS

Environmental Control SystemWe set up environmental control centers for eachstation to control routine operation of the air-conditioning and ventilation equipment, and toactivate the emergency ventilation modes. Wealso set up a remote control center that can op-erate the equipment at all three stations inemergency conditions.

Optical-fiber cables link the stations togetherand join the control stations to the damper con-

trol panels. Electrical wiring joins the controlstations to the motor-control centers. This lay-out was chosen to provide generous informa-tion capacity and connectivity with minimumwiring requirements.

Ventilation Capacity Verification TestsWe measured the various airflow velocities inall seven smoke-ventilation modes, using a pre-viously qualified hot-wire anemometer (M6611).

Fig. 3 Measured airflow velocities at various cross sections.

March 1996 · 13

TF-1 TF-2 TF-3 TF-4 TF-5 RF-21, AH-21

KenchomaeStation

Shirokita StationHondori Station

Outbound trains

Inbound trains

2.50(2.79)

2.53(2.69)

3.99(2.67)

2.17(2.68)

3.79(2.66)

2.17(2.77)

StairwayEscalator

a) In tunnels (m3/min)

1,439(1,205)

1.829(2,205)

3,879(3,381)

TF-6

b) Through platform doors (m/s)

Velocity (m/s)

2.62

2.62

2.49

2.36

2.23

2.10

1.97

1.84

1.70

1.57

1.44

1.31

1.10

1.05

1.05 Velocity (m/s)

5.50

5.50

5.04

4.58

4.13

3,67

3.21

2.75

2.29

1.83

1.38

0.916667

0.458333

0.00

–0.458333

Light across

Fig. 4 A comparison of measured and calculated airflow velocity values for a train fire at the KenchomaeStation platform (calculated values in parentheses).

a) In the Kenchomae-to-Shirokita tunnelduring a tunnel fire

b) Through the platform doors during a trainfire at Kenchomae Station platform.

Roger Williams

Roger Williams

Roger Williams

TECHNICAL REPORTS

Smoke was used to determine the flow direc-tions. We measured airflow at 50 to 60 points atevery tunnel cross section, and at 16 points overthe platform door openings. Ten readings weresampled at each point, one per second, and theaverage value recorded. These measures wereintegrated over the effective cross section toobtain the inflow volume across boundaries.

Using these values, we predicted airflow be-havior under several scenarios. Fig. 3a showsthe predicted air velocities across the tunnelbetween Kenchomae and Shirokita in the eventof a tunnel fire. Fig. 3b shows the air velocitiesat the platform door openings and platform stair-ways should a fire occur on the tracks in frontof the platform at Kenchomae Station, and Fig.4 contrasts the air velocities in the tunnel andat the platform doors under these conditionswith average values. The large amount of airleakage predicted at Hondori Station is borneout by actual measurements.

We then performed airflow measurements un-der all the emergency ventilation modes andverified adequate airflow to remove smoke fromthe facility. Finally, we conducted a full-scalesmoke test. We stopped a train at Kenchomaeplatform, opened the train and platform doors,started a smoke plume from the train towardthe platform, and set the ventilation mode for atrack fire. The exhaust fans quickly drew smokefrom the platform through the space betweenthe train and platform doors into the train land-ing area and out through the exhaust vents.

A fire has the potential to turn an undergroundstation into a death trap. Now that the technol-ogy to simulate a station's airflows exists, thisrisk can be greatly reduced by designing a venti-lation system that exhausts smoke away frompassenger hallways and exits. ❑


Roger Williams

Roger Williams

Roger Williams

Roger Williams

Roger Williams

TECHNICAL REPORTS

*Kiyoshi Sakai and Satoru Hoshino are with the Nagoya Works

With growing public awareness of global environ-mental problems, manufacturers need to be espe-cially conscious of the environmentalconsequences of their products. This article de-scribes the environmental, safety and cost incen-tives for use of gas-insulated power-distributiontransformers, and considers their environmentalimpact through the entire product life cycle.

Product SafetyThe windings of power-distribution transform-ers are insulated and cooled in one of three ways:

Oil-immersed transformers use paper-wrapped windings immersed in mineral oil,which serves as both the insulation and coolingmedium. Although inexpensive and widelyused, these transformers are undesirable in high-rise buildings and densely populated urban areasbecause of the high fire risks that accompanythe use of transformer oil.

Gas-insulated transformers use polyethyleneterephthalate (PET) film to insulate the wind-ings, which are placed in a sealed tank filledwith SF6 gas that cools the windings and pro-tects them from moisture and dust. In contrastwith transformer oil, SF 6 gas is extremely safe.It is highly inert, and has been given a Group 6UL safety rating, which puts it in the same high-safety class as nitrogen gas. Its safety has beenverified in other tests as well. (1)

Encapsulated-winding transformers use plas-tic to surround the windings, which are also aircooled. The fire danger is low, and no tank isrequired, making encapsulated transformerssmaller than either oil or SF6 gas-insulated types.However the windings are somewhat exposed,and gradually deteriorate due to exposure to air,moisture and other environmental factors.

MaintenanceMaintaining substation performance is essen-tial in urban contexts where power consump-tion is heavy. Hong Kong Electric reported thatthe maintenance costs of gas-insulated trans-formers were dramatically lower than those ofoil-immersed transformers (Fig. 1), leading themto replace all obsolete transformers with gas-

Environmental Assessment ofGas-Insulated Power-Distribution

Transformersby Kiyoshi Sakai and Satoru Hoshino*

insulated types.Transformer oil must be periodically filtered

and exchanged because it degrades over time,losing its insulating qualities. Fire-extinguish-ing equipment must also be maintained. SF 6,on the other hand, does not degrade (2) and pro-tects the insulation system from environmen-tal factors that might reduce performance.Maintenance is practically non-existent in com-parison.

Gas-insulated transformers turn out to becheaper than oil-immersed transformers whenmaintenance costs are factored in.

RecyclingPower-distribution transformers have a highrecycling value because they can be easily dis-assembled and their chief constituents, whichare high-purity steel, aluminum and copper, canbe recycled indefinitely.

Gas-insulated transformers are far more eas-ily recycled than oil-immersed types. SF6 gas canbe reused and PET film recycled into contain-ers, carpets and other products, allowing fully96% of the natural resources in gas-insulatedtransformers to be recycled after decomissioning.The oil and paper insulation of oil-immersedtransformers cannot be reused, which lowers thereuse ratio to only 71%.

Fig. 2 lists the materials and reuse ratios ofthese two types of transformer. Fig. 3 shows

March 1996 · 15

20

10

0

70

60

50

40

30

80

90

100

Cos

t (re

lativ

e to

oil-

fille

d tr

ansf

orm

ers,

%)

Oil-filled Gas-insulated

KeyFire extinguishing deviceOil changesLabor

Fig. 1 Comparative maintenance costs.

TECHNICAL REPORTS

the relatively simple construction of gas-insu-lated transformers, which assists in their recy-cling. The main components are the core, thewindings and the tank.

Environmental ImpactFig. 4 shows the resource flows involved intransformer manufacture, use and decommis-sioning. Almost all of the components of obso-lete products are recycled or reused.

Another facet of the environmental impact isthe energy cost. Table 1 shows the energy con-sumption calculated for the manufacture andoperation of 1,500kVA oil-immersed and gas-in-


sulated distribution transformers. The figuresare based on conversions of 3.72 x 107 J/l for fueloil, 3.88 x 107 J/l for crude oil and 9.22 x 106 J/kWh for electrical energy. The table shows thatalthough gas-insulated transformers requiremore energy to fabricate and assemble, they areactually cheaper in the long run due to theirlower operating losses.

Carbon steel

Aluminum5%

Copper7%

Misc.2%Insulated paper

1%

Oil26%

Siliconsteel32%

a) Oil-immersed transformers

SF6gas0.4%

Aluminum8%

Pet film3%

Misc.3.6%

Siliconsteel36%

Carbon steel36%

Resuable material: 71%

b) Gas-insulated transformers

c) Material purity

Material Element Purity (%)

Silicon steel Fe 98.5

Carbon steel Fe 99.0

Copper Cu 99.9

Aluminun Al 99.7

Radiator(Steel)

LeadAluminumCopper Core

(Silicon steel)

Tank(Steel)

Insulation(SF6)

CoilPet filmAluminumCopper( )

( )

Fig. 4 Resource flows over transformer productlife.

Humanresources

Design Manufacture

Use Scrap

ReconditioningRawmaterials

Recycling

From otherproducts For other

products

Fig. 2 Transformer composition.

Fig. 3 Construction of an SF 6-insulateddistribution transformer.

TECHNICAL REPORTS

Factoring this into the comparison gives gas-insulated transformers even greater cost andenergy advantages.

In addition to a well-earned reputation for safetyand reliability, gas-insulated transformers offeradvantages of easy recycling, low environmen-tal impact and lifetime costs well below thoseof common oil-immersed transformers. ❑

References1. Koshi, K,. Hiro’oka, K., Yoshioka, T., Noshiro, M. and Hashimoto, T.

“Characteristics of SF6 Gas from the Hygienic Point of View.”Reports of the Research Laboratory, Asahi Glass Co., Ltd., Vol. 27,Chapter 2, pp. 123 - 141, 1977.

2. “The Use of Sulfur Hexafloride (SF6) in High-Voltage Switchgearand Control Gear.” IEC/TC and SC 17A, 1994.

TypeManufacturing energy cost

Materials refining Forming and assembly TotalOperating energy cost*

Oil-filled 107 16 123 16,700

Gas-insulated 190 13 203 11,100

*The operating costs assume 20-year operation.

Table 1 Estimated Energy Cost Over Entire Life Cycle of 1,500kVA Power-Distribution Transformers(billions of Joules)

March 1996 · 17

TECHNICAL REPORTS

*Katsuhisa Ootsuta and Dr. Shuichi Tani are with the Advanced Technology Research & Development Center.

Fig. 2 shows the basic construction of theacoustic panel. It consists of a rear supportingplate that prevents sound leakage and a layer ofthe sound-absorbent plastic insulation separatedby a lattice that maintains the dead-air spaceand sets up smaller sound-absorption cells. Thefront surface of the sound-absorbent plastic iscovered with a protective punched metal sheet.

The lattice period was chosen to keep the cellssmaller than a half-wavelength at the centralabsorption frequency. This restriction ensuresthat the phase of the sound front arriving ateach cell is approximately uniform, which leadsto better resonator excitation.

Sound Absorption PerformanceFig. 3 shows a simple module that forms a reso-nator. The thickness of the dead-air space con-trols the maximum absorption frequency.Additions to this basic lower-frequency mod-ule make it possible to cover a wider spectrumof frequencies.

The Application of Sound-AbsorbentPlastic to Acoustic Paneling

by Katsuhisa Ootsuta and Dr. Shuichi Tani*

Mitsubishi Electric has developed a durablehigh-performance acoustic panel using a spe-cial sound-absorbent plastic acoustic-insulationmaterial formed by subjecting thermoplasticresin beads to heat and pressure. The plastic isincorporated into a module that enhances itssound-deadening properties. Rugged, weather-resistant design and excellent longevity makethe paneling suited to both indoor and outdooruse.

Features of the Sound-Absorbent PlasticConventional acoustic paneling loses its abil-ity to absorb sound as its fibers absorb mois-ture, and the binder degrades under ultravioletexposure. Fiberglass-based paneling sheds glassfibers and the filling compacts over time. Thesound-absorbent plastic we developed is im-mune to these problems, can be formed in anydesired shape and manufactured in any color.The forming process does not compromise thebasic noncombustibility and weather resistanceof the raw plastic. Finally, use of a known com-position facilities later recycling.

Panel ConstructionFig. 1 shows the basic sound-absorbing struc-ture, which consists of a layer of the new acous-tic insulation material, a dead-air space and rearplate to prevent sound leakage. The acousticinsulation is formed using plastic granules0.5~2.0mm in size, and is denser toward the frontand more porous toward the back.

The maximum absorption frequency is deter-mined by the acoustic mass of the insulationlayer and the thickness of the air space, whichwe can predict by analyzing an electrical cir-cuit. The insulation layer can be treated as re-sistance and inductance in series, and dead-airspace as capacitance. Together, the elementsform a series resonator.

By forming an insulation layer that nearlymatches the acoustic impedance of air, it is pos-sible to achieve a sound-absorption rate closeto 100% at the resonant frequency. The acous-tic resistance and characteristic acoustic im-pedance of the insulation layer can be controlledby adjusting its porosity during manufacture.


Incident soundwaves

Plastic beadsPore

Dead-air space

Rear plate

Rear plate

Punched metalcover

Sound-absorbentplastic

Sound-absorbingmodule

Sound-absorbentplastic

Fig. 1 Sound-absorbing structure.

Fig. 2 Panel construction.

TECHNICAL REPORTS

March 1996 · 19

Fig. 4 shows a compound module with bothhigh- and low-frequency sound-absorbent struc-tures. As with the low-frequency cells, the air-space thickness of the high-frequency cellsdetermines the frequency of maximum energyabsorption. These cells have a large frontal areato maximize the high-frequency absorption; at

the same time, they allow low-frequency soundwaves to diffract around behind, so that theeffective area for the low-frequency cells is notdiminished.

Fig. 5 shows a module with sound-reflectingbars in front that further increase the high-fre-quency sound-absorption efficiency. The barsare mounted in front of the high-frequency cells,and help by containing sound energy initiallyreflected off the cell surfaces.

Fig. 6 shows the absorption coefficients ofthese three types of modules measured in a re-verberation room. The simple module is 50mmthick and has a single absorption peak at 800Hz.The compound module is 50mm thick and hasa second absorption peak at 2,000Hz. Addingthe sound reflecting bar, creating a total thick-ness of 70mm, results in nearly uniform absorp-tion between 600 and 2,000Hz.

Weather ResistanceWe used accelerated artificial exposure tests andthermal cycling to verify the sound-absorbentplastic’s weather resistance. The exposure testwas made using a carbon-arc lamp to simulatesolar radiation over a period of 2,000 hours.Thermal cycling between –18 and +18°C was

0.2

0.4

0.6

0.8

1.0

1.2

0250160 400 630 1,000 1,600 2,500 4,000

Center frequencies of third-octave bands (Hz)

Simple panel

Compound panel

Compound panel with bars

Key

Fig. 6 Panel absorption coefficients in areverberation room.

Abs

orpt

ion

coef

ficie

nt

Sound-absorbent plastic

Low-frequency cellHigh-frequency cell

Dead-air space

Lattice Individual blocks


Rear plate

Fig. 4 A compound sound-absorbent panel.

Sound-reflecting bar

High-frequency cell


Low-frequency cell

Lattice Individual blocks Rear plate

Fig. 5 A compound sound-absorbent panel withsound-reflecting bars.

Individual blocks Rear plate

Lattice

Fig. 3 A simple sound-absorbent panel.

TECHNICAL REPORTS


conducted for a few weeks with one cycle last-ing 3.75 hours. The sound-absorbent plastic wasalso immersed in a bath and frozen and thawed300 times.

Fig. 7 shows the bending strength of the sound-absorbent plastic after thermal cycling and ex-posure tests, showing that neither test had mucheffect on the plastic’s physical properties, al-though the exposure test did cause some sur-face discoloration. Freezing and thawing alsocaused no damage.

This high-tech replacement for conventionalacoustic panels offers better sound-deadeningperformance, together with durability sufficientto last the life of a building. ❑

Accelerated solar radia-tion exposure (2,000h)

Before experiment Thermal cycling(300 cycles)

Ben

ding

str

engt

h σ f

(MP

a)

6.0

5.0

4.0

3.0

2.0

1.0

0

Fig. 7 Bending strength at 20°C after exposureand thermal cycling.

TECHNICAL REPORTS

*Dr. Yoshio Hanazato and Saori Kimura are with the Advanced Technology Research & Development Center.

A Highly Sensitive AtmosphericNOX Sensor

by Dr. Yoshio Hanazato, and Saori Kimura*

Mitsubishi Electric Corporation is developingsensors that can detect atmospheric oxides ofnitrogen (NOX) in concentrations at the parts-per-billion (ppb) level. Studies of gas-sensitivefilms and NOX adsorption/desorption mecha-nisms led to development of a surface acoustic-wave device with a chromium tetraphenylpor-phyrin film that selectively detects NOXconcentrations in the ppb to tens of ppb range.This article reports on the aforementioned sen-sors, their operating principles and responsecharacteristics.

BackgroundOxides of nitrogen from auto exhausts are amajor source of atmospheric pollution in urbanareas. Health considerations require that webegin to monitor indoor and outdoor NOX pol-lution and take necessary measures to reduceunsafe concentrations through ventilation, fil-tering or catalytic breakdown. Highly sensitive,highly selective NOX measuring instrumentssuitable for automated use will make it practi-cal to implement monitoring on a wider scale.

Current NOX sensors offer only parts-per-million (ppm) sensitivity, which limits their useto fixed pollution sources such as industrialsmokestacks and incinerators where the NOXconcentration is high. Sensors for general at-mospheric monitoring and having sensitivitiesin the ppb range are under development, butcommercial products are not yet available.

NOX Adsorption and Desorption on MetalPorphyrin Thin FilmsSensitivity and selectivity of gas sensors is de-termined by the adsorption/desorption charac-teristics of the sensor material with respect tothe molecules of the intended gas. Understand-ing the adsorption/desorption mechanism istherefore essential to the development of highlysensitive and selective sensors. It is known thatorganic semiconductors such as metal-porphy-rin and metal-phthalocyanine compounds ex-hibit high sensitivity and selectivity toward acidgases such as NO2,but the mechanisms are stillpoorly understood. The authors conducted stud-ies on the NO2 adsorption/desorption behavior

of metal tetraphenylporphyrins (MTPPs) andultimately chose them for developing gas-sen-sitive films.(1)

Through this work, we learned that theadsorption/desorption characteristics of MTTPsdepend strongly on the material’s redox poten-tial and surface morphology, with a lower re-dox potential corresponding to faster adsorptionand desorption. Because of their rough surface,chromium tetraphenylporphyrin (CrTTP) thinfilms show faster adsorption and desorptionthan would be expected on the basis of redoxpotential alone, suggesting that surface mor-phology considerations are of great importanceas well. We ultimately selected CrTTP as thedetector material for an experimental sensor dueto the excellent stability, reproducibility and am-plitude of its NO2 adsorption/desorption re-sponse. To convert these adsorption effects toelectrical signals, we chose to use piezoelectricsurface acoustic-wave resonator (SAW) devices,which offer high sensitivity while being suitedto mass production.

Sensor Operating PrinciplesThe oscillation frequency of piezoelectricdevices such as SAW resonators and quartz crys-tals mainly depends on the change in mass, andtherefore is affected by the mass of adsorbed gasmolecules. The relationship between change inmass and change of frequency in the piezoelec-tric devices is given by:

∆f = –Cfo2(∆m/A) ..................................... (Eq. 1)

where ∆f is the change of frequency in Hz, ∆mthe change in mass in grams, and A is the activearea of the SAW resonator in cm2. The constant(C) for an ST-cut quartz substrate is 1.3 x 10–6

cm2s/g (SAW resonator), which would corre-spond to a 1Hz change in the frequency of an80MHz SAW resonator with gas adsorption of0.12ng/cm2.

NOX Sensor ConstructionFig. 1 shows the construction of a NOX sensorbased on a SAW resonator. Two 78.8MHz SAWdevices are formed side-by-side on a single sub-

March 1996 · 21

TECHNICAL REPORTS

strate. One is coated with a thin, vapor-depos-ited CrTPP layer, and serves as the NOX detec-tor; the other, uncoated, serves as a frequencyreference for comparison. The sensor measures23 x 18mm, and provides outputs for measuringthe frequency difference. The sensor surfacesare kept at an operating temperature of120~130°C.

Sensor Response CharacteristicsFig. 2 shows the sensor response curves associ-ated with a 10min exposure to NO2 concentra-tions of 27, 254 and 508ppb. The vertical axisshows the magnitude of the change in frequency,and therefore shows positive values even thoughthe actual frequency output of the SAW sensordecreases when NO2 is introduced. The sensorreturns to its baseline output approximately40min after being returned to air without NO2.

Fig. 3 shows a calibration curve derived fromthe Fig. 2 peak values, which indicates that thesensor will be useful down to at least the tensof ppb range. From Fig. 2, it is clear that ten-minutes’ exposure was not long enough for thesensor to reach a steady state—about 20minwould have been required. However, when us-ing the first differential response, the peak ofthe response curve is received in 30~40s (Fig. 4).There is also a relation between this peak valueand the NO2 concentration, suggesting that wemight be able to reduce the measurement timeusing differential responses.

Table 1 lists the sensor’s selectivity with re-gard to other gases. The sensor does not respondto CO, CO2, NO nor n-butane (a typical hydro-

carbon compound utilized), although it does re-spond to the acid gas SO2 with a sensitivity aboutan order of magnitude less than the NO2 re-sponse. This should not present a problem inpractice because petroleum refining and smoke-stack desulfurization processes keep the atmo-


Amplifier

Interdigitalelectrodes

Absorption film

Reference SAWresonator

Mixer∆f = Fo – F1

SAW resonator withabsorption film

Amplifier

∆f (

Hz)

250

200

150

100

50

1,2001,0008006004002000

0

100

150

50

10 20 30 40 6050

NO2 concentration508ppb

254ppb

27ppb

Time (min)

∆f (

Hz)

00

Fig. 1 Schematic diagram.

Fig. 2 Response curves (exposure to No2 shownbetween arrows).

NO2 concentration (ppb)

Fig. 3 Calibration curve

Table 1 Gas Selectivity

Gas Concentration (ppm) Response ∆f (Hz)

NO2 0.98 242.5

NO 10.3 Not measurable

SO2 1.1 21.6

CO 49.9 Not measurable

n-butane 50.2 Not measurable

CO2 10,000 Not measurable

TECHNICAL REPORTS

March 1996 · 23

Time (s)

df/d

t (H

z/s)

1.0

0.8

0.6

0.4

0.2

0

–0.20 50 100 150 200 250 300

Fig. 4 Differential response curve on exposure toNO2 at 979 ppb (arrow shows exposurestart).

spheric concentration of SO2 at relatively lowlevels.

These studies demonstrated that by usingCrTPP film as an adsorption medium and a SAWresonator to monitor mass change it is possibleto measure extremely small NO2 concentrationsof the order of 10 ppb with excellent selectivity.

Although effective, the NOX sensors presentedhere had a response in the tens of minutes,whereas a faster response would be desirablefor field use. The authors plan to continue theirdevelopment work towards a reliable device thatmeets these requirements. ❑

ReferencesReferencesReferencesReferencesReferences1. Hanazato, Y., Kamiya, T., Ohta, N., Miyamoto, M. and Isoda, S.

“Absorption/Desorption Mechanism of NO2 on Metal-PorphyrinThin Films.” Proceedings of the 5th International Meeting onChemical Sensors, pp. 1,148 ~ 1,151, 1994.

R&D PROGRESS REPORT

*Dr. Junji Hirotsuji and Yoshitaka Kawaai are with the Advanced Technology R&D Center and Tetsuya Tamura iswith the Power & Industrial Systems Center.

R & D PROGRESS REPORT

Advanced OzoneWater-TreatmentTechnologyby Dr. Junji Hirotsuji, YoshitakaKawaai and Tetsuya Tamura*

Mitsubishi Electric has developedcommercial ozone water-treatment technolo-gies that can provide safe, odor-free drinkingwater, establish environmentally soundsewage-treatment processes and implementhigh-quality water reclamation systems. Thisarticle introduces advanced ozonization sys-tems the corporation has delivered for treatingdrinking water and sewage, and a combinedprocess employing ozone and hydrogen perox-ide that is currently under development.

Advanced Ozonization Technology forTreatment of Drinking Water

BENEFITS. Ozone treatment of drinking waterbenefits water quality in several ways.

It prevents formation of trihalomethanes andother organochlorine compounds by decom-posing humic acids. Humic acids react withchlorine to produce this class of substances.

It deodorizes drinking water by breakingdown two major compounds that contribute tomusty smell, geosmine and 2-methyliso-borneol, which other processes do not remove.

Combined with activated carbon filtration, itserves to remove agricultural chemicals,wastes from high-tech industrial processes andother substances listed in water-quality regula-tions.

Japanese water-quality regulations requirethat trihalomethane, formed by the reaction ofchlorine disinfectants and humic substances,be present in tap water at concentrations nohigher than 100µg/l. Ozone has long been usedas a decolorizing agent to decompose humicacids and other pigmented compounds, andtherefore ozone removal of humic substancesreduces the potential for trihalomethane forma-tion.

A WATER-TREATMENT PLANT IN OKINAWA.The corporation has already delivered 18 com-mercial ozone and activated carbon water-treatment systems. Here we introduce an

Ozone reactor tank

Construction Reinforced concrete

No. of tanks 4 (2-stage x 2)

Capacity 194,000m3/day

Tank dimensions 3.85 x 8.8 x 5m (W x L x D*)

Contact time 10 min. (5 min./stage)

TreatmentDiffusion with simultaneous air andwater flow

Ozone generator8.1kg/h x 4 capacities

Ozone injection rate 0~4mg/l

Additional equipment Catalytic ozone breakdown unit

*Effective depth

Activated charcoal absorption tank

Construction Reinforced concrete

No. of tanks 17 tanks (4 systems with 1 spare)

Capacity 219,800m3/day

Tank dimensions 5.05 x 10.85m (W x L)

Contact time 12min

TreatmentFixed-layer, downward-flow activatedcharcoal

Activated charcoal2m thickness

Cleaning method Blowback with air and water

Lower water collector Porous concrete

Additional equipment Activated charcoal supply

Table 1 Main Specifications of Ozone TreatmentFacility at Chatan Water-Treatment Plant


Reservoir

Holding trough

Microbial oxidation tank

Mixing tank

Flocculation tank

Setting tank

Rapid filtering tank

Intermediate pumping station

Ozone reactor tank

Activated charcoal absorption tank

Purified water tank

Drinking water

Fig. 1 The water-treatment process at the ChatanWater-Treatment Plant.

R&D PROGRESS REPORT

microbicidal effects. A portion of the treatedwastewater can be reclaimed through ozoneprocessing to feed streams and fountains,supplement rivers, and for other recreationalpurposes, as well as applications in the treat-ment facility itself.

Ozone processing can also be adopted on alarger scale to decolorize the entire outflow ofsewage-treatment plants where pigmentedcompounds—which the activated sludge pro-cess does not remove—are present in highconcentrations. Ozone is an effective decoloriz-ing agent because it selectively attacks thedouble-bonds that give pigments their charac-teristic colors.

Chlorination byproducts such as trihalo-methanes and other hazardous organochlorinecompounds in treated-sewage outflows affectecosystems and can have a negative impact onwater quality if they enter water sources.Ozone is more lethal to microorganisms thanchlorine without forming these substances.

Many sewage-treatment plants are expectedto install ozonization facilities due to theseenvironmental benefits.

A SEWAGE TREATMENT PLANT IN OSAKA.The corporation has delivered 16 ozonizationsystems for sewage treatment. Here we willintroduce an installation at the Chubu Treat-ment Plant of the South Osaka Central CoastSewage District.

Industrial wastewater comprises most of theplant’s inflow, however it also receives highlycolored fiber and food-processing plant wastesthat result in discolored waters where theplant discharges its outflow to Osaka Bay—which happens to be a highly visible locationnear a popular beach area and the New KansaiInternational Airport.

The plant had used sodium hypochlorite andpolyaluminum chloride decolorizing agents;however, residual chlorine from these com-pounds caused a variety of problems, includingbreakup of the activated sludge floc, equipment

ozonization facility delivered to the ChatanWater-Treatment Plant of the Okinawa Prefec-ture Enterprise Bureau.

The plant processes up to 194,000m3 of waterper day, concluding with ozonization and activecharcoal filtration. Conventional treatment wasjudged incapable of satisfying water qualityrequirements because the rivers used as a watersource were polluted with domestic wastewater,and the required chlorination would have resul-ted in excessive trihalomethane formation.

We designed the ozonization system to limittrihalomethanes at the consumers’ faucet to60µg/l and chloroform to 30µg/l, based on Japa-nese Ministry of Health and Welfare regula-tions, which limits trihalomethane-formingpotential to less than 100µg/l, and WHO water-quality guidelines.

Table 1 lists the facility specifications. Fourair-fed glass-tube silent-discharge ozone genera-tors are used, each with an ozone productioncapacity of 8.1kg/hr. The water is ozonated bymixing ozonated air and water from oppositedirections in a large tank, and repeating theprocess in a second tank. The tanks are 3.85 x8.8m, with a 5m water depth. The water reten-tion time is 10min.

PERFORMANCE. Table 2 lists the water qualityat each stage of treatment in the facility. Theozone treatment and activated charcoal filter-ing accomplish the greatest reduction intrihalomethane formation potential. Theseprocesses both contribute to lower levels oftotal organic carbon (TOC) and methyleneblue active substances (MBAS), and reducerequirements for chlorine and potassium per-manganate. The facility met the original designobjectives, and has contributed to a safer andbetter-tasting water supply.

Ozone Processing in Sewage Treatment

BENEFITS. Ozone processing is used in sewagetreatment for deodorizing, decolorizing and

Stage of treatmentTHM-FP TOC MBAS Chlorination KMnO 4 requirement (µg/l) (mg/l) (mg/l) requirement (mg/l) (mg/l)

Reservoir 59 1.9 0.08 2.2 7.6

After microbial treatment 57 (3) 1.75 (8) 0.05 (38) 1.0 (55) 6.8 (11)

After settling tank 44 (25) 1.43 (25) 0.05 (38) 0.5 (77) 4.5 (41)

After filtering 41 (31) 1.28 (33) 0.04 (50) 0.4 (82) 3.7 (51)

After ozonation 24 (59) 1.25 (34) 0.01 (88) 0.1 (95) 2.6 (66)

After activated charcoal 15 (75) 0.72 (62) 0.01 (88) 0.0 (100) 1.5 (80)filtering

Note: Figures in parentheses list the cumulative removal of the substance in percent.

Table 2 Operation Results of Chatan Water-Treatment Plant

March 1996 · 25

R&D PROGRESS REPORT


Forced-air intake

Coolingunit

Desiccation unit

Ozone generator

Cooling waterRefrigerated

air unit

Final setting tank

Ozone reactor tank

Osaka

Bay

Ozone decomposer

Key

Water flow

Untreated water

Air or ozone flow

Treated water

Fig. 2 The ozonation process at the Chubu Treatment Plant.

generator and two 5kg/hr generators, all of theair-fed glass-tube silent-discharge type. Thewater and ozone are mixed in two single-stagediffuser-type reactor tanks that are 2.55 x 4.5mwith a 4.5m water depth. The retention time is14.9 minutes (Table 3).

PERFORMANCE. Table 4 shows the results of theozone decolorization treatment. Spectropho-tometry was used to measure the decolorizingperformance. In general the degree of coloringwas measured at under 10% (practically color-less), indicating that the facility functioned asplanned, although the changing compositionand color degree of the effluent from the finalsettling tank results in some variations.

Runs 1~4 in the table show that even whenthe retention time (the period of contactbetween the water and ozone) was shorteneddue to large throughput, constant decolorizingperformance could be achieved by boosting theozone-injection rate. A side benefit of the pro-cess is that the chemical oxygen demand(COD) of the effluent dropped by 20~30%.

Item Type Number

Roots compressor,Air blower 9.81N/cm3 (1kgf/cm3), 6

4.94m3/min, 22kW

Air-fed glass-tubeOzone generator silent-discharge, 3

4kg/h (1), 5kg/h (2)

Ozone injector Diffusion pipe 2

Reinforced concreteOzone reaction tank 2.55 x 4.5 x 4.5m 2

(W x L x D)

Activated charcoalOzone decomposer decomposer, 200m3/h 3

(standard state)

Table 3 Main Specifications of Ozone TreatmentFacility at Chubu Treatment Plant

corrosion and high operating costs.We planned an ozone decolorizing facility for

the plant to alleviate these problems. The pro-duction system came online in August 1992following extensive testing.

The ozone facility consists of an ozone gen-erator, ozone reaction tank and catalyzer tobreak down residual ozone in the vented gas(Fig. 2). The facility employs one 4kg/hr ozone

R&D PROGRESS REPORT

Combined Ozone and Hydrogen Peroxide WaterReclamation Technology

BACKGROUND. Advanced wastewater treat-ments hold the potential to increase the watersupply and reduce water pollution through ex-tensive water reclamation. Use of reclaimedwater is already on the rise, and further growthis expected.

Reclaimed wastewater needs to be suffi-ciently pure to serve as a source for water-supply systems or to use directly in agricultureand industry. The maximum total TOC forthese applications is 2~3mg/l, which requiresremoval of refractory substances, such as theproducts of biological metabolism, and residualorganic substances that remain in wastewatereven after ozone treatment.

Several new processes with high oxidativepotential have been studied for this purpose:high-pH ozonization, UV ozonization, and com-bined ozone and hydrogen peroxide treatment.At Mitsubishi Electric, we investigatedcombined ozone and hydrogen peroxide treat-

Run No.Inflow Reaction Injection rate Initial Final water Impurities Initial Final COD

rate (m 3/h) time (min.) (mg/l) water purity(%) purity(%) reduction % COD(mg/l) COD(mg/l) reduction %

1 274 13.9 30.9 21.9 6.0 73 26.4 19.1 28

2 248 15.4 39.0 15.3 7.1 54 22.8 17.4 24

3 219 17.4 27.0 9.6 2.4 75 16.3 11.5 29

4 234 16.3 17.4 4.3 1.6 63 13.0 11.0 15

Avg.244 15.6 28.6 12.8 4.3 66 19.6 14.8 24

(1~4)

5 138 27.6 29.1 23.7 7.6 68 21.3 15.7 26

6 164 23.2 23.9 20.4 6.6 68 20.9 14.5 31

7 165 23.1 22.2 20.1 6.9 66 21.6 17.4 19

8 162 23.5 20.2 14.7 3.7 75 17.9 14.1 21

Avg.157 24.2 23.9 19.7 6.2 69 20.4 15.4 25

(5~8)

Note: Runs 1~4 employed two ozone generators, and runs 5~8 one ozone generator.

Table 4 Operation Results of Ozone Treatment Facility at Chubu Treatment Plant

March 1996 · 27

Target1 5 10 15

Table 5 Water Quality Levels and ApplicationRequirements

Total Organic Content (TOC) (mg/l)

∆ Tap water Reuse oftreatedsewage

Standards

Wastewater treatment2

Agricultural water2

Industrial water2

Steel processing

Pulp processing

Tap water2

Water quality

Note 1: Target for Mitsubishi water-reclamation technologyNote 2: Measured values

ment, with the goal of achieving TOC levels of3mg/l or lower.

The combined process is relatively simple toimplement. All it requires is that we supple-ment a conventional ozone injection processwith a small amount of hydrogen peroxide.

REACTION MECHANISM. The hydrogen peroxidereacts with ozone to produce hydroxy free radi-cal ·OH (Eq. 1). Even more highly oxidizingthan ozone, this species is capable of breakingdown refractory compounds and oxidizing al-most all residual organics into carbon dioxideand water.

O3 + H2O2 ➔ ·OH + ·O2H + O2

·OH + O3 ➔ ·O2H + O2 ........(Eq. 1)·O2H + O3 ➔ ·OH + O2

Although the hydroxy free radical easilydecomposes alcohol and other organic com-pounds in laboratory tests, we anticipate thatinorganic ions, such as carbonate ions, presentin wastewater would react with and consumemuch of the species. Numerous other com-pounds in wastewater complicate the issue,requiring further investigation.

RESEARCH AND DEVELOPMENT. Engineers inEurope and the United States are studying thevarieties of wastewater, preprocessing steps tolimit the ineffective consumption of hydroxyfree radical, and suitable reactor vessel designsfor the radical reaction. Treatment facilitiesusing the combined process have already beenset up at several water-treatment plants. Japanlags the west in the research and developmentof this technology, with no commercial systemsimplemented to date, but promising resultsfrom initial studies at Mitsubishi Electric sug-

R&D PROGRESS REPORT

28· Mitsubishi Electric ADVANCE

TO

C (m

g/1)

10

5

04 128 16

Reaction time (min)

Ozone only10mg/I H2O2

43mg/I H2O2

Key By supplementing existing ozonization facili-ties with hydrogen peroxide, we can expect toraise the absorption efficiency to 20~25% intanks 4~5m deep, or convert processes to usingcompact, contact-type tanks without loss ofefficiency.

In summary, the combined ozone and hydro-gen peroxide treatment effectively lowers theTOC, allows construction of more compactequipment and is well suited to water-reclama-tion schemes.

WORK IN PROGRESS. Our current R&D is aimedat determining the best pretreatment processesand conditions, determining the optimumamount of hydrogen peroxide and its bestmethod of introduction, and finally, the opti-mum ozone injection conditions.

We are also conducting design studies on apractical water reclamation system. A pilotplant will enter operation by March 1996 tohelp determine the technology’s performanceunder real-world conditions, and we aredesigning future systems that will be simple,economical to run and easy to maintain.

This R&D project was conducted in affilia-tion with the Public Utility System ResearchProject of the Engineering Advancement Asso-ciation of Japan.

Water purification technology is increasinglyimportant as we face increasing water pollu-tion, growing urban populations and greaterwater demand. Mitsubishi Electric believesthat its work in the field of ozonization tech-nology for water-supply purification and sew-age treatment will contribute to the health andenvironmental quality of future generations. ❑

Fig. 3 TOC removal by H2O2/O3 treatment afterpretreatment by PAC coagulation and fil-tration.

gest that this process will be suitable for futurewater reclamation projects.

EXPERIMENTAL RESULTS. Fig. 3 shows theresults of a batch processing experiment wherewe subjected treated wastewater to PACcoagulation and filtration, and then used acombined ozone and hydrogen peroxide pro-cess. While ozone alone does not significantlyreduce the TOC, the addition of hydrogen per-oxide causes the TOC to decline to as low as1.5mg/l.

The combined process is also more efficient:the amount of ozone consumed per TOC re-moved is less than that required for conven-tional ozonization, and the ozone absorptionefficiency is higher than that with conven-tional ozonization.

Fig. 4 shows the results of batch experimentsin water 30cm deep: absorption efficiency is10% under conventional ozonization, while itrises to 40% with the addition of hydrogenperoxide. The absorption continues to remainhigh even after the reaction time has elapsedand the hydrogen peroxide has been consumed.The high absorption occurs because the dis-solved ozone is quickly utilized in reactionswith hydrogen peroxide and hydroxy free radi-cal.

KeyOzone only

43mg/I H2O2

10mg/I H2O2

10Reaction time (min)A

bsor

bed

ozon

e (s

uppl

ied

ozon

e%)

50

100

0

Fig. 4 Ozone absorption characteristics.

NEW TECHNOLOGIES

March 1996 · 29

NeNeNeNeNew Manw Manw Manw Manw Manufufufufufacturacturacturacturacturing Process fing Process fing Process fing Process fing Process for or or or or Thin-Film Solar CellsThin-Film Solar CellsThin-Film Solar CellsThin-Film Solar CellsThin-Film Solar CellsMitsubishi Electric is developing aprocess to produce efficient andinexpensive thin-film polycrystallinesilicon solar cells. The solar cell isformed on the surface of a siliconsubstrate, then stripped off with theaid of a special via-hole etchingprocedure. The process dramaticallylowers the manufacturing cost be-cause each device requires only10% of the silicon used to manufac-ture a conventional device, and be-cause the silicon substrates can beused many times. The cells have Pand N electrodes on the rear surface,which boosts conversion efficiencyand facilitates mass production ofmodules. Thin, light and flexible, thedevices can be mounted in a widevariety of ways. Land, mobile andsatellite applications are anticipated.

pn junction

Si thin film

Development has been supportedby the New Energy and IndustrialTechnology Development Organiza-

tion (NEDO) as a part of the NewSunshine Program under the Ministryof International Trade and Industry. ❑

The structure of a thin-film solar cell.

EnEnEnEnEnvironment-Fvironment-Fvironment-Fvironment-Fvironment-Frrrrriendly Piendly Piendly Piendly Piendly Pacacacacackaging kaging kaging kaging kaging TTTTTechnologiesechnologiesechnologiesechnologiesechnologiesThe returnable package shown in

Fig. 3 consists of two paperboardpackages shipped in a single plasticbox. It can be reused many times.

Low-mass packages (Fig. 4) con-sume fewer resources than conven-tional packages. The corporationdesigns appliances such as VCRs,air-conditioners and washing ma-chines to be sufficiently rugged forshipping in these packages, and

Mitsubishi Electric has developedfour environment-friendly packagingtechnologies that satisfy governmentregulations, consumer demand andin-house environmental standards.

An expanded-polystyrene (EPS)recycling process enables EPS reusein the same molding process asvirgin styrofoam (Fig. 1). The used

EPS is ground up,processed into uni-form beads, treatedwith anti-static chemi-cals, and mixed withvirgin beads prior tomolding.

An all-paperboardpackage reducespackaging waste bysubstituting paper-board triangles forstyrofoam blocks. TheJapan PackagingInstitute awardedMitsubishi Electric aprize for the paper-board lighting fixturepackage shown in Fig. 2. One boxhouses five lighting fixtures. Thepaperboard is easily recycled.

conducts fragility testing to ensurethat the packages provide sufficientprotection. ❑Fig. 2 All-paperboard package for lighting

fixtures.

p-electrode n-electrode

Textured antireflection coating

Fig. 3 Returnable package for lighting fixtures.

Fig. 4 Low-mass paperboard package for a VCR

Fig. 1 Recycled EPS (left) and virgin product (right)l

NEW PRODUCTS

this kind of washing accounts for two-thirds of all washing done in thekitchen.

The Cooking Washer uses a high-speed water jet to wash away oily dirtwithout the use of detergents, andthen uses a high-speed jet of air toremove water droplets. It is fast andflexible enough to handle all of thewashing tasks in the kitchen, includ-ing those involved in cooking. It is

extremely easy to operate, with alarge opening for inserting dirty itemsinto the washer, where they are im-mediately detected and washed.Anything that enters the washer, fromdishes to cooking utensils, includingpots and pans and even the ingredi-ents to be cooked, can be quicklyand easily washed. Thrifty with waterand energy, the Cooking Washer isvery easy on the environment. ❑

The JT-16C “Jet-Towel” Hand Dryer


Cooking Washer

The Cooking Washer.

The widespread use of electricalhome appliances has greatly light-ened the burden of general house-work. In the kitchen, however,“washing” has usually meant “wash-ing by hand,” and rationalization ofthis task has long been sought. Previ-ous dishwashers, while they weresuitable for washing a number of dirtydishes at the same time, have notbeen able to perform the washingoperations involved, for example, incooking. Our research suggests that Model VL-30SL and VL-30SL-BE Lossnay ventilation units.

Compact Lossnay Ventilation Units

Intended for continuous use in well-sealed residences, Models VL-30SLand VL-30SL-BE serve fresh-air sup-ply and exhaust functions using anenergy-saving Lossnay heat-exchange element. The units occupyhalf the volume of previous modelsand can be easily installed to improve

the ventilation in existing dwellings.They mount in a 65mm hole, thesame size used for air-conditioners,and the outdoor hood uses knurledscrews for attachment without tools.The fresh-air intake is fitted with adust filter. ❑

In recent years, devices for drying thehands—from paper or cloth toweldispensers to hot-air hand dryers—are increasingly found whereverpeople live and work. Paper towelshave the disadvantage of using valu-able natural resources, and otherproblems associated with these de-vices include waste disposal andprocessing, hygiene and length oftime taken to completely dry thehands.

Mitsubishi “Jet-Towel” hand dryers,first introduced in Advance Vol.70,adopt a completely new approach todrying that solves all of these prob-lems. Previous dryers used a flow ofwarm air to evaporate droplets ofmoisture on the hands. They there-fore suffered the disadvantage oftaking a long time to dry the hands(30~40s).

In contrast, the JT-16C Jet-Towel iscompact, with a long useful life, andit uses a highly reliable brushlessblower motor to generate a high-speed blast of air (60m/s) that literallyblows away all droplets of moisture,drying the hands in a matter of only5~10s.

Operation is completely automaticand only requires that the hands bebriefly inserted in, and then with-drawn from, the device. At no timedo the hands need to come intocontact with any part of it. The drop-lets blown off the hands are collectedin the drain tank under the device.The product boasts outstandinghygiene and ease of maintenance,and is expected to generate rapidlyexpanding sales. ❑

The Jet-Towel hand dryer, JT-16C.

March 1996 · 31

Energy-Saving Ozone-Friendly Refrigerator

The 407-liter Model MR-J41B em-ploys the world’s first mass-produc-tion rotary compressor for use withenvironmentally acceptable HFC-134a refrigerant. The refrigerator isenergy efficient, consuming 20% lesspower than previous models. This isachieved by use of a compressormotor control system providing highstartup torque and a highly efficientcontrol setting for when the motorreaches operating speed, and byaddition of a valve that maintains thepressure difference between thehigh-pressure and low-pressuresides of the refrigerant circuit whenthe motor shuts down. In addition, anew lubrication technology reducescompressor vane wear by 50% com-pared with previous products, ensur-ing long, reliable operation. Thefour-compartment model comprises arefrigerator compartment on top, atwo-level drawer-type freezer, and avegetable compartment. The auto-matic icemaker is designed to pre-vent ice from picking up food odors.The control system incorporatesneural-network and fuzzy-logicprinciples. ❑

Energy Conservation Measures for Room Air-Conditioners

The MR-J41B refrigerator using HFC-134arefrigerant and a rotary compressor.

Series MSZ-FX255 room air-condi-tioners for 1995 consume only halfthe power of previous models at ratedoutput, and are estimated to con-sume 40% less energy per year.Several improvements have madethis possible. All models have a com-pressor with an energy-saving brush-less DC motor that provides the samecooling power with 15% lower energyinput. The area of the heat exchang-ers has been expanded by 50% inthe indoor units and 100% in theoutdoor units. The units feature largerdiameter fans with a new blade de-

sign that is 35% more efficient atrated output. Additional resourcesavings have been achieved byreducing the component count by25% in the indoor unit and 26% in theoutdoor unit.

Consumer air-conditioners nowconsume more electric power perhousehold than refrigerators inJapan. About 80% of Japanesehouseholds have at least one air-conditioner installed and 50% havetwo or more. Environmental and costconsiderations make more energy-efficient appliances essential. ❑

The front panel and remote control unit of an MSZ-FX255 room air-conditioner.

NEW PRODUCTS

SERVING THE WORLD


Country Address TelephoneU.S.A. Mitsubishi Electric America, Inc. 5665 Plaza Drive, P.O. Box 6007, Cypress, California 90630-0007 714-220-2500

Mitsubishi Electronics America, Inc. 5665 Plaza Drive, P.O. Box 6007, Cypress, California 90630-0007 714-220-2500Mitsubishi Consumer Electronics America, Inc. 2001 E. Car negie A venue, Santa Ana, California 92705 714-261-3200Mitsubishi Semiconductor America, Inc. Three Diamond Lane, Durham, North Carolina 27704 919-479-3333Horizon Research, Inc. 1432 Main Street, Waltham, Massachusetts 02154 617-466-8300Mitsubishi Electric Power Products Inc. Thorn Hill Industrial Park, 512 Keystone Drive, Warrendale, Pennsylvania 15086 412-772-2555Mitsubishi Electric Manufacturing Cincinnati, Inc. 4773 Bethany Road, Mason, Ohio 45040 513-398-2220Astronet Corporation 37 Skyline Drive, Suite 4100, Lake Mary, Florida 32746-6214 407-333-4900Powerex, Inc. Hills Street, Youngwood, Pennsylvania 15697 412-925-7272Mitsubishi Electric Research Laboratories, Inc. 201 Broadway, Cambridge, Massachusetts 02139 617-621-7500

Canada Mitsubishi Electric Sales Canada Inc. 4299 14th Avenue, Markham, Ontario L3R 0J2 905-475-7728Mitsubishi Electronics Industries Canada Inc. 1000 Wye Valley Road, Midland, Ontario L4R 4L8 705-526-7871

Mexico Melco de Mexico S.A. de C.V. Mariano Escobedo No. 69, Tlalnepantla, Edo. de Mexico 5-565-6269

Brazil MELCO do Brazil, Com. e Rep. Ltda. Av. Rio Branco, 123, a 1507, 20040, Rio de Janeiro 21-221-8343MELCO-TEC Rep. Com. e Assessoria Tecnica Ltda. Av. Rio Branco, 123, a 1507, 20040, Rio de Janeiro 21-221-8343

Argentina MELCO Argentina S.R.L. Florida 890-20º-Piso, C.P. 1005, Buenos Aires 1-312-6982

Colombia MELCO de Colombia Ltda. Calle 35 No. 7-25, Oficinas No. 1201/02, Edificio, Caxdac, Apartado Aereo 1-287-927729653, Bogotá

U.K. Mitsubishi Electric U.K. Ltd. Travellers Lane, Hatfield, Herts. AL10 8XB, England 707-276100Apricot Computers Ltd. 3500 Parkside, Birmingham Business Park, Birmingham, B37 7YS, England 21-717-7171Mitsubishi Electric Europe Coordination Center Centre Point (18th Floor), 103 New Oxford Street, London, WC1A 1EB 71-379-7160

France Mitsubishi Electric France S.A. 55, Avenue de Colmar, 92563, Rueil Malmaison Cedex 1-47-08-78-00

Netherlands Mitsubishi Electric Netherlands B.V. 3rd Floor, Parnassustoren, Locatellikade 1, 1076 AZ, Amsterdam 20-6790094

Germany Mitsubishi Electric Europe GmbH Gothaer Strasse 8, 40880 Ratingen 2102-4860Mitsubishi Semiconductor Europe GmbH Konrad Zuse Strasse 1, 52477 Alsdorf 2404-990

Spain MELCO Iberica S.A. Barcelona Office Polígono Industrial “Can Magi”, Calle Joan Buscallà 2-4, Apartado de Correos 3-589-3900420, 08190 Sant Cugat del Vallés, Barcelona

Italy Mitsubishi Electric Europe GmbH, Milano Office Centro Direzionale Colleoni, Palazzo Persero-Ingresso 2, Via Paracelso 12, 39-6053120041 Agrate Brianza, Milano

China Shanghai Mitsubishi Elevator Co., Ltd. 811 Jiang Chuan Rd., Minhang, Shanghai 21-4303030

Hong Kong Mitsubishi Electric (H.K.) Ltd. 41st Floor, Manulife Tower, 169 Electric Road, North Point 510-0555Ryoden Holdings Ltd. 10th Floor, Manulife Tower, 169 Electric Road, North Point 887-8870Ryoden Merchandising Co., Ltd. 32nd Floor, Manulife Tower, 169 Electric Road, North Point 510-0777

Korea KEFICO Corporation 410, Dangjung-Dong, Kunpo, Kyunggi-Do 343-51-1403

Taiwan MELCO Taiwan Co., Ltd. 2nd Floor, Chung-Ling Bldg., No. 363, Sec. 2, Fu-Hsing S. Road, Taipei 2-733-2383Shihlin Electric & Engineering Corp. No. 75, Sec. 6, Chung Shan N. Rd., Taipei 2-834-2662China Ryoden Co., Ltd. Chung-Ling Bldg., No. 363, Sec. 2, Fu-Hsing S. Road, Taipei 2-733-3424

Singapore Mitsubishi Electric Singapore Pte. Ltd. 152 Beach Road #11-06/08, Gateway East, Singapore 189721 295-5055Mitsubishi Electric Sales Singapore Pte. Ltd. 307 Alexandra Road #05-01/02, Mitsubishi Electric Building, Singapore 159943 473-2308Mitsubishi Electronics Manufacturing Singapore Pte. Ltd. 3000, Marsiling Road, Singapore 739108 269-9711Mitsubishi Electric Asia Coordination Center 307 Alexandra Road #02-02, Mitsubishi Electric Building, Singapore 159943 479-9100

Malaysia Mitsubishi Electric (Malaysia) Sdn. Bhd. Plo 32, Kawasan Perindustrian Senai, 81400 Senai, Johor 7-5996060Antah MELCO Sales & Services Sdn. Bhd. 3 Jalan 13/1, 46860 Petaling Jaya, Selangor, P.O. Box 1036 3-756-8322Ryoden (Malaysia) Sdn. Bhd. 2nd Fl., W isma Yan, Nos. 17 & 19, Jalan Selangor, 46050 Petaling Jaya 3-755-3277

Thailand Kang Yong Watana Co., Ltd. 15th Floor, Vanit Bldg., 1126/1, New Petchburi Road, Phayathai, Bangkok 10400 2-255-8550Kang Yong Electric Co., Ltd. 67 Moo 11, Bangna-Trad Highway, Km. 20 Bang Plee, Samutprakarn 10540 2-312-8151MELCO Manufacturing (Thailand) Co., Ltd. 86 Moo 4, Km. 23 Bangna-Trad, Bangplee, Semudparkarn 10540 2-312 -8350~3Mitsubishi Elevator Asia Co., Ltd. Bangpakong Industrial Estate, 700/86~92, Moo 6 Tambon Don Hua Roh, 38-213-170

Muang District Chonburi 20000Mitsubishi Electric Asia Coordination Center 17th Floor, Bangna Tower, 2/3 Moo 14, Bangna-Trad Highway 6.5 Km, 2-312 -0155~7(Thailand) Bangkawe, Bang Plee, Samutprakarn 10540

Philippines International Elevator & Equipment, Inc. Km. 23 West Service Road, South Superhighway, Cupang, Muntinlupa, 2-842 -3161~5Metro Manila

Australia Mitsubishi Electric Australia Pty. Ltd. 348 Victoria Road, Postal Bag No. 2, Rydalmere, N.S.W. 2116 2-684-7200

New Zealand MELCO Sales (N.Z.) Ltd. 1 Parliament St., Lower Hutt, P.O. Box 30-772 Wellington 4-569-7350

Representatives

China Mitsubishi Electric Corp. Beijing Office SCITE Tower, Rm. 1609, Jianguo Menwai, Dajie 22, Beijing 1-512-3222Mitsubishi Electric Corp. Shanghai Office Room No. 1506-8, Shanghai Union Building 100, Yanan-East Street, Shanghai 21-320-2010

Korea Mitsubishi Electric Corp. Seoul Office Daehan Kyoyuk Insurance Bldg., Room No. 1204 #1, Chongno 1-ka, 2-732 -1531~2Chongno-ku, Seoul

Viet Nam Mitsubishi Electric Corp. Ho Chi Minh City Office 8 B2, Han Nam Officetel 65, Nguyen Du St., 1st District, Ho Chi Minh City 8-243-984

MITSUBISHI ELECTRIC OVERSEAS NETWORK (Abridged)

MITSUBISHI ELECTRIC CORPORATIONHEAD OFFICE: MITSUBISHI DENKI BLDG., MARUNOUCHI, TOKYO 100-8310, FAX 03-3218-3455

vol. 74/mar. 1996 mitsubishi electric · vol. 74/mar. 1996 mitsubishi electric advance a quarterly...

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