Heat transfer for flow of an absorbing, emitting and isotropically scattering medium in a gray diffuse wall duct
This study examines the interaction of conductive, convective, and radiative heat transfer for a thermally developing gas flowing through a circular duct. The gas contains absorbing and emitting nongray gases and soot, and absorbing, emitting and isotropically scattering gray particles. Heat generation may also exist within the gas. The absorbing gases, soot, and particles have identical temperatures and velocities. The duct walls or deposit surfaces are opaque, gray, and diffusely emitting and reflecting. The radiative transfer analysis is formulated by the zone method with the weighted sum of gray gases model expressions to consider total as well as multi-dimensional aspects of radiation. Results are presented for both gray gas and non-gray gas cases. Gray gas cooling and heating cases for a prescribed wall temperature are studied for gas-temperature profiles, wall Nusselt number, and heat-exchanger effectiveness in terms of the Boltzmann number, gas conduction to radiation parameter, gas optical thickness, gas scattering albedo, and wall emittance. Non-gray gas results for wall and gas temperatures, wall heat flux, Nusselt number, and heat exchanger effectiveness are presented. Heat transfer to the wall is strongly governed by the radiation, and is reduced as wall emittance decreases, as particle scattering albedo and deposit parameter increases; it is enhanced as the gas opacity increases up to optimum value and system size increases.
- Research Organization:
- Iowa Univ., Iowa City (USA)
- OSTI ID:
- 7245577
- Country of Publication:
- United States
- Language:
- English
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