Investigation of Flow of the Disc-and-Doughnut Baffles and 40% Cut Segmental Baffles

Abstract

Heat exchanger is usually used in manufacturing process. At present, many researchers have efforts to increase the performance of the heat exchanger with less of the cost. This research discussed about the performance of heat exchanger using 40% cut segmental baffles compared with modified double segmental baffles disc-and-doughnut type. In this study, the investigation of the computational results consisted of heat flux, velocity profile along the heat exchanger, pressure distribution and, theoretical heat transfer coefficient and heat exchanger effectiveness. The model was calculated using finite difference method forward modeling with Multiphysics Software and focuses on the performance evaluation of the small shell-and-tube heat exchanger (STHE) – laboratory type. The tubes are composed of 14 tubes with 0.583 m length, triangular 30° rotated pitch. The pipe radius of shell and tube are 0.055 m and 0.00635 m, respectively. The baffle radius of disc and doughnut are 0.055 m and 0.025 m, respectively, and the baffle radius of 40% cut segmental baffles are 0.055 m. Both types of the baffle have a distance of 0.116 m which is evenly distributed along the shell. The generalized minimal residual (GMRES) method for the fluid flow case used as an iterative method for solving some of the complex linear equations shows good performance as in reliability and validity. For the 40% cut segmental baffles, fluid flow makes a zigzag pattern, an Eddy or swirling of a fluid, and there was some back mixing of fluid stream which caused several dead zones along the shell. The occurrence of the dead zones caused the heat transfer to be ineffective and gave lower value compared to the double segmental disc-and-doughnut baffles. The 40% cut segmental baffles was also seen to have a higher pressure at the outlet region than the double segmental disc-and-doughnut baffles. The disc-and-doughnut baffles leads to a turbulent fluid flow which causes an increase in heat transfer characteristics and also lower pressure drop than the 40% cut segmental baffles. Based on the theoretical, both types of disc-and-doughnut baffles and the 40% cut segmental baffles of heat exchanger investigated have highest effectiveness at the lowest mass flow rate of the hot fluids (tube).