Numerical Simulation Prediction Of Heat Transfer Of Natural Convection From Open-ended Inclined Channels Formed By An Array Of Slats Of Shutter

This paper presents a numerical prediction of natural convection heat-transfer from inclined channels formed by slates of shutter with variable fluid-property in refrigerating engineering. The inclined angles and curvatures of slates and the end effect of natural convection channels have been considerated carefully.(1) Results for slates of shutter simulated in two-dimensional space.1) The effect of variable fluid-property is initial to influence the air mass fluxes of channels formed by inclined-plate slates with 45 degree when the quantity of slates is eight. The Numerical study shows that the influence of variable fluid-property can not beignored.2) The smaller the inclination angle of plate slates becomes, the larger the total average Nusselt number of slates and the ratio of radiation heat-transfer rate to total heat-transfer rate become. It can enhance the natural convection heat-transfer of slates to decrease the inclination angle.3) The total average Nusselt number and the ratio of radiation heat-transfer rate to total heat-transfer rate are increased with the increase of curvature of inclined arc slates of shutter. Exceeding a certain value of curvature, the natural convection heat-transfer of arc slates is better than inclined-plate slates with 45degree.4) The spacing of slate tip to a isothermal wall has influence on heat-transfer of slates as the inclined-plate slates of shutter get closer to the isothermal wall. The natural convection heat-transfer of slates is enhanced with an increase of the spacing.5) The numerical study shows that radiative convective heat-transfer are of the same magnitude for either the inclined-plate slates of shutter or the arc inclined slates of shutter in refrigerating engineering. The radiative heat-transfer can not be ignored.(2) Results for inclined-plate slates of shutter simulated in three-dimensional space.1) The end effect of natural convection channel flow becomes more strongly as the length of channel becomes shorter and becomes more strongly as the increase of temperature difference between slates and environment. Under the same numerical condition, the end effect is weaker from the bottom channel to the top channel.2) Whether two lateral gaps are closed or not, the total average Nusselt number is decreased and the ratio of radiation heat-transfer rate to total heat-transfer rate is increased as the length of channel becomes longer.3) The natural convention channel flow is mainly influenced by the end effect for unclosed two lateral edge gaps and is mainly influenced by chimney effect for closed two lateral edge gaps. The total average Nusselt number for unclosed two lateral edge gaps is higher than for closed two lateral edge gaps. So, the end effect is more strongly than the chimney effect to enhance the natural convection heat-transfer of slates of shutter.(3) The ratio of radiative heat-transfer rate to total heat-transfer rate for two-dimensional space is a little lager than for three-dimensional space. However, the radiative and convective heat-transfer are of the same magnitude in refrigerating engineering. The radiative heat transfer can not be ignored.