Study On Temperature Field Of Photovoltaic Glass During Calendering And Annealing

Photovoltaic glass is one of the most important components of solar cells,mainly used as the encapsulation of crystalline silicon solar cell modules and thin film solar cell modules,and its quality seriously affects the power generation efficiency of solar cells.The most important production method for solar photovoltaic glass is the roll-to-roll calendering method.Because of the high requirements for all aspects of photovoltaic glass performance,temperature control is particularly important in the calendering and annealing process.If the surface temperature distribution of calendering rollers is not uniform,it will cause the glass to produce lateral temperature difference,which will affect the quality of glass forming;if the temperature regime in the annealing process is unreasonable,it will easily lead to excessive internal stress in the glass,which will affect the subsequent deep processing link and lead to a decrease in the product qualification rate.Therefore,it is important to study the temperature field during the calendering and annealing of photovoltaic glass to obtain calendered glass products with excellent quality.This paper investigates the factors influencing the surface temperature of the press rolls during the forming process of photovoltaic rolled glass and the change law of temperature and stress during the annealing process of photovoltaic glass by using a combination of numerical simulation and experimental study,the main research contents are as follows:(1)A three-dimensional model of the calendering roll was established using UG software,and the corresponding temperature boundary UDF program was written through the secondary development port of FLUENT software.The heat transfer process between the glass strip and the calender roll,the inner wall of the calender roll and the cooling water during the calendering process was simulated and analyzed,and the distribution of each physical field of the roll during the forming process was obtained,and the effects of different flow rates and temperatures of the cooling water and the production environment temperature on the surface temperature of the calender roll were simulated.The results show that the press roll surface temperature increases with the increase of cooling water temperature and ambient temperature,and decreases with the increase of cooling water flow rate.Under certain conditions,for every5℃ rise in cooling water temperature,the average surface temperature of the calender roll increases by about 0.4℃,and for every 5℃ rise in ambient temperature,the average surface temperature of the calender roll increases by about 1.4℃.(2)In order to improve the heat transfer ability of calendering rolls,based on the heat transfer mechanism of rough elements,rough elements are added to the inner wall of calendering rolls.Three-dimensional models of calendering rolls with different shapes of rough elements are established using UG software.The distribution of physical fields of calender rolls with different rough element shapes is obtained by simulation analysis.Furthermore,the structure of calendering roll with different height and pitch ratio of rectangular rough element is constructed,and its influence on the surface temperature of calendering roll is analyzed.The structure of calender roll with different shape of cooling channel was established and its influence on the surface temperature uniformity of calender roll was analyzed.The results show that the calender roll with rough element structure can effectively improve its heat transfer capacity.When the height of roughness element is 5 mm,the heat transfer capacity of calendering roll can be effectively improved,and its uniformity can be taken into account.When the pitch ratio s/h = 4,the calender roll has the strongest heat transfer ability.The cooling water channel with arc structure can effectively improve the high temperature of the middle position of the calender roll,and the conical structure can effectively improve the high temperature of the outlet section of the calender roll compared with the inlet section.(3)The thermal coupling module of ANSYS was used to simulate the temperature difference between the surface layer and the central layer in the annealing process,and the fitting curve of the temperature difference between the surface layer and the central layer with the thickness of the glass strip was obtained.The temperature curve of 2mm glass strip in annealing kiln A-B zone was simulated,and the stress variation and distribution in annealing kiln A-B zone were simulated and analyzed.Finally,the permanent stress value at the exit position of annealing kiln B zone was obtained by calculation.(4)As the production process of photovoltaic calendered glass is a high-risk operating environment and it is difficult to build the experimental platform,the experiment is carried out on the production line of a photovoltaic glass production enterprise,and the temperature of different positions on the surface of the calendered roll in the forming process is measured.The stress of the annealed glass was measured.By comparing the simulation results with the experimental results,it can be seen that the relative error between the two results is less than15%,which verifies the feasibility of the numerical simulation method for the photovoltaic glass in the process of calender forming and annealing.