Purdue University
Purdue e-Pubs International Compressor Engineering Conference
School of Mechanical Engineering
1986
Performance Testing of an Open Reciprocating Refrigeration Compressor Over a Range of Speeds J. A. McGovern
Follow this and additional works at: http://docs.lib.purdue.edu/icec McGovern, J. A., "Performance Testing of an Open Reciprocating Refrigeration Compressor Over a Range of Speeds" (1986). International Compressor Engineering Conference. Paper 529. http://docs.lib.purdue.edu/icec/529
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TING REFRIGERATION PERFORMANCE TESTING OF AN OPEN RECIPROCA S COMPRESSOR OVER A RANGE OF SPEED James A. McGovern ring Engi neeri ng, Depa rtmen t of Mech anica l and Manu factu nd Irela Z, in Dubl ge, Trin ity Colle
ABSTRACT deter mine the A load stand has been buil t and used to gera tion comp resso r refri ting roca perfo rman ce of an open type recip over a range of speed s. desc ribed and samp le The load stand and instr umen tatio n are ce char acte risti cs for rman Measured perfo test readi ngs are given . Aspe cts of nted. prese are s speed of range a the comp resso r over from the drawn are ns lusio conc the load stand are discu ssed and . tests r resso comp the resu lts of SYMBOLS
m Q h·I
comp resso r, kg/s mass flow rate of refri gera nt throu gh the r, W rate of heat trans fer in the heat exch ange urement locat ion i, spec ific entha lpy of refri gera nt at meas J/kg
A,B,C,D
load stand cont rol valve s
a,b,c , ••
measurement locat ions on the load stand
M.E.P.
mean effec tive press ure, bar
TDC
top dead centr e posit ion
BDC
botto m dead centr e posi tion
Emech
mech anica l effic ienc y
Evol
volum etric effic ienc y 242
INTRODUCTION This paper describ es work which has been carried out at Trinity Colleg e Dublin as part of a researc h programme entitle d "Capac ity Contro l of Recipr ocating Piston Compressors for Heat Pump or Refrig eration Applic ations by Speed Variat ion". A load stand has been built accord ing to the princip les outline d in a previou s paper (1) and has been found to operat e satisfa ctorily . Work is continu ing in develo ping the instrum entatio n and data logging facilit ies and in automa ting the test proced ures. DESCRIPTION OF THE LOAD STAND AND INSTRUMENTATION The load stand is shown schem atically in Fig. 1. It gas bypass type, employing a single heat exchan ger, in whichis a hot of the total refrige rant flow is fully conden sed to the liquidpart state and then mixed with the remain der. The suction and discha rge pressu res and the suction superh eat temper ature are contro lled by means of throttl e valves . Contro l of Operat ing Condit ions The compre ssor is belt driven by a standa rd inducti on motor and speed is varied by means of an electro nic frequen cy invert er. The satura tion temper ature in the heat exchan ger is determ ined by the temper ature and flow rate of the cooling water and by the rate of heat rejecti on from the refrige rant. This rate is approx imately equal to the indicat ed power of the compre For the water flow condit ions describ ed in the sample resultsssor. the sensit ivity of the heat exchan ger satura tion temper ature to compre ssor indica ted power is about 5 K/kW. Thus it change s little with the operati ng condit ions of the compre ssor. Discha rge pressu re is contro lled by valve A while valve D is used to contro l the compre~sor suction pressu re. The setting s of valves B and C determ ine the suction superh eat temper ature. Valve B in the vapour bypass line provid es a pressu re differe nce across valve C and ensure s adequa te liquid feed to that valve which is located above the conden ser level. Adjustment of valve B necess ary only when major change s in operati ng condit ions is are made, e.g. for most operati ng conditi ons it can be left fully open, but, it must be closed partia lly at very low compre ssor speeds . Valve C is a fine meterin g valve and contro ls the flow rate of liquid from the heat exchan ger. It was found necess ary to instal l two valves , one for coarse and one for fine adjustm ent, to obtain adequa te meterin g over a wide range of operati ng condit ions. These valves are fitted with microm eter handle s so that their setting s can be noted and repeate d. The four main contro l valves A,B,C,D are interac tive to some extent and an adjustm ent in one may require a compen sating adjustm ent in the others .
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