ME 3322C Mid Term Exam #2; Summer 2012 Problem 1 (5 points) Water substance, with 520 °F temperature and 98% quality enters a well-insulated throttling valve. The pressure at exit from the valve is 100 psia. Neglecting the changes in potential and kinetic energy, find the change in specific internal energy of water as it flows through the valve. Problem 2 (7 points) In a heat exchanger refrigerant R-134a is cooled by water. The refrigerant enters at 1.0 MPa pressure and 60C temperature at the rate of 0.4 kg/s, and leaves as a liquid at 0.9 MPa pressure and 35.5C temperature. Liquid water at 1 bar pressure enters the system at 8C and leaves at 16C. Assuming steady state, and assuming that the heat exchange is adiabatic, calculate the mass flow rate of water. Also, find the rate of heat transfer from R-134a to water. Problem #3 (8 points) Steam at 2 MPa pressure, 350C temperature, and 50 m/s velocity enters a turbine. Steam leaves the turbine as saturated vapor at a pressure of 0.1 MPa and a velocity of 100 m/s. The mass flow rate of steam is 1.5 kg/s. Measurements show that heat is transferred from the turbine to the surroundings at the rate of 9 kW. Determine the rate of work out put of the turbine. Also, calculate the isentropic efficiency of the turbine.
Problem 1 (5 points) Water substance, with 520 F temperature and
98% quality enters a well-insulated throttling valve. The pressure
at exit from the valve is 100 psia. Neglecting the changes in
potential and kinetic energy, find the change in specific internal
energy of water as it flows through the valve. Problem 2 (7 points)
In a heat exchanger refrigerant R-134a is cooled by water. The
refrigerant enters at 1.0 MPa pressure and 60 C temperature at the
rate of 0.4 kg/s, and leaves as a liquid at 0.9 MPa pressure and
35.5 C temperature. Liquid water at 1 bar pressure enters the
system at 8 C and leaves at 16 C. Assuming steady state, and
assuming that the heat exchange is adiabatic, calculate the mass
flow rate of water. Also, find the rate of heat transfer from
R-134a to water. Problem #3 (8 points) Steam at 2 MPa pressure, 350
C temperature, and 50 m/s velocity enters a turbine. Steam leaves
the turbine as saturated vapor at a pressure of 0.1 MPa and a
velocity of 100 m/s. The mass flow rate of steam is 1.5 kg/s.
Measurements show that heat is transferred from the turbine to the
surroundings at the rate of 9 kW. Determine the rate of work out
put of the turbine. Also, calculate the isentropic efficiency of
the turbine.
