Performance evaluation of a solar air heater with staggered/longitudinal finned absorber plate integrated with aluminium sponge porous medium

Abstract

Solar air heaters are used to heat air for drying and space heating applications, however, the low heat transfer between air and absorber plate accounts for its low efficiency. In this paper, an experimental study of a staggered/longitudinal finned plate solar air heater (SLFPSAH) with a built-in aluminium sponge porous media as a sensible heat storage material is presented. The fins with the direction of airflow are arranged in a staggered manner by covering a length of 1.25 m, while the remaining 0.75 m is arranged with longitudinal fins. The parameters influencing the performance of the SLFPSAH are investigated with and without using a porous medium. These parameters include solar irradiance, the temperature difference of air through the heater, air temperature ratio, convective heat transfer coefficient, useful heat gain, daily energy efficiency, and exergy efficiency. Experiments are conducted under different air mass flow rates; namely, 0.0078, 0.01, 0.02, and 0.049 kg/s. The results revealed that the implementation of an aluminium sponge porous media over the absorber plate significantly increases the energetic and exergetic performances of the SLFPSAH. It is found that the average air temperature ratio, daily exergetic efficiency, and daily exergy efficiency of the SLFPSAH integrated aluminium sponge porous medium are about 11.52%, 3.97%, and 45.61% greater than that without the aluminium sponge porous medium, at airflow rate of 0.02, 0.049 kg/s, respectively. Moreover, the maximal increase in the convective heat transfer coefficient of the SLFPSAH integrated with aluminium sponge porous medium is more than 1.62 times that obtained with the SLFPSAH without porous media, at the same conditions. Thus, the SLFPSAH with an integrated aluminium sponge porous medium is an effective way to enhance the exergetic and energetic performances of solar air collectors for solar drying applications.