A compression system is used to compress 1 m3/sec of dry air at 30oC

A compression system is used to compress 1 m3/sec of dry air at 30oC from
atmospheric pressure which is 1.013 bar A to 7.5 bar A for adiabatic compression.
Given:
Density of air, kg/m3 =
????
??????1000
Where P pressure in Pa, (1 bar A = 1×105 Pa )
R = 8.314 J/K-mol (Note the value and units of ‘R’ are different for this equation)
M= 28.97 kg/kg.mol
T= Temp oK
Polytropic Exponent n=1.4 for air
Polytropic Compression work W (Gas HP)

η – compressor efficiency typically 0.75
Compressor BHP = W / η
Suction filter pressure drop is 100 mm WC at clean conditions (1 m WC = 0.0981
bar)
1(a) Calculate compressor BHP (in KW/Nm3) using above equations. (2 marks)
1(b) Calculate variation of power consumption if the discharge pressure is reduced by 1
bar. Complete the sentence –
For ____ % reduction in discharge pressure the compressor power is reduced by
_____ % (2 marks)
CL 5863 2022 MDS – Assignment 2
1(c) Calculate increase in power consumption for base case due to reduction in suction
pressure as the suction filter fouls up and pressure drop increases from 100 mm WC
to 400 mmWC . Complete following sentence
For every 100 mm increase in suction filter pressure drop, compressor power
increases by _____ % (2 marks)
1(d) Calculate increase in the power consumption when in air suction temperature drops
to 15 oC in winter. Complete the sentence –
For every 10 oC drop in suction temperature, compressor power reduces by _____ %
(2 marks)