The pressure of refrigerant R-22 drops from 14 bar to 3.5 bar by passing through an expansion valve. The temperature of the refrigerant at the inlet of the valve is 28 C. Determine the entropy production and the rate of exergy destruction for unit mass of refrigerant passing through the expansion valve. The temperature of the environment is To = 25 C.

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

Apump is used to circulate hot water in a home heating system. water enters the well-insulated pump operating at steady state at a rate of 0.42 gal/min. the inlet pressure and temperature are 14.7 lbf/in.2, and 180°f, respectively; at the exit the pressure is 60 lbf/in.2 the pump requires 1/15 hp of power input. water can be modeled as an incompressible substance with constant density of 60.58 lb/ft3 and constant specific heat of 1 btu/lb or. neglecting kinetic and potential energy effects, determine the temperature change, in °r, as the water flows through the pump.

Thermal stresses are developed in a metal when its a) initial temperature is changed b) final temperature is changed c) density is changed d) thermal deformation is prevented e) expansion is prevented f) contraction is prevented