Circular tubes suspended in pyrolysis furnaces suffer from significant nonuniformities in heat flux, tube skin temperature, and coking rate profiles around the tube perimeter, due to the presence of front sides and shadow sides on the tubes. Simulation results for an ethane cracker with cracking tubes of elliptical cross section reveal that smoother circumferential heat flux, tube skin temperature, and coking rate profiles are obtained as the eccentricity of the elliptical tubes increases. The circumferential maximal values in coking rates are reduced by 30%. The more uniform tube skin temperature distributions and coke layers in tubes of elliptical cross section favor the run length of the furnace and the tube metal life.
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