Abstract
Results of a numerical study of the flow structure and turbulent heat transfer in a round tube with a mounted single diaphragm with height h and some clearance c between the tube and the diaphragm. The size of the clearance between the diaphragm and the tube wall was varied within range A = c/h = 0 – 0.33. It was determined that an increase in the gap between the diaphragm and the tube wall alters the structure of the recirculation region and eliminate the stagnation zones in the region of secondary vortex. The flow regime, when the values of average heat transfer behind the diaphragm in the presence of a clearance exceed those for the attached rib, was distinguished. When increasing the gap height from A = 0 to 0.33, the thermal enhancement factor increases by 30%.
Highlights
Study of the flow structure and heat and mass transfer behind a flat obstacle and the system of such obstacles were relatively extensive since the 60s of the last century
Additional difficulties in analyzing are caused by interference of separated flows from the alternating obstacles. In this connection it is necessary to study in detail the flow structure under the simpler conditions of the flow around a single two-dimensional obstacles with varying disconnection parameter A = c/h, where c is the size of a clearance between the diaphragm and the tube wall, and h is the height of the diaphragm (Fig. 1)
Data of thermal enhancement factor for different values of tested parameter c/h are shown in clearance between the diaphragm and tube wall from 0 to 5 mm, thermal enhancement factor increases by 30%
Summary
Study of the flow structure and heat and mass transfer behind a flat obstacle and the system of such obstacles were relatively extensive since the 60s of the last century. The detailed experimental studies were carried out in [2,3], where they studied the effect of Reynolds number, obstacle sizes and relative height of the clearance on the flow structure and turbulent heat transfer in a rectangular channel with the ribbed wall. Additional difficulties in analyzing are caused by interference of separated flows from the alternating obstacles In this connection it is necessary to study in detail the flow structure under the simpler conditions of the flow around a single two-dimensional obstacles with varying disconnection parameter A = c/h, where c is the size of a clearance between the diaphragm and the tube wall, and h is the height of the diaphragm (Fig. 1). The previous studies of the authors prove that for the models, implemented in the given set, the results obtained with application of the mentioned model are the best to match the physics of the given flow type
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