Study On The Effect Of Structures And Medium Parameters To Heat Exchanger With Helical Baflfes

In the time of heat transfer enhancement technology extensively promoted, the heatexchangers with helical baffles gets fast development, by right of its higher heat transfercoefficient, lower pressure drop, less bypass effects and prevention of flow inducedvibration, compared to the conventional heat exchangers with segmental baffles. Previousstudies focused on the experiments of shell-and-tube heat exchangers with small shelldiameter、low viscosity and big helical angle, but the shell-and-tube heat exchangers with bigshell diameter、high viscosity and small helical angle is the most frequently used exchangersin industry. So studies on heat exchangers with big shell diameter、high viscosity and smallhelical angle are particularly important.This paper studies the continuous helical baffles of shell-and-tube heat exchangers withbig shell diameter、different viscosity media(viscosity big to small order: vacuum residue,heat-conducting oil and condensate oil)by means of CFD. By changing structural parametersand process conditions, this paper investigates shell side flow behavior, heat transfer andresistance performance of shell-and-tube heat exchangers with continuous helical baffles. Themain contents are as follows:The overall model is established. Heat exchangers with segmental baffles and heatexchangers with helical baffles of helix angle of9°, the flow range of30~50kg/s, which shelldiameter is700mm, are simulated, that mainly used the comparison of helical baffleexchangers and the segmental baffle heat exchangers; Simulation of spiral angle rangeextended to5°~23°(1°intervals, a total of ten kinds of spiral angles), the shell medium atdifferent flow numerical calculation, used to study the helix angle, flow rate and mediumviscosity of the shell within the heat exchanger flow field, heat transfer performance and theperformance of resistance.Comparison the shell side pressure drop, shell side heat transfer coefficient and shell sideheat transfer coefficient per unit pressure drop of two heat exchangers on different flows. Weobtained: no matter what kind of media, under the same conditions, shell side pressure drop ofhelical baffle heat exchanger is only13%to17%of heat exchanger with the segmental baffle;heat transfer coefficient of segmental baffle heat exchanger is approximately1.3times that ofhelical baffle heat exchanger; the shell side heat transfer coefficient per unit pressure drop isabout4to5times that of the segmental baffle heat exchanger. Be seen that the comprehensiveperformance of the helical baffle heat exchanger is better than the segmental baffle heatexchanger.When spiral angel is constant, analyze the effect of flow rate on heat transferperformance and resistance properties of the continuous helical baffle heat exchanger. Weobtain: no matter what kind of media, with flow rate augmentation, heat transfer coefficientincreases and pressure drop also increases, heat transfer coefficient per unit pressure dropdecreases.When flow rate is constant, analyze the effect of spiral angel on heat transfer performance and resistance properties of the continuous helical baffle heat exchanger. Weobtain: no matter what kind of media, with the helix angle increases, the shell side heattransfer coefficient and the shell side pressure drop rapidly decreased and then leveled off, thelast is essentially the same; heat transfer coefficient per unit pressure drop in each flow arefirst a sharp rise and then declines, and reaches its maximum at19°~21°, so the best helixangle of the heat exchanger was19°~21°, and does not change with the change of the flow.At last, analyze the effect of shell medium viscosity on heat transfer performance andresistance properties of the continuous helical baffle heat exchanger. We obtain: with themedia viscosity increase, the heat transfer coefficient, shell side pressure drop and heattransfer coefficient per unit pressure drop decrease.