Energy Efficient Processing Using Spray Evaporation Cooling Techniques

Abstract

Experiments have been carried out to determine heat transfer coefficients for evaporative cooling due to water jet impingement onto a continuously moving sheet of polymeric material. Operating conditions were selected so as to simulate conations encountered in industry wherever possible. The initial sheet temperature was varied between 373 and 423K. The maximum average air jet velocity was 40 m/s and the separation distance between the nozzle and the sheet surface was between 10 mm and 18 mm. The sheet velocity was kept constant during the course of the tests at 0.0025 m/s, and the temperature of the water used for the liquid spray was more or less constant at 291K. It has been found that an average heat transfer coefficient of 5000 W/m² K can be achieved for an nozzle exit Reynolds number of 30000 and for L/D, the ratio between the distance between the tip of the nozzle and the surface of the sheet, and the diameter of the air nozzle, of 13.3. Cost analysis has also been included in order to demonstrate that spray evaporation technique can be both economical and energy efficient.

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