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ISSN Online: 2377-424X

ISBN Print: 978-1-56700-421-2

International Heat Transfer Conference 15
August, 10-15, 2014, Kyoto, Japan

Experimental Study of Two Phase Flow Boiling Heat Transfer and Pressure Drop of Water in a Minitube

Get access (open in a dialog) DOI: 10.1615/IHTC15.fbl.009049
pages 2645-2653

要約

Flow boiling in minitubes is a promising heat transfer process for high heat flux devices like compact heat exchangers and cooling. However, there is still a lack of comprehensive understanding of the flow boiling mechanism in small diameter tubes and the factors affecting the fluid flow and transport processes. The present work mainly focuses on two phase heat transfer and flow boiling pressure drop in a horizontal circular minitube. The experimental test setup consists of a pump, mass flow meter, preheater, test section made of stainless steel and condenser. The test section is heated directly by DC power supply. The test section consists of horizontal stainless steel tube with an inside diameter of 1.21 mm, an effective length of 300 mm and a heated length of 260 mm subject to a uniform heat flux with water as the working fluid. The outer wall surface temperature was measured at eight locations by K type thermocouples fixed on the tube. Further, flow visualization was done at the end of the test section. The present study analyzed the heat transfer and two phase pressure drop at various values of mass flux, heat flux and inlet subcooling. The experimental results show that two phase frictional pressured drop increases with vapor quality and mass flux. This data was analyzed carefully and compared with two phase frictional pressure drop correlations including both conventional and micro\minichannel correlations in the literature. The experimental heat transfer co-efficients were also compared with existing correlations. It was found that the pressure drop and heat transfer are distinctly different from those predicted by conventional correlations and are closer to minichannel correlations available in literature. These correlations are either a modification of the homogeneous model or the separate flow model with surface tension as an additional parameter. This clearly indicates that minichannel fall in a separate category where both inertial and surface forces compete with each other without complete dominance of either unlike those in conventional and microchannels. These experiments were conducted with a high surface tension liquid (water) which clearly indicates that inertial effects are important for both momentum and thermal transport in minichannels.