Time-dependent study of boiling heat transfer coefficient in a vertical minichannel
International Journal of Numerical Methods for Heat & Fluid Flow
ISSN: 0961-5539
Article publication date: 7 June 2019
Issue publication date: 22 May 2020
Abstract
Purpose
The purpose of this paper is to determine the time-dependent heat transfer coefficient during FC-72 flow boiling in a 1.7-mm-deep vertical and asymmetrically heated minichannel.
Design/methodology/approach
The temperature of the minichannel heated wall was recorded continuously with the use of thermocouples. The heat transfer coefficients for the subcooled and saturated boiling regions at the heated wall–fluid contact surface were calculated from the Robin boundary condition. Both the wall and fluid temperatures were obtained from the solution of the inverse nonstationary problems in two adjacent domains: the heated wall and flowing fluid. The FEM with Trefftz-type basis functions was applied to solve the inverse problem.
Findings
The obtained time-dependent heat transfer coefficient in subcooled boiling achieved rather low values, whereas in saturated boiling, the coefficient was the highest at the channel inlet. The boiling curves were plotted to illustrate the results.
Practical implications
The results of experiments are the best source of information for the design of minichannel cooling systems used for thermoregulation of components and heat exchangers. High-tech minichannel heat exchangers are applied in various industrial applications as microelectronics devices, gas turbines, internal combustion engines, nuclear reactors, X-ray sources and organic rankine cycle (ORC) modules.
Originality/value
In the study, the Trefftz functions for the nonstationary Fourier–Kirchhoff equation with the factor describing void fraction were determined and then used to construct the time-dependent basis functions in FEM.
Keywords
Acknowledgements
The research reported herein was supported by a grant from the Polish National Science Centre (No. NCNM. ZKIS.18.001 0400600/2.02.03.01.0020 2018/02/X/ST8/01271).
Citation
Maciejewska, B. and Piasecka, M. (2020), "Time-dependent study of boiling heat transfer coefficient in a vertical minichannel", International Journal of Numerical Methods for Heat & Fluid Flow, Vol. 30 No. 6, pp. 2953-2969. https://doi.org/10.1108/HFF-12-2018-0781
Publisher
:Emerald Publishing Limited
Copyright © 2019, Emerald Publishing Limited