A New Method of Evaluating Effective Thermal Conductivities and Wall Heat Transfer Coefficients in a Packed Bed

Abstract

Effective thermal conductivities and wall heat transfer coefficients in packed beds were measured by various investigators and several kinds of methods for evaluating them have been suggested by them. But these methods are complicated and not easy to use. The new method which we present here is simple in principle and practicable. When the temperature profiles are presented by lnφr vs. Z/L in the ranges of linear correlation given by Eq. (14), the value of ks can be obtained by using the slope of asymptote at Z/L=1 and the intercepts on the ordinate. The intercepts of asymptote and ordinate are expressed by C1 and C2 for r1/r0, r2/r0, respectively (Fig. 1). In case r1/r0=0, the ratio of C1 to C2 (C0) is presented by Eq. (18). Thus by evaluating the value of C0 from the intercepts, the value of the root a1 can be easily calculated by means of Eq. (18), As α is equal to the slope of the line, ks is directly evaluated from Eq. (15).