Q1.A single stage reciprocating compressor has a swept volume of 0.4 litres and operates at 1440 rpm through a pressure ratio of 8.5 and has a clearance volume of 7% of the swept volume. It is assumed that the gas compression is treated as a polytropic process, with an index of 1.3, and the inlet air conditions of atmospheric pressure, 101 kPa and temperature 25º C. Take Rair = 287 J/kgK.
a). Draw and label the swept, clearance and effective volumes on a P-V diagram and also show the indicated work.
b). Calculate volumetric efficiency.
c). Calculate theoretical mass flow rate.
d). Calculate isothermal efficiency.
e). Calculate power to drive the compressor, assuming ?mech = 81%.
Q2.In order to measure the volume flow rate of fresh water flowing in the pipe of internal diameter of 50 mm, a horizontal venturi tube, of throat diameter of 30 mm, is inserted into a pipe system. When operating; a differential pressure of 18 kPa is measured across the venture meter.
a). Derrive an equation, from first principles, to determine the mean water flow velocity in the pipe.
b). Ignoring any losses, determine, the water volume flow rate.
c). Determine the coefficient of discharge (Cd) for the venture meter if the mass flow rate is measured to be 4 litres/s.