NUMERICAL STUDY OF RELATIONSHIP OF HEAT TRANSFER INTENSITY AND ABSOLUTE VORTEX FLUX INTENSITY OF FLAT TUBE BANK FIN WITH VORTEX GENERATORS MOUNTED ON BOTH SURFACES OF FIN

摘要

Tube bank fin heat exchangers are employed in a wide variety of engineering applications. If vortex generators (VGs) are mounted on fin surface, heat transfer can be enhanced. It is known that with increasing of height of VGs mounted on one surface of fin, the pressure losing increased at the same time. It is clear that we cannot use VGs with very large height. Recently, a new fin pattern with vortex generators mounted on both surfaces of the fin is studied by authors of this paper, such fin pattern can enhance heat transfer, and can reduce pressure loss at the same time compared with the same configuration heat exchangers with VGs of large height which are mounted on only one surface of the fin. Until now it is not clear that why the second flow generated by VGs can enhance heat transfer efficiently, even the height of VG is small. We have found that absolute vortex flux along the main flow can describe the second flow intensity and corresponds to the heat transfer enhancement in span wise direction average. In order to verify this statement we carried out the investigations reported here. The main aim of this paper is to study the relationship of heat transfer characteristics with the absolute vortex flux in main flow direction of flat tube bank fin with VGs mounted on both sides of the fin. For the configuration studied in this paper, results show that there has a similar distribution curve for absolute vortex flux in main flow direction compared with that for span averaged Nusselt number. The conformance of Nu and Γ shows that Γ can be not only not only can be effectually defined to describe the flow second flow intensity, but also can reflect the intensity of heat transfer.