FLOW BOILING PRESSURE DROP IN A SINGLE MICROCHANNEL AND COMPARISON WITH CORRELATIONS

Abstract

Flow boiling pressure drop results of HFE-7100 in a single microchannel, focusing on the influence of heat flux, mass flux, and inlet pressure are presented in this paper. The microchannel, with dimensions of 0.811 mm in height, 0.753 mm in width, and 74.15 mm in length, was tested at mass fluxes ranging from 100 to 1000 kg/m²s and heat fluxes up to 204.74 kW/m², with inlet pressures varying from 1.0, 1.5 and 2 bar. Four distinct flow regimes, bubbly, slug, churn, and annular were observed. The two-phase pressure drop increased with heat flux. The effect of mass flux depended on the heat flux applied and prevailing flow pattern. At low heat fluxes increasing mass flux resulted in a reduction in the pressure drop, while it resulted in an increase in pressure drop at subsequent high values of heat flux. The pressure drop was higher at lower system pressures (channel inlet pressure) with the pressure drop. The experimental data were compared to existing pressure drop correlations, highlighting the strong performance of the homogeneous flow model and revealing discrepancies with other models.