Abstract
The paper presents the results of flow boiling heat transfer in a minichannel 1.0 mm deep and 40 mm wide, vertically oriented. The heating element for the working fluid (FC-72) that flows along the vertical minichannel is thin, single-sided enhanced alloy foil. In the selected area or on the entire enhanced side of the heating foil mini-reentrant cavities distributed unevenly were formed. Liquid crystal thermography has been used for measuring the two-dimensional temperature distribution on the plain side of the heating foil. Simultaneously, the observations of the flow structures have been carried out on the enhanced side of the heating foil contacting fluid in a minichannel. The results are presented as void fraction dependence along the minichannel length for the selected cross-sections. Exemplary boiling curves obtained from initial increasing and subsequent decreasing the heat flux supplied to the foil are also presented.
Highlights
IntroductionAn increasing number of high-tech heat exchange devices use heat transfer for cooling liquids flowing in narrow spaces, such as gaps, mini- and microchannels diversified in geometrical terms
Abbreviations A Cross section area, m2 BI Boiling incipience G Mass flux, kg/(m2s) hue Component of the system HSI p Pressure, N/m2 qV Volumetric heat flux, W/m3 qw Heat flux density, W/m2 T Temperature, K U Velocity, m/s V Volume, m3In recent years, an increasing number of high-tech heat exchange devices use heat transfer for cooling liquids flowing in narrow spaces, such as gaps, mini- and microchannels diversified in geometrical terms
The results of experimental research provide design information for cooling systems furnished with minichannel devices and can be applied in cooling, thermostabilization and thermoregulation of devices with high heat flux, especially for heat exchangers and electronic devices equipped with microscale cooling systems
Summary
An increasing number of high-tech heat exchange devices use heat transfer for cooling liquids flowing in narrow spaces, such as gaps, mini- and microchannels diversified in geometrical terms. They could be used in advanced electronic devices, nuclear reactors, water-cooled gas turbines, internal combustion engines, X-ray sources and certain components of particle accelerators. Extensive efforts have been aimed at understanding boiling phenomena in such mini spaces. These efforts include theoretical analyses and models, direct experimental measurements and observations, empirical correlations, etc. The studies concentrating on enhanced structure systems attract attention due to their use in their theoretical enhancement potential for heat transfer
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