Abstract

Accurate quantification of local heat transfer coefficient is imperative for design and development of heat exchangers for high heat flux dissipation applications. Liquid crystal and infrared thermography are typically employed to measure detailed surface temperatures, where local heat transfer coefficient (HTC) values are calculated by employing suitable conduction models, e.g. one-dimensional semi-infinite conduction model, where a test surface with low thermal conductivity and low thermal diffusivity (e.g. acrylic) is used. The assumption of one-dimensional heat conduction, often times lead to significant errors in HTC determination and this error depends on the true HTC, nature of wall temperature evolution with time and the local HTC gradient. Prior studies have identified this problem and quantified the associated errors in HTC determination for some representative cooling concepts, by accounting for lateral heat diffusion. In this paper, we have presented a procedure for solution of three-dimensional transient conduction equation using alternating direction implicit (ADI) method and an error minimization routine to find accurate heat transfer coefficients at relatively lower computational cost. Representative cases of a single jet and an array jet impingement under maximum crossflow condition has been considered here, for Infrared and Liquid crystal thermography respectively. Results indicate that the globally averaged HTC obtained using the 3D model was consistently higher than the conventional 1D model by 7-14%, with deviation levels reaching as high as 20% near the stagnation region. Proposed methodology was computationally efficient and is recommended for studies aimed towards local HTC determination.

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