J Factor for heat transfer

The analogy has been reasonably successful for simple geometries and for fluids of very low Prandtl number (liquid metals). For high-Prandtl-number fluids the empirical analogy of Colburn [Trans. Am. Tn.st. Chem. Ting., 29, 174 (1933)] has been veiy successful. A J factor for momentum transfer is defined asJ =//2, where/is the friction fac tor for the flow. The J factor for heat transfer is assumed to be equal to the J factor for momentum transfer... 

Experimental data on heat transfer in fixed and fluidized bed reactors are correlated in terms of a j factor for heat transfer. 

For gases, h/CpG is approximately equal to the j factor for heat transfer, and U/CpG is approximately equal to aj factor since for gases is approxi-... 

Comparisons between the datawhichwere obtained in this work and previously published data for compact exchangers are presented in Fig. 10. The over-all J factor for heat transfer for the helically finned and coiled heat exchanger is only slightly less than the individual j factor reported for the Collins-t3rpe ribbon-packed heat exchanger [6]. The approximate j factor reported in this work is substantially higher than the j factor reported above. 

It is convenient to express results for tests on heat transfer and mass transfer to particles in the form of /-factors. If the concentration of the diffusing component is small, then the j-factor for mass transfer may be defined by ... 

The /-factors were first used by Colburn [7] for successful empirical correlations of heat and mass transfer data. The/-factor for heat transfer, J, was defined as... 

Individual heat-transfer coefficient, W/m -°C or Btu/ft -h-°F Mass flux relative to a plane of zero velocity, kg mol/m -s or lb mol/ft -h J, Jg, of components A and B, respectively average value of component A, caused by turbulent action Colburn factor for heat transfer, hlCpG) Cgfifkfl, dimensionless Colburn j fector for mass transfer, (ky MlG lpD Y, dimensionless Overall mass-transfer coefficient in gas phase, kg mol/m -s-unit mole fraction or lb mol/ft -h-unit mole fraction Ky, new value in Example 21.5... 

Chilton and Colburn (1934), based on experimental data, defined the j-factor for mass transfer and established the analogy with heat transfer ... 

Moreover, the previously given relationship for yo—the j factor for mass transfer [Eq. (2.2.12)]—may also be used for estimating the heat transfer coefficient by assuming that... 

Chilton-Colburn j factors for mass transfer, heat transfer... 

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... 

Kaye, J., Survey of Friction Coefficients, Recovery Factors, and Heat Transfer Coefficients for Supersonic Flow , J. Aeronaut. Sci., Vol. 21, No. 2, pp. 117-229,1954. 

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. 

Hwang, G.J., Cheng, Y.C., Ng, M.L., 1993b. Friction factors and heat transfer correlations for gaseous reactant flow in fuel cell power modules. In Proceedings of the 6th International Symposium on Transport Phenomena in Thermal Engineering, vol. 1, pp. 685-690. 

Average transport coefficients for transfer between the bulk-fluid and particle surface can be correlated in terms of dimensionless groups that characterize the flow conditions. It is common practice to correlate experimental data in terms of y -factors. Usually, the mass transfer coefficient is obtained from the j factor for mass the heat transfer coefficient is obtained from j factor analogy. There have been many experimental studies of mass transfer in fixed-beds and summaries and analyses of the results are available (Whitaker 1972 Dwivedi and Upadhay 1977). For Reynolds numbers greater than 10, the following relationship (Dwivedi and Upadhay 1977) between jo and the Reynolds number represents available data ... 

The correlation for heat transfer was based on the over-all heat transfer coefficients. Using a standard design calculation for the inside film coefficient [3], however, it was estimated that the individual outside heat transfer coefficients and outside J factors were approximately equal to twice the over-all heat transfer coefficients and J factors. The resistances to heat transfer on the inside of the tubes and the outside of the tubes were approximately equal. 

Colburn j factor (Symbol j ) A semi-empirical equation used for heat transfer in mr-bulent flow with Reynolds numbers tanging from 5,000 to 200,000 inside long mbes and defined as ... 

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