Pool Boiling of Novec-649 on Inclined Microchannel

Abstract

Significant amounts of heat flow can be removed with small temperature differences by boiling. This process is used in a variety of industries, e.g., cooling electronics, digital circuits, power sources, etc. Heat dissipation from equipment that generates significant heat flows involves the movement of thermal energy through a wall into a cooling fluid. In the present study, this mechanism was analysed during the boiling of Novec-649 fluid at atmospheric pressure. The heat transfer surfaces were samples made of copper with milled, parallel grooves with a depth of 0.3 mm and a width ranging from 0.2 to 0.5 mm in 0.1 mm increments for straight channels and channels inclined with respect to the vertical by 30° and 60°, respectively. The study was carried out from the onset of nucleate boiling, approximately q = 7 kWm−2 with a heat flux increase until the critical heat flux was reached. The maximum heat flux was 262 kWm−2 and the heat transfer coefficient was 19.4 kWm−2K−1, achieved for surfaces with straight microchannels. A maximum heat flux increased by 80% and a heat transfer coefficient twice as high compared to a smooth surface was obtained. The performance of the experiment can be deemed adequate, considering that it compares well with the correlation results of different authors.

Enhanced Nucleate Boiling of Novec 649 on Thin Metal Foils Via Laser-Induced Periodic Surface Structures

“…Lastly, we can observe with treated and untreaded samples that Novec 649 produces steep boiling curve where the superheat practically does not change with increasing heat flux. This in accordance with results (only for non-polished samples) by other authors [35,[69][70][71][72] for low-heat-flux operation up to 100 kW/m 2 . Dielectric fluids in general produce significantly smaller bubbles in comparison to water and it can be postulated that any increase in heat flux (up to a certain value) results in activation of additional nucleation sites, thus maintaining the average surface temperature relatively constant.…”

Experimental Study on the Effect of Microchannel Spacing and Fractal Angle on Bubble Growth Behavior

“…In the pool boiling experiments conducted by Ji Hoon Kim et al [6], an astonishing 473% enhancement in CHF was achieved when a mixture of alumina particles (Al 2 O 3 ) and reduced graphene oxide (RGO) colloid particles were combined in a certain proportion, compared to pure water as the working fluid. Other researchers also conducted pool boiling experiments using different nanofluids as the working fluid [7][8][9], and they found that CHF was enhanced compared to water in all cases; Lian Duan et al [10] discovered a significant improvement in CHF when comparing surfaces with microstructures to smooth surfaces. Other studies also showed that surface microstructures can significantly enhance boiling heat transfer performance [11,12].…”