Study On The Heat Transfer Characteristics Of Ellipsoidal Particle Heap With Vacancy

In recent years,a large amount of industrial waste heat has been generated and the recovery rate is low,which wastes resources and pollutes the environment.If industrial waste heat can be reasonably recycled,it can greatly alleviate the burden on energy and environmental protection of China.The problems of the one-time recovery method of solid waste heat,the effect of particle vacancy on heat transfer,and the heat transfer of non-spherical particles is rarely studied.So,the one-time heat exchange method is adopted,the steady-state heat transfer model of the ellipsoidal particle heap with vacancy in a simple cubic stacking was constructed,and the model is calculated by Fluent software.The heat transfer experiment platform of the vacancy ellipsoidal particle heap was designed and built to test the reliability of the heat transfer model.The difference in heat transfer law between spherical particle heaps with vacancy and ellipsoidal particle heaps is compared and analyzed.Effect of particle characteristic parameters,particle packing parameters and particle heap parameters on the heat transfer of ellipsoidal particle heap with a vacancy were studied.Finally,the predictive correlation formula of the effective thermal conductivity of the ellipsoidal particle heap with the changes of some parameters is fitted.The main research contents and results are as follows:(1)Effects of particle characteristic parameters on the heat transfer of ellipsoidal particle heap with vacancy were studied.The aspect ratio of the particles increases from0.5 to 2.0 while keeping the equivalent diameter of the particles unchanged,the average heat flux of particles heap increases from 23.13 k W/m~2 to 29.12 k W/m~2,the apparent thermal resistance decreases from 23.33 K/W to 9.27 K/W.The vacancy affected area increases.The effective thermal conductivity of particle heap decreases.As the thermal conductivity of particles increases from 0.5 W/(m·K)to 50 W/(m·K),the average heat flux of particle heap increases from 0.45 k W/m~2 to 31.10 k W/m~2;the apparent thermal resistance decreases from 799.12 K/W to 10.98 K/W.The vacancy affected area increases.The effective thermal conductivity of particle heap increases.As the equivalent diameter of particles increases from 8mm to 24mm,the average heat flux of particles heap decreases from 54.34 k W/m~2 to 18.70 k W/m~2;the apparent thermal resistance decreases slightly.The vacancy affected area ratio remains unchanged,and the effective thermal conductivity increases slightly.(2)Effects of particle packing parameters on the heat transfer of the ellipsoidal particle heap with vacancy were studied.As the contact coefficient between the ellipsoidal particles increases from 0.02 to 0.17,the average heat flux of particles heap increases from22.49 k W/m~2 to 42.17 k W/m~2;the apparent thermal resistance decreases from 14.94 K/W to 8.66 K/W.The vacancy affected area increases slightly.The effective thermal conductivity of particles heap increases.As the rotation angle of particles turns from 0°to90°,the isotherm of the particle heap slope from left to right,and the degree of slope first increases and then decreases.The average heat flux of particle heap decreases from 34.88k W/m~2 to 31.71 k W/m~2,the apparent thermal resistance increases from 9.96 K/W to 13.88K/W.The vacancy affected area decreases.The effective thermal conductivity increases.(3)Effects of particle heap parameters on the heat transfer of ellipsoidal particle heap with vacancy were studied.During the movement of vacancy in the Y direction,the influence distance of cold wall to vacancy action is about 2 times width of the ellipse,and the influence distance of hot wall to vacancy action is about 3 times width of the ellipse.When the vacancy is close to the walls,the average heat flux of particle heap is the largest,the apparent thermal resistance is the smallest,and the effective thermal conductivity of particle heap is the largest.As the temperature difference between the hot wall and cold wall of the ellipsoidal particle heap increases from 175°C to 975°C,the average heat flux increases from 13.70 k W/m~2 to 60.59 k W/m~2,the apparent thermal resistance increases from 11.63 K/W to 14.65 K/W.The vacancy affected area decreases.The effective thermal conductivity of particles heap decreases.(4)Based on the Maxwell-Eucken I effective thermal conductivity calculation model,considering particle aspect ratio,particle contact coefficient and other parameters,the correlation equation of effective thermal conductivity of the particle heap is obtained.By comparing with the calculated value of the heat transfer model,the maximum relative error is 5.54%,and the average relative error is 2.13%.