一种用于污垢监测的温差热阻新方法

在恒壁温条件下,在结垢过程中,管内流体温度和垢层内壁面温度逐渐降低,会引起流体与内壁面间对流传热热阻增加,因而必须对现有的计算污垢热阻的公式进行修正。综合考虑各种因素,建立了恒壁温条件下计算污垢热阻的改进模型。计算实例表明,其他条件一定时,流体进口温度越低,流量越小,则修正值和修正系数越大。随着结垢过程的进行,修正值增大,修正系数减小。在结垢的初始阶段,修正系数最大,说明应用改进公式计算的结垢诱导期较长,更接近于实际情况。

An improved method for measuring and inspecting thermal resistance of scale in tube by temperature difference

The temperatures of fluid and inner wall of tube covered by scale may fall down gradually during fouling under the constant temperature of tube wall,which causes the increase in thermal resistance of convection heat transfer in a tube. The existing formula for calculating the thermal resistance of scales must be amended.The improved equation for calculating the thermal resistance of scale was proposed in consideration of different condition.The calculation example shows that if the inlet temperature of fluid is low and the flux is small,the amendatory value and coefficient are great when the other conditions are fixed.With the scale growing up,the amendatory value will increase while the amendatory coefficient will decrease.In the initial stage of scale,the amendatory coefficient is the greatest. The fouling induction period calculated by the improved formula is longer and more accordant with the fact than that by the existing formula.