An adiabatic heat exchanger is used to heat cold water at 8°C entering at a rate of 3 kg/s using hot air at 150°C entering with the same mass flow rate. If the air’s exit temperature air is 30°C, what is:
The water’s exit temperature, calculated using both constant room temperature specific heats and temperature average specific heats (specific heats at average of inlet and exit temperatures)
The specific heat transfer rate from the air to the water, calculated using both specific room temperature and average heat assumptions.
Discuss briefly (no more than three or four sentences) whether or not you think there is any reason to prefer one method of determining specific heats over the other in this case. Be sure to justify your answer using quantitative results (% differences, etc.).
Notes:
Assume constant room temperature specific heats for the water flowing through the heat exchanger and average temperature specific heats for the air.