Flow Boiling over Tube Bundles with Combination of Plain and Coated Tubes

Abstract

The present Paper focuses on studying the effect of the number of coated tubes in a tube bundle under flow boiling heat transfer. The coated tubes are prepared by creating a porous layer of copper using plasma spraying of copper powder on stainless steel tubes. The experimental results in terms of heat transfer coefficients are presented for different configurations of tube bundles by varying the number of coated tubes. The operating parameters are heat flux (), mass flux (), and pitch-to-diameter ratio (1.25, 1.6, and 1.95). The results show that using coated tubes only in the lower portion of the horizontal tube bundle is beneficial during vertical crossflow of liquid. The performances of two rows coated, three rows coated, and all five rows coated are found to be comparable to each other. The number of rows of coated tubes that should be used for a tube bundle depends on the degree of enhancement and configuration of tube bundle. The result is useful in reducing the cost of shell and tube heat exchangers by using the optimized number of coated tubes in the tube bundle during flow boiling heat transfer.