Experimental Study On The Performance Of Enhancing Heat Transfer By Vortex Generators In The Rectangular Channel

In this paper, the performance of enhancing heat transfer of the rectangular diagonal inner rib pairs and triangular winglets, which were respectively designed and installed on the collector surface in the channel of SCPPVC system, was studied by experimental methods based on heat-mass transfer analogy principle and naphthalene sublimation technology. The influence rule of rib size, structure and arrangement impacted on the enhancing heat transfer performance were analyzed. The results show that:(1) When the inclination was 45°, the distance from inlet was 0.2m of inner rib pairs were arranged within the channel, the value of Nu number increased by 119%.(2) When the inclination was 45°, the distance from inlet was 0.2m of triangular winglets were staggered arranged within the channel, the value of Nu number increased by 132%.(3) By comparing the two kinds of vortex generator strengthening the heat transfer performance of SCPPVC system under the same conditions, it is concluded that: the triangular winglets is more suitable for strengthening the heat transfer performance in rectangular air channel of SCPPVC system.Although the two kinds of vortex generator could enhance the performance of heat transfer, but their ability of enhancing performance are still limited because the characteristics of SCPPVC system are slightly different from ordinary heat exchanger. Based on above results, a new type of vortex generator, which is named as truncated cylinder vortex generator, was designed based on the characteristics of SCPPVC system and the structure characteristics of vortex generator. The heat transfer area of truncated cylinder vortex generator is large, and the inclined section can effectively block the development of the boundary layer, result in enhancing heat transfer performance better. The truncated cylinder vortex generator strengthening heat transfer performance was analyzed by using combination method of numerical simulation and experimental research. The results show that:(1) The value of Nu number increased by 144% when the arrangement of truncated cylinder vortex generator within the channel as followings: the inclination was 45°, the distance from inlet was 0.2m and staggered arrangement.;(2) From the heat transfer characteristics correlations by multivariate regression. The relative rib length, the relative rib width, the relative leading edge height and the relative trailing edge height increase can enhance the effect of heat transfer, increasing the relative rib spacing would weaken the convective heat transfer because the disturbed effect of airflow was reduced can be seen from the formula;(3) The truncated cylinder vortex generator can make the value of Nu number increased by 12% compared with the triangular winglets.