Abstract
This paper reports an impact of selected thermal and flow parameters i.e., mass flux and inlet pressure on flow boiling heat transfer in a minichannel. Research was carried out on the experimental set up with the test section fitted with a single, rectangular and vertically oriented minichannel 1.7 mm deep. Infrared thermography was used to determine changes in the temperature on the outer side of the heated minichannel wall in the central part of the minichannel. The heated element for HFE-649 flowing in the minichannel was a thin alloy plate, made of Haynes-230. Local values of heat transfer coefficient for stationary state conditions were calculated using a simple one-dimensional method. Analysis of the results was based on experimental series obtained for the same heat flux, various mass fluxes and average inlet pressures. The experimental results are presented as the relationship between the heat transfer coefficient and the distance along the minichannel length and boiling curves. The highest local heat transfer coefficients were obtained for the lower average inlet pressure and for the highest mass flux at lower heat flux.
Highlights
Small confined spaces such as minichannels are an attractive option for two-phase cooling applications
Analysis of the experimental results for different mass fluxes indicates that: the highest heat transfer coefficient was observed at the highest mass flux (G = 616 kg∙m-2s-1) and lower heat fluxes (29 and 40 kW∙m-2, Fig. 4a,b), at the lowest mass flux (G = 209 kg∙m-2s-1), the highest local heat transfer coefficients were obtained at higher heat fluxes (55 and 71 kW∙m-2, Figs. 4c,d) in the outlet section of the minichannel
This paper presents impact of mass flux and inlet pressure carried out on the experimental set up for HFE-649 flow boiling heat transfer in a vertical minichannel 1.7 mm deep, 16 mm wide and 180 mm long
Summary
Small confined spaces such as minichannels are an attractive option for two-phase cooling applications. Konishi et al [1] studied flow boiling critical heat flux (CHF) in a rectangular channel at different mass velocities, inlet qualities and orientations relative to Earth’s gravity. Kanizawa et al [2] reported their heat transfer coefficient experiment during flow boiling of different refrigerants inside small diameter tubes at mass velocities from 49 to 2200 kg∙m-2s-1 and heat fluxes up to 185 kW∙m-2. The data were analysed and the influence of experimental parameters (mass velocity, tube diameter, heat flux, refrigerant type and saturation temperature) on the heat transfer coefficient and dryout vapor quality was identified. The heat transfer coefficient was dependent on thermal parameters of the condensation process (including saturation temperature), inner diameter of the tubular minichannel, mass flux and vapor quality. Studies on heat transfer in confined spaces as face seals were described in [27,28,29]
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