Noting from Figure 13.16 that gas emissivity can be increased by adding water vapor, it is proposed to enhance heat transfer by injecting saturated steam at 100C at the entrance of the pipe of Problem 13.133. The mass flow rate of injected steam is 50% of the mass flow rate of water vapor in the combustion products. Determine the gas radiation to the pipe wall without and with steam injection.

Data From Problem 13.133

In an industrial process, products of combustion at a temperature and pressure of 2000 K and 1 atm, respectively, flow through a long, 0.25-m-diameter pipe whose inner surface is black. The combustion gas contains CO2 and water vapor, each at a partial pressure of 0.10 atm. The gas may be assumed to have the thermophysical properties of atmospheric air and to be in fully developed flow with m = 0.25 kg/s. The pipe is cooled by passing water in cross flow over its outer surface. The upstream velocity and temperature of the water are 0.30 m/s and 300 K, respectively. Determine the pipe wall temperature and heat flux.

Transcribed Image Text:

Emissivity, Ew 0.8 0.6 0.4 0.3 0.2 0.1 0.08 0.06 0.04 0.03 0.02 0.01 0.008 0.006 300 0.015 0.02 0.01 0.007 PL = 0.005 ft-atm 600 900 0.1 0.06 0.04 0.6, 0.4 0.2 1200 1500 Gas temperature, Tg (K) 22532 20 1800 2100