A counterflow heat exchanger operates at steady state while being well-insulated from the surroundings with air and ammonia flowing in separate streams. Ammonia enters at state 1 with -30°C and a quality of 30% and exits at state 2 as saturated vapor at -30°C. Air enters at state 3 with pressure 1 bar and temperature 295 K and exits at state 4 with pressure 1 bar and temperature 265 K. The flow rate of air is 10 kg/s. Ignore kinetic and potential energy effects, and take the dead state as 1 bar and 300 K. a. Describe the heat transfer inside the heat exchanger (what is transferring heat to what?) b. Determine the specific enthalpy of each state, in kJ/kg. c. Determine the mass flow rate of ammonia, in kg/s.
Heat Exchangers
Heat exchangers are the types of equipment that are primarily employed to transfer the thermal energy from one fluid to another, provided that one of the fluids should be at a higher thermal energy content than the other fluid.
Heat Exchanger
The heat exchanger is a combination of two words ''Heat'' and ''Exchanger''. It is a mechanical device that is used to exchange heat energy between two fluids.
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A counterflow heat exchanger operates at steady state while being well-insulated from the surroundings with air and ammonia flowing in separate streams. Ammonia enters at state 1 with -30°C and a quality of 30% and exits at state 2 as saturated vapor at -30°C. Air enters at state 3 with pressure 1 bar and temperature 295 K and exits at state 4 with pressure 1 bar and temperature 265 K. The flow rate of air is 10 kg/s. Ignore kinetic and potential energy effects, and take the dead state as 1 bar and 300 K.
a. Describe the heat transfer inside the heat exchanger (what is transferring heat to what?)
b. Determine the specific enthalpy of each state, in kJ/kg.
c. Determine the mass flow rate of ammonia, in kg/s.
d. Determine the rate of exergy destruction within the heat exchanger, in kW.
e. Devise and evaluate an exergetic efficiency for the heat exchanger.
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