Pool Boiling Heat Transfer From Enhanced Surfaces to Dielectric Fluids

Abstract

Pool boiling heat-transfer measurements were made using a 15.8 mm o.d. plain copper tube and three copper enhanced surfaces: a Union Carbide High Flux surface, a Hitachi Thermoexcel-E surface and a Wieland Gewa-T surface. The dielectric fluids were Freon-113 and Fluorinert FC-72, a perfluorinated organic compound manufactured to cool electronic equipment. Data were taken at atmospheric pressure, and at heat fluxes from 100 W/m2 to 200,000 W/m2. Prior to operation, each test surface was subjected to one of three aging procedures to observe the effect of surface past history upon boiling incipience. For Freon-113 the enhanced surfaces showed a two to tenfold increase in the heat-transfer coefficient when compared to a plain tube, whereas for FC-72 an increase of two to five was measured. The High Flux surface gave the best performance over the range of heat fluxes. The Gewa-T surface did not show as much of an enhancement at low fluxes as the other two surfaces, but at high fluxes its performance improved. In fact, it was the only surface tested which delayed the onset of film boiling with FC-72. The degree of superheat required to activate the enhanced surfaces was sensitive to both past history of the surface and to fluid properties.

Effects of carbon nanotube arrays on nucleate pool boiling

“…These include porous sintered coatings (Union Carbide HIGH-FLUX), re-entrant grooves (Wielanderke AG GEWA-T), and tunneled surfaces formed by bending notched fins (Hitachi, THERMOEXCEL-E). Of these three surfaces, Marto and Lepere [8] showed that only the GEWA-T surface enhanced CHF for FC-72 compared to a smooth surface. This enhancement was attributed to increased surface area and the large spacing between reentrant grooves, which resisted coalescence of vapor columns.…”

Recent Advances in Vapor Chamber Transport Characterization for High-Heat-Flux Applications

“…The most extreme example was provided by Altman et al [81], who performed testing of ultra-thin vapor chamber devices containing sintered powder wicks, and observed incipience at superheats of 20 to 70 °C. The increased incipience superheat due to reduced vapor chamber operating saturation pressure can be calculated using a nucleation parameter [82] that predicts the relative required incipience superheat based on thermophysical fluid properties. Clearly, reduced saturation pressure alone does not account for the large incipience superheat discrepancy between capillary-fed boiling in vapor chambers and pool boiling at atmospheric pressure.…”

Assessment of high-heat-flux thermal management schemes

“…Examples include those having porous surfaces (Union Carbide, HIGH-FLUX), re-entrant grooves (Wielanderke AG, GEWA-T), and surfaces formed by bending notched fins to form porous cover plates with subsurface tunnels (Hitachi, THERMOEXCEL-E). Pool boiling experiments by Bergles and Chyu [8] and Marto and Lepere [9] showed the incipience temperature drop in FC-72 was more pronounced for all these surfaces than for smooth surfaces. Efforts in recent years have been focused more on developing re-entrant cavities on a silicon substrate to prevent the incipience temperature drop [10]- [12].…”