The sketch shows a gas-fired radiant tube of the single- ended recuperative (SER) type. A mixture of air and natural gas is injected at the left end of the central tube, and combustion is essentially complete while the gases are still in the inner tube. The products of combustion are exhausted through the annulus. Thermocouple measurements at a particular axial location indicate an inner tube wall temperature of 1200 K and a gas temperature of 1050 K in the annulus. The radiant tube is located in a furnace, the walls of which are 950 K, and the furnace atmosphere is quiescent and also at 950 K. The thin-walled tubes are made of silicon carbide with an emissivity of 0.6. The gas mass flow rate is 0.13 kg/s. and the gas pres- sure is 101.5kPa. Calculate the temperature of the outer tube at the axial location where thermocouple measurements are being made. Assume the gas to be radiative nonparticipating and to have the following thermo physical properties: p = 0.32 kg/m³, v = 130 X 10^-6 m²/s, k = 70 X 10^-3 W/m ? K, and Pr = 0.72.

Transcribed Image Text:

T 1050 K T- 1200 K TD, - 0.20 m D=0.10m Air and natural gas Flame