12.11
3
Data
water-cooled
(122°C; 6.23 m³/kWh; 87.6%)
A single-cylinder, single-acting reciprocating air compressor supplies a
receiver from which the air is drawn off for process work. Taking the polytropic index
of.compression and re-expansion as 1.3, and using the data below, calculate:
(i) the pressure in the receiver;
$Q_{rej}$
(ii) the rate of heat rejection from the receiver;
(iii) the volumetric efficiency of the compressor; $\eta_v$
(iv) the required power input to the compressor.
Cylinder bore, 200 mm; stroke, 250 mm; rotational speed, 440 rev/min; clearance volume,
5% of swept volume; ambient pressure and temperature in compressor house, 1.01 bar
and 10°C; average pressure and temperature during the induction stroke, 1 bar and
273
83k 20°C; volume flow rate of air drawn off for process work, 0.6 m³/min at 17°C.
Note: Use a trial-and-error method for part (i). 200
3k
(5 bar; 8.14 kW; 83.9%; 9.85 kW)
of
3 in to 175 har
