An experimental investigation of free convection heat transfer to carbon dioxide in the region of its critical point

[摘要] Experimental results are presented for an investigation of free convection heat transfer to carbon dioxide in the region of its critical point. Shadowgraph images of the flow patterns accompanying the heat transfer have been recorded photographically. A horizontal 0.010-inch-diameter cylindrical Nichrome wire was used as the test section for the primary investigation. Tests were conducted in carbon dioxide with pressures from 1000 psia to 1500 psia and bulk temperatures from 49.0° to 137.0°F."Bubble-like" and oscillating flow conditions were observed in the experiments conducted with the cylindrical test section. The occurrence of "bubble-like" flow conditions, along with pronounced changes in the fluid properties, resulted in significant improvementsin the heat transfer process, as compared to heat transfer resulting with laminar flow at lower heat fluxes. Additional experiments with a vertical wire and a horizontal strip indicated that the occurrence of the "bubble-like" flow depends on the shape and orientation of the heat transfer surface. The results of heat transfer with the "bubble-like" flow condition in supercritical carbon dioxide are compared with heat transfer results with" boiling at subcritical pressures.

[发布机构] University:California Institute of Technology;Department:Engineering and Applied Science

[关键词] Mechanical Engineering