Chapter 11, Problem 11.34P

The compartment heater of an automobile exchangesheat between warm radiator fluid and cooler outsideair. The flow rule of water is large compared to the air, and the effectiveness, $\epsilon$ , of the heater is known todepend on the flow rate of air according to the relation $\epsilon \sim {\stackrel{\dot{}}{m}}_{air}^{-0.2}$ .
(a) It the fan is switched to high and ${\stackrel{\dot{}}{m}}_{air}$ is doubled,determine the percentage increase in the heatadded to the car, if fluid inlet temperatures remainthe same.
(b) For the low-speed fan condition, the heater warmsoutdoor air from 0 to 30°C. When the fan is turnedto medium, the airflow rate increases 50% and theheat transfer increases 20%. Find the new outlettemperature.