The Effect Of Fins On Convection And Heat Transfer In Enclosure With Heat Source

Natural convection is widely existed in daily life and industrial production practices,such as nuclear reactor design,flat panel solar collectors,building insulation,and heat dissipation of electronic components.Among them,the natural convection in differentially heated cavity has become a research hotspot in this field due to its several industrial demands.However,at present,there are few literature reports on the cavity with a heat source and the fins attached to its hot wall to enhance or restrain heat transfer.At the same time,such problems are also urgently needed to be solved in practical engineering applications,so it has become the research goal of this paper.In this paper,ANSYS FLUENT numerical simulation software is used to compare and analyze the parameters such as flow field,temperature field,horizontal velocity and vertical velocity,turbulent viscosity,average Nusselt number of hot wall and heat source surface to investigate the effect of fin position,fin inclination angle,fin shape,heat source position,wall surface emissivity,and Rayleigh number on convection and heat transfer in the enclosed cavity.The main work of this paper is as follows:?1?The effects of thin fins and thick fins on the convection and heat transfer in the cavity when they are located at different positions of the hot wall are studied respectively.The results show that the fins have obvious effects on the convection and heat transfer in the cavity when they are in different positions on the hot wall.When the thin fins are located at H/4 position of the hot wall,the average Nusselt number of the hot wall is the largest,while the average Nusselt number of the heat source surface is the smallest.It shows that when the thin fins are at H/4 position of the hot wall,the heat transfer rates between the hot wall and the interior of cavity is the largest and the heat transfer rates between the heat source surface and the interior of cavity is the smallest.When the thin fins are located at 3H/4 position of the hot wall,the average Nusselt number of the heat source surface is maximum.However,for the thick fins,the average Nusselt number of the hot wall and the heat source surface reaches the maximum,when the thick fins are located at at the 3H/4 position of the hot wall.?2?The fin inclination angle has a significant effect on the natural convection and heat transfer in the cavity.For example,when the fin is located at H/4 position of the hot wall,changing the fin inclination angle has a significant effect on convection and heat transfer in the cavity,especially near the hot wall.When the fin inclination angle is 90⁰,the average Nusselt number of the hot wall is the largest,indicating that the heat transfer efficiency between the hot wall surface and the interior of cavity is maximum when the fin inclination angle is 90⁰.?3?The influence of the fin shape on the natural convection and heat transfer in the cavity is that when the fin is located at the 3H/4 position of the hot wall,the horizontal velocity at the half height of the cavity and the dimensionless temperature at the half width of the cavity are changed significantly owing to changing the fin shape.Among them,when the fin shape is rectangular,the average Nusselt number of the hot wall is the largest,the heat transfer efficiency of the hot wall and the interior of cavity is the highest,and the convective heat transfer ability of the hot wall surface and the air in the cavity is the strongest.?4?The influence of the position of the heat source on the bottom wall on the natural convective heat transfer in the cavity was studied.The results show that the average Nusselt number of the heat source surface always increases with the distance between the heat source and the hot wall increased.For the rectangular thin fin cavity,when the Rayleigh number is low?Ra<1.28×10⁹?,the average Nusselt number of hot wall is the largest when the heat source is located at W/4 position of the bottom wall and the average Nusselt number is the smallest when located at 3W/4 position of bottom wall.When the Rayleigh number is 1010,the average Nusselt number of the hot wall is the largest when the heat source is located at3W/4 position of bottom wall.For rectangular thick fins,at low Rayleigh number,the average Nusselt number of the hot wall is the largest when the heat source is located at W/2 position of the bottom wall,and when the Rayleigh number increases to 10¹⁰,the average Nusselt numbers the largest when the heat source is located at the 3W/4 position of bottom wall.?5?The effect of surface radiation on convection and heat transfer in the cavity.When the Rayleigh number is 1.28×10⁹,as the wall surface emissivity of the wall increases,the average Nusselt number of the hot wall and the horizontal velocity at the half height of the cavity?Y=0.5?increased,and the thermal stratification in the cavity becomes more uniform.For the thin fin located at H/4 position of the hot wall,compared to the case where the wall surface does not consider surface radiation,when the wall emissivity surface are 0.25,0.5,0.75 and 1,the average Nusselt number of the hot wall surface increases by 50.4%,107.6%,176.7%,262.4%;for the rectangular thick fin located at H/4 position of the hot wall,the average Nusselt number of the hot wall surface increases by 51.8%,109%,177.4%,262.5%respectively.?6?The influence of Rayleigh number on convection and heat transfer in the cavity is mainly manifested as that,when the Rayleigh number is low,the influence of changing the fin inclination and shape on the convection and heat transfer in the cavity is relatively small.The average Nusselt number of the hot wall and the heat source surface differs slightly.At high Rayleigh numbers,the average Nusselt number of the hot wall and the heat source surface differ greatly.