Evaluation of a Direct Evaporative Roof-Spray Cooling System

Abstract

Roof-Spray cooling systems are being extensively used to reduce the air-conditioning usage in industrial and commercial buildings. In buildings without air-conditioning, evaporative roof spray cooling systems help to reduce the interior temperatures. The spray cooling systems also have been found to increase roof life and decrease maintenance. The present work involved designing and installing a roof-spray cooling system- on a storage building in the Research Annex of Texas A&M University. The roof spray cooling system and the associated hardware were donated and set up on the roof by a commercial vendor. Tests were done during the summer of 1986 to compare the sprayed and unsprayed conditions on the roof surface temperatures , heat transfer through the roof, and the interior temperatures. The results showed that there was an 60 percent reduction in the heat transfer through the roof and also a reduction in inside temperatures. A numerical simulation was also developed to be able to predict the temperatures and the various heat transfer rates based on a simple energy conservation model. The model underpredicted the temperatures and the heat transfer through the roof when the roof was dry. But the results were closer to the experimental values when the heat loss due to evaporation was also included in the sprayed case.