Abstract
An optimization methodology for a microchannel, plate-fin heat sink suitable for the cooling of a linear parabolic trough Concentrating Photovoltaic/Thermal (CPVT) system is applied in this study. Two different microchannel configurations are considered, Fixed (FWμ) and stepwise Variable-Width (VWμ) microchannels respectively. The performance evaluation criteria comprise the thermal resistance of the heat sink and the cooling medium pressure drop through the heat sink. Initially, the effect of the geometric parameters on the heat sink thermal and hydrodynamic performance is investigated using a thermal resistance model and analytical correlations, in order to save computational time. The results of the 1-D model enable the construction of surrogate functions for the thermal resistance and the pressure drop of the heat sink, which are considered as the objective functions for the multi-objective optimization through a genetic algorithm that leads to the optimal geometric parameters. In a second step, a 3-D numerical model of fluid flow and conjugate heat transfer for the optimized FWμ heat sink is developed in order to investigate in detail the flow and thermal processes. The overall analysis demonstrates that microchannel heat sinks achieve very low values of thermal resistance and that the use of variable-width channels can significantly reduce the pressure drop of the cooling fluid. Furthermore, it is proven that the 1-D model is capable of providing a good estimate of the behavior of the heat sink.
Highlights
Microchannel heat sinks constitute an innovative cooling technology capable of dissipating high heat fluxes from confined areas
5.1 Validation The results of the developed 1-D thermal resistance model for the heat transfer and the pressure drop correlations were compared against the experimental values published by Tuckerman and Pease, who investigated the performance of a silicon microchannel heat sink of total dimensions (1 cm) x (1 cm), cooled by water with an initial temperature of 296 K
A multi-objective methodology was applied in order to optimize the geometrical parameters of two different microchannel heat sink configurations suitable for a linear Concentrating Photovoltaic/Thermal (CPVT) system
Summary
Microchannel heat sinks constitute an innovative cooling technology capable of dissipating high heat fluxes from confined areas. Tuckerman and Pease [2] were the first to introduce the concept of liquid cooling by utilizing microchannels They created three different heat sink configurations by chemically etching parallel channels onto silicon chips. Harms et al [3] conducted an analytical and experimental evaluation of laminar flow and forced convection inside a heat sink of total dimensions 2.5 cm x 2.5 cm incorporating deep microchannels with an aspect ratio (Hch/Wch) of 4.1 They pointed out that microchannels with a high aspect ratio exhibit enhanced thermal and hydrodynamic performance. Husain and Kim [13] used a full three-dimensional numerical model of a parallel microchannel heat sink, in order to produce an initial number of objective function values required for the multi-objective optimization. A three-dimensional numerical model of the optimal FW configuration is developed to further illustrate the features of the flow and temperature fields inside the heat sink
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