| With the improvement of people’s living standards,architectural ceramics have been booming,and the emerging rock plate has gradually been sought after by all.Compared with ordinary ceramic tile,rock plate has the characteristics of large size,small thickness,light weight,high hardness and low water absorption,so it is accepted by the majority of consumers.Due to many characteristics of the rock slab,its firing requirements are more stringent than those of ordinary ceramic tiles.Especially in the slow cooling stage of quartz transformation,the rock slab needs lower cooling rate,more uniform temperature distribution and temperature gradient.Therefore,a new type of slow cooling structure of rock plate roller kiln is proposed,which is different from ordinary ceramic roller kiln.By changing the laying mode of heat exchange tube and using hot air to cool the heat exchange tube,it can not only meet the slow cooling demand of rock plate,but also achieve certain energy saving effect.In this paper,the new slow cooling structure of rock plate roller kiln is analyzed by numerical simulation.The main contents of the study are as follows:the comparison between the new slow cooling structure of rock plate roller kiln and the slow cooling structure of ordinary building ceramic roller kiln;the influence of air velocity,temperature and flow direction in the heat exchange tube of the new slow cooling structure of rock plate roller kiln on the velocity field and temperature field in the kiln.By analyzing the results of numerical simulation,the following conclusions are drawn:（1）The heat transfer mode studied is inter-wall heat transfer.The change of air condition and flow direction in the heat transfer tube mainly causes the change of temperature field in the kiln,and has little effect on the velocity field in the kiln.The simulation results show that when the air velocity in the tube is 1～8 m/s,the temperature is 30～240℃,and the flow direction changes in the range of mixed flow,downstream flow and counter flow,the variation range of velocity inhomogeneity coefficient in the kiln is less than 1.5%.（2）The new structure can uniform the temperature difference between the upper and lower surfaces of the rock plate.The temperature difference of the highest temperature point on the upper and lower surfaces of the new structure rock plate is close to 0℃,while that of the ordinary structure rock plate reaches 8℃.In addition,when studying the heat transfer effect of the two structures under the same working condition,it is concluded that the heat flux of the new structure is 428.3 W/m~2 higher than that of the ordinary structure.（3）When the air temperature in the heat exchanger tube is 30℃,the temperature gradient in the position of the rock plate can be most uniform by controlling the air velocity in the tube to 6 m/s;the new structure can be cooled by hot air.When the temperature of the heat exchange tube reaches 240℃,the temperature gradient at the position of the rock plate is the most uniform,the temperature distribution of the cross section in the kiln is the most uniform,and the average heat flux of the heat exchange tube is the lowest,which is conducive to the slow cooling of the rock plate.（4）The numerical simulation of the new slow cooling structure is carried out by using the working condition parameters of the rock plate roller kiln.Multiple temperature monitoring points are set up.The maximum relative error between the simulated temperature value of the monitoring point and the measured temperature value is 2.66%,and the error is within a reasonable range,which provides data support for the accuracy of the simulation results. |
PDF Full Text Request