The fire tube of a hot water heater consists of a long

Chapter 13, Problem 13.120

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The fire tube of a hot water heater consists of a long circular duct of diameter D?0.07 m and temperature Ts?385 K, through which combustion gasesflow at a temperature of Tm,g?900 K. To enhanceheat transfer from the gas to the tube, a thin partitionis inserted along the midplane of the tube. The gasesmay be assumed to have the thermophysical proper-ties of air and to be radiatively nonparticipating.(a) With no partition and a gas flow rate ofm.g?0.05 kg/s, what is the rate of heat transferper unit length, q?, to the tube?(b) For a gas flow rate of m.g?0.05 kg/s and emis-sivities of ?s??p?0.5, determine the partition temperature Tp and the total rate of heat transferq?to the tube.(c) For m.g?0.02, 0.05, and 0.08 kg/s and equiva-lent emissivities ?p??s?, compute and plotTpand q?as a function of ?for 0.1?1.0.For m.g?0.05 kg/s and equivalent emissivities,plot the convective and radiative contributionsto qa? s a function of ?.