exv
TRANSCRIPT
-
7/28/2019 EXV
1/20
International Journal of Energy Research
Volume 13 Issue 2, Pages 167 - 178
Published Online: 14 Mar 2007
Copyright 2009 John Wiley & Sons, Ltd.Get Sample Copy
Recommend to Your Librarian
Save journal to My Profile
Set E-Mail Alert
Email this page
Print this page
RSS web feed (What is RSS?)
< Previous Abstract | Next Abstract >
Save Article to My Profile Download Citation
Abstract | References | Full Text: PDF (Size: 568K) | Related Articles | Citation
Tracking
Article
Digital control of heat pumps with minimized power consumption
D. Parnitzki
Swiss Federal Aircraft Factory, CH-6032 Emmen, Switzerland
Keywords
Heat pump Digital control Refrigerator Energy conservation
Abstract
The paper describes the development of a microcomputer based control system for a
heat pump containing an electrical variable speed compressor drive and a motorized
expansion valve. It is designed to operate under very much varying load conditions with
minimum power consumption. Difficulties that were encountered during engineering
tests could finally be overcome by a relatively simple, practical regulator configuration.
It operates near optimum efficiency by regulating a temperature difference in the
evaporator.Received: 3 November 1987
International Journal of Energy Research
Volume 13 Issue 2, Pages 167 - 178
Published Online: 14 Mar 2007
Copyright 2009 John Wiley & Sons, Ltd.
Get Sample Copy
Recommend to Your LibrarianSave journal to My Profile
-
7/28/2019 EXV
2/20
Set E-Mail Alert
Email this page
Print this page
RSS web feed (What is RSS?)
< Previous Abstract | Next Abstract >
Save Article to My Profile Download Citation
Abstract | References | Full Text: PDF (Size: 568K) | Related Articles | Citation
Tracking
Article
Digital control of heat pumps with minimized power consumption
D. Parnitzki
Swiss Federal Aircraft Factory, CH-6032 Emmen, Switzerland
Keywords
Heat pump Digital control Refrigerator Energy conservation
Abstract
The paper describes the development of a microcomputer based control system for a
heat pump containing an electrical variable speed compressor drive and a motorized
expansion valve. It is designed to operate under very much varying load conditions with
minimum power consumption. Difficulties that were encountered during engineering
tests could finally be overcome by a relatively simple, practical regulator configuration.
It operates near optimum efficiency by regulating a temperature difference in the
evaporator.
ternational Journal of Thermal Sciences
Article in Press, Corrected Proof - Note to users
Font Size:
Abstract
- selected
References
Purchase PDF (645 K)
Article Toolbox
E-mail Article
Add to my Quick Links
Related Articles in ScienceDirectExperimental investigation on mass flow characteristics...
-
7/28/2019 EXV
3/20
Energy Conversion and Management
Experimental analysis of R22 and R407c flow through ele...
Energy Conversion and Management
Experimental investigation of R407C and R410A flow thro...Energy Conversion and Management
Experimental evaluation of electronic and thermostatic ...
Applied Thermal Engineering
Experimental research on refrigerant mass flow coeffici...
Applied Thermal Engineering
View More Related Articles
The research collaboration tool
No user tags yet
This article has not yet been bookmarked
Not yet shared with any groups
doi:10.1016/j.ijthermalsci.2008.10.002
Copyright 2008 Elsevier Masson SAS All rights reserved.
A new model of mass flow characteristics in electronic expansion valves considering
metastability
Liang Chen, a, , Jinghui Liua, Jiangping Chena and Zhijiu Chena
aSchool of Mechanical Engineering, Shanghai Jiaotong University, Shanghai 200240,
China
Received 9 July 2007; revised 7 October 2008; accepted 8 October 2008. Available
online 30 October 2008.
Abstract
This paper presents an experimental study on the mass flow characteristics of electronic
expansion valves in a wide operating condition range. It was found that flow choking
always occurs under common operating conditions in refrigeration systems. Based on
metastability in EEVs, a new model predicting mass flow rate was proposed under flow
choking conditions. Different from the conventional models using Bernoulli equation
which employed downstream pressure at the EEV exit and a corrected mass flowcoefficient, the present model considered metastable liquid flow caused by rapid
-
7/28/2019 EXV
4/20
depressurization, and employed single-phase incompressible flow coefficient and
metastable pressure at the throat. An empirical correlation of the metastable pressure,
based on the experimental data for R22 and its substitutes, R407C and R410A, was
developed in a power law form of dimensionless parameters including upstream
operating parameters and refrigerant thermophysical properties and throat area. The
predictions of the present model were found to be in good agreement with the measureddata, and approximately 95% of the measured data fall within a relative deviation of
7.0%. The comparison with a prior model shows that, in terms of flashing mechanism
application and predicting accuracy, the present model is better than the conventional
model without considering metastability.
Keywords: Electronic Expansion Valve (EEV); Mass flow characteristics;
Metastability; Flashing inception; Refrigeration
Simulation and Control of Electronic Expansion Valve
Liu Tingrui Wang Jidai Chen GuangqingMech. & Electron. Inst., Shandong Univ. of Sci. & Technol., Qingdao;
This paper appears in: Computational Intelligence and Industrial Application, 2008.
PACIIA '08. Pacific-Asia Workshop on
Publication Date: 19-20 Dec. 2008
Volume: 1, On page(s): 123-126
Location: Wuhan,
ISBN: 978-0-7695-3490-9
INSPEC Accession Number: 10416087
Digital Object Identifier: 10.1109/PACIIA.2008.11
Current Version Published: 2009-01-20
Abstract
The paper mainly expatiates on control theories, parameters, and transfer functions of
electronic expansion valve system. It realizes optimal PD controller based on genetic
algorithm acceptable for unstable object, with more conspicuous effect, and can be put
to use in flux process control with high precision. The paper, in the meantime, illustratesthe hardware connections and driving process of the stepper motor.
Energy Conversion and Management
Volume 48, Issue 5, May 2007, Pages 1624-1630
Font Size:
Abstract
- selected
Article
Figures/TablesReferences
-
7/28/2019 EXV
5/20
Purchase PDF (626 K)
Article Toolbox
E-mail Article
Add to my Quick Links
Cited By in Scopus (0)
Related Articles in ScienceDirect
Experimental investigation on mass flow characteristics...
Energy Conversion and Management
Experimental research on refrigerant mass flow coeffici...Applied Thermal Engineering
A new model of mass flow characteristics in electronic ...
International Journal of Thermal Sciences
Experimental analysis of R22 and R407c flow through ele...
Energy Conversion and Management
Mass flow characteristics and empirical modeling of R22...
International Journal of Refrigeration
View More Related Articles
View Record in Scopus
The research collaboration tool
No user tags yet
This article has not yet been bookmarked
Not yet shared with any groups
doi:10.1016/j.enconman.2006.11.011
Copyright 2006 Elsevier Ltd All rights reserved.
Experimental investigation of R407C and R410A flow through electronic expansion
valve
Qifang Ye, a, , Jiangping Chena and Zhijiu Chena
-
7/28/2019 EXV
6/20
aInstitute of Refrigeration and Cryogenics, Shanghai Jiao Tong University, Huashan
Road 1954, Shanghai 200030, PR China
Received 6 May 2006; accepted 12 November 2006. Available online 16 January
2007.
Abstract
The objective of this study is to present test results and to obtain a dimensionless
correlation on the basis of experimental data of an electronic expansion valve (EEV) for
R407C (R32/125/134a, 23/25/52 wt.%) and R410A (R32/125, 50/50 wt.%). Several
EEVs with different valve needle half tapers were selected as test sections. The mass
flow rate through the EEVs was measured for different condensing temperatures and
degrees of subcooling at the inlet of the EEVs and evaporating temperatures at the
outlet of the EEVs. A new correlation by introducing dimensionless parameters based
on extensive experimental data of R407C and R410A to predict the mass flow ratepassing through the EEV was presented. The dimensionless parameters were chosen by
considering the effects of EEV geometry, inlet conditions and refrigerant properties.
The relative deviations for the dimensionless correlation were from 9.65% to 8.68%
for R407C and from 12.27% to 11.36% for R410A.
Keywords: Electronic expansion valve; Mass flow rate; Correlation
Energy Conversion and Management
Volume 47, Issue 5, March 2006, Pages 529-544
Font Size:
Abstract
- selected
Article
Figures/Tables
References
Purchase PDF (490 K)
Article Toolbox
E-mail Article
Add to my Quick Links
Cited By in Scopus (6)
Related Articles in ScienceDirect
Experimental evaluation of electronic and thermostatic ...
Applied Thermal Engineering
Experimental investigation of R407C and R410A flow thro...
-
7/28/2019 EXV
7/20
Energy Conversion and Management
Experimental research on refrigerant mass flow coeffici...
Applied Thermal Engineering
06/02228 Experimental evaluation of prototype thermoele...Fuel and Energy Abstracts
06/02229 Experimental investigation of a CO2 automotive...
Fuel and Energy Abstracts
View More Related Articles
View Record in Scopus
The research collaboration tool
No user tags yet
This article has not yet been bookmarked
Not yet shared with any groups
doi:10.1016/j.enconman.2005.05.005
Copyright 2005 Elsevier Ltd All rights reserved.
Experimental analysis of R22 and R407c flow through electronic expansion valve
Chuan Zhang, , Shanwei Ma, Jiangpin Chen and Zhijiu Chen
Institute of Refrigeration and Cryogenics, Shanghai Jiao Tong University, Huashan
Road 1954, Shanghai 200030, PR China
Received 7 November 2004; accepted 18 May 2005. Available online 15 July 2005.
Abstract
The objective of this study is to present test results and to develop a dimensionless
correlation on the basis of experimental data to predict the mass flow rate of R22 and its
alternative refrigerant R407c through an electronic expansion valve (EEV). The mass
flow rate was measured at a series of condensing temperatures, evaporating
temperatures and degrees of subcooling at the EEV inlet with five opening setting
degrees of the EEV. The experimental results were analyzed, and it was found that the
operation condition, flow area and the thermophysical properties of the refrigerant
would affect the mass flow rate through the EEV. A new correlation based on the
Buckingham theorem was developed to predict the mass flow rate of refrigerantsthrough the EEV. The relative deviations of the predicted value by using this correlation
-
7/28/2019 EXV
8/20
are from 10.74% to 9.26% for R22 and from 14.20% to 22.10% for R407c. The
average deviations and standard deviations are 0.79% and 5.02% for R22 and 0.67%
and 8.08% for R407c, respectively. The relative deviation was analyzed in terms of the
operation condition and flow area of the EEV. This correlation can be used to predict
the mass flow rate through EEVs whose largest flow area is less than 2.544 mm2.
Keywords: Electronic expansion valve; Refrigerant; Correlation; Mass flow rate
Applied Thermal Engineering
Volume 22, Issue 2, February 2002, Pages 205-218
Font Size:
Abstract
- selected
Article
Figures/Tables
ReferencesPurchase PDF (461 K)
Article Toolbox
E-mail Article
Add to my Quick Links
Cited By in Scopus (8)
Related Articles in ScienceDirect
An experimental evaluation of the vapour compression pl...
Applied Thermal Engineering
Experimental analysis of R22 and R407c flow through ele...
Energy Conversion and Management
Experimental comparison of electronic and thermostatic ...
International Journal of Refrigeration
Experimental research on refrigerant mass flow coeffici...
Applied Thermal Engineering
Experimental investigation of R407C and R410A flow thro...
Energy Conversion and Management
View More Related Articles
View Record in Scopus
-
7/28/2019 EXV
9/20
The research collaboration tool
No user tags yet
This article has not yet been bookmarked
Not yet shared with any groups
doi:10.1016/S1359-4311(01)00071-0
Copyright 2001 Elsevier Science Ltd. All rights reserved.
Experimental evaluation of electronic and thermostatic expansion valves performances
using R22 and R407C
Ciro Aprea, , a and Rita Mastrullob
a Department of Mechanical Engineering, University of Salerno, Via Ponte Don
Melillo, 84084 Fisciano (Salerno), Italy
b DETEC, University of Napoli Federico II, P. le Tecchio 80, 80125 Naples, Italy
Received 7 February 2001; accepted 9 July 2001. Available online 6 November 2001.
Abstract
An experimental study to evaluate the energetic performances in steady-state and in
transient operating modes of an electronic and thermostatic expansion valve is
presented. Both valves have been assembled to feed an air cooled evaporator connected
to an experimental vapour compression plant with a water cooled condenser operating
with a semihermetic compressor. The performances of the valves have been examined
at different conditions when the experimental plant works with R22 and with a
substitute as the non-azeotropic blend R407C that is chlorine free. Indeed the HCFC
designated as R22 contains chlorine that is harmful for the ozone layer and must be
replaced in the future. The final results of this study show an overall better performance
of the electronic expansion valve compared with the thermostatic expansion valve under
transient conditions while in steady-state conditions both the valves are equal inperformance. These results apply to both R22 and R407C.
Applied Thermal Engineering
Volume 22, Issue 2, February 2002, Pages 205-218
Font Size:
Abstract
- selected
Article
Figures/TablesReferences
-
7/28/2019 EXV
10/20
Purchase PDF (461 K)
Article Toolbox
E-mail Article
Add to my Quick Links
Cited By in Scopus (8)
Related Articles in ScienceDirect
An experimental evaluation of the vapour compression pl...
Applied Thermal Engineering
Experimental analysis of R22 and R407c flow through ele...Energy Conversion and Management
Experimental comparison of electronic and thermostatic ...
International Journal of Refrigeration
Experimental research on refrigerant mass flow coeffici...
Applied Thermal Engineering
Experimental investigation of R407C and R410A flow thro...
Energy Conversion and Management
View More Related Articles
View Record in Scopus
The research collaboration tool
No user tags yet
This article has not yet been bookmarked
Not yet shared with any groups
doi:10.1016/S1359-4311(01)00071-0
Copyright 2001 Elsevier Science Ltd. All rights reserved.
Experimental evaluation of electronic and thermostatic expansion valves performances
using R22 and R407C
Ciro Aprea, , a and Rita Mastrullob
-
7/28/2019 EXV
11/20
a Department of Mechanical Engineering, University of Salerno, Via Ponte Don
Melillo, 84084 Fisciano (Salerno), Italy
b DETEC, University of Napoli Federico II, P. le Tecchio 80, 80125 Naples, Italy
Received 7 February 2001; accepted 9 July 2001. Available online 6 November 2001.
Abstract
An experimental study to evaluate the energetic performances in steady-state and in
transient operating modes of an electronic and thermostatic expansion valve is
presented. Both valves have been assembled to feed an air cooled evaporator connected
to an experimental vapour compression plant with a water cooled condenser operating
with a semihermetic compressor. The performances of the valves have been examined
at different conditions when the experimental plant works with R22 and with a
substitute as the non-azeotropic blend R407C that is chlorine free. Indeed the HCFCdesignated as R22 contains chlorine that is harmful for the ozone layer and must be
replaced in the future. The final results of this study show an overall better performance
of the electronic expansion valve compared with the thermostatic expansion valve under
transient conditions while in steady-state conditions both the valves are equal in
performance. These results apply to both R22 and R407C.
Author Keywords: Thermostatic expansion valve; Electronic expansion valve; R22;
R407C
Energy
Volume 28, Issue 2, February 2003, Pages 141-155
Font Size:
Abstract
- selected
Article
Figures/Tables
References
Purchase PDF (236 K)
Article Toolbox
E-mail Article
Add to my Quick Links
Cited By in Scopus (15)
Related Articles in ScienceDirectExperimental study on the performance of a simultaneous...
-
7/28/2019 EXV
12/20
International Journal of Refrigeration
Capacity modulation of an inverter-driven multi-air con...
Fuel and Energy Abstracts
Multivariable control-oriented modeling of a direct exp...International Journal of Refrigeration
Analysis of the variation mechanism in the main energet...
Applied Thermal Engineering
Cooling performance of a variable speed CO2 cycle with ...
International Journal of Refrigeration
View More Related Articles
View Record in Scopus
doi:10.1016/S0360-5442(02)00113-5
Copyright 2002 Elsevier Science Ltd. All rights reserved.
Capacity modulation of an inverter-driven multi-air conditioner using electronic
expansion valves
J. M. Choi and Y. C. Kim,
Department of Mechanical Engineering, Korea University, Anam-dong, Sungbuk-ku,
Seoul 136-701, South Korea
Received 12 April 2001. Available online 12 December 2002.
Abstract
An inverter-driven multi-air conditioner provides the benefits of comfort, energy
conservation and easy maintenance. Recently, the multi-air conditioner has been
employed in small and medium-sized buildings. However, the performance data and
control algorithm for multi-air conditioners are limited in literature due to complicated
system parameters and operating conditions. In the present study, the performance of an
inverter-driven multi-air conditioner having two indoor units with electronic expansion
valves (EEV) was measured by varying indoor loads, EEV opening, and compressor
speed. Based on the experimental results, the operating characteristics and capacity
modulation of the inverter-driven multi-air conditioner are discussed. As a result, it is
suggested that the superheats for both indoor units have to be maintained around 4oC by
utilizing the EEVs in this system, and consequently, the compressor speed needs to beadjusted to provide optimum cooling capacity for each indoor unit.
-
7/28/2019 EXV
13/20
SAE Home > Publications > Papers
Automotive A/C System Integrated With Electrically Controlled Variable Capacity
Scroll Compressor and Fuzzy Logic Refrigerant Flow Management
Document Number: 2001-01-0587
Date Published: March 2001
Author(s):
Xin Zeng - General Motors Corp.
Greg Major - GM Adv Tech. Vehicles
Toyataka Hirao - Mitsubishi Heavy Industries, Ltd.
M. Sekita - Mitsubishi Heavy Industries, Ltd.
M. Fujitani - Mitsubishi Heavy Industries, Ltd.
Abstract:
This paper describes the recent efforts on developing an automotive climate control
system throughout integrating an electrically-controlled variable capacity scroll
compressor with a fuzzy logic control-based refrigerant flow management.
Applying electrically controlled variable capacity compressor technology to climate
control systems has a significant impact on improving vehicle fuel economy, achieving
higher passenger comfort level, and extending air and refrigerant temperature
controllability as well. In this regard, it is very important for automotive climate control
engineers to layout a system-level temperature control strategy so that the operation of
variable capacity compressor can be optimized through integrating the component
control schemes into the system-level temperature control.
Electronically controlled expansion devices have become widely available in
automotive air conditioning (A/C) systems for the future vehicle applications. An
electronic expansion valve (EXV), similar to the mechanically actuated thermostatic
expansion valve (TXV), is a flow control device whose operational goal is to throttle
and regulate the refrigerant flow rate. Principally, TXV regulates the refrigerant
entering the evaporating equipment in response to the superheat variation. Comparing to
the mechanical actuation mechanism of TXV, the electronically modulated EXV givesthe additional flexibility to apply the microprocessor-based intelligent control.
Accordingly, a fuzzy logic algorithm of EXV has been incorporated to the A/C system
control in order to achieve a high efficiency and optimal operation.
The primary objectives of this paper are to (a) present the design features and control
mechanism of an electrically-controlled variable capacity scroll compressor; (b)
describe the temperature control system architecture of refrigeration circuit and air flow
management; (c) describe the architecture of fuzzy logic control of a refrigerant flow
control; and (d) discuss and analyze the results obtained in bench testing.
International Journal of Energy ResearchVolume 30 Issue 15, Pages 1313 - 1322
-
7/28/2019 EXV
14/20
Published Online: 1 Aug 2006
Copyright 2009 John Wiley & Sons, Ltd.
Get Sample Copy
Recommend to Your LibrarianSave journal to My Profile
Set E-Mail Alert
Email this page
Print this page
RSS web feed (What is RSS?)
< Previous Abstract | Next Abstract >
Save Article to My Profile Download Citation
Abstract | References | Full Text: PDF (Size: 308K) | Related Articles | CitationTracking
Research Article
Performance of thermostatic and electronic valves controlling the compressor capacity
C. Aprea 1, R. Mastrullo 2, C. Renno 1 *
1Department of Mechanical Engineering, University of Salerno, Via Ponte Don Melillo
1, 84084 Fisciano (Salerno), Italy
2DETEC, University of Naples Federico II, P.le Tecchio 80, 80125 Naples, Italy
email: C. Renno ([email protected])
*Correspondence to C. Renno, Department of Mechanical Engineering, University of
Salerno, Via Ponte Don Melillo 1, 84084 Fisciano (Salerno), Italy
Keywords
thermostatic valve electronic valve experimental plant energy saving
Abstract
The performance of the energy consumption of an electronic valve and a classical
thermostatic valve has been compared when these expansion valves are adopted in a
vapour compression plant subjected to a cold store. The main aim is to verifyexperimentally which type of expansion valve would be preferable from energy point of
view when a classical thermostat or a fuzzy logic algorithm are used as the control
system for the refrigeration capacity. The fuzzy logic-based control is able to modulate
continuously the compressor speed through an inverter. The results show that with a
fuzzy algorithm, the thermostatic expansion valve allows an energy saving of about 8%
in comparison with the electronic valve. When on-off control is used, the electric energy
consumption obtained both with the electronic valve and with the thermostatic valve is
comparable. Copyright 2006 John Wiley & Sons, Ltd.
Received: 5 May 2005; Revised: 9 February 2006; Accepted: 20 April 2006
-
7/28/2019 EXV
15/20
Effect of the thermostatic expansion valve characteristics on the stability of a
refrigeration system-Part I
Kulkarni, A.; Mulay, V.; Agonafer, D.; Schmidt, T.
Thermal and Thermomechanical Phenomena in Electronic Systems, 2002. ITHERM
2002. The Eighth Intersociety Conference on
Volume , Issue , 2002 Page(s): 403 - 407Digital Object Identifier 10.1109/ITHERM.2002.1012484
Summary: The combination of increased power dissipation and increased packaging
density has led to substantial increases in chip and module heat flux in high-end
computers. The challenge has been to limit the rise in chip temperature. In the past
virtually all-commercial computers were designed to operate at temperatures above the
ambient. However researchers have identified the advantages of operating electronics at
low temperatures. The current research focuses on IBM's S/390 mainframe, which uses
a conventional refrigeration system to maintain chip temperatures below that of
comparable air-cooled systems, but well above cryogenic temperatures. Attention will
be to investigate the characteristics of the thermostatic expansion valve, specifically, the
effect of variation of evaporator outlet superheat on the flow through the TXV atvarying evaporator temperature, and the effect of sudden changes in evaporator heat
load and condenser pressure variation on the temperature oscillations at the evaporator.
The paper also discusses the effect of changes in the thermostatic bulb location and bulb
time constant on the hunting phenomena at the evaporator.
View citation and abstract
Electronic Expansion Valves: The Basics
By John TomczykJuly 28, 2004ARTICLE TOOLS
-
7/28/2019 EXV
16/20
-
7/28/2019 EXV
17/20
The electronic expansion valve (EEV) operates with a much more sophisticated design. EEVs control the flow of refrigerant entering a direct expansionevaporator. They do this in response to signals sent to them by an electronic controller. A small motor is used to open and close the valve port. The motor iscalled a step or stepper motor. Step motors do not rotate continuously. They are controlled by an electronic controller and rotate a fraction of a revolution foreach signal sent to them by the electronic controller. The step motor is driven by a gear train, which positions a pin in a port in which refrigerant flows. Acutaway of an EEV with step motor and drive assembly is shown in Figure 2.Step motors can run at 200 steps per second and can return to their exact position very quickly. The controller remembers the number of step signals sent by thecontroller. This makes it possible for the controller to return the valve to any previous position at any time. This gives the valve very accurate control ofrefrigerant that flows through it. Most of these EEVs have 1,596 steps of control and each step is 0.0000783 inches.
Sensors
The electronic signals sent by the controller to the EEV are usually done by a thermistor connected to discharge airflow in the refrigerated case. A thermistor isnothing but a resistor that changes its resistance as its temperature changes. Other sensors are often located at the evaporator inlet and outlet to senseevaporator superheat. This protects the compressor from any liquid floodback under low superheat conditions.
Pressure transducers can also be wired to the controller for pressure/temperature and superheat control. Pressure transducers generally have three wires. Twowires supply power and the third is an output signal. Generally, as system pressure increases, the voltage sent out by the signal wire will increase. The controlleruses this voltage to calculate the temperature of the refrigerant with the use of a pressure/temperature table programmed into the controller.
The SEH-100 EEV from Sporlan Valve Co.
Figure 2. A cutaway of an electronic expansion valve (EEV) with step
motor and drive assembly.
-
7/28/2019 EXV
18/20
A combination of compressor floodback protection and the ability to maintain refrigerator case discharge air temperature set point control makes the EEV usefulin many diverse applications. Some EEV controllers can also be programmed for custom control applications.
Feedback Loop
The controller may open the EEV too much and cause an overcooling condition. The sensors connected to the refrigeration system and wired to the controllerwill sense this overcooling condition and feed this information to the electronic controller and the EEV. This will cause the step motor to move in the closingdirection and close the valve more. The feedback loop is shown in Figure 3.Next month: Advanced aspects of EEVs will be covered in the Sept. 6 issue ofThe News.John Tomczyk is a professor of HVACR at Ferris State University, Big Rapids, Mich., and the author ofTroubleshooting and Servicing Modern AirConditioning & Refrigeration Systems,published by ESCO Press. To order, call 800-726-9696. Tomczyk can be reached by e-mail at [email protected]. Publication date: 08/02/2004
3 Energy-Saving Strategies for Freezers
by Pat Melvin
September 1, 2006
ARTICLE TOOLS
EmailPrintReprintsShare Use
Enlarge this picture
An electric expansion valve allows the head pressure control to be eliminated, which
permits a lower head pressure and condensing temperature.
Following some simple best practices can help you ensure that your small freezers areenergy efficient.
Figure 3. The feedback loop.
-
7/28/2019 EXV
19/20
As summer comes to an end and high energy bills have been paid in full, many
manufacturers and processors are left wondering what they can do to increase energy
efficiency and decrease costs. With rolling California blackouts, increasing gasoline
costs and high energy bills, any words of wisdom seem to go a long way. Following is ashort list of best practices for keeping your freezers energy efficient while also staying
current on the latest technological advances.
1. Specify an Electric Expansion Valve
Only a few manufacturers offer refrigeration systems with an electronic expansion
valve. One equipment manufacturer uses a valve with 1,600 steps that can efficiently
maintain superheat from the pull-down cycle through the normal refrigeration mode.
Conventional thermostatic expansion valves typically are less adjustable and efficient.
With a standard mechanical system, the head pressure must be maintained with a head
pressure control valve or fan cycling because a thermostatic expansion valve requires
about 100 lb across the valve to operate properly. Because the electric expansion valve
does not require this high head pressure, the head pressure control can be eliminated,
which allows for a lower head pressure and condensing temperature. A compressor
operating at a lower condensing temperature yields higher capacity with less energy
input.
2. Maintain Proper Defrost Schedules
Frost buildup reduces a refrigeration systems efficiency, so an efficient defrost system
is a must. Some traditional refrigeration systems are preset to defrost about six to eight
times during the day, regardless of the amount of frost buildup on the evaporator.
However, frost accumulation is not always consistent; it is influenced by changeable
conditions, such as ambient temperature, humidity and product load. Defrosting before
a significant amount of frost accumulates is an energy-wasting process. Instead,
defrosting should only take place when the coils need to be cleaned.
Demand defrost, which constantly checks for ice buildup on the evaporator to determine
if defrosting is required, can be an efficient alternative to the conventional method andis a good way to minimize defrost time. Extensive laboratory tests indicate that many
unnecessary defrosts can be eliminated with demand defrost technology. Electricity
consumption is also dramatically reduced -- in some applications, up to a 26 percent
energy savings is possible.
3. Consider Reverse Cycle Defrost
Another defrost option involves a reverse cycle valve added to the condensing unit and
used with an electronic system that controls the entire refrigeration system.
-
7/28/2019 EXV
20/20
The valves primary function is to reverse the direction of refrigerant flow during
defrost. When the master controllers demand defrost determines that a defrost is
necessary, the reverse cycle valve is activated, and the high-temperature refrigerant flow
is reversed. The refrigerant flows back through the evaporator coil, heating it along its
entire length and eliminating frost buildup. When defrost heaters are used, sometimes
only part of the coil is heated, leaving ice deposits that diminish the evaporatorsperformance.
For those freezers sized to use reverse cycle technology, the technology offers other
benefits. It uses less energy than electric defrost heaters and can reduce defrost energy
usage by 80 percent. It eliminates the need for defrost heaters, head pressure control
valves, check valves and expansion valves at the condenser. Removing these
components reduces the evaporator cost and the cost of installation and wiring. Defrost
time also is lessened.
Pat MelvinPat Melvin is engineering manager at Master-Bilt Products, New Albany, Miss., a
manufacturer of refrigerated coolers and freezers. Melvin has nearly 12 years of
experience in refrigeration, designing and engineering walk-ins, cabinets and
refrigeration systems. For more information, call (800) 647-1284 or visit www.master-
bilt.com.