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An experimental investigation was made of temperature gradients in air streams being cooled while flowing through a cylinder of diameter 81 mm packed with high thermal conductivity (iron and copper) and low thermal conductivity solids of spheres, cylinders and Raschig rings. From the measured temperature gradients at various bed depths and radial posi-tions, and for the different particle sizes and flow rates, the effective thermal conductivity Ke, and the heat transfer coefficient of the wall hw, were determined... An experimental investigation was made of temperature gradients in air streams being cooled while flowing through a cylinder of diameter 81 mm packed with high thermal conductivity (iron and copper) and low thermal conductivity solids of spheres, cylinders and Raschig rings. From the measured temperature gradients at various bed depths and radial posi-tions, and for the different particle sizes and flow rates, the effective thermal conductivity Ke, and the heat transfer coefficient of the wall hw, were determined by the integral, graphical and the direct-current electric analog methods. 作者用低导热系数(包括玻璃、磁)的球体、圆柱体、环柱体与高导热系数(包括铜、铁的球体,圆柱体为填充物,以空气为传热介质,使其在管径为81毫米之填充床层内冷却,改变流体流量,床层高度及填充物大小,通过试验测出在不同的条件下床层的径向温度分布,并应用积分法、直流电模拟计算法及图解法求得床层的有效导热系数及管壁薄膜传热系数.在试验范围:低导热系数填充物D_P/D_t自0.074—0.254;高导热系数填充物D_p/D_t自0.12—0.2,L/D_t自5—15,Re汇数自130—1400,即直线速度自0.5—1.6公尺/分,若以床层进出口平均温度之数学平均值为定性温度,则床层之有效导热系数及管壁薄膜传热系数可分别归纳于下式:低导热系数填充物:K_e=0.182(D_t/D_p)~(0.45)Re~(0.75),h_w=65e~(-4)(D_p/D_t)(K/D_t)((D_t/L))~(0.2)Re~(0.4)高导热系数填充物:K_e=0.3k(D_t/D_p)~(0.6)Re~(0.72),h_w=5.1(K/D_t)(D_t/D_p)~(0.8)(D_t/L)~(0.1)Re~(0.46)填充物形状... 作者用低导热系数(包括玻璃、磁)的球体、圆柱体、环柱体与高导热系数(包括铜、铁的球体,圆柱体为填充物,以空气为传热介质,使其在管径为81毫米之填充床层内冷却,改变流体流量,床层高度及填充物大小,通过试验测出在不同的条件下床层的径向温度分布,并应用积分法、直流电模拟计算法及图解法求得床层的有效导热系数及管壁薄膜传热系数.在试验范围:低导热系数填充物D_P/D_t自0.074—0.254;高导热系数填充物D_p/D_t自0.12—0.2,L/D_t自5—15,Re汇数自130—1400,即直线速度自0.5—1.6公尺/分,若以床层进出口平均温度之数学平均值为定性温度,则床层之有效导热系数及管壁薄膜传热系数可分别归纳于下式:低导热系数填充物:K_e=0.182(D_t/D_p)~(0.45)Re~(0.75),h_w=65e~(-4)(D_p/D_t)(K/D_t)((D_t/L))~(0.2)Re~(0.4)高导热系数填充物:K_e=0.3k(D_t/D_p)~(0.6)Re~(0.72),h_w=5.1(K/D_t)(D_t/D_p)~(0.8)(D_t/L)~(0.1)Re~(0.46)填充物形状对K_e及h_w的影响,仅需将D_p用 D’_p代替,同时把K_e式中之常数0182及03各改为0.22及0.38即可.直流电模拟计算法系利用电压表示温度,电阻表示传热阻力,电流表示热的流动,是简单的模拟计算机的一种,它在近代工程上的应用日渐广泛,有了传热数据应用它来求床层的温度分布异常方便. ~~ 本文较详细的介绍了作者和哈尔滨工业大学自动装置实验室同志一起所自制的电子模拟计算机,并按主要部件:直流计算放大器,典型非线性元件,函数变换器,变系数装置,定迟后装置,控制线路和记录方法,讨论了它们的种类、基本原理与所采用的结构形式。最后还举了一些计算的例题。 ~~ 本文首先论证了函数表示方法的三种解析形式(公式9、10、11)与函数产生器的三种结构形式(图1)之间的基本关系:正函数由计算放大器的非线性输入电导模拟;反函数由计算放大器的非线性反馈电导模拟;分离隐函数由计算放大器的非线性输入电导和反馈电导共同模拟。根据所得的关系,讨论了用二极管网络作非线性电导的函数产生器的综合方法,以保证函数产生器的精确度提高,而所费元件减少。同时还提出了利用已有的正函数(或反函数)的产生器,产生反函数(或正函数)的方法,比旧有的方法节省元件,而且误差也低。
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