Abstract
Results concerning flow boiling heat transfer in a vertical minichannel of 1.7 mm depth were shown. The channel was asymmetrically heated by a thin foil. Its surface temperature was recorded continuously in points by thermocouples. Measurements were carried out in 0.01 s intervals. The objective of the numerical calculations was to determine the heat transfer coefficient on the heated foil–fluid contact surface in the minichannel from the Robin boundary condition. Both the foil and fluid temperatures were the result of solving the nonstationary two-dimensional problem in the foil and flowing fluid. The problem was solved by using the FEM combined with Trefftz-type basis functions. The values of the time-dependent local heat transfer coefficient were presented and discussed.
Highlights
Miniaturization of devices is being progressively applied in cooling technologies designed to prevent exceeding operating temperatures
In order to estimate the intensity of heat transfer accompanying flow boiling in a mini heat exchanger device, the main experimental data are needed for the heat transfer coefficient identification: the heated wall temperature, the temperature gradient and the temperature of the fluid flowing along a minichannel
The study shows the results obtained for the subcooled boiling region and the most important concern was to the heat transfer coefficient identification
Summary
Miniaturization of devices is being progressively applied in cooling technologies designed to prevent exceeding operating temperatures. In order to estimate the intensity of heat transfer accompanying flow boiling in a mini heat exchanger device, the main experimental data are needed for the heat transfer coefficient identification: the heated wall temperature, the temperature gradient and the temperature of the fluid flowing along a minichannel. These quantities were obtained by solving the inverse problem [1] in the heated wall and in the flowing fluid. To solve the nonstationary two-dimensional problem in the flowing fluid the time-dependent Trefftz functions for the Fourier– Kirchhoff equation were determined. These functions were used to construct the nonstationary FEM basis functions
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