Verification of heat transfer enhancement in tube with spiral corrugation

Abstract

Demand of high performance heat exchanger in industrial application is increasing since the depletion of energy resources such as in food processing plant, air-conditioning system and power plant. One of the ways of saving energy is by enhancing heat transfer performance, which in return will give a high performance heat exchanger. Existing enhancing techniques can be classified into three different categories which are active method, passive method and compound method. Spirally corrugated tube is one of the passive heat transfer enhancement method which involve surface extensions. The type of surface extension used in heat transfer performance will contribute to heat transfer coefficient and pressure drop, and directly affected the heat transfer performance. Traditionally, experimental studies were carried out to get the desired results but with the help of technology, numerical simulation is one of the promising alternatives in predicting reliable results for real application. For reliable numerical results, experimental studies are still necessary for the validation process and the verification process which comes before it is also mandatory. Thus, this paper focus on verification the numerical simulation of flow in a double-pipe heat exchanger with spirally corrugated internal tube. It was done for laminar flow with Reynolds number of 1000. Numerical simulation model using commercial CFD software were run with different mesh sizes to determine the grid independent solution and to choose which mesh is suitable to use for the whole simulation process. Minimizing and choosing the right mesh were done through Grid Convergence Index (GCI). Solutions of three different grids with their residuals convergence are also presented to fulfil the verification steps. The level of grid independence is evaluated using a form of Richardson extrapolation and the study shows that the finest grid solution has a GCI of less than 5%.