Hydrodynamic and thermal characteristics of metal foam filled compact heat exchanger in cryogenic conditions

Thermal performance of metal foam heat exchanger in cryogenic environments was examined through experiment and computational fluid dynamics (CFD) simulation. A plate type heat exchanger with metal foam 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 data obtained through the experiment were compared with those of CFD simulations and previous correlations obtained at room temperature conditions. 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 to 20% higher than that of the previous correlations obtained at room temperature conditions. This can be explained that the hydraulic performance is not being affected by the temperature difference, while the heat transfer of the metal foam filled channel has higher Nusselt number due to lower heat conductivity of gas at a cryogenic environment.