Reconsider Prob. 19€“100. Using an appropriate 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 19-100.

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?

Attic space Air 85C 70C 0.1 m?/s