Experimental and numerical study on the thermal and hydraulic characteristics of porous-media heat exchangers in cryogenic conditions

Abstract

The thermal performance of a metal-foam heat exchanger in cryogenic environments was examined through an experiment and a computational fluid dynamics (CFD) simulation. A plate-type heat exchanger with metal foam inserted in the channels was designed and manufactured. The metal foam was 20-pore-per-inch nickel metal foam and brazed to stainless-steel channel plates. Nitrogen gas in cryogenic conditions was supplied to both hot and cold-side channels with a counter-flow configuration. The pressure drop was measured in a wide range of mass-flow rates of 8–48 kg/h. Heat transfer experiments were conducted while adjusting the gas temperature using heating wires in a range of mass-flow rate of 10–20 kg/h. The data obtained through the experiment were compared with those of CFD simulations and previous correlations obtained at room-temperature conditions. The CFD prediction of the pressure drop agreed well with the experimental data with less than 10 % discrepancy. Furthermore, the pressure-drop correlation models at room-temperature conditions agreed well with the experimental results in cryogenic conditions. Among the pressure-drop models, the Dietrich model showed the best agreement. CFD predicts the heat transfer well within 10 % discrepancy from the experiment. However, the heat transfer in cryogenic conditions is 15–20 % higher than that of the previous correlations obtained at room-temperature conditions. This can be explained by the hydraulic performance not being affected much by the temperature difference, while the Nusselt number of the metal-foam-filled channel has higher value due to lower thermal conductivity at a cryogenic environment.