OT-88-04-2 — An Experimental and Numerical Modeling of a Roof-Spray Cooling System

Roof-spray cooling systems are being extensively used to reduce the use of air conditioning in large industrial and commercial buildings. In buildings with air conditioning, on the other hand, evaporative roof-spray cooling systems help reduce the interior temperatures.

This paper describes the design and installation of a roof-spray cooling system on a large well-insulated office building. Extensive tests of the system were carried out during the summer of 1987 in order to compare the effects of the sprayed and unsprayed conditions on the surface temperatures of the roof, heat transferred through the roof, and the interior temperatures of the building. The results showed a substantial reduction in the heat transfer rates and the surface temperatures of the roof, together with a reduction in the inside temperatures.

A numerical simulation model was also developed to predict the transient variation in the temperatures and the heat transfer rates throughout a given day. Input to the model included the hourly insolation data of both the solar heat flux and the sol-air temperature values for the local geographical area.