This paper contributes to the field of improving the performance of heat exchangers using metal foam (MF) full-filled and partially/periodically-filled within the gap between the two pipes. The effect of configuration and arrangement of copper MF (15PPI and porosity of 0.95) installed on the outer surface of the inner pipe of a counter-flow double-pipe heat exchanger on the thermal and hydraulic performance was studied experimentally. The test section consisted of concentric two pipes; the inner pipe which was made of copper while the outer pipe was a Polyvinyl chlo-ride. Air was used as a working fluid in both hot and cold sides. A wide cold air flow rate range was covered from 3 to 36 m3/h which corresponds to Reynolds number (Re) range from 2811 to 31,335. The hot air flow rate was kept constant at 3m3/h. The temperature difference (ΔT) be-tween the inlet hot air and inlet cold air was adopted to be (20°C, 30°C, 40°C, and 50°C). The re-sults revealed that the higher Nusselt number (Nu) was at ΔT= 50°C and the thermal performance of the heat exchanger with the MF for all the arrangements was greater than the smooth heat exchanger. The highest and lowest friction factor was 1.033 and 0.0833 for the case 1 and 8, re-spectively, and the optimal performance evaluation criteria (PEC) was 1.62 for case 7 at Re = 2800. The Nu would be increased with a moderate increase in the friction factor by optimizing the arrangement of the MF. The two essential parameters that played an important role for in-creasing the PEC were the MF diameter and the MF arrangement along the axial length of the cold air stream.
Heat transfer through porous media has gained considerable interest in recent years due to its ability to enhance the thermal performance in various engineering applications. There are two key advantages of using porous materials. First, the effective heat dissipation surface area is larger than that of traditional solid fins, which intensifies convective heat transfer. Second, the irregular motion of fluid around the internal porous structure improves mixing, promoting greater thermal uniformity by breaking the boundary layer and generating vortices, while in contrast, there is a drop in the pressure of the working fluid. This review provides a structured overview of the developments in heat transfer within porous media, focusing on two categories of working fluids: conventional fluids and nanofluids. Each category is further classified according to the flow regime involved: natural, forced and mixed convection. For conventional fluids, porous structures demonstrate considerable improvements in Nusselt number and thermal efficiency in compact heat exchangers and flow channels. For nanofluids, enhanced thermal conductivity and the possibility of coupling with magnetic fields (MHD) show promising results, especially under forced and mixed convection conditions. The findings from this review reveal that while both conventional and nanofluid systems benefit from the use of porous media, nanofluids exhibit superior heat transfer capabilities when properly optimized. Additionally, the effectiveness of porous media strongly depends on geometric properties, porosity, flow regime, and thermal boundary conditions. This paper offers a comparative understanding of these systems and identifies potential directions for future research in advanced thermal system design.
The present paper addresses the numerical study of non-Darcy laminar forced convectionflows in a pipe partially filled with grooved metallic foam attached in the inner pipe wall,which is subjected to a constant heat flux. Computations are carried out for nine differentdimensions of grooves with different Reynolds numbers namely; (250 ≤ Re ≤ 2000) andtheir influences on the fluid flow and heat transfer are discussed. The governing and energyequations are solved using the finite volume method (FVM) with temperature-dependentwater properties. The novelty of this work is developing of a new design for the metallicfoam, which has not studied previously yet. It is observed that the two helical grooves withtwo pitches increase the Nu around 5.23% and decrease the pumping power nearly 12%. Itis also showed a reduction in the amount of material required for manufacturing the heatexchanger, which leads to a decline in the weight of the system 8.29%.