Study On Flow Field Characteristics And Heat Transfer Performance Of Sextant Helical Baffle Heat Exchanger

Heat exchangers are widely used in chemical,pharmaceutical,energy,electric power and other industries.Among all kinds of heat exchangers,arcuate baffle heat exchangers have been widely used because of their simple manufacture and low price.However,it has problems such as flow dead zone,easy scaling and vibration.Helical baffle heat exchangers have been used more and more because of overcoming such problems.This paper adopts the method of numerical simulation,uses liquid water as the working medium,adopts the operating conditions of high temperature and high pressure,and uses three-dimensional software to establish a physical model of a sextant helical baffle heat exchanger.The influence of the helix angle,overlapped size and flow on the flow field,heat transfer and comprehensive performance of the heat exchanger.From the analysis of the numerical simulation results,it can be seen that the shell-side flow field can be divided into four stages along the axial direction.In the piping area,the flow velocity decreases,and the fluid near the inner wall also flows spirally.There is no linear flow along the axial direction.As the helix angle decreases and the overlapped size increases,the shell-side velocity increases.The temperature of the shell-side fluid gradually decreases along the axial direction,the shell-side pressure gradually decreases along the axial direction,forming a counterclockwise pressure difference on the cross section,forming a helical flow,and the heat flux density distribution of the heat exchange tube is related to the velocity distribution.Through the data analysis of the influence of the heat exchanger helix angle,overlapped size and flow rate on the performance of the heat exchanger and its variation law,the shell-side heat transfer coefficient increases with the increase of the flow rate,decreases with the increase of the helix angle,and increases with the overlapped size.The pressure drop on the shell side increases with the increase of the flow rate,decreases with the increase of the helix angle,increases with the increase of the overlapped size.The comprehensive performance parameters all decrease with the increase of the flow rate,increases with the increase of the helix angle,and decreases with the increase of the overlapped size,so the combination of a large helix angle and a small overlapped size can achieve better comprehensive performance.Based on the obtained data regression,the calculation correlations of the shell-side heat transfer coefficient and pressure drop of the hexagonal helical baffle heat exchanger are obtained,which can provide an important reference for the engineering application of the hexagonal helical baffle heat exchanger.