Simulation And Analysis Of Roll Heat Transfer In Straw Calendering And Papermaking Equipment

Every year in our country can produce a large number of straw,direct burning will bring serious harm to the land,the environment and the health of the people,for this reason,the study of non-polluting straw calendering paper technology,with straw as the main raw material of the new paper making method to partially replace the traditional paper making method with wood,fiber and other raw materials,reducing the waste of resources and environmental damage,more energy-saving and environmental protection.The rolls are an important part of the non-polluting straw calendering paper making equipment.Based on the working principle and requirements of paper making equipment for non-polluting straw,the rolls were modelled and heat transfer simulations were carried out.To investigate the influence of different influencing factors(media oil inlet flow rate,roll sleeve thickness,number of runners,inner runner dividers)on the heating process of the rolls of a papermaking machine with straw and on the heating efficiency.By comparison the appropriate simulation data is selected to optimise the design of the rolls.First of all,a nested roll model with circumferential flow paths was designed based on the calendering paper technology for non-polluting corn stover.The simulation software was used to mesh the roll model and numerically simulate the heat transfer of the rolls to obtain the simulation results of the surface temperature field,the temperature field of the key sections and the velocity field of the rolls at different times,to explore the data of the heat transfer of the rolls and to provide some basis for the numerical simulation of the single factor.Then,based on the heat transfer to the rolls under a single factor,the influence of four process parameters,namely the medium oil inlet flow rate,the thickness of the roll sleeve,the number of runners and the inner runner spacer,on the heating process of the rolls was analysed.The simulation analysis compares the cross-sectional and surface temperature fields of the rolls under each factor as well as the variation of the temperature data,which provides a design guarantee for the selection of the better factor for the orthogonal experiment.Finally,the heat-conducting oil inlet flow rate,the thickness of the roll's sleeve,the number of runners as three factors,the temperature of the outer surface of the roll uniform zone and the heating to the target temperature time as two experimental indicators to establish a three-factor,three-level orthogonal test table.The law of the influence of each factor on the index value was determined using extreme difference analysis,and the optimum combination of factors within the test range was obtained.The optimum combination was a roll type with an inlet flow rate of 3m/s,a roll sleeve thickness of 15mm and a runner number of 14,which was heated for 470s to initially reach the required temperature.The comparative analysis of the temperature field from the simulation results shows that the surface temperature,temperature gradient and heating efficiency of the optimal combination of rolls are better than the initial design combination,which also provides a certain theoretical basis for future research on paper machine rolls.