Development of High-performance Cooling Devices for Space Application by Using Flow Boiling in Narrow Channels

Compared with conventional channels, narrow and micro channels have significant heat transfer enhancement characteristic. With smooth internal surface, such channels can efficiently avoid encrustation at the washing of the high-speed liquid. Moreover, heat transfer elements can be easily assembled. These types of channels have been adopted extensively in many engineering applications, e.g. microelectronic cooling, advanced nuclear reactor, cryogenic, aviation and space technology and thermal engineering. Geometrical size of flow passage-away affects heat exchange of flow boiling, with the result that the bubble in narrow channel acts very different from those in non-narrow channel. This paper experimentally compared the bubble behavior with different heating methods of narrow rectangular channels, and the bubble behavior of subcooled flow boiling of R-12 in the narrow channels both with double side and single heating. Experimental settings are: the heating length of test-section is 400 mm, the cross-section is 35 mm in width and 2mm in gap size, mass flux is 700∼1500 kg.m−2.s−1, the heat flux is 25∼70kW.m−2 and the pressure is 1.3∼2.0 MPa. Comparisons were made on Onset of Nucleate Boiling (ONB) point and bubble characters with various flow patterns. Results revealed that the characteristics of double and single side heating shown good agreement with proper modifications.

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Flow Boiling of Sub-Cooled Pentane on a Micro-Porous Coating

ASME 2012 6th International Conference on Energy Sustainability, Parts A and B ◽

10.1115/es2012-91316 ◽

2012 ◽

Author(s):

Paul J. Laca ◽

Richard A. Wirtz

Keyword(s):

Heat Flux ◽

High Speed ◽

High Performance ◽

Flow Boiling ◽

High Heat ◽

Surface Coatings ◽

Porous Coating ◽

High Heat Flux ◽

Characteristic Curves ◽

High Speed Video

Flow boiling experiments with sub-cooled Isopentane and n-Pentane at 3.0bar pressure assess the utility of compressed copper- and steel-filament screen laminate surface coatings as high performance boiling surfaces. High-speed video show that at high heat flux ebullition is unsteady. Isopentane and n-Pentane are found to produce nearly identical boiling characteristic curves. At the same applied heat flux, the superheat of copper filament coatings are much smaller than the steel filament coating superheats.

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Optimal design of subcooled triangular microchannel heat sink exchangers with variable heat loads for high performance cooling

Journal of Physics Conference Series ◽

10.1088/1742-6596/2116/1/012052 ◽

2021 ◽

Vol 2116 (1) ◽

pp. 012052

Author(s):

David Olugbenga Ariyo ◽

Tunde Bello-Ochende

Keyword(s):

Heat Sink ◽

High Performance ◽

Flow Boiling ◽

High Heat ◽

Geometric Optimization ◽

Heat Fluxes ◽

Heat Sinks ◽

Subcooled Flow Boiling ◽

Subcooled Flow ◽

Microchannel Heat Sinks

Abstract Deionized water at a temperature of 25 °C was used as the cooling fluid and aluminium as the heat sink material in the geometric optimization and parameter modelling of subcooled flow boiling in horizontal equilateral triangular microchannel heat sinks. The thermal resistances of the microchannels were minimized subject to fixed volume constraints of the heat sinks and microchannels. A computational fluid dynamics (CFD) ANSYS code used for both the simulations and the optimizations was validated by the available experimental data in the literature and the agreement was good. Fixed heat fluxes between 100 and 500 W/cm2 and velocities between 0.1 and 7.0 m/s were used in the study. Despite the relatively high heat fluxes in this study, the base temperatures of the optimal microchannel heat sinks were within the acceptable operating range for modern electronics. The pumping power requirements for the optimal microchannels are low, indicating that they can be used in the cooling of electronic devices.

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Boiling Incipience in Narrow Channels

10.1115/imece2000-1506 ◽

2000 ◽

Author(s):

M. S. Lakshminarasimhan ◽

D. K. Hollingsworth ◽

Larry C. Witte

Keyword(s):

Flow Boiling ◽

Heated Surface ◽

Transition Process ◽

Nucleate Boiling ◽

Nucleation Theory ◽

Hysteresis Phenomenon ◽

Transfer Coefficients ◽

Narrow Channels ◽

Liquid Crystal Thermography ◽

Boiling Incipience

Abstract Experiments were performed to investigate nucleate flow boiling and incipience in a flow channel, 1 mm high × 20 mm wide × 357 mm long, vertical, with one wall heated uniformly and others approximately adiabatic. Subcooled R-11 flowed upward through the channel; the mass flux varied from 60 to 4586 kg/(m2s). The inlet subcooling varied from 3.0 to 15.3 °C, and the inlet pressure ranged up to 0.20 MPa. Liquid crystal thermography was used to measure distributions of surface temperature from which the heat transfer coefficients on the heated surface were calculated. Observations of the boiling incipience superheat excursion and the hysteresis phenomenon are presented and discussed. In laminar flow, a boiling front was observed that clearly separated the region cooled by single-phase convection from the region experiencing nucleate boiling. A prediction for the wall temperature and heat flux at boiling incipience based on nucleation theory compared favorably with the data. An incipience turning angle was defined to describe the transition process from the point of incipience to fully developed nucleate boiling. Fully developed saturated nucleate boiling was correlated well by Kandlikar’s technique.

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