A Critical Review on Thermo-Hydraulic Performance of Wire Screen Matrix Packed Solar Air Heaters

Abstract

Solar air heaters (SAHs) have an important role in applications such as spaceheating and industrial drying worldwide. The packing of SAH bed not onlyincreases the heat transfer area but also increases the pumping power lossesthereby limiting the thermo-hydraulic performance. In the present study,efforts have been made for a critical assessment of the literature dealingwith the impact of collector bed and operating parameters over thermal andthermo-hydraulic performance for different configurations of wire screenmatrix packed SAH. The porosity of bed and mass flow rate of the air have amajor influence on the thermo-hydraulic performance of wire screen matrixpacked SAH. It is found that the enhancement in the volumetric heat transfercoefficient due to a decrease in bed porosity is obtained at the expense ofincrease in pumping power which ultimately affects the thermo-hydraulicperformance of wire screen matrix packed SAH. In general it is observedthat porosity is an important parameter that affects the thermo-hydraulic performance. It is seen that matrix having porosity 0.937 yields thermo-hydraulic performance of 68% at mass flow rate 0.023 kg/s where as for thesame mass flow rate porosity of 0.887 results thermo-hydraulic performanceof only 42%.