the reality of a small household thermoacoustic refrigerator

7/27/2019 The Reality of a Small Household Thermoacoustic Refrigerator

1/7

Purdue University

Purdue e-Pubs

International Refrigeration and Air ConditioningConference

School of Mechanical Engineering

1996

Te Reality of a Small Household TermoacousticRefrigerator

R. StarrUniversity of Auckland

P. K. BansalUniversity of Auckland

R. W. JonesUniversity of Auckland

B. R. MaceUniversity of Auckland

Follow this and additional works at: hp://docs.lib.purdue.edu/iracc

Tis document has been made available through Purdue e-Pubs, a ser vice of the Purdue University Libraries. Please contact [email protected] for

additional information.

Complete proceedings may be acquired in print and on CD-ROM directly from the Ray W. Herrick Laboratories at hps://engineering.purdue.edu/

Herrick/Events/orderlit.html

Starr, R.; Bansal, P. K.; Jones, R. W.; and Mace, B. R., "Te Reality of a Small Household Termoacoustic Refrigerator" (1996).International Reigeration and Air Conditioning Conference. Paper 344.hp://docs.lib.purdue.edu/iracc/344
http://docs.lib.purdue.edu/?utm_source=docs.lib.purdue.edu%2Firacc%2F344&utm_medium=PDF&utm_campaign=PDFCoverPageshttp://docs.lib.purdue.edu/iracc?utm_source=docs.lib.purdue.edu%2Firacc%2F344&utm_medium=PDF&utm_campaign=PDFCoverPageshttp://docs.lib.purdue.edu/iracc?utm_source=docs.lib.purdue.edu%2Firacc%2F344&utm_medium=PDF&utm_campaign=PDFCoverPageshttp://docs.lib.purdue.edu/me?utm_source=docs.lib.purdue.edu%2Firacc%2F344&utm_medium=PDF&utm_campaign=PDFCoverPageshttp://docs.lib.purdue.edu/iracc?utm_source=docs.lib.purdue.edu%2Firacc%2F344&utm_medium=PDF&utm_campaign=PDFCoverPageshttps://engineering.purdue.edu/Herrick/Events/orderlit.htmlhttps://engineering.purdue.edu/Herrick/Events/orderlit.htmlhttps://engineering.purdue.edu/Herrick/Events/orderlit.htmlhttps://engineering.purdue.edu/Herrick/Events/orderlit.htmlhttp://docs.lib.purdue.edu/iracc?utm_source=docs.lib.purdue.edu%2Firacc%2F344&utm_medium=PDF&utm_campaign=PDFCoverPageshttp://docs.lib.purdue.edu/me?utm_source=docs.lib.purdue.edu%2Firacc%2F344&utm_medium=PDF&utm_campaign=PDFCoverPageshttp://docs.lib.purdue.edu/iracc?utm_source=docs.lib.purdue.edu%2Firacc%2F344&utm_medium=PDF&utm_campaign=PDFCoverPageshttp://docs.lib.purdue.edu/iracc?utm_source=docs.lib.purdue.edu%2Firacc%2F344&utm_medium=PDF&utm_campaign=PDFCoverPageshttp://docs.lib.purdue.edu/?utm_source=docs.lib.purdue.edu%2Firacc%2F344&utm_medium=PDF&utm_campaign=PDFCoverPages


2/7


3/7


4/7

VAPOUR COMPRESSION REFRIGERATION SYSTEMA basic vapour compression refrigeration system consists of four major components: a compressor, condenser, capillaryrube, and evaporator as shown in Figure 4(b). Heat is absorbed at low temperature in the evaporator and rejected at thecondenser. Work is supplied through the compressor. Non-adiabatic capillary rubes are normally used in householdrefrigerators where the capillary is soldered to the suction line or run inside the suction side to superheat the suction gasto ambient temperatures. In the future compressors are likely to have variable speed drives, enabling them to runcontinuously to meet lower load situations but at higher compressor efficiencies.

COMPARISON OF THERMOACOUSTIC AND VAPOUR COMPRESSION REFRIGERATION SYSTEMSThe coefficient of performance (COP) is the standard measure of the efficiency of refrigeration systems. The COP of thethermoacoustic and vapour compression refrigeration systems shown in Figure 4 are respectively

C O P = ~w"

(1)

where, for the thermoacoustic system, Qc is the heat load into the cold end of the stack and W" is the acoustic powerinto the resonator. For the vapour compression system Qev"" represents the evaporator capacity (i.e. the heat load thatthe refrigerant in the evaporator has to remove to keep the fridge air at the desired temperature; normally 3 C) and Wc,mpthe mechanical work into the compressor. For a refrigeration cycle the COP is bounded by the Carnot efficiency whichis given by

(a)

Q Cold Heat Exchangerj Tc

Hot Heat ExchangerTH

(2)

(b)Figure 4. (a)' A simple thermoacoustic refrigerator. (b) Component diagram of a vapour compression householdrefrigerator/freezer with Non-Adiabatic Capillary Tubes (NACT) as expansion valves.

325


5/7


6/7

For the system analysed no acco unt was taken ofsubc ooling or sup erheating, howev er a ris e of 27 C in th e gassu ction line w as assumed, with th e capillaryexposed toam bi enta ir (a bout 32 C) so tha tth e re turn gas tempe ra tureto theco mpres sor is 32 C. It is also assum ed th at the pressu re losses in both the heat ex cha nge rs (the ev ap ora tor and condenser) are about 10%. The computations were mad e using BICYCLE [8] for b oth th e re friger ator and fr eezer .COP Co mp arisonA com parison of th e COP ofeach system was made fo r both the re friger ator and fr eezer a t a va riety ofheat loads,na mely Qc and Qevq> of 50, 100, 150, and 20 0W. The results areshown in Figure6.

The am ount ofheat that th e therm oac ous tic sys tem co uld pum p was altere dby chang ingth e dr iving ratio as sho wn inFig ur e 7(a). The hi gh er the driving ratio, the mo re heat th at could be pu mped, butat a lower efficiency. The hig hes tdr iving ratio obtained wa s 0.049, which corresponds to a fre ezer with a 200 Wheat load. Here, non -linea r ef fects ar ebeco min g significant, but linea r theory still gives rea son ably accurate results. As already sta ted, the hea t lo ad in th evap our compression system was altered by va rying the sp eed of the compresso r, the ap propriate com pressor size ascalcula ted by BIC YCLE for ea ch hea t load is given in Fig ure 7(b).

FR ID G E (-15, 43)210 III2001.90

=- 1.80w 1.70

II~ I

1.601.50

FRE EZER ( 25,4 3)

1.66 -.='"----"''"'"'---'"'''"''"'''"''"''"'"1.641.621.601.58w 1.561.541.521.50

leTA ! iI IICOMP I

50 100 150 200 50 100 150 200

~ " 7 " e - a t _ ( W ) = = = - - - - - _ . . J _ Uud Figure6. Comparison betwee n the COPof a thermoa co ustic(T A) andvapour comp ression (COM P) refrigerator andfreezerforheat lo ad sof 50, 100, 150, and 20 0 W.0.05 90.045 8

-=: 0.04 7-; O.D35 6c::: 5.. 0.03.$ 4... 0.025::: 3~0. 02 20.0150.01

50 100 150 200 100 150 200Heat Load (W ) HeatLo ad (W )

(a) 0b)Fig ure 7. (a) Var iation ofthe driv ing ratio with hea t load f o r a th erm oa cou stic refrigerator and freezer , an d(b)The CCrating ofa va pou r co mpressionre frigerator and f reeze ra t d if ferent heat loads.

327


7/7

the reality of a small household thermoacoustic refrigerator

Documents