PRESSURE DROP AND HEAT TRANSFER IN SPIRALLY CORRUGATED TUBE FOR A COUNTER-FLOW HEAT EXCHANGER

This research studied heat transfer enhancement of a counter-flow heat exchanger by replacing a smooth inner tube with a spirally corrugated tube inside the heat exchanger. Results are obtained from the computational fluid dynamics (CFD) program. Performance of heat exchanger can be enhanced by increasing heat transfer area and increasing the turbulent intensity of fluid flow. A three-dimensional, steady, forced turbulent, and convectional flow model of fluid were developed in this research, water flowing inside smaller tube with an inner diameter of 20 mm., oil flowing in the annulus with the outer diameter of 76 mm., and domain length of 900 mm. The flow and physical parameters of the spirally corrugated tube; the corrugated pitch (p) and Reynolds number (Re) which affect friction factor (f) and Nusselt number (Nu) of the tube were studied in order to provide equations in which, later, was used to predict solutions numerically by calculating friction factor and Nusselt number of the tube. From the numerical results, we found that the friction factor depended on the corrugated pitch and Re as shown in the equation; f -0.0091Re +0.0715, and f= (3x10(-5)) p(3)- 0.002p(2)-0.004 p(2)-0.0043. However, the Nusselt number is expressed numerically as Nu. 89.93Re. 3.4578, and f=-1.5674p(3)-20.217p(2)- 84.042 p(2)+ 232.34. This simulation is valid for following ranges; 10000<Re<40000 and the pitch distances between 20 mm. and 120 mm.