RADIATIVE ENHANCEMENT OF TUBE-SIDE HEAT-TRANSFER

The potential of augmenting film coefficient by uniformly dispersing t hin metallic/ceramic filaments oriented longitudinally along a tube is investigated. The purpose of the rigidly held filaments is to create a participating medium from a gas otherwise transparent to thermal rad iation. The filaments absorb the thermal radiation emitted by the tube and transfer the heat convectively to the flowing gas. Wave theory sh ows that optical thickness > 10 can be achieved with 50 mum SiC filame nts at 300 cm-2 number density in a 2.54 cm diameter tube. Solution of the radiation transport equation indicates that the radiative film co efficients are a function of filament material, diameter and number de nsity, and gas and surface temperatures.