theorie part 2 air treatment

7/28/2019 Theorie Part 2 Air Treatment

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Air Treatment

Capt. K. De Baere



Introduction

Air quality in the cargo holds is important,damage that can be caused by inadequate

ventilation; Damage to the cargo

Overheating of the cargo

Depreciation of the cargo

Rotting of the cargo Contamination by odour

Accumulation of inflammable, toxic and noxious gasses

Spontaneous combustion of the cargo



Introduction

Damage to the ship

Sweating of ship and cargo

Staining of the holds

Oxidation of the ships structure



Purpose Ventilation and

Conditioning Controlling humidity – Absorption and

condensation as a consequence of temperature

variations Controlling dust during cargo operations

Controlling oxygen

Evacuation of;

Contaminating vapours

Exhaust gas on board of Ro-Ro’s

Explosive cargo gas by means of IG on board of tankers

Toxic gas



Purpose Ventilation and

Conditioning Managing temperature

Managing chemical composition of the hold

atmosphere

IG on board of tankers

Ripening (maturing) process on board of fruit

carriers (N2, CO2 en ethylene)



Ventilation

Natural ventilation

Mechanical ventilation



Natural Ventilation

Use the natural circulation of air

Wind

Natural movements of the air f.i. warm air rises

and cold air comes down (convection)

This natural ventilation is realized by;

Ventilation ducts

Opening and/or closing of hatch covers



Ventilators – not mechanical

Provision of an

eductor improves the

evacuation of air (Venturi principle)



Ventilation cowls




Inside the ventilator coaming a metal cross is provided to prevent the passage of thieves or

stowaways The ventilator cowl is closed by a grid

Fire screen

To prevent the passage of unwanted objects

In case of very bad weather the air ducts (cowls)on deck can be removed and the openings areclosed by means of a metal lid



In case of bad

weather theventilation

cowls are

turned and

covered




In case of bad weather the ventilator cowls

are swivelled in the opposite direction of the

wind and covered with canvas

Samson posts are often used as ventilator

ducts and are provided with mushroom

shaped caps



Ventilation caps



First ‘assisted’ ventilation – wind

sails with 2 or 4 sails



Problems related to natural

ventilation Insufficient capacity

Incorrect positioning of the air ducts

Corners of the hold are insufficiently ventilated

Positioned so that they are exposed to the weather

conditions, green water and seas on deck => they have

to remain closed => insufficient ventilation

Insufficient number of ducts on each side of the

hold (ventilation is interrupted by a temporary

separation in the hold f.i. by the cargo)




ventilation

Hot and damp air escaping from the cargo is captured

between the deck stringers => condensation




ventilation

Ventilation is improved by providing ventilation

holes in frames, deck stringers and brackets




ventilation

If the ventilation tunnels are not going deep enough only a

surface ventilation is provided This is OK for coal or other bulk cargoes but not for

general cargo

Sometimes special constructions are provided to allowadequate ventilation inside the cargo



Inside ventilation

Rice and Soya beans

These products release alot of humidity and CO2

during transport => must be evacuated

Tank top is covered withdunnage and separation

cloth 1 layer of bags is spread

out

On top of these bags theventilation ducts are

installed



Inside ventilation

On the intersection

between the longitudinal

and transversal duct a

vertical duct is constructed

After 3 to 5 layers of bags

the whole constructing is

repeated




ventilation This can be solved when the

inlet ducts are extended till the

bottom of the compartment The cold air on the bottom will

rise to the top of the hold

Outlet ducts to be provided ator near the top of the cargohold

The inlet ducts are providedwith flaps allowing surfaceventilation



Natural ventilation is regulated

by trimming the cowls



Natural ventilation

A lot of hot damp air can be evacuated when the hatchesare opened and all of the cowls are turned towards thewind

This is very effective in cold regions



Natural ventilation – smoother

method

All cowls are turned away from the wind => the

hot air is sucked out (warm air rises)




The only difference with natural ventilationis that mechanical ventilators – fans – are

used Fans are reversible

Operation is electrical

Fans are operated from the bridge or E.R. The ventilation ducts can be opened or

closed on each level by means of flaps



Mechanical ventilation on board

of a PCC = Pure Car Carrier




Capacity of the ventilation system is

expressed by the number of air changes per

hour

On board of a car carrier the capacity during

sea voyage must be 10 changes per hour

this will be increased till at least 20changes per hour during loading and

discharging operations



Distribution of ventilators on

board of a ro-ro ship



Air conditioning



Psychometrics

Study of the thermodynamics and the

humidity of air

Important on deciding if an air treatment

method is appropriate

Psychometrics or hygrometry is the study of

how the properties of moist air can changeas a result of air conditioning processes.



Psychrometer

By means of a psychrometer we canmeasure the hygrometric state of the air

A psychrometer consists out of a wet and adry bulb

Because of the evaporation the wet bulb

will indicate a lower temperature Relative humidity can be determined by

means of special tables



Humidity

Humidity is the amount of water vapour in

the air and can be described in different

ways.



Absolute humidity [gr/m3]

1. The ratio of the mass of water vapour to

the volume occupied by a mixture of

water vapour and dry air.

2. Mass of water contained in a unit volume

of moist air.



Actual vapour pressure

The partial pressure exerted by the water

vapour present in a parcel. Water in a

gaseous state (i.e. water vapour) exerts a pressure just like the atmospheric air.

Vapour pressure is also measured in

millibar .



Saturation of air

The condition under which the amount

of water vapour in the air is the

maximum possible at the existingtemperature and pressure.

Condensation or sublimation will begin if

the temperature falls or water vapour isadded to the air.



Table van Regnault – saturation

vapour pressureTemp [°C] Press [mb]

0 6.1

5 8.7

10 12.3

15 17.1

20 23.3

25 31.7

30 42.4

35 56.3



Table Regnault



Dew point

The temperature air would have to be

cooled to in order for saturation to occur.

The dew point temperature assumes there isno change in air pressure or moisture

content of the air.



Relative humidity

The amount of water vapour actually in the

air divided by the amount of water vapour

the air can hold. Relative humidity isexpressed as a percentage and can be

computed in a variety of ways. One way is

to divide the actual vapour pressure by thesaturation vapour pressure and then

multiply by 100 to convert to a percent



Dry bulb temperature

The dry-bulb temperature of air is measured

by a thermometer which is freely exposed to

the air but is shielded from radiation andmoisture



Wet bulb temperature

The Wet-bulb Temperature of air is

measured by a thermometer whose bulb is

covered by a muslin sleeve which is keptmoist with distilled and clean water, freely

exposed to the air and free from radiation



Sling psychrometer - animated



Sling psychrometer



Psychometric charts

The psychometric chart is a useful design tool for

ventilation purposes. The chart presents a number

of properties of moist air: dry-bulb temperature

sling wet-bulb temperature

moisture content

specific enthalpy

specific volume

percentage saturation

http://www.taftan.com/thermodynamics/DRYBULB.HTM

http://www.taftan.com/thermodynamics/WETBULB.HTM

http://www.taftan.com/thermodynamics/SPHUMID.HTM

http://www.taftan.com/thermodynamics/ENTHALPY.HTM

http://www.taftan.com/thermodynamics/SPVOLUME.HTM

http://www.taftan.com/thermodynamics/PERCESAT.HTM

http://www.taftan.com/thermodynamics/PERCESAT.HTM

http://www.taftan.com/thermodynamics/SPVOLUME.HTM

http://www.taftan.com/thermodynamics/ENTHALPY.HTM

http://www.taftan.com/thermodynamics/SPHUMID.HTM









Psychometric charts



Psychometric chart



Psychometric charts simplified

At first glance, even a simple psychometric

chart appears complex. However, separating

the various lines and scales on the chartsimplifies understanding their location,

meaning and use.



Dry bulb temperature

The dry bulb

temperature scale is

located at the base of the chart. Vertical

lines indicate

constant dry bulb

temperature



Dew point temperature

Dew point temperature is the

temperature below which moisture

will condense out of air.(saturated)

The dew point temperature scale is

located along the same curved

portion of the chart as the wet bulb

temperature scale. However,

horizontal lines indicate equal dew point temperatures



Relative humidity

Lines representing conditions of

equal relative humidity sweep from

the lower left to the upper right of

the psychometric chart. The 100 %relative humidity (saturation) line

corresponds to the wet bulb and the

dew point temperature scale line.

The line for zero percent relativehumidity falls along the dry bulb

temperature scale line.



Example 2 – image is not correct

The air in a cargo hold

has a dry bulb

temperature of 80° F andis at 70 percent relative

humidity. How warm do

the bulkheads have to be

to prevent condensation?

The dew point temperature is 69°F. The bulkhead temperature must

be warmer than this to prevent condensation.



Consequences of an excessive

humidity Ship’s sweat

Cargo sweat

Foodstuff becoming mouldy

Fungus

Rust and oxidation of the ship’s structural

elements

Rotting wood



Practical Ventilation On Board

If the relative humidity is < 30% non of the abovementioned problems will arise.

Natural ventilation wants to replace the air in theholds with dryer air (< relative humidity)

In case of low outside temperature the relativewarm hold air will condense in the exhaust

ventilation shafts => humidity runs back into thehold => damage. This is especially the case whenhigh exhaust air shafts are used f.i. Samson posts.

Sometimes ventilation has to be stopped at night




Suppose air temperature – dry bulb – 19°

Vapour tension is 14mb (absolute humidity)

At 19°C saturation vapour tension is 22mb(see Regnault – next slide)

Relative humidity is 14/22x100% = 63.6%

At 12°C saturation vapour tension is 14mb => the temperature has to drop to 12°C

before condensation will occur




Air will condensate on every surface with a

temperature < or = 12°C

A ship loaded with agricultural products (highhumidity) going to colder regions => a lot of

condensation on the ship skin (will take over

lower outside air- and sea temperatures quickly)

Solution: replace the hold atmosphere with dryer

air (air with a lower dew point)




Cargo sweat

Cargo products that have been stored ashore inrefrigerated spaces

On board of ships going warmer regions

Cargo will take over the outside temperature slower that the ships structure

Condensation of the warm air on the colder cargo

surfaces = Cargo sweat Especially important on steel products, tins, cardboard

boxes etc.




Heat or cold, generated on board, can also bring aboutcargo- or ship sweat

Poorly isolated boiler rooms or engine rooms radiate heat

=> condensation on colder ship or cargo surfaces Bulkheads in the neighbourhood of cooled or refrigerated

spaces => condensation of the warmer surroundingatmosphere

The air that comes in contact with these colder surfaceswill cool down=> higher relative humidity =>condensation & absorption by hygroscopic products

l i



Montreal -> Vancouver via

Panama



When ventilating?

Dew point of the outside air < dew point of

the hold air => atmosphere of the hold will

become dryer Temperature of ships structure and cargo

must be > dew point of the air if not cargo-

or ship sweat will occur.



Drying of air



Drying of air

Drying of air means – extract the water

1. By cooling the air. Humidity will condensate

and can be evacuated. Air is heated againafterwards

2. By using hygroscopic substances absorbing

the humidity

Th



Cooling of air 1. The compressor compresses

cool Freon gas, causing it tobecome hot, high-pressure

Freon gas (red in the diagramabove).

2. This hot gas runs through a setof coils so it can dissipate itsheat, and it condenses into a

liquid.

3. The Freon liquid runs throughan expansion valve, and in theprocess it evaporates tobecome cold, low-pressureFreon gas (light blue in thediagram above).

4. This cold gas runs through a setof coils that allow the gas toabsorb heat and cool down theair inside the building.



Mechanical drying systems

Composing elements

Closed circuit with containing a cooling medium(freon)

Compressor

Condenser – liquefies the freon

Liquefied freon is collected in a pressure vessel

The cooling medium is released by means of an

expansion valve The medium is passed trough an evaporator (heat

exchanger)

The air is cooled => condensation

P h t i h t h i th



Psychometric chart showing the

drying process1. Start of the cooling

process

2. Saturation (dew point) is reached

3. Temperature dropsand humiditycondensates.Humidity ratio hasdropped from 80% to 45%



Drying IG on board of a tanker

1. Compressing and cooling of IG



Drying IG on board of a tanker

2. Drying of the IG with PSA (Pressure Swing

Absorbtion)



PSA - systeem

D i t i



Drying systems using

hygroscopic substances

2 principles are used

Absorption -> the product changes fysically

and chemically on absorbing moisture Lithium chloride

Triethylene glycol

Adsorption -> no chemical or physical change

takes place after the adsorption of humidity

Sillicagel



Drier with absorbing liquid

Consists out of 2 chambers

and a pumping unit

1. Dehumidification chamber

(contact with absorbing liquid – litthium chloride – in the left

part and filter in the right part)

2. Regeneration chamber –

regeneration of the absorbingliquid

Drier ith do ble adsorbing in a



Drier with double adsorbing in a

drying tower

2 towers each filled

with sillicagel

1 in use, the other being regenerated with

warm, dry air.

PSA – Pressure Swing

Absorption



Drier with rotating adsorbing bed

The beds containing thesillicagel are constantly turning

The drying part and

regeneration part are onlydivided by a flexible bulkhead

Drying and regeneration take place at the same time

The regeneration air is dried atthe inlet while the dried air iscooled (transformation of vapour in water dropletsgenerates heat) at the outlet



Installation using sillicate rotors

Hygroscpic installation on board



Hygroscpic installation on board

of a chemical tanker



Honeycomb driers



Honeycomb

technology

Industrial installation



Industrial installation –

Honeycomb technology



Recirculation



Instruments

Dewpointaire console – compares dry and

wet bulb temperatures of outside air and the

hold atmosphere Cargo sweat and hold sweat can be avoided

by analysing these values

Dew point of the hold can be influenced byventilation, drying or cooling



Cooling of cargo holds



History

In 1876, the French

engineer Charles

Tellier transported a

meat shipment from

Buenos Aires to

Rouen. aboard his own

steamer « leFrigorifique ».



Evolution in cooled transport

The primary refrigerated products are

bananas, meat, citrus fruit, fish and seasonal

fruit. Developments over the last 15 yearswith regard to these various refrigerated

goods can be seen from the following

tables. The highest growth in absolute terms

is in bananas and meat, which have a large

share of the overall market anyway.



Evolution in cooled transport

Proportions of the different



Proportions of the different

refrigerated transported by sea



h l d ?



Why cooled transport?

Ever increasing distance between producer andconsumer

Necessary for consumables to arrive in optimal

condition

The cold slows down the ripening process of fruitsand vegetables

The cold avoid meat and fish to be destructed bygerms

Certain chemical reactions are inhibited

The cold extends the conservation time of

consumables



Preservation of refrigerated



Preservation of refrigerated

commodities

Temperature control

Level of CO2 in the stowage compartment

Ripening fruit produces ethylene and CO2

Ethylene and CO2 must be removed to minimise theripening process

Excess humidity will cause moisture deposits onthe cargo space structure => development of

micro-organisms

To dry atmosphere will lead to moisture loss =>freezer burn

F B



Freezer Burn

Freezer burn(deshydration) istypified by a loss of

moisture that affects both texture andflavor. Freezer burn isindicated by a dry

surface, which mayalso have white or gray spots on it.

Freezer burn on ox-tongue



R f i t d



Refrigerated cargoes

Frozen

- 12°C => - 25°C

Exact temperature is not so important as long as it is

below the freezing temperature of the product

Chilled

- 2°C => + 13°C

Technique is much more delicate. Each product must be

transported at an exact temperature and in a controlledatmosphere.

Air-cooled



Frozen meat in boxes



Frozen meat in boxes

Transport of fish



Transport of fish

Chilled or frozen

Conservation time between 15 days (0.5 à

2°C) and 4 months (-18°C) Fish is transported in carton boxes or crates

Transport of fruit and vegetables



Transport of fruit and vegetables

Fruits and vegetables are harvested atmaximum size before maturation

Fruit and vegetables are living organisms,they absorb O2 and release CO2, heat andwater vapour

2 categories are distinguished

Without amylum (zetmeel)

With amylum (zetmeel)



Chilled

products



Cargo

compatibility

refrigerated

products

O = yes N = No

R = Risk



Cargo

compatibility

frozen

products

O = yes N = No

R = Risk



Bananas

Musa familie = bananas



Musa familie = bananas

Musa family is very large

2 major edible varieties

Banana (Musa Paradisiaca AAA) – fruit eatenuncooked

Plantain (Musa Paradisiaca ABB) – must be

cooked before consumption

Banana



Banana

Plantain



Plantain



Banana Plant



Banana Plant

Banana plants are the largest plants on earth without awoody stem. They are actually giant herbs of the samefamily as lilies, orchids and palms.

Today's commercial bananas are scientifically classifiedinto the genus Musa of the Musaceae family.

The Cavendish is the most common variety of bananasnow imported to the United States. The Cavendish is ashorter, stubbier plant than earlier varieties. It was

developed to resist plant diseases, insects andwindstorms better than its predecessors. The Cavendishfruit is of medium size, has a creamier, smooth texture,and a thinner peel than earlier varieties.

Banana Plant



Banana Plant

Bananas are perennial (vorstbestendige overblijvende)crops that are grown and harvested year-round. Thebanana plant does not grow from a seed but rather from arhizome or bulb. Each fleshy bulb will sprout new shoots

year after year.

Each banana plant bears only one stem of fruit. Toproduce a new stem, only two shoots - known as thedaughter and the granddaughter - are allowed to grow and

be cultivated from the main plant. The banana plant reaches its full height of 15 to 30 feet in

about one year.



Banana Plant



Banana Plant

After the stem forms on the plant, it is covered with alarge, transparent plastic bag which shields it frominsects, birds and leaf damage, yet allows the sun toreach the fruit.

On each stem, ten or more bananas growing together are called "hands" and a single banana is called a"finger." Four to six bananas sold in the retail storeare called a "cluster.“

Banana plants require intensive, individual care:clearing away of jungle growth, propping to counter bending from the weight of the growing fruit, andirrigation during the dry season.



Banana Flower



Banana Flower

Bananas ready to be harvested



approx. 100 days after flowering

Bunches after harvesting



Bunches after harvesting



Sorting



Boxing



A hand of bananas



A stem consists out of

a number of hands

(from a few to > 10)

A freshly cut hand of

bananas.

A hand consists out of

10 to 20 bananas, alsocalled fingers



Transport of bananas



Modern reefers – anno 2004



Basic principles



p p

The degree of ripeness when the banana was cut.

The pre-critical phase of « lean » fruit is better

than the pre-critical phase of « full » fruit

Temperature: The pre-critical phase takes 15 to 18

days at 12°C and only a few days at a temperature

slightly higher

Humidity: When the humidity is to high therespiration of the fruit accelerates while when the

humidity is too low the fruit dries out.



Basic principles



p p

Immediately after the cut the bananas are stored in boxes or on pallets and are loaded ASAP.

The holds are cleaned and disinfected

(permanganate). N2 installations take care of theodours in the holds and eventual parasites

The holds are cooled down till 6°C before loading

The loading temperature of the banana is between

20°C and 30°C => the temperature in the hold will become > 12°C

The banana boxes are stowed in a very compactway



Basic Principles



p



Loading bananas – by hand



g y



Palletised cargo



Pallets are loaded

through horizontal or

vertical openings in

the hold

Pallets are loaded with

a pallet cage or cradle

Pallets are positionedin the holds by means

of forklifts

Palletised cargo



Palletised cargo



Partly filled holds



Cooling of the holds



At the end of the 19th century deepfreeze ships

were developed

Temperature had to be low but not very exact

This kind of ships is not suitable for fresh products

(fruit, vegetables)

Next generation of ships controls the hold

atmosphere in every aspect Today – Poly-thermal ships – 25°C -> +13°C

Mechanical Cooling System



A. Evaporator

B. Compressor

C. Expansion valve De compressor compresses the

cooling medium => Temperaturerises (orange)

In de condensor the cooling mediumgives off heat and liquefies (dark

blue) After the expansian valve the

pressure drops => temperaturedrops. In the evaporator the heat isabsorbed (cooling)



Cooling systems



With bottom gratings

Without gratings

Cooling system with bottom

gratings



gratings

a. Evaporator

b. Ventilator

c. Nil

d. Robsonchannels

e. Cargo space

f. Nilg. Bottom

gratings



Overview of « CA » techniques



Maintaining N2 concentration

Injection of pure N2

Admission of IG Use of N2 separators

Increasing CO2 concentration

Injection CO2

Natural breathing of the fruit




Lowering CO2 concentration

Ventilation

Absorption

Chemical process Adsorption

Separation by means of a membrane separator

Increasing relative humidity

Injection mist droplets Natural breathing of the fruit

Steam injection

Evaporation of water




Controlling ethylene concentration

Potassium permanganate

Active carbon

Ozone

Ultra Violet

An increased CO2 concentration will undo the

ripening effect of ethylene. Most of the ships with« CA » do not have any means on board to control

the ethylene concentration



Porthole refrigerated containers



Porthole technology was developed before

the seventies and used on the North-South

routes which carried large volumes of

refrigerated cargo. The first generation of

container ships with porthole refrigerated

containers is now over 25 years old and will

soon be replaced by ships with a greater capacity for integral refrigerated containers.



Porthole containers are thermally insulatedand have two sealable openings on the endwalls (the portholes) through which cold air

can be blown into the container and warm aircan be extracted. The cold air is forced throughthe lower opening into the container, thendistributed throughout the load via the T-barfloor, and subsequently flows through the loadto the top of the container and is extractedthrough the upper opening.




Collective systems

1 refrigeration unit takes care of a group of containers

1 large unit is installed in the double hull of thecontainer vessel an refrigerates a larger block of containers

1 cooling unit per vertical column of containers

Individual systems Clip-on unit refrigerates 1 individual container




Cooler integrated in the double

hull



Central cooling unit



Vertical distribution of

cooled air



Porthole installation ashore



Individual systems



Clip on units – porthole containers

Mechanical refrigeration

Diesel aggregate

Gasoline or LPG aggregate External electrical supply

Units using liquefied N2 or CO2 – obsolete

Temperature is maintained by injecting liquefied N2 or CO2

The gas is stored in an isolated reservoir fixed at the outside of

the container

Temperature is monitored by a sensor


Container with clip on unit



Porthole versus integral

refrigerated containers



Integral refrigerated containers



In contrast to porthole containers, integral

refrigerated containers are equipped with

their own refrigeration unit.

Cold air flows through and around the

goods in the container. This air is blown in

through the gratings in the floor and then

drawn off again below the container ceiling.

Integral refrigerated containers



Componenets of an integral

refrigerated container



Rear en of an integral

refrigerated container

Circulating fans (2)

and air cooler (17) areclearly visible

Cooling circuit with additional

water cooled condensor



Connections for the additional

water cooled condensor



Cooling the

condensers with water

is a solution to get rid

of the heat when thereefers are stored

beneath deck

Fresh air



When transporting vegetables or fruits theCO2 and ethylene generated during theripening process must be removed

This is achieved by ventilation The amount os fresh air is < 2 times the

volume of the container per hour

Exception when using CA (ControlledAtmosphere)

Fresh air



Fresh air flap

Discs to fine tune the

quantity of fresh air

administered

Atmosphere sampling

point

Coolants



Originally, all refrigerated containers wereoperated using the coolants R11 and R12. After the destruction of the ozone layer became an issueand consequently these coolants were banned bythe Montreal Protocol, a number of manufacturersswitched briefly to R22 as a substitute coolant.However, as this is also being phased out, the twocoolants R134a and R404a are now generally used

instead.

Data loggers - local



Temperatures are stillrecorded today for use asevidence in the event of adamage claim, mainly

with circular temperaturecharts, which generallycover a period of 31 daysThe return air temperatureis generally recorded on

these charts.




Due to the progress made in data technology, many moderncontrollers are able to store their measured values on dataloggers. The storage period is generally one year. The main

benefit of this type of data logger is that it records not only the

return air temperature but also the supply air temperature andUSDA temperatures. In addition, they can register alarms, onand off times and manual intervention.One disadvantage of the data loggers is that they only supplydiscrete values and do not provide the crew with a quick

overview of the history of a particular refrigerated cargotransport. In addition, it is often difficult in the event of adamage claim to localize the container and have the contents of the data logger read out.




Nowadays, several data

loggers are often also

placed within the load

when transporting

refrigerated goods. Theseare used to monitor the

temperatures inside the

container during transport

and allow this data to bemade available to the

recipient of the goods.

Remote controlling



With an increasing number of integral refrigerated

containers being used in maritime transport, there is also a

greater need for effective ways of monitoring these

containers. On ships, many of which can nowadays

transport over 1,000 integral refrigerated containers, usinga remote monitoring system can cut the costs of inspecting

the containers while also enabling the crew to react more

rapidly to potential problems in the event of a refrigeration

unit failing.

Remote monitoring



Nowadays 2 techniques are used for remotemonitoring. Both are using electrical cables andstandard sockets. – PCT = Power CableTransmission Narrowband transmissions

Wideband transmissions

ISO 10368 standard for data exchange – no agreementwas reached for the frequencies (narrow or wide band).

Following values are monitored Compressor running

Defrost

Temperature in range

Remote monitoring



Around 80-90 %of all refrigeratedcontainers have a

socket to connectthem to this typeof monitoringsystem.



Example of

datalogger extract

Data loggers



These loggers can provide evidence of

periods of insufficient refrigeration leading

to damage. For certain highly sensitive

products (for example, blood plasma) the

use of such loggers is required as proof that

the cold chain has not been broken at any

time.

Remote monitoring



It is expected that it will bepossible to transmit data by radiofrequency in the future, e.g. using

"wireless LAN" technology.

CA-containers



The use of CA extends the storage life of fruit andvegetables not only through cooling, but also by changingthe air composition in the space (container) in which the

goods are located. This generally involves reducing

the oxygen content to 1 - 3 % (normal air:21%) and increasing the carbon dioxidecontent to 5 - 25 % (normal air: 0.03%). Thecomposition of the atmosphere that produces the longest

possible storage life primarily depends on the type of fruit,the variety, its origin and the time of harvest.

CA-containers



The correct atmosphere will slow respiration inthe fruit , thus ensuring longer storage life. Fruitrespiration can be reduced by around 30 - 60 % incomparison with normal atmospheric conditionswith CA. This, of course, means that transporttimes can be extended, so that fruit, for instance,that is normally transported by air can also betransported by sea in refrigerated containers.

Another possibility is to harvest the fruit later andhence achieve better quality fruit.

CA-containers



Reduction of O2 is achieved by inerting the

container with N2

CO2

can be increased by injecting CO2

Production of N2



Membrane generators

PSA = Pressure Swing Absorption

Membrane generators



The membrane consists of a polymer that is permeable todifferent degrees for different gases. In principle, almostall gases can pass through the membrane, but at different

permeation rates. For the gases involved in CAapplications, the following applies: Water vapor permeatesfastest, followed by CO2, O2 and finally N2.

PSA - generators



Oxygen is bound by

the active carbon

under high pressure

and released againunder low pressure

The carbon filters

theorie part 2 air treatment

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