Based on finite volume method, the pressure drop and heat transfer characteristics of one smooth tube and ten different axisymmetric corrugated tubes, including two with uniform corrugation and eight with non-uniform ...Based on finite volume method, the pressure drop and heat transfer characteristics of one smooth tube and ten different axisymmetric corrugated tubes, including two with uniform corrugation and eight with non-uniform corrugation, have been studied. A physical model of the corrugated tube was built, then the numerical simulation of the model was carried out and the numerical simulation results were compared with the empirical formula.The results show that: the friction factor decreases with the increase of Reynolds number ranging from 6000 to 57000, the value of which in the corrugated tubes with non-uniform corrugation(tube 03–10) are smaller than those with uniform corrugation(tube 01–02). The geometry parameters of tube(01) have advantages on the heat transfer enhancement in low Reynolds number flow region(from 6000 to 13000) and tube(07–08)have advantages on the heat transfer enhancement in high Reynolds number flow region(from 13000 to 57000). The vortex, existed in each area between two adjacent corrugations called second flow region, is the root of the enhancement on heat transfer in the corrugated tubes. The effectiveness factor decreases with the increasing of Reynolds number and the performances of the corrugated tubes with pitch of 12.5 mm have advantages than these of 10 mm under the same corrugation geometric parameter.展开更多
In recent years, with the acceleration of urbanization, medium-sized cities face increasingly severe, fog and haze increase, the heavy air pollution concentration, which caused acute health problems such as irritation...In recent years, with the acceleration of urbanization, medium-sized cities face increasingly severe, fog and haze increase, the heavy air pollution concentration, which caused acute health problems such as irritation and cardiovascular diseases caused widespread concern in the community. Most scholars believe that the haze is toxic and harmful gases; particulate matter and other pollutants together lead to reduced visibility as the main manifestation of the phenomenon of air pollution. Population health effects caused by the haze have been proven in many studies. The system summarizes the polluting haze weather physicochemical characteristics, introduced widely accepted definition of haze, haze hazard to residents and the proposed requirements.展开更多
文摘Based on finite volume method, the pressure drop and heat transfer characteristics of one smooth tube and ten different axisymmetric corrugated tubes, including two with uniform corrugation and eight with non-uniform corrugation, have been studied. A physical model of the corrugated tube was built, then the numerical simulation of the model was carried out and the numerical simulation results were compared with the empirical formula.The results show that: the friction factor decreases with the increase of Reynolds number ranging from 6000 to 57000, the value of which in the corrugated tubes with non-uniform corrugation(tube 03–10) are smaller than those with uniform corrugation(tube 01–02). The geometry parameters of tube(01) have advantages on the heat transfer enhancement in low Reynolds number flow region(from 6000 to 13000) and tube(07–08)have advantages on the heat transfer enhancement in high Reynolds number flow region(from 13000 to 57000). The vortex, existed in each area between two adjacent corrugations called second flow region, is the root of the enhancement on heat transfer in the corrugated tubes. The effectiveness factor decreases with the increasing of Reynolds number and the performances of the corrugated tubes with pitch of 12.5 mm have advantages than these of 10 mm under the same corrugation geometric parameter.
文摘In recent years, with the acceleration of urbanization, medium-sized cities face increasingly severe, fog and haze increase, the heavy air pollution concentration, which caused acute health problems such as irritation and cardiovascular diseases caused widespread concern in the community. Most scholars believe that the haze is toxic and harmful gases; particulate matter and other pollutants together lead to reduced visibility as the main manifestation of the phenomenon of air pollution. Population health effects caused by the haze have been proven in many studies. The system summarizes the polluting haze weather physicochemical characteristics, introduced widely accepted definition of haze, haze hazard to residents and the proposed requirements.
