Pool boiling from enhanced structures under confinement

A study of pool boiling of a dielectric liquid (PF 5060) from single-layered enhanced structures was conducted. The parameters investigated were the heat flux and structure geometry (overall length, width and pitch of the microchannels). The boiling performance of the enhanced structures improves with increase in channel width and decrease in channel pitch. Simple multi-line curve fits are provided as empirical predictive correlations for the nucleate boiling regime.; The influence of confinement on the thermal performance of the enhanced structures was assessed by varying (0 mm--13 mm) the top gap S between top surface of the structure and a confining plate. High-speed visualization was used for precise observation of the boiling phenomena. For the total confinement (S = 0 mm), the heat transfer performance depends weakly on the channel width. For S >0 mm, the maximum heat flux for a prescribed surface temperature (85°C) increased with the increase in S . Two characteristic regimes of pool boiling have been identified and characterized: isolated flattened bubbles regime and coalesced bubbles regime.; A semi-analytical predictive model applicable to pool boiling under confinement is developed. The model assumes that the main heat transfer mechanism is the evaporation of a thin liquid film form between the top surface of the structure and the confining plate. It requires a limited number of empirical constants and is capable of predicting the experimental heat flux within 30%.