A food storage locker requires a refrigeration capacity of 50 kW. It works between a condenser temperature of 35° C and an evaporator temperature of –10°C. The refrigerant is ammonia. It is sub-cooled by 5° C before entering the expansion valve by the dry saturated vapour leaving the evaporator. Assuming a single cylinder, single-acting compressor operating at 1000 rpm with stroke equal to 1.2 times the bore, determine (a) the power required, and (b) the cylinder dimensions.
|
Saturation
Temperature
0C
|
Pressure
bar
|
Enthalpy, kJ/kg
|
Entropy, kJ/kg K
|
Specific volume,
m3 / kg
|
Specific heat
kJ/kg K
|
|
|
|
Liquid
|
Vapour
|
Liquid
|
Vapour
|
Liquid
|
Vapour
|
Liquid
|
Vapour
|
|
–10
|
2.9157
|
154.056
|
1450.22
|
0.82965
|
5.7550
|
–
|
0.417477
|
–
|
2.492
|
|
35
|
13.522
|
366.072
|
1488.57
|
1.56605
|
5.2086
|
1.7023
|
0.095629
|
4.556
|
2.903
|