Question

015) A1 a) Define volumetric efficlency and indicate ts significance on the design of refrigeration systems. List he most important factors that infuence the volumetric efficiency of reciprocating refrigeration compressors [20%) est of an ammonia refrigeration plant employing a twin cytinder single acting compressor, running at 320 rpm, the following data were obtained Refrigerant temperatures Ater expansion valve, entering brine cooling evaporator Entering compressor Entering condenser Entering expansion valve -24 "С -8℃ 134 ℃ 30"С Others: 0.793 mng Specific volume at compressor inlet Condenser pressure Brine mass flow rate: Temperature drop of brine in evaporator Specific heat of brine Electrical input to compressor motor Electrical motor efficiency at this load 13.11 bar 17 kg/s 7 K 3.14 k.VCkg K 13.5 kWw 92% The properties of ammonia are given in the Properties Table supplied Determine: ) The mass flow rate of ammonia in the refrigeration system (20%) (i) The mechanical efficiency of the [20%) (ia) The volumetric efficiency of the compressor if the cylinder bore is 150 mm and the stroke is 200 mm, [30%) (v) The COP of the refrigeration cycle [10%)

Answer 1

is is defined as the actual volume o is bein Compressed and theorast Compressed inside tendr aur S it Can be 4 ma - mous Fw ate d-bore。 L-Sto ke

etric effidienu decides the vojume (mau 9) is also exprssed in -tem o Gendenser presruote and eva poyator pTesuuwne depends Clearance Vosume V tors on which VS Uy Pessueo xPone 2. 131° Bac

0 C 322.9 KJ 2 240 c | ニ 1448.44 KJ 1 211 (13Y-3) ()enern balance For evaporeto by brine Het Releate by NH3 X3.14xm 44-322.9 Mass Flow rate of re 13.5

(iiv 4- Toinnde 63.07 8.4 322.9) (695.66- 4844 CoP - 455