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Research on the Entrainment of Path Material by the Granular Flow
Yunyun Fan,Fengyuan Wu,Ming Li,Li Liang 대한토목학회 2019 KSCE JOURNAL OF CIVIL ENGINEERING Vol.23 No.12
The experiment and numerical simulation were used to study the entrainment of path material by the granular flow. The effects of several factors on the entrainment were observed through the experiment. Research results show that when the granular flow passes on the loose material, the entrainment and deposition occur simultaneously. The final mass reduction in the entrainment area is a comprehensive performance of the entrainment and deposition. In general, the mass reduction in the entrainment area is directly proportional to the relative position of the source area and inversely proportional to the length of the entrainment area. The longer the entrainment area, the stronger the retarding effect on the granular flow. Within the ability of the entrainment area to support grains, the deposition mass increases as the mass of the material from the source area increases. The numerical results show that the entrainment mainly passes through three main stages. In the first stage, the shear friction and collision between grains form a limited entrainment. In the second stage, the granular flow mainly scales up the entrainment by scraping. In the last stage, the rear part of the granular flow is deposited in the formed pit due to resistance.
Heat transfer of a sustainable personal garment cooling system
Yijie Zhang,Ziyi Guo,Tao Li,Yexin Lyu,FengYuan Zou 대한기계학회 2022 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.36 No.10
This paper provides examines sustainable personal cooling systems. The impact of micro-fan configuration and inflow airspeed was tested. First, three different types of test models-a garment with side seam micro-fans, scatter-fans, and bottom-fans, was used to analyze and compare the heat transfer characteristic. Second, a new index of convective heat transfer was used to evaluate the cooling performance of these models. Third, the selected model was calculated with three different inflow properties, and the performance of efficiency and energy saving was analyzed. The results show that the bottom-fans model yields the best performance both on efficiency and cooling effect. The evaluation of thermal environment shows that the defined indexes are reliable to reflect heat transfer characteristics in the air gap. The comparison study of different airspeeds shows that the inflow air velocity should be set at a suitable range due to the view of energy saving.