An air compressor takes in air at standard conditions (use 14.7 psia and 70°f) at a negligible velocity. the air is discharged at 115 psia and 125°f with a den- sity of 0.5 lbm/ft 3. the mass fl ow rate out of the 0.5 ft2 discharge pipe is 12 lbm/s. if the compressor input horsepower is 800, find the magnitude and direction (in words) of the heat transfer to/from the compressor in units of btu/s. assume a steady flow. draw a control surface for the calculation.

Amass of m 1.5 kg of steam is contained in a closed rigid container. initially the pressure and temperature of the steam are: p 1.5 mpa and t 240°c (superheated state), respectively. then the temperature drops to t2= 100°c as the result of heat transfer to the surroundings. determine: a) quality of the steam at the end of the process, b) heat transfer with the surroundings. for: p1.5 mpa and t 240°c: enthalpy of superheated vapour is 2900 kj/kg, specific volume of superheated vapour is 0. 1483 m/kg, while for t 100°c: enthalpy of saturated liquid water is 419kj/kg, specific volume of saturated liquid water is 0.001043m/kg, enthalpy of saturated vapour is 2676 kj/kg, specific volume of saturated vapour is 1.672 m/kg and pressure is 0.1 mpa.

The temperature of air decreases as it is compressed by an adiabatic compressor. a)- true b)- false

Acompressor receives the shaft work to decrease the pressure of the fluid. a)- true b)- false