Saturated ammonia vapour enters a 15cm dia 14 cm stroke twin-cylinder single -acting compressor at 0.2365 MPa whose volumetric efficiency is 79% and speed 420 r.p.m. The delivery pressure is 1.1672 MPa. Liquid NH3 at 210C enters the expansion valve. For ideal cycle, find (i) the ammonia circulated in kg/min, (ii) the refrigeration in tons and (iii) COP of the cycle. Assume specific heat of NH3 as 2.19 kJ/kg-K and density 0.77 kg/m3. Properties of NH3 are given below:
|
Pressure
(MPa)
|
Sat.
temp.
(oC)
|
Sp. Vol.
of vap. at sat. (m3/kg)
|
Enthlpy
(kJ/kg)
|
Entropy
(kJ/kg - K)
|
|
|
|
|
Sat.
liq
|
Sat. vap.
|
Sat. liq.
|
Sat. vap.
|
|
0.2365
|
–15
|
0.5106
|
– 831.46
|
481.52
|
5.4387
|
10.526
|
|
1.1672
|
+30
|
0.11084
|
– 620.70
|
523.42
|
6.1853
|
9.9606
|