A vapour compression refrigerator operates between the pressure limits of 462.47 kN/m2 and 1785.90 kN/m2.At entry to the compressor the refrigerant is dry saturated and after compression it has a temperature of 590C. The compressor has a bore and stroke of 75 mm and runs a 8 rev/s with a volumetric efficiency of 80 percent. The temperature of the liquid refrigerant as it leaves the condenser is 320C and the specific heat capacity of the superheated vapour may be assumed constant. Determine :
- The coefficient of performance of the regrigerator
- The mass flow of the refrigerant in kg/h.
- The cooling water required by the condenser in kg/h if the cooling water temperature rise is limited to 120C.
Take the specific heat capacity of water as 4.187 kJ/kg K and the specific heat of liquid refrigerant as 1.32 kJ/kg.K. The relevance properties of the refrigerant are given in the table beow.
|
Pressure
|
Sat. temp.
|
Sp. enthalpy
|
Sp vol. (m3/kg)
|
Sp. entopy
|
|
kN/m2
|
tf0c
|
hf
|
hg
|
Vf
|
Vg
|
Sf
|
Sg
|
|
462.47
|
–10
|
35.732
|
231.40
|
0.0008079
|
0.04573
|
0.1418
|
0.8614
|
|
1785.90
|
40
|
99.270
|
246.40
|
0.0009487
|
0.01105
|
0.3537
|
0.8093
|