Chapter 11, Problem 11S.15P

A cooling coil consists of a bank of aluminum $\left(k=237\text{ W/m}\cdot \text{K}\right)$ finned tubes having the core configuration of Figure 11S.5 and an inner diameter of 13.8mm. The tubes are installed in a plenum whosesquare cross section is 0.4 m on a side, thereby providing a frontal area of 0 $0.16{\text{ m}}^2$ . Atmospheric air at1.5 kg/s is in cross flow over the robes, while saturated refrigerant-134a at 1 atm experiences evaporation in the tubes. If the air enters at 37°C and its exittemperature must not exceed 17°C, what is the minimum allowable number of tube rows in the flow direction? A convection coefficient of $5000{\text{ W/m}}^2\cdot \text{K}$ is associated with evaporation in the tubes.