Double Pass Solar Air Heater: A Review

Abstract

Improvement in heat transfer rate and effectiveness of a solar air heater is always a matter of concern in the scientific community. Different steps have been taken to improve it, including the application of artificial roughness, double glazing, colour coating, and multi-pass flow. In this article, a detailed assessment of the efficiency and effectiveness of a solar air heater has been conducted by applying various types of double-pass arrangements. The effects of various methods applied so far are deeply analysed and discussed to create a better understanding. Future opportunities, challenges, and concerns are also addressed, with a fruitful conclusion in the last. Keywords: Solar energy, solar air heater, double-pass, artificial roughness, thermal performance