Influence Of Cross Section Shape And Vortex Generators On Turbulent Flow And Heat Transfer Characteristics In Helical Channel

The tank reactor is typical equipment in the production of chemical industry, where materials happen chemically or physical reaction, accompanying exothermic or endothermic situation. In order to ensure the best technological conditions, it’s necessary to control the material temperature in a certain scope. Usually, the jacket and spirally tube act as heat transfer component. Because of dead zone in whole jacket, the heat transfer effect is poor. It’s difficult to meet the requirements of temperature control. Whereas, the spiral semicircle pipe jacket, angle steel jacket, jacket with spiral guide plate and spiral coils etc meet the needs. Duo to the fluid helical channel, there is little dead fluid zone and a secondary flow caused by centrifugal force occurs, which is supposed to reduce the thickness of boundary layer, thus strengthening heat transfer.Firstly, in order to explore the optimal form of spiral jacketed structure, this paper investigates the influence of cross section shapes on turbulent flow characteristics in six different helical channels. The results showed that cross section shape influence the fluid flow characteristic. In the condition of the same cross-section area, pressure loss of circle helical channel is the minimal, but triangular helical channel is the maximum. Besides four vortexes structures are found in rectangular helical channel, the rest channels are two vortexes structures. The vorticity analysis show that the value of triangular channel is the largest and square channel is the smallest.Secondly, the heat transfer characteristics of semi-circle, rectangular and triangle helical channel were studied under the condition of equal cross-section area and the heating area. The results show that the semicircle spiral channel has the best heat transfer characteristics and comprehensive performance. Moreover, field synergy analysis show that the fluid velocity field and temperature field of semicircle section helical channel coordinates better, which indicates that semicircle helical channel is beneficial to heat transfer. Entropy theory analysis show that the irreversible loss of semicircle helical channel is smaller.Then, the paper studied the influence of vortex generator to semicircle spiral channel, investigated the influence of hemisphere vortex generators’ size and arrangement to flow and heat transfer characteristic and compared the effect of strengthening heat transfer by hemisphere, cylindrical and conical vortex generator. Whereas, the comprehensive performance evaluation factor PEC values are less than one, indicating that the value of flow resistance added greater than heat transfer under turbulent state. Therefore, it’s unfavorable to use these three kinds of vortex generators to improve the comprehensive heat transfer performance of semicircle helical channel in turbulent flow condition.