Thermal Performance Analysis of Biporous Metal Foam Heat Sink

Abstract

The present study presents a concept of biporous metal foam heat sink applicable to electronic cooling. This heat sink has two metal foam layers arranged in parallel along the primary flow direction, with different metal foam thickness, porosity, and pore density for each layer. The forced convective heat transfer in biporous metal foam heat sink is numerically investigated by employing the Forchheimer–Brinkman extended Darcy momentum equation and local thermal nonequilibrium energy equation. The effects of geometrical and morphological parameters on thermal and hydraulic performance are discussed in detail, and the heat transfer enhancement mechanism of biporous metal foam is analyzed. The thermal performance of biporous metal foam heat sink is compared with that of uniform metal foam heat sink. The results show that the thermal resistance of the biporous metal foam heat sink decreases with decrease of top layer metal foam porosity at a fixed bottom metal foam porosity of 0.9. It is seen that the biporous metal foam heat sink can outperform the uniform metal foam heat sink with a proper selection of foam geometrical and morphological parameters, which is attributed to the presence of high velocity gradient at the boundary layer that can enhance the convective heat transfer. The best observed thermal performance of biporous metal foam heat sink is achieved by employing 30 pores per inch (PPI) metal foam at the bottom layer, with a fixed 50 PPI metal foam at the top layer for the porosities of both layers equal to 0.9, and the optimal thickness of the bottom foam layer is about 1 mm.

A Review of Thermo-Hydraulic Performance of Metal Foam and Its Application as Heat Sinks for Electronics Cooling

“…The nonuniform porous structure provides a better heat transfer performance than the uniform 15PPI heat sink, which is similar to the results for biporous metal foam heat sink presented in Ref. [95]. Broughton and Joshi [139,140] also used AM metal foams to design power electronics cold plates for eliminating the substrate/foam thermal resistance, and reported improved performance using AM metal foams over traditionally manufactured foams.…”

“…Apart from varying metal foam pore size along the flow direction, nonuniform metal foam with pore size varied vertical to the flow direction, has been studied for heat transfer enhancement under asymmetrically heated condition. These nonuniform porous structures including the gradient-porous heat sink [93], five-layer porous heat sink [94] and the bi-porous heat sink [95], can effectively force the working fluid toward the heated wall by employing large pore size metal foam adjacent to the heat source, and result in an appreciable heat transfer enhancement [93][94][95][96]. The concept of bi-porous metal foam heat sink proposed in Ref.…”

“…Based on the experimental work of Bhattacharya and Mahajan [101], De-Groot et al [102,103] numerically Fig. 14 Physical model of biporous metal foam heat sink [95] investigated the heat transfer in the finned metal foam heat sink, and investigated the effects of contact thermal resistance on the thermal performance, by using the LTNE heat transfer model for predicting the heat transfer performance. They concluded that the finned metal foam heat sink outperforms the plate-fin heat sink, and the contact thermal resistance effect on thermal performance is negligible when reasonable interface bonding material is used.…”

“…3.6 Metal Foam Heat Sink Optimization. Numerous studies have focused on the fluid flow and heat transfer characteristics of various metal foam heat sink designs, covering fully and partially filled metal foam heat sink [84], nonuniform metal foam heat sink [95], and finned metal foam heat sink [71]. It should be pointed out that these designs were not optimized, so further performance improvement in the heat dissipation rate, along with reducing pumping power consumption could be expected.…”

“…Shen et al [67] indicate that, for a given pumping power, the thermal resistance of metal foam heat sinks are lower than the traditional heat sink. Li et al [95] presented a concept of bi-porous metal foam heat sink applicable to electronic cooling. The optimum structure of bi-porous metal foam is by employing 30 PPI and 50 PPI foam at the bottom and top layer, respectively, with the optimal bottom layer foam thickness of about 1-2 mm.…”