Performance of a solar air heater incorporating thermal storage

[摘要] ENGLISH ABSTRACT:In the present study, research was conducted to determine thefeasibility of water energy storage through which the output ofheated air by an upward facing solar air heater could be prolonged.Following a systematic approach, a number of experimental testswere initially performed on an upward facing solar air heater inorder to obtain a benchmark that could be used to evaluate theinfluence of water storage during the day-time performance of asolar air heater. As expected, an increase in the air mass flow ratenot only led to an increase in the collector efficiency but also to adecrease in the temperature gain across the collector. In addition,a number of day- and night-time experiments were executed on aplastic covered water tank in order to evaluate it's ability to storeand discharge thermal energy. Results clearly indicated that theplastic covered water tank was both an ideal collector and storagemedium of solar energy. Experimental results also revealed thatthe plastic covered water tank was an ideal source of thermalenergy for a solar air heater during night-time operation.Subsequently, both day- and night-time experiments wereperformed on an upward facing solar air heater in which plasticcovered water tanks were installed. Day-time experimental resultsrevealed that the modified solar air heater still had the samecollector efficiency tendency, as observed in the initial solar airheater experiments, but that the water energy storage led to adramatic decrease in the absorber plate temperature and in thecorresponding temperature gain experienced across the collector.In contrast, the night-time operation results clearly indicated thatthe water energy storage was not only able to prolong the output ofheated air by the solar air heater, but was further able to increasethe air temperature by between 7.5 and 1.5 °e, depending on theair mass flow rate. It was furthermore shown in the study thatavailable theory is able to accurately predict the performance of anupward facing solar air heater, either with or without water energystorage, as long as the equations are employed within their rangeof validity

[发布机构] Stellenbosch University