Abstract
Experimental nucleate pool boiling data were collected for structures in the form of extended surfaces sintered with perforated foil. The article describes experimental investigations for two kinds of surfaces: smooth and mini-fins with sintered perforated foil (MFP). The MFP surfaces were manufactured out of perforated copper foil (pore diameters: 0.05 – 0.3 mm) sintered with the mini-fins, uniformly spaced on the base surface.The experiments were carried out at atmospheric pressure for four kinds of the fluids: water, ethanol, FC-72 and Novec 649. The results for these working fluids were compared in terms of the Bond number and other dimensionless parameters. For all working fluids, the heat transfer coefficients obtained for the MFP surfaces were from 2 to 5 times higher than those for the smooth surface.Using a regression analysis with reference to selected physical properties and several characteristic dimensions, it was possible to develop a correlation for the Nusselt number.
Highlights
Pool boiling heat transfer has generally been associated with a combination of microconvection, vapor-liquid exchange, evaporation, latent heat and transient conduction
The heat transfer coefficients obtained for the mini-fins with sintered perforated foil (MFP) surfaces were from 2 to 5 times higher than those for the smooth surface
For MFP surfaces this similarity number was calculated from the following formula dp L1·2 (1)
Summary
Pool boiling heat transfer has generally been associated with a combination of microconvection, vapor-liquid exchange, evaporation, latent heat and transient conduction. The experimental data have been obtained for seven kinds of fluids (water, ethanol, CCl4, acetone, n-hexane, R113, R141b) and for the plain surfaces without capillary structures under variable pressure. These surfaces include ordinary metal, metal with a coating and nonmetals of high thermal conductivity. The correlation in [2] has been obtained for five fluids (R-113, n-pentane, ethanol, water and R-11) boiling on the plain, low finned surfaces and on the Gewa-T surfaces at atmospheric pressure. The experiment were carried out with used refrigerants R-134a, R-236fa and R-1234ze(E) Their correlation was based on a boiling heat transfer mechanism in the near-wall region. The authors of this paper presented the effect of Bond number on boiling heat transfer coefficient and proposed their own correlation equation for the Nusselt number related to five dimensionless numbers
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