Waste Crown Corks as Alternative Materials for Solar Air Heater Absorber Plates: A Preliminary Experimental Evaluation

Abstract

Flat plate solar air heaters (SAH) are suitable for low and medium temperature domestic uses, including space heating and the drying of agricultural products. Conventionally, SAH utilize flat metal absorber plates, but these suffer from low coefficients of heat transfer between the absorber and the heated air, high cost and weight (depending on the absorber material). In this study, two novel absorber configurations were developed using waste metal and plastic crown corks. These being virtually free of cost, the costs of resulting absorbers were significantly low in comparison with those of the conventional absorber plates. The absorbers were formed by bonding the crown corks to wire mesh screens for air transpiration during heating. Two identical SAH casings were constructed, and separately fitted with a conventional absorber and the crown cork absorber plates. Subsequently, simultaneous tests were performed to compare their performances under identical ambient and air flow conditions. Temperatures at various positions in the SAH were measured, alongside ambient temperatures and the prevailing insolation. Exit temperatures in the SAH with crown cork absorber plates were comparable and at times even higher than those in the conventional SAH. The maximum exit temperatures for the SAH having novel absorbers with plastic crown corks attached to the top and bottom of a wire mesh (compared with exit temperatures from convention SAH) were 53.2°C (47.5°C) and 66.2°C (51°C), respectively, whereas maximum exit temperatures for the SAH having novel absorbers with metal crown corks attached to the top and bottom of a wire mesh were 50.6°C (54.3°C) and 41.5°C (43.3°C), respectively. By utilizing waste crown corks which ordinarily are environmental nuisance, and with the acceptable performance shown, reused crown corks have been demonstrated as sustainable alternative materials for SAH absorbers.