The horizontal single belt casting(HSBC)incorporating a single-impingement feeding system was simulated with an improved numerical model.Physical experiments were carried out on the pilot-scale caster for validation.T...The horizontal single belt casting(HSBC)incorporating a single-impingement feeding system was simulated with an improved numerical model.Physical experiments were carried out on the pilot-scale caster for validation.The results show that the meniscus turbulence neither comes from the tundish region,nor from the impingement between the melt and the moving belt.It is the moving belt that gives rise to this high turbulence region,and this region can stir the melt near the meniscus.The feeding system studied and the moving belt give rise to a buffer region,which can optimize casting parameter variations,especially melt depth changes in the tundish.The temperature change rate of the bottom surface of the strip is around 4 times faster than that of the upper surface.展开更多
As an efficient and energy-saving heat exchange technology, horizontal tube falling film evaporation has a great application prospect in refrigeration and air conditioning. The three-dimensional models of falling film...As an efficient and energy-saving heat exchange technology, horizontal tube falling film evaporation has a great application prospect in refrigeration and air conditioning. The three-dimensional models of falling film flow evaporation outside horizontal single tube and inside evaporator were established, and the accuracy of flow and heat transfer simulation process was verified by comparison. For horizontal single tube, the results showed that total heat transfer coefficient was low and increased with larger spray density and evaporation temperature. The thickness of liquid film outside tube decreased gradually with the increase of tube diameter, and the total heat transfer coefficient of small tube diameter was significantly greater than that of the large tube diameter. The total heat transfer coefficient presented an increasing trend with larger liquid distribution height and density. In addition, the fluctuation of tube axial liquid film thickness distribution decreased with larger liquid distribution density. For evaporator, the results indicated that part of liquid refrigerant was carried into the vapor outlet. The temperature of tube wall and fluid presented a gradually rising trend in vertical downward direction, while tube wall temperature within the same horizontal and transverse row had little difference. The high-temperature zone on the outer wall of heat exchange tube moved towards the inlet and gradually decreased, and the outlet temperature of water in the tube also gradually decreased with the increase of refrigerant spray density. The local heat transfer coefficient of heat exchanger tube in the vertical direction presented a downward trend which was more obvious with the smaller spray density and it was obviously higher located in the middle of upper tube row and both sides of lower tube row for horizontal tube rows.展开更多
基金financial support received from the research grant of Shandong University of Technology (4041/419099)the Natural Sciences and Engineering Research Council of Canada (NSERC)the International Advisory Board of Supporting Companies of the McGill Metals Processing Centre (MMPC).
文摘The horizontal single belt casting(HSBC)incorporating a single-impingement feeding system was simulated with an improved numerical model.Physical experiments were carried out on the pilot-scale caster for validation.The results show that the meniscus turbulence neither comes from the tundish region,nor from the impingement between the melt and the moving belt.It is the moving belt that gives rise to this high turbulence region,and this region can stir the melt near the meniscus.The feeding system studied and the moving belt give rise to a buffer region,which can optimize casting parameter variations,especially melt depth changes in the tundish.The temperature change rate of the bottom surface of the strip is around 4 times faster than that of the upper surface.
基金financially supported by National Natural Science Foundation of China (No. 52006031)international cooperation project of China Manned Space Program (6903001173)。
文摘As an efficient and energy-saving heat exchange technology, horizontal tube falling film evaporation has a great application prospect in refrigeration and air conditioning. The three-dimensional models of falling film flow evaporation outside horizontal single tube and inside evaporator were established, and the accuracy of flow and heat transfer simulation process was verified by comparison. For horizontal single tube, the results showed that total heat transfer coefficient was low and increased with larger spray density and evaporation temperature. The thickness of liquid film outside tube decreased gradually with the increase of tube diameter, and the total heat transfer coefficient of small tube diameter was significantly greater than that of the large tube diameter. The total heat transfer coefficient presented an increasing trend with larger liquid distribution height and density. In addition, the fluctuation of tube axial liquid film thickness distribution decreased with larger liquid distribution density. For evaporator, the results indicated that part of liquid refrigerant was carried into the vapor outlet. The temperature of tube wall and fluid presented a gradually rising trend in vertical downward direction, while tube wall temperature within the same horizontal and transverse row had little difference. The high-temperature zone on the outer wall of heat exchange tube moved towards the inlet and gradually decreased, and the outlet temperature of water in the tube also gradually decreased with the increase of refrigerant spray density. The local heat transfer coefficient of heat exchanger tube in the vertical direction presented a downward trend which was more obvious with the smaller spray density and it was obviously higher located in the middle of upper tube row and both sides of lower tube row for horizontal tube rows.
