Methane gas is to be compressed at a flow rate of 500 m3 min-1 (measured at 1.013 bar and 15.6 °C) from 6.9 bar and 26.7 °C to 34.5 bar. The compressor has an efficiency of 80 % compared
with an isentropic system. After compression, the methane is to be cooled at a constant pressure
of 34.5 bar to a temperature of 37.8 °C.
(a) Draw and label clearly a schematic diagram of this process [5%]
(b) Calculate the power requirements of the compressor [13%]
(c) Calculate the rate of heat removal in the cooler [5%]
(d) Calculate the temperature of the methane gas at the compressor outlet [2%]
Thermodynamic data for methane CH4
At 6.9 bar and 26.7 °C: H = 946.8 kJ kg-1 S = 6.071 kJ kg-1 K-1
At 34.5 bar: T (°C) H (kJ kg-1) S (kJ kg-1 K-1)
37.8 948.9 5.264
148.9 1233.4 6.033
154.4 1248.9 6.071
160.0 1264.0 6.109
165.6 1279.0 6.142
171.1 1294.1 6.176
176.7 1309.2 6.209
182.2 1324.2 6.238