Numerical investigation of heat transfer intensification in shell and helically coiled finned tube heat exchangers and design optimization

摘要

In this work, the heat transfer intensification in shell and helically coiled tube heat exchangers via installing annular fins on the outer surface of the helical coil, has been numerically investigated. Thirteen heat exchangers were designed for this purpose. All geometrical parameters of the heat exchangers are same except, fin's number or height. All of the heat exchangers have been studied at three different shell side Reynolds number (Resh=7500, 15,000 and 30,000). In order to validation of the numerical model two method has been used. In the first method, the calculated heat transfer has been compared with the approximate method which is based on the experimental correlations for both coil and shell side Nusselt numbers and consideration of the E-NTU relations of these types of heat exchangers. In the second method, the heat transfer coefficient of the shell side has been compared with the experimental heat transfer coefficients of the previous works. An acceptable agreement has been observed in these comparisons. Furthermore, the optimum cases and some correlations have been obtained for prediction of the heat transfer coefficient of the shell side. Results indicate that, in the range of 7500≤Resh≤30,000, the heat transfer rate can increase up to 44.11%.