Experimental investigation of heat transfer characteristics of steam generator with circular-ring turbulators

Abstract

Heat transfer has been improved by creating turbulence in the fluid flow of heat exchangers through introducing various techniques. The present study investigated the heat transfer characteristics of steam generator with circular-ring tabulators with an inclination angle of 45° and a blocked ratio (BR) of 0.20 mm. The length ratios (LR) of 25%, 50%, 75% and 100%, pitch ratios (PR) of 1.0, 2.0, 3.0 and 4.0 and water flow rates of 12, 24 and 36 l/h were studied. The heat source used waste lubricating oil as fuel to produce steam. The results showed that the heat exchanger with circular-ring inserts provided a higher steam rate than that of a smooth tube by 6.88–10.35%, vapor quality (x) by 0.21–0.92, heat transfer by 1.27–1.55 times and the thermal efficiency by 0.46–0.68 depending on the PR, LR and FR. The optimum insert ratio was LR = 50% while 75% and 100% were not significantly different. The circular-ring inserts changed the flow behavior to turbulent flow. This increased the surface area, causing boundary layer interruptions leading to more heat exchange on the tube surface.