Colburn J factor

J Ordinate, Colburn j factor, equals f/2 for heat transfer for inner wall of annulus /h2 for outer wall of annulus jy for heat transfer for ideal tube bank Dimensionless Dimensionless... 

The dimensionless relations are usually indicated in either of two forms, each yielding identical resiilts. The preferred form is that suggested by Colburn ran.s. Am. In.st. Chem. Eng., 29, 174—210 (1933)]. It relates, primarily, three dimensionless groups the Stanton number h/cQ, the Prandtl number c Jk, and the Reynolds number DG/[L. For more accurate correlation of data (at Reynolds number <10,000), two additional dimensionless groups are used ratio of length to diameter L/D and ratio of viscosity at wall (or surface) temperature to viscosity at bulk temperature. Colburn showed that the product of the Stanton number and the two-thirds power of the Prandtl number (and, in addition, power functions of L/D and for Reynolds number <10,000) is approximately equal to half of the Fanning friction fac tor//2. This produc t is called the Colburn j factor. Since the Colburn type of equation relates heat transfer and fluid friction, it has greater utility than other expressions for the heat-transfer coefficient. 

Colburn j-factor = Used in heat-transfer applications. 

The correlation due to Kelly (1965) indicates relatively modest coefficients below 200Wm-2K i for particles up to about 8mm in diameter. The equations proposed by Vazquez and Calvelo, based on the Chilton-Colburn j-factor model, suggest rather higher coefficients of fhe order of 300-400for the fluidization of particles up to 20mm in diameter at gas velocities reasonably in excess of those required for minimum fluidization. 

In fixed-bed operation, Satterfield [1] recommends correlations for mass (and heat) transfer coefficients based on the Colburn j factor, defined as follows ... 

Jd = Chilton-Colburn j-factor for mass transfer, dimensionless... 

Here the Chilton-Colburn j-factors and the Reynolds number Re are defined by... 

Most mass transfer correlations in the literature are reported in terms of the Colburn J factor as a function of the Reynolds number. The relationship between and the numbers we have been discussing is... 

A correlation for flow through packed beds in terms of the Colburn J factor... 

THE Cia. BtlKN ANALOGY COLBURN j FACTOR. Over a range of Reynolds numbers ffopa 5000 to 200,000 the friction factor for smooth pipes is adequately given by the empirical equation... 

Colburn j factor. It is used in a number of other semiempirical equations for heat transfer. While the Reynolds analogy [Eq. (12.50)] applies only to fluids for which the Prandtl number is close to unity, the Colburn analogy [Eq. (12.52)] applies over a range of Prandtl numbers from 0.6 to about 100. 

H modified Colburn j factor, defined by correlation Eq. 13.7.2 /H.surt modified Colburn j factor in the region adjacent to the heater surface K thermal conductivity of gas... 

The reduction in heat transfer is reflected in the other curve on Fig. 17.15 which is a plot of the change in the so-called Colburn j factor with time as the deposition progresses. 

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