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International Journal of Energy Research

Volume 13 Issue 2, Pages 167 - 178

Published Online: 14 Mar 2007

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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.

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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

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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

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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.


Volume 48, Issue 5, May 2007, Pages 1624-1630

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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

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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


Volume 47, Issue 5, March 2006, Pages 529-544

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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

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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


Volume 22, Issue 2, February 2002, Pages 205-218

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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.



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doi:10.1016/S1359-4311(01)00071-0


Experimental evaluation of electronic and thermostatic expansion valves performances

using R22 and R407C

Ciro Aprea, , a and Rita Mastrullob

7/28/2019 EXV

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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


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doi:10.1016/S0360-5442(02)00113-5


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.

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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

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Published Online: 1 Aug 2006

Copyright 2009 John Wiley & Sons, Ltd.

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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

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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

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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.

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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.

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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.

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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.

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