An ammonia ice plant operates between a condenser temperature of 35o C and an evaporator temperature of -15 C. It produces 10 tonnes of ice per day from water at 32° C to ice at -3° C Assuming simple saturation cycle determine.
(i) the capacity of the refrigeration plant
(ii) the mass flow rate of refrigerant
(iii) the compressor cylinder diameter and stroke if its volumetric efficiency is 70% rpm = 1250 and stroke to bore ratio is = 1.3
(iv) the power of the compressor motor if the adiabatic efficiency of the compressor = 0.86 and mechanical efficiency = 0.94.
(v) the theoretical and actual COP
Assume latent heat of ice = 335 kJ/kg
Specific heat of water = 4.1868 kJ/kgK
Specific heat of ice = 1.94 kJ/kgK
The properties of NH3 are given below.
|
T
(°C)
|
vf $\times$ 103
(m3/kg)
|
vg
(m3/kg)
|
hf
(kJ/kg)
|
hg
(kJ/kg)
|
sf
(kJ/kg K)
|
sg
(kJ/kg K)
|
|
-15
|
1.52
|
0. 508
|
131.3
|
1443.9
|
0.7426
|
5.8223
|
|
35
|
1.7
|
0 .096
|
366.1
|
1488.6
|
1.566
|
5.2086
|
Average specific heat of ammonia vapour is 2.2 kJ/kg K