A cross flow heat exchanger similar to the one shown in Figure 5.31 is being used to recover heat from a flow of hot air that enters the heat exchanger at 200°F with a mass flow rate of 14,400 lbm/h. Cool water, flowing in the tubes, enters the heat exchanger at 50°F and leaves at 80°F while flowing at 12,000 lbm/h. Determine the

a. Heat transfer rate recovered from the hot air flow (Btu/h)

b. The exit temperature of the air (°F)

c. UA product for this heat exchanger (Btu/h-°F)
Consider a situation where the mass flow rates of the air and water are the same, and the entering air temperature is the same. However, the entering water temperature is now 60°F rather than 50°F. Based on your previous analysis, estimate the

d. Temperature of the air and water leaving the heat exchanger (°F)

e. Heat transfer rate recovered from the hot air flow (Btu/h)

Transcribed Image Text:

300 Air passing through the fins FIGURE 5.31 Example of a continuous plane finned tube cross flow heat exchanger. Liquid flowing through the tubes