Experimental and machine learning investigation of a solar air heater with a novel compact thermal absorber design

Abstract

This study presents the development and evaluation of a novel and sustainable solar air heater (SAH) incorporating an enhanced compact heat-absorbing structure made from recycled aluminum radiator fins, designed to improve thermal and exergetic-performance while promoting material-reuse and sustainability. The reuse of waste radiator materials provides a multilayered-fin configuration that increases the effective heat-transfer surface area, enhances turbulence, and reduces overall heat loss without additional manufacturing cost. A comparative methodology was employed to assess the influence of this compact thermal-storage element on SAH performance under typical Autumn and Spring conditions. The baseline and modified SAH models were evaluated using dimensionless performance parameters and validated through experimental testing. The average thermal-efficiency of the baseline system was 64.81 %, while the compact heat-exchanger-integrated system reached 78.54 %, indicating a significant improvement of about 13.7 percentage points (21 % relative increase). Furthermore, the oriented-configuration (ochxSAH) provided an additional 3.23 percentage points improvement, corresponding to a further 4 % performance gain. The heat loss rate for chxSAH increase 5.9 % that accompanied a much larger rise in useful heat-gain, confirming improved energy utilization efficiency. These gains were achieved through the improved energy-saving capacity of the recycled radiator-based absorber and its ability to maintain higher outlet temperatures. To complement the experimental study, a machine-learning (ML) approach was applied to predict SAH efficiency. The ML results validated the superior thermal and exergy performance of the sustainable SAH design, demonstrating that integrating waste-material-based compact heat exchangers can enhance system efficiency while supporting circular-economy principles in solar-thermal technologies.