Investigation of a falling film tube bank heat exchanger with baffle design for water recovery applications

Abstract

Shell and tube heat exchangers (STHE) are essential thermal equipment and widely used in daily life. A novel thermosyphon system called falling-film thermosyphon (FFTS) is introduced and integrated into STHE system, resulting in a better thermal performance. In this study, a rectangular solid tube bank of FFTS bundles with a baffle design is studied. The numerical simulation for heat and mass transfer of the FFTS heat exchanger is developed to predict the condensation rate of the vapor in the flue gas, and a lab-scale prototype is also built up in COMSOL. The prediction is validated with the experimental data from references, and the model's accuracy is verified within 10%-12% error. Also, the Non-dominated Sorting Genetic Algorithm, version 2 (NSGA-II) is implemented to improve the thermal performance of rectangular tube banks in this paper. Several parameters, e.g., baffle number, tube number, and tube space, are optimized. As a result, compact configurations with more baffles are preferred to enhance the performance associated with a high-pressure drop correspondingly. The optimized layout for the lab-scale prototype can increase by 18 to 32% condensation with a pressure loss of less than 200 Pa.