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사각채널에서 경사진 거칠기가 열전달과 유체유동에 미치는 효과
안수환(S. W. Ahn),김명호(M. H. Kim),배성택(S. T. Bae),강호근(H. K. Kang) 한국동력기계공학회 2006 한국동력기계공학회 학술대회 논문집 Vol.- No.-
Experiment and three dimensional numerical investigations of incompressible turbulent flow through square channels with one- and two-sided ribbed walls are performed to determine pressure drop and heat transfer. The CFX(version 5.7) software package is used for the computation. The ribbed walls have a 45° inclined square rib. Uniform heat flux is maintained on whole inner heat transfer channel area. The numerical results coincide with experimental data that obtained for 7,600 ≤ Re ≤ 24,900, the pitch-to-rib height ratio (p/e) of 8.0, and the rib height-to-channel hydraulic diameter ratio (e/Dh) of 0.0667. The results show that values of local heat transfer coefficient and friction factor in the channel with two-sided ribbed wall are higher than those in the channel with one-sided ribbed walls.
안수환(S. W. Ahn),김명호(M. H. Kim),배성택(S. T. Bae),강호근(H. K. Kang) 한국동력기계공학회 2006 한국동력기계공학회 학술대회 논문집 Vol.- No.-
Surface modifications like rib-roughening and displaced insert devices like the twisted tape are commonly used in applications such as compact heat exchangers and cooling systems. In this paper, regionally averaged heat transfer distributions in square channels with twisted tape inserts and with twisted tape inserts plus interrupted ribs are respectively investigated. The square ribs are arranged to follow the trace of the twisted tape and along the flow direction defined as axial interrupted ribs. Each wall of the square channel is composed of isolated aluminum sections. Regionally averaged Nusselt number and channel averaged Nusselt number in turbulent air flows are presented for Reynold numbers from 8,900 to 29,000. We have obtained the following conclusions from the experimental study: 1) The local Nusselt number in the two-sided heated case is higher than that in the four-sided heated condition. 2) In the 4 heating wall channel with twisted tape inserts, Nusselt number based on bottom wall temperature is enhanced by 1.2 - 1.6 times if adding the axial interrupted ribs on the bottom wall only. 3) The twisted tape with interrupted ribs under the two-sided heating condition produces the highest heat transfer coefficient.
김명호(M. H. Kim),배성택(S. T. Bae),안수환(S. W. Ahn) 한국동력기계공학회 2004 한국동력기계공학회 학술대회 논문집 Vol.- No.-
Repeated ribs are used on heat exchange surfaces to promote turbulence and enhance convective heat transfer. Applications include fuel rods of gas-cooled nuclear reactors, inside cavities of turbine blades, and internal surfaces pipes used in heat exchangers. Despite the great number of literature papers, only few experimental data concern detailed distributions of friction factors and heat transfer coefficients in square channels varying the number of rough walls. This issue was tackled by investigating effects of different number of ribbed walls on heat transfer and friction characteristics in square channel. The rough wall had a 45° inclined square rib. Uniform heat flux was maintained on whole inner heat transfer channel area. The heat transfer coefficient and friction factor values increased with increasing the number of rough walls.