保温材料管道保温性能分析

Analysis of the property of insulated material around the pipeline

利用牛顿冷却方程和圆筒传热公式推导出了保温材料管道保温的热流损失数学模型,并基于该模型推导出了热流损失随保温层厚度增减变化的临界半径的理论计算公式.假定保温材料外表面与周围环境之间的对流传热系数为常数时,临界半径与保温材料导热系数成正比,而与保温材料外表面与周围环境之间的对流传热系数成反比.当管道裸管半径大于临界半径时,管道热流损失随着保温层厚度的增加而减小;当管道裸管半径小于临界半径,且裸管半径与保温材料厚度之和小于临界半径时,管道热流损失随着保温层厚度的增加而增加;而当裸管半径与保温材料厚度之和大于或等于临界半径时,管道热流损失随着保温层厚度的增加而减小.最后,对保温材料导热系数、保温材料外表面与周围环境之间的对流传热系数对管道热流损失的影响也进行了计算和分析.图5,表1,参8.

A mathematical model for the heat loss of insulated pipe was deduced from Newton＇s cooling equation and cylinder heat transfer formula. Based on the model, a formulation is developed for critical radius. Suppose that the convection-heat-transfer coefficient between the external surface of insulation materials and the environment is constant, the critical radius is proportional to the thermal conductivity of insulation materials and inversely proportional to the convection-heat-transfer coefficient between the external surface of insulation materials and the environment. The heat loss of the pipeline decreases with the increase of the insulation thickness when the bare radius of the pipeline is greater than the critical radius. When the bare radius of the pipeline is less than the critical radius, at the same time, the sum of the bare radius and the thickness of the insulation material is less than the critical radius, the heat loss of the pipe increases with the increase of the insulation thickness; the heat loss of the pipe decreases with the increase of the insulation thickness while the sum of the bare radius and the thickness of the insulation material is greater than the critical radius. Finally, the effects of thermal conductivity of insulation materials and the convection-heat-transfer coefficient between the insulation material surface and the surrounding on the heat loss of the pipeline were also calculated and analyzed.