Experimental investigation of condensation heat transfer on chlorotriethylsilane coated grooved vertical tube

The role of surface modification technology in augmenting condensation heat transfer from surfaces had been recently of significant interest due its application in various industrial systems. In this work, steam condensation test was conducted to estimate the heat transfer characteristics of bare vertical copper tube, helically grooved vertical copper tube with and without coating. The pitch helical grooves were varied by 3.17 mm, 4.35 mm, 6.35 mm each with depth 0.4 mm and the bare, grooved copper tube coated with chlorotriethylsilane of thickness 150 mu m. Experiments were conducted by varying the degree of sub-cooling from 3.8 degrees C <= Delta T <= 28.5 degrees C. Results showed that helically grooved copper tube outperformed bare copper tube for the range of sub-cooling. Among the grooved copper tubes, tube with pitch of 6.35 mm showed an enhancement in condensation heat transfer coefficient up to 37.1% compared to the bare copper tube at a degree of sub-cooling Delta T = 28 degrees C. Furthermore, coating the grooved copper tube of pitch 6.35 mm chlorotriethylsilane reported a heat transfer improvement of 67.7% at a degree of sub-cooling Delta T = 28 degrees C compared to bare copper. However at low degree of sub-cooling (Delta T <= 17 degrees C) even though similar trend was observed it cannot be quantified due to the large experimental uncertainties.