Reconsider Prob. 8–87. Using EES (or other) software, investigate the effect of the volume flow rate of air on the exit temperature of air and the rate of heat loss. Let the flow rate vary from 0.05 m³/s to 0.15 m³/s. Plot the exit temperature and the rate of heat loss as a function of flow rate, and discuss the results.

Data from problem 87

Hot air at atmospheric pressure and 85°C enters a 10-m-long uninsulated square duct of cross section 0.15 m × 0.15 m that passes through the attic of a house at a rate of 0.1 m³/s. The duct is observed to be nearly isothermal at 70°C. Determine the exit temperature of the air and the rate of heat loss from the duct to the air space in the attic. Evaluate air properties at a bulk mean temperature of 75°C. Is this a good assumption?

Transcribed Image Text:

Attic space Air 85°C 70°C 0.1 m³/s =