Numerical Study On The Flow And Heat Transfer Characteristics Of Channel In Rectangular Cross Section With Triangular Vortex Generators Mounted On Three Sides

The plate fin heat exchanger is widely used in many industrial fields due to its high efficiency, high strength, light weight, small size and so on. With the continuous improvement of technology, people's demand for the heat transfer capability of the plate fin heat exchanger is obviously increased, so it is necessary to improve the heat transfer capability of the plate fin heat exchanger. At present, there are various methods used to enhance heat transfer of the plate fin heat exchanger, such as using corrugated fins to increase the transversal vortex intensity and heat transfer area, using serrated fin to cut off the boundary layer, etc. Based on the fact that secondary flow can enhance heat transfer greatly but does not increase more flow resistance, we put forward a special fin structure which is to enhance the longitudinal vortex intensity by adding triangular vortex generators on the three side walls of a channel in rectangular cross section in this paper, and thus to achieve the goal of heat transfer enhancement.This study selects a periodic domain as the computational domain. The computational domain is discretized. The triangle vortex generators are marked with the solid identification, the heat transfer characteristics of the channel in rectangular cross section with vortex generators on three side walls are obtained by using a numerical calculation method. With the Reynolds number ranging from 200 to 1000 and the Prandtl number ranging from 0.7 to 200, the variations of Nusselt number Nu and resistance coefficient f with the change of the Reynolds number, the aspect ratio of the rectangular channel, the vortex generator height, the attack angle of the vortex generator and the distance between vortex generators are analyzed in this paper by changing the position of the triangle vortex generator, and the dimension of the triangle vortex generator in the channel, respectively. Finally, the mechanism of the heat transfer enhancement is explained by the variation of the secondary flow intensity with each parameter, and the numerical results are fitted by multi parameters.The results show that the triangle vortex generators arranged in different places of rectangular cross section passage can make the fluid flow of the channel rotated when it moving forward, which improves the heat transfer performance of the channel surfaces. The triangle vortex generators can generate stronger secondary flow that increases the heat transfer capacity in large area of the wall surfaces of the channel. Nu and f decrease with the increase of the aspect ratio of the channel and the spacing between vortex generators in main flow direction, while they increase with increasing the vortex generator height at the same Reynolds number. Nu and f all increase with increasing the attack angle when it is less than 45 degrees, but Nu and f decreases with increasing the attack angle when it is more than 45 degrees. Nu increases with increasing Reynolds number but f decreases with increasing Reynolds number at the same geometric parameters. For the studied cases, the variation tendency of the secondary flow intensity with each parameter is identical with that of Nu at different Re. There is a close relationship between Nusselt number and the intensity of secondary flow, thus enhancing the intensity of secondary flow can enhance heat transfer. In addition to the geometric parameters of the channel of heat exchanger, thermal properties of fluid have different degrees of influence, and different working mediums also have significant influence on the heat transfer performance of heat exchanger. With the increase of Prandtl number Pr, heat transfer capacity of the wall increases.