Air at 25C flows at 30106kg/s within 100-mm-long channels

Chapter 8, Problem 8.81

(choose chapter or problem)

Air at 25C flows at 30?10?6kg/s within 100-mm-long channels used to cool a high thermal conductivitymetal mold. Assume the flow is hydrodynamically andthermally fully developed.(a) Determine the heat transferred to the air for a circu-lar channel (D?10 mm) when the mold tempera- ture is 50C (case A).(b) Using new manufacturing methods (see Problem8.105), channels of complex cross section can bereadily fabricated within metal objects, such asmolds. Consider air flowing under the same condi-tions as in case A, except now the channel is seg-mented into six smaller triangular sections. Theflow area of case A is equal to the total flow area ofcase B. Determine the heat transferred to the air forthe segmented channel.(c) Compare the pressure drops for cases A and B.