Boiling Performance of Single-Layered Enhanced Structures

Abstract

A study of pool boiling at atmospheric pressure from single-layered enhanced structures was conducted for a dielectric fluorocarbon liquid (PF 5060). The parameters investigated in this study were: (a) Heat flux (1-45W∕cm2); (b) width of the microchannels (65-105μm); and (c) microchannel pitch (0.2-0.7mm). The boiling performance of the enhanced structures was found to increase with the increase in channel width and decrease in channel pitch. A simple single line curve fit is provided as a practical way of predicting the data over the entire nucleate boiling regime. The exponent n in the single line power curve fit was found to be between 1 and 2. The modes of boiling from an enhanced structure proposed by previous researchers were unable to explain the boiling curves obtained in this study. The present data are explained in light of the contribution from the top finned surface of the enhanced structure.

Saturation and Subcooled Boiling of HFE-7100 on Pinned Surfaces at Different Orientations

“…The reported results on saturation boiling of FC-72, HFE-7100, and other dielectric liquids on surfaces with micro-and macrostructures showed significant decreases in or elimination of the temperature excursions before boiling incipience and measurable increases in the total thermal power removed by nucleate boiling (e.g., [1,[4][5][6][7][8][9][10][11][12][13][14][15][16]18,19]). When based on the actual surface area in contact with the liquid, CHF values are lower than on a plane surface with the same footprint area.…”

“…The macrostructured surfaces investigated by various researchers had spacing between pins or fins of greater than 0.5 mm, and the microstructured surfaces had much smaller spacing. Most of the reported results for dielectric liquids on microstructured and macrostructured surfaces have been for saturation boiling in the upward-facing orientation ( 0 deg) [6,9,[11][12][13][14][15][16], except Anderson and Mudawar [7], who investigated saturation boiling in the vertical orientation, and Misale et al [8] and Wei and Honda [10], who investigated nucleate boiling in the upward-facing and vertical orientations.…”

“…To increase the removed thermal power in nucleate boiling and reduce or eliminate temperature excursion before the boiling incipience, researchers have considered increasing the surface roughness and covering the surface with a microporous coating or a microporous structure (e.g., [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19]). Numerous results have also been reported on boiling of dielectric liquids on porous and microstructured surfaces and surfaces with reentrant cavities (e.g., [1][2][3][4][5]).…”

“…Pool boiling of dielectric liquids has been investigated using surfaces with microfins; microand macrostructures; and pins of various lengths, cross sections, and densities (e.g., [6][7][8][9][10][11][12][13][14][15][16]). Microstructured surfaces are defined here as those with a length scale less than 0:5 mm, and macrostructured surfaces have a larger length scale of greater than 0:5 mm.…”

Experimental studies on the effect of the enhancemet of the heating surface on the heat transfer coefficient for boiling in closed volume

“…Piasecka, Pastuszko and Strąk [7] have performed a study on the intensification of heat exchange on the surface from microfins. The finned surfaces are additionally covered with perforated foil.…”