Air at 25C flows at 30 x 10-6 kg/s within 100-mm-long channels used to cool a high

Air at 25°C flows at 30 x 10-6 kg/s within 100-mm-long channels used to cool a high thermal conductivity metal mold. Assume the flow is hydrodynamically and thermally fully developed.

(a) Determine the heat transferred to the air for a circular channel (D = 10 mm) when the mold temperature is 50°C (case A).

(b) Using new manufacturing methods (see Problem 8.99), channels of complex cross section can be readily fabricated within metal objects, such as molds. Consider air flowing under the same conditions as in case A, except now the channel is segmented into six smaller triangular sections. The flow area of case A is equal to the total flow area of case B. Determine the heat transferred to the air for the segmented channel.

(c) Compare the pressure drops for cases A and B.

Transcribed Image Text:

Air, T= 25°C Mold, T = 50°C- Case A Case B