A Numerical Simulation Study to Improve Heat Transfer Rate in a Double Pipe Heat Exchanger using Different ways.

Abstract

In this work the thermo hydraulic performance of double pipe heat exchanger made of stainless-steel with inner and outer diameters are (11.43 and 16.83cm) respectively, 0.305cm thickness and150cm length, studied numerically by using Solid Works 2016 package. It is used to the purpose of preheat heavy fuel oil flow in the outer pipe by hot air flow inside the inner one. Helical tape with different pitches (11, 14, and 17) cm the inner side of the inner tube and helical fin with different fin spaces (10, 20, and 30) cm over the inner tube are used as an enhancement heat transfer device. The study was conducted with specific identifiers, Reynold’s number (Re) values are (31668, 47361, 63008, 78589) for air side (inner tube), oil inlet temperature is (313) K and flow with rate of oil (0.1 and 0.06 kg/s). The results were first verified by using both the inner helical tape and outer helical fin separately and comparing the results of them with the plain tube, and then combining each of the helical tape and helical fin together and indicating the improvement in heat transfer rate, the result show that the maximum heat transfer is (4559.726 W) obtained by merged the helical tape with smaller pitch (11 cm) and helical fin with low fin pitch (10 cm) at oil flow rate (0.1 kg/s) as compared with (2052.385W) for plain tube, the maximum enhancement percentage in heat transfer rate and overall heat transfer coefficient were is (122.167 % and 142.941%) at the same conditions. The maximum enhancement in Nusselt number (Nu) and convection heat transfer coefficient were (224.572 % and 129.523 % W/m2. K) respectively were achieved by using helical tape with pitch (11 cm). At higher Reynolds number, the higher-pressure drop for air side is (7437.8 pa) obtained when using minimum pitch for helical tape and it is (1086.26 pa) for oil side by using helical fin with pitch (10 cm).