Research On Performance And Optimization Of Hollow Circular Platform Phase Change Packaging Unit

The combination of latent heat energy storage technology and solar water heating system can effectively solve the intermittent and unstable problems of solar energy.However,at present,the thermal conductivity of phase change materials is generally low,which leads to the problem of poor thermal conductivity of phase change packaging units in water tanks.To alleviate this problem,this paper proposes a hollow circular frustum type phase change packaging unit,which uses a numerical model to simulate and analyze its heat transfer performance,and further optimization work is carried out.The middle part of the phase change unit is designed as a hollow form,which can increase the contact area with water;The side wall design is inclined,which can make the solid phase change material closer to the wall surface during the melting process and promote melting.In order to further enhance the heat transfer performance of the encapsulated phase change unit,fins were added inside and the arrangement of the fins was optimized.The main work and conclusions of this article are as follows:Firstly,a physical model of a hollow circular frustum type phase change packaging unit was designed,and a mathematical model of the phase change packaging unit was established.Based on the established mathematical model,the melting and solidification performance of phase change packaging units under different wall temperatures were simulated and analyzed.The results show that natural convection plays a significant role in the melting process;Increasing the wall temperature can effectively shorten the complete melting time;During the solidification process,natural convection is relatively small,and heat conduction is the main heat transfer method;Reducing the boundary temperature can effectively shorten the complete melting time.When the wall temperature decreases from32 ℃ to 22 ℃ and 12 ℃,the complete solidification time is shortened by 44.20% and28.42%,respectively.Then,in order to further elaborate on the heat storage and release performance of the phase change packaging unit,research and analysis were conducted on its structural parameters.The research results indicate that when the angle between the upper wall and the side wall is greater than 90 ° during the melting process,the complete melting time will decrease with the decrease of the angle;When the included angle is greater than 90 °,increasing the included angle has no significant effect on the complete melting time;During the solidification process,the complete solidification time will first increase and then decrease with the increase of the included angle.When the included angle is 99 °,the complete solidification time used is the shortest.When the height is increased,both the melting rate and solidification rate will increase.Afterwards,a comparative analysis was conducted between the hollow cone type phase change packaging unit and the commonly used cylindrical phase change packaging unit.The results showed that the complete melting time and complete solidification time of the studied phase change packaging unit were shortened by 33.14% and 38.62%,respectively,compared to the cylindrical type.Finally,the heat storage and release performance of the proposed phase change packaging unit is further improved by setting internal fins.The results show that installing fins on inclined walls has a more significant promoting effect on melting compared to vertical walls;When the fins are installed on an inclined wall,the smaller the inclination angle of the fins,the more obvious their promoting effect on melting.However,when the fins are installed vertically,their promoting effect on melting is the least significant;When the total length of the fins is kept consistent while changing the number of fins,its promoting effect on melting will first increase and then weaken with the increase of the number of fins.When the number of fins is 3,its promoting effect on melting is most obvious.