Critical heat flux enhancement in the presence of stream-wise curvature
Abstract
An experimental study was undertaken to evaluate a novel cooling concept designed to cool high power heat sources by forced convective boiling in the presence of stream-wise curvature. The critical heat flux, CHF, determines the maximum nucleate boiling heat transfer limit beyond which permanent damage to the heat source may result. Stream-wise flow curvature developed an artificial body force which propelled vapor away from the heater surface, thereby extending the nucleate boiling regime to higher heat fluxes. A parametric study was made to investigate the effects of surface curvature, heat length, system pressure, and flow velocity on CHF. Detailed flow visualization experiments conducted in linear and curved channel heaters improved the fundamental understanding of liquid-vapor exchange near the heater surface and helped to identify the trigger mechanism responsible for initiating CHF. Greater liquid contact was observed and higher CHF was measured for the curved heater surface compared to the linear heater surface at equal flow velocities. Flow visualization observations were used in conjunction with experimental measurements to develop a mechanistically based CHF model that explicitly accounted for the effects of a body force. The CHF model was based on geometrical arguments, a hydrodynamic two-phase flow model and an interfacial instability analysis. Experimental measurements taken in the linear and curved channel compared well with theoretical predictions. The primary contributions of this study are the development of a unique system designed to enhance CHF, the identification of hydrodynamic conditions necessary for triggering CHF and the verification of the stream-wise curvature enhancement effect on CHF.
Degree
Ph.D.
Advisors
Mudawar, Purdue University.
Subject Area
Mechanical engineering
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