Porosity effect on thermal and fluid dynamic behaviors of a compact heat exchanger in aluminum foam

摘要

Metal foams are a relatively recent categoiy of materials used in dijferent applications, such as: compact heat sinks, geothermal operations, heat exchanger and solar thermal plants. The use of metal foams in heat exchangers gives it efficiency, compact and light for the open porosity, a high thermal conductivity and a large accessible surface area per unit volume. A numerical study has been conducted to evaluate the thermal and fluid dynamic behaviors of a tubular aluminum foam heat exchanger. The thermal non-equilibrium energy condition is considered to execute two-dimensional simulations on metal foam heat exchanger. The examined foams are characterized by distinct porosity, from 0.90 to about 0.97, for different values of pores per inch, equal to 5, 10, 20 and 40. Dijferent airflow rates and an assigned surface tube temperature are imposed. The results are given in terms of heat transfer coefficient and local Nusselt number evaluated on the external surface of the tube. Typical global parameters in a compact heat exchanger, such as effectiveness and NTV, are showed. Moreover, local air temperature and velocity profiles are presented in the cross section, between two consecutive tubes. Finally, the Energy Performance Ratio (EPR) is showed in order to demonstrate the effectiveness of the metal foams.