ANALYSIS OF ENERGY LOSSES IN SMALL COMPRESSION REFRIGERATORS · ANALYSIS OF ENERGY LOSSES IN SMALL COMPRESSION REFRIGERATORS ... Freon 22 is used as a refriger-ant. In the tested

ANALYSIS OF ENERGY LOSSES IN SMALL COMPRESSION REFRIGERATORS

Anna Warminska1 and Stefan Fijalkowski2

1Department of Thermodynamics, Fluid Mechanics and Aviation Propulsion Systems, Lublin University of Technology, Nadbystrzycka 36,20-618 Lublin, Poland, [email protected]

2Department of Thermodynamics, Fluid Mechanics and Aviation Propulsion Systems, Lublin University of Technology, Nadbystrzycka 36,20-618 Lublin, Poland, [email protected]

Abstract: Results of theoretical and experimental investiga-tions of loss of energy which arise in the small compressionrefrigerators used in agriculture and food industry have beenpresented in the paper. Operation of the refrigerating com-pressor has been treated as a system, composed of subsys-tems which represent the main parts of the set. In each sub-system all internal processes have been defined and then rela-tionships between subsystems and the external environmenthave been found. On the basis of the proposed model, themain factors and sources of the internal and external lossesand their localization have been distinguished [2]. Experi-mental investigations have been done on an especially de-sign experimental setup, allowing for measurement of pres-sure and temperature in selected characteristics points. Theexperimental results have been obtained for various sets ofinitial temperature of the refrigerated liquid and external en-vironmental temperature, varied mass of refrigerated liquidand two different sets of cooling temperature [3]. The analy-sis has shown that the most essential energy losses have oc-curred during starting period of the refrigerating compressorwork. The relationship between an amount of refrigeratedliquid and energy used in cooling process has been deter-mined. It has been found that energy, used for refrigeratingof unit mass in one cooling cycle, depends essentially on theamount of the refrigerated mass. This leads to a conclusionthat it is possible to chose an adiabatic tank of an optimalsize, adequate for a chosen refrigerating compressor. Sucha solution may help minimise the energy supplied to the re-frigerating system with respect to the amount of refrigeratedmass.

Keywords: compressor refrigerators, energy losses, heattransfer

1. INTRODUCTION

Rapid technological development leads to a big energyconsumption. Therefore large efforts of engineers are needed

to minimise energy losses. European Union published afew regulations to force countries to change standards in amachines design to protect the natural environment. Smallvapour refrigerators are in common use in family houses andfarms. About 80% of total refrigeration power is exploited bythose small refrigerators. They are, therefore, in the group ofthe machines of significant energy consumption. Thereforeeven a small improvements in those devices result in hugeamount of energy saving [1]. The purpose of this research isto decrease energy losses in such type of devices.

It should be noted that about 80% of the energy neededto refrigerate is used to power household refrigerating ma-chines, including refrigerators and freezers as well as refrig-erating equipment in retail, and refrigerating units in agricul-ture. It is estimated that the energy consumption in house-hold refrigerated food storage is about from 100 to 200 timesmore for the same amount of product than in commercialcool stores. Taking into consideration that the efficiency ofhousehold refrigerators is about 50% lower than of commer-cial cool stores and is still growing; much attention should bepaid to improve energy processing in these units. This can bedone if basic and additional processes are improved, refrig-erating units designs are developed and they are used moreefficiently.

In the past, energy saving in refrigerating engineering wasnot so important, which results from:

• the amount of energy that is actually used for those pur-poses is relatively small with respect to total energy con-sumption;

• the amount of energy to cool and freeze is merely asmall part of the energy necessary to grow plants andprocess food;

• users of refrigerating machines are hardy ever qualifiedenough to estimate properly the quality of those ma-chines so they decide to install the cheapest and leastefficient units.

Proceedings of the 9th Brazilian Conference on Dynamics Control and their Applications Serra Negra, SP - ISSN 2178-3667 782

Vapour compression refrigerators of low and mediumpower have got the refrigerating power ranging from 1 to5 kW and are frequently used in refrigerating engineering.They are the most popular refrigerating machines since theyare in almost all households. They are also used in farms andlaboratories.

The processes that occur inside such machines (Fig.1)concern processing various energy types, depending on theirdistinctive properties and practicability. If these processesare under real conditions, there are external energy losseswhen various types of energy flow between a refrigeratingsystem and the environment; and internal energy losses in-side a system due to the irreversibility of thermodynamic andflow phenomena followed by the unwanted entropic increaseinside a system.

Compression

Throttlingprocess

Control�ofthe�operational

refrigerator

Heat�transferin�regenerator

Heat�transferto�environment

Heat�transferfrom�cold�space

Thermodynamicalprocesses:evaporation,condensation,subcooling,heating

Transport�ofrefrigerant

Realcoolingprocess

Energysupply�to

the�refrigeratingsystem

Figure 1 – The most important processes in the vapour com-pression refrigerator with a regenerator

2. STRUCTURAL FEATURES AND OPERATIONALPROPERTIES OF THE REFRIGERATOR

The tested machine is the IC/P refrigerating unit 253 byALFA LAVAL, used in agriculture. The machine cools aspecified amount of liquid, e.g. milk at ∼ 100l/h when aliquid temperature was decreased constantly and monoton-ically within the two specified temperature levels (for milkfrom 35oC to 4oC).The basic technical data of the machine is given in Table 1.The machine diagram, including the subsystems is in Fig. 2The characteristic refrigerant flow sections are marked withnumbers in the diagram.

The refrigerator main systems include a hermetic com-pressor, a condenser, an evaporator and a regenerator con-nected to a throttling element. Freon 22 is used as a refriger-ant. In the tested machine, the evaporator is dipped to reacha specified level in a cooled liquid that circulates and swirlsthanks to the mixer. The liquid is in an insulated container.

Table 1 – Basic technical data of the IC/P 253 machine by ALFALAVAL

Power rating 0.7kW

Average refrigerating capacity 3328W

Amount of milk cooled (milk was cooledfrom 35oC to 4oC, at ambient temperature of25oC)

from 150l to 250l

Amount of milk cooled per hour 100l

Adjusted cooling temperature 4oC or 10oCFan capacity 2200m3/h

Condenser capacity 4.1kW

Compresor

Thermalinsulation

Evaporator

Flow�of�refrigerantin�the�evaporator

Container

Regenerator

Throttlingdevice

Condenser Controlsystem

Figure 2 – Diagram of the compression refrigerator for milk byALFA LAVAL with its basic subsystems. The typical refriger-ant flow sections are given in the figure: 1-flow section - inputto the compressor, 2-flow section - output of the compressor, 3-flow section - input to the condenser, 4-flow section - output ofthe condenser, 5-flow section - input to the regenerator and cap-illary pipe, 6(7 = 8)-flow section - output of the capillary pipe,9 = 10-flow section - output of the evaporator and - input to theregenerator, 11-flow section - output of the regenerator

3. ANALYSIS OF THE MOST SIGNIFICANT EN-ERGY LOSSES IN THE REAL MACHINE

Regardless of a refrigerant applied, the losses of energyin the tested refrigerator are caused by the following interac-tions:

• internal interactions related to the irreversibility of ther-modynamic and flow changes. They lead to the un-wanted increase in entropy inside the refrigerator sys-tem and consequently decrease refrigerant effectiveness


to absorb heat from the cold space,

• external interactions including the efficiency to processelectric energy into mechanical energy directly suppliedto the refrigerant that is on the surface of the compressorpiston head, the useless decompression of the refriger-ant in the decompressing device, the finite value of thethermal resistance of the container insulation as well asthe conversion of the energy caused by the mixer intoheat.

The further analysis deals with the most important lossesbecause of the following external interactions: the losseswhen electric energy is converted into mechanical energywhich is directly supplied to the refrigerant, the loss due to ir-reversible decompression work and the losses resulting fromimperfect container insulation and conversion of mixing en-ergy into heat in a cooled liquid. The diagram in Fig. 3 showsschematically where the sources of the losses occur.

Regenerator

Evaporator

Compresor

Condenser

3 4

(6)7=8

5a

9=10

5 111 2

Sourceof�power

Controlblock

Ambientconditions

Cold�space

zst

SZM

SZ =LR R

SWS

SWR

SWP

SZS

SZPO

SW = QR �

SZZ

.

.

Compressionspace

Compressionsystem

Motor

.

.

.

..

Q.

Q.

PO

Q.

Z

Q.

O

Nm

New

N Nesi

Nem

Q.

R

Ns�Nm�

Ni�

SWQ0

.SWQ

.

SWS

SZW

Figure 3 – Diagram of the refrigerator system with the con-tainer for a cooled liquid and the sources of the most significantlosses.

NotationFpo - contact area of liquid and airFz - surface of a tankh5 - specific enthalpy in point No.5,k - adiabatic exponentkz - coefficient of heat transferNe - electric powerNi - indicated powerNm - mechanical powerNtt - theoretical powerx5 - vapour quality in point No.5,s′

- entropy of boiling liquids” - entropy of dry saturated vapourNmix - mixer powerTc - liquid’s temperatureTot - ambient temperatureTpa - temperature in evaporator

αpo - surface film conductanceηi - indicated efficiencyηm - mechanical efficiencyηs - efficiency of a motorλ - volumetric efficiencyπs - compression ratio.

The average values of the most important energy lossesduring cooling in time τ a liquid portion are determined bythe formulae:

• Internal losses

The refrigerant compression irreversibility loss insidethe cylinder:

SWs = Nm (1− ηi) (1)

where:ηi = λ

Ntt

Ni(2)

Ntt =k

k − 1p1V1

[Π

k−1k

s − 1

](3)

The compression irreversibility loss of the liquid in thedecompression device

SWr = mcTpa (x5 − x5c) [s,, (Tpa)− s, (Tpa)] (4)

Indicated power loss

SWni = ∆Ni = Ni (1− ηi) (5)

• External losses

The loss of processing electric energy in the compressor

SZs = (1− ηm) ηsNe (6)

The loss of decompression work in the decompressingdevice

SZr = mc (h5 − h5c) (7)

The loss of heat reaching the liquid due to insulation

SZz = Fzkz (Tc − Tot) (8)

The loss of converting mixing energy into heat

SZM = Nmix (9)

The loss of heat reaching the air in the container

SZpo = Qpo = Fpoαpo (Tpo − Tc) (10)

The loss of engine power

SZmn = ∆Nm = Ns (1− ηm) (11)

The loss of electric power supplied to the engine

SZns = ∆Ns = Ne (1− ηs) (12)


4. EXPERIMENTAL INVESTIGATION

Having analysed the research problem, the tested refrig-erator was measured in its typical measurement points. Fig.4 shows the most important measurement points and the dia-gram of the temperature and pressure measurement.

The experimental values ( T, p, N ) were measured at thetest stand. Based on the results obtained, there were madethe characteristics of the refrigerator operation.

Evaporator

Thermometer

Pressuremeasurementand�datarecording

Temperaturemeasurementand�datarecording

Refrigerator’sthermometer

Controlsystem

Nel

Nel

p T2 2, p T44,p T3 3,p T55, p T11,

p T66,p T77,

y��p7 7�

y��p5 5�

y��p6 6�

y��p1 1�

y��p4 4�

y��p3 3�

x T7 7�

x T4 4�

x T5 5�

x T6 6�

y��p2 2�

Regenerator

Condenser

Compresor

W

A

W

1

12

2

3

3

4

4

5

5

6

6

7

7

4

7 6

5

1 2 3

xT

11

��

xT

22

�

xT

33

��

Figure 4 – Diagram of the temperature and pressure measure-ment

One of the parameters changed at the constant liquidmass during the experiment was the initial temperature ofthe cooled liquid. The changes of the evaporator pressure forvaried initial temperatures of the cooled liquid are given inthe diagram in Figure 5. The pressure time courses at the se-lected cooling level are similar. They differ in cooling timeonly.

0 1000 2000 3000 4000 5000 6000

time t, s

0.2

0.4

0.6

0.8

1

pre

ssu

rep

pa

,M

Pa

20 oC

30oC

40 oC

Figure 5 – Pressure course ppa for the same amount of the liquidat varied initial temperatures of the cooled liquid

Figure 6 shows how the pressure in the evaporator andcondenser changed in one working cycle at the varied initialtemperatures of the cooled liquid and the same cooling tem-perature. During cooling the liquid, the pressure changes inthe condenser at the end of a working cycle resulted from thechanges in ambient temperature.

Diagram 7 shows the dependence of the changes in the

0 1000 2000 3000 4000 5000 6000

time t, s

0

0.4

0.8

1.2

1.6

2

pre

ssu

rep

pa,p

sk

,M

Pa

20oC

30oC

40oC

Figure 6 – Comparision of the pressures ppa and psk in coolingfor varied initial temperatures for the same liquid mass

0 1000 2000 3000 4000 5000 6000

time t, s

1

2

3

4

5

pre

ssu

rep

sk/

pp

a

30oC

35oC

40oC

50oC

Figure 7 – The changes in psk/ppa ratio in cooling for variedinitial temperatures for the same liquid mass

compression ratio for various values of the initial tempera-tures of the cooled liquid.

The following diagrams specify the pressure drops duringflowing through the pipes that were connected each subsys-tem.

0 50 100 150 200 250 300

time t (s)

16

20

24

28

32

36

40

tem

pe

ratu

ret 2

,t3

(oC

)

temperature behind compresor t2

temperature before condenser t3

Figure 8 – Temperature changes in the pipe between the com-pressor and condenser

Diagrams 8 and 9 show how the temperature and pressurein the pipes between the compressor and condenser changed.Diagrams 10 and 11 determine how the temperature and pres-


0 50 100 150 200 250 300

time t (s)

0.6

0.8

1

1.2

1.4

pre

ssu

rep

2,p

3(M

Pa

)

pressure behind

compresor p2

pressure before

condenser p3

Figure 9 – Pressure changes in the pipe between the compressorand condenser

sure between the condenser and regenerative heat exchangerchanged. The pressure drops were very little. The temper-ature drop was due to the ambient heat exchange. Simulta-neously, the refrigerant temperature was higher than ambienttemperature. Based on the diagrams, it can be noted thatthe losses due to the refrigerant flow between the subsystemswere slight.

0 50 100 150 200 250 300

time t (s)

10

14

18

22

26

30

tem

pera

ture

t 4,t

5(o

C)

temperature behindcondenser t4

temperature beforeregenerator t5

Figure 10 – Temperature changes in the pipe between the con-denser and regenerative heat exchanger

0 50 100 150 200 250 300

time t (s)

0.6

0.8

1

1.2

1.4

pre

ssu

rep

4,p

5(M

Pa

)

pressure behind

condenser p4

pressure before

regenerator p5

Figure 11 – Pressure changes in the pipe between the condenserand regenerative heat exchanger

Diagrams 12 and 13 show the temperature and pressurechanges between the condenser inlet and outlet.

0 50 100 150 200 250 300

time t (s)

14

18

22

26

30

34

tem

pe

ratu

ret 3

,t4

(oC

)

temperature before

condenser t3temperature behind

condenser t4

Figure 12 – The temperature changes at the input and output ofthe condenser

0 50 100 150 200 250 300

time t (s)

0.6

0.8

1

1.2

1.4

pre

ssu

rep

3,p

4(M

Pa

)

pressure before

condenser p3

pressure behind

condenser p4

Figure 13 – The pressure changes at the input and output of thecondenser

The condenser in the tested refrigerator was cooled byair which was flowing thanks to the fan. Based on the mea-surements, it was noted that the losses due to the refrigerantflow through the condenser were slight. The temperature dis-crepancies between input and output of the condenser weresignificant (heat exchanger) and followed the intensive heatexchange between the refrigerant and the environment.

The pressure drops due to flow resistance can be esti-mated from the diagrams or calculated according to the for-mula:

∆p = λ · 1

di· ρ · w

2

2+ ξ · ρ · w

2

2(13)

where:∆p - pressure drop,λ - coefficient of friction,l - pipe length,di - pipe inner diameter,ρ - refrigerant density,w - refrigerant speed,ξ - local resistance coefficient.

The first part of the formula in 13 refers to the pressuredrops due to the flow resistance in the pipes of specifiedlengths and diameters. The second one deals with the lo-cal losses resulting from the flow resistance caused by the


changes of geometric structures of the flow passages, e.g.elbow, branching or elements mounted in pipes. Flow re-sistance depends above all on how fast a refrigerant can flowthrough a pipe. To avoid any significant pressure drops, pipesthat connect particular subsystems are short and have fewcurves, branching and places where choking could occur.The flow speed of the refrigerant should be kept at as lowas possible but within its permissible variation range.Calculating the pressure losses in the pipes, due to a refrig-erant flow, one should include also static pressure discrep-ancies that result from the discrepancy in the levels of theanalysed typical sections of the refrigerant slotted line. Thisdiscrepancy can be determined according to the formula:

∆pstat = g · ρ · h (14)

where:g - gravitational acceleration,h - height difference.

5. ANALYSIS OF THE LOSSES

A refrigerating efficiency coefficient εt measures therefrigerator working efficiency and is specified in accordancewith the ratio in (15). However, it cannot estimate correctlythe energy in a given refrigerating cycle because of the pos-sible values ranging from 0 to ∞. That is why it is better touse exergy efficiency coefficient ηb.

εt =qolob

(15)

ηb =εtεc

(16)

where:

εt =qolob

; εc =Tpa

Tsk − Tpa(for Carnot cycle)

(17)

An exergy efficiency can help to determine how much arefrigerating system is near an ideal cycle.Cycle thermal efficiency, known as refrigerating efficiencycoefficient is also useful to estimate refrigerating cyclethermal efficiency ηch.

ηch = εt · T ∗ (18)

where:T ∗ is the so called reduced temperature difference

T ∗ =Tsk − Tpa

Tsk(19)

Exergy efficiency deals with the impact of many parame-ters on the working efficiency of a given refrigerating cycleand helps estimate the suitability of various working factorsto process a cycle so that they can be selected optimally.

The diagrams in 14, 15, 16 are based on the data obtainedfrom the measurements. The diagrams show the changes

Figure 14 – Exergy efficiency during refrigerator operation

Figure 15 – The changes in thermal efficiency during refrigera-tor operation

Figure 16 – Changes in cycle power during refrigerator opera-tion

in the refrigerator efficiency and power in one of the re-peated refrigerating cycles, i.e. the moment the aggregatewas switched on until the compressor was switched off assoon as the refrigerated liquid reached the expected tempera-ture. The compressor started automatically when the cooledliquid was heated and reached a too high temperature due tothe heat going though the container insulation. The changesin parameters occurred during a full working cycle. Thetypes of efficiency given in the diagrams reached their lowestvalues at the beginning of a refrigerating cycle that increasewith time. The compressor working cycle, keeping the tem-perature of the cooled liquid that was warmed up due to theheat from outside constant, was short.

A compressor refrigerator can operate thanks to a com-


pressor which is the most important element and generatesthe greatest losses. The efficiency of a piston compressor isdetermined not only by a mass flow or refrigerant volume butalso the cooling efficiency of a machine it cooperates with.Indispensable volumetric and energetic losses make a com-pressor less efficient and more power is used. The volumetriclosses are, above all, due to a harmful space and are specifiedby a volumetric efficiency λ. They do not increase the workof compression. However, they make that a compressor isused less efficiently. The energy losses cause that more workto compress a gas mass unit is needed.

Figure 17 – The changes in a volumetric efficiency λ dependingon the compressor compression

Based on the measurements, there was made the diagramin 17 which specifies the changes in a volumetric efficiency λdepending on the compressor compression. Its value dependsmuch on the relationship between the pressures of the con-denser and evaporator, which is closely related to the temper-ature levels in those exchangers. On the basis of the previousdiagrams, it can be noted that the temperatures and pressuresin the heat exchangers, i.e. evaporator and condenser, changeduring the refrigerator operation. The greater compression is,the greater supply power losses in the compressor are.

The amount of ambient heat that reaches the refrigeratedliquid influences how much supply power is used. Thefollowing formula can be used for calculating the averageheat flow value based on the heat that reaches a liquidthrough insulation and the flow of the heat from the airabove the surface of the liquid in a container:

Qdop =mckcck|Tk

Tp(Tk − Tp)

τog(20)

where :mck – cooled liquid mass,cck|Tk

Tp– liquid average specyfic heat,

Tp, Tk – initial and final liquid temperature,τog – time for heat inflow through the insulation and from theair in the container into the liquid.

The changes in the average inflowing heat depending onambient temperature are shown in Figure 18. As the inflow-ing heat increases, the powering/supply energy increases.The evaporator needs to absorb more heat from the cooledliquid.

Figure 18 – Average flux of heat flow from ambient medium tothe container as a function of an ambient temperature

Besides the losses due to the processes during refrigeratoroperation, there are the losses that result from wearing theaggregate parts.

A compressor is at the greatest risk of failures and wearand tear. Its failures result from the wear and tear of pistons,bearings and crankshafts.

Condenser cooling�fan+44% 28%

Evaporator cooling�fan27% 39%

Compresor

Motor

Throttling�loss

Theoretical�work�of�the�Carnot�cycle 100%

72%

66%

78%

32%

51%

Figure 19 – Energy losses in relation to the theoretical demandfor supply power

Figure 19 compares the energy losses in relation to thetheoretical demand for supply power to show the percentageof the losses that occurred in each part of the refrigeratingsystem. These refer to the most important subsystems. Thegreatest losses of about 78 % were in the compressor, andthe slightest in the evaporator - about 27 %. Another signifi-cant loss of about 51 % was the throttling loss. At the sametime, it is necessary to bear in mind that these values relate tothe theoretical demand for supply power (the Carnot cycle).Thus, all the losses and not only the theoretical demand forsupply power increase as a result of the irreversibility of theprocesses that occur in a compressor. The compressor en-ergy efficiency matters essentially for the loss balance of theentire machine.

The demand for powering energy is closely connectedwith cooled liquid mass. The larger this mass is, the more


Figure 20 – The changes in the average unit supply energy de-pending on the cooled liquid mass for the specified cooling tem-peratures, i.e. 4oC and 10oC

powering energy is needed. To estimate the refrigerating ma-chine efficiency, powering energy was related to a cooled liq-uid mass unit where an average unit powering energy wasdefined as:

er =E

m(21)

Diagram 20 shows the changes in the demand for an av-erage unit powering energy necessary to cool a liquid massunit depending on the cooled liquid mass at the specifiedcooling temperatures. It can be noted that the value of av-erage unit powering energy decreased as the cooled liquidmass increased (according to the test-stand-measurements).Therefore, the consumption of average unit powering energyduring the cooling cycle in a refrigerator depends essentiallyon a cooled liquid in a given machine. Based on the experi-mental data and literature on this issue, it can be concludedthat for all containers where a refrigerating machine cools aliquid, one possibly can find the optimal amount of a cooledliquid where powering energy consumption is the least.

6. CONCLUSION

The paper shows the results of the theoretical and experi-mental research on the powering energy losses that occurredwhen a compressor refrigerator was working.

There were determined the sources of the most significantinternal and external losses as well as their location in thesystem.

The most essential internal losses are the loss of refrig-erant compression irreversibility in relation to the cylinderinside, the loss of refrigerant compression irreversibility inthe expander and the indicated power loss. The most crucialexternal losses are the loss of electric energy conversion inthe compressor, the loss of expansion work in the expander,the motor power loss , the loss of electric power supplied tothe motor, the loss due to the exchange of mixing energy intoheat and the losses due to the heat inflow though the container

insulation and from the air in the container.The measurements were done for the selected points of

the refrigerator. The results were recorded at the stand foracquiring data in real time. The measurements were doneat varied initial refrigerated liquid temperatures and ambi-ent temperatures. Also, the cooled liquid mass was changedduring the measurements. The obtained changes of pressure,temperature and supply power during the operation indicatedthat the pressure drops due to the refrigerant flow though theindividual elements of the refrigerator were small and didnot affect much the powering energy loss. The largest losseswere when the machine was started up.

It was indicated in the research that the unit supply energyconsumption in a cooling cycle of such a machine dependsmuch on the cooled liquid mass in this machine. Diagram20 shows how the amount of the cooled liquid depends onunit energy needed to cool it. The larger mass of the cooledliquid requires more powering energy under given consump-tion conditions. The amount of powering energy for cool-ing unit mass changed as the amount of cooled liquid in thecontainer increased. During the measurements, unit energydecreased. It is expected that the further mass increase willincrease unit energy with regard to a limited efficiency of therefrigerator. The practical conclusion is that for any refrig-erating machine, one can possibly select a relevant mass ofa cooled liquid for which powering energy consumption thatfalls on a mass unit will be as small as possible.

REFERENCES

[1] A. Stegou-Sagian, N. Paignigiannis, “Exergy losses inrefrigerating systems. A study for performance com-parisons in compressor and condenser”, Int. J. EnergyRes., 27, pp. 1067-1078, 2003.

[2] S. Fijalkowski, A. Warminska, “Analysis of lossesof small power refrigirating systems in a quasi-steady state. Part I: Influence of parameters determin-ing losses in the refrigerating system”,RefrigerationXXXII, No. 4, pp. 14-19, April 1997.Title in Polish : Analiza strat energii przy quasi-ustalonym dzialaniu sprezarkowych chlodziarek malejmocy. Czesc I: Analiza czynnikow warunkujacychpowstanie istotnych strat energii w chlodziarkachmalej mocy. Chlodnictwo, XXXII, 4 (1997), 14-19.

[3] S. Fijalkowski, A. Warminska, “Analysis of lossesof small power refrigirating systems in a quasi-steady state. Part II: On the level of energy consump-tion under the variable temperature of a cold stor-age”,Refrigeration XXXII, No. 5, pp. 9-17, May 1997.Title in Polish: Analiza strat energii przy quasi-ustalonym dzialaniu sprezarkowych chlodziarek malejmocy. Czesc II: O poziomie wykorzystania energiinapedowej w procesie chlodniczym przy zmiennejtemperaturze przestrzeni schladzania. Chlodnictwo,XXXII, 5 (1997), 9-17.


ANALYSIS OF ENERGY LOSSES IN SMALL COMPRESSION REFRIGERATORS · ANALYSIS OF ENERGY LOSSES IN SMALL COMPRESSION REFRIGERATORS ... Freon 22 is used as a refriger-ant. In the tested

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