Chilton-Colburn j -factor

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. 

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

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

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

Chilton and Colburn J-factor analogy. The most successful and most widely used analogy is the Chilton and Colburn J-factor analogy (C2). This analogy is based on experimental data for gases and liquids in both the laminar and turbulent flow regions and is written as follows ... 

The correlation studies of heat and mass transfer in pellet beds have been investigated by many, usually in terms of the. /-factors (113-115). According to Chilton and Colburn the two. /-factors are equal in value to one half of the Fannings friction factor / used in the calculation of pressure drop. The. /-factors depend on the Reynolds number raised to a factor varying from —0.36 to —0.68, so that the Nusselt number depends on the Reynolds number raised to a factor varying from 0.64 to 0.32. In the range of the Reynolds number from 10 to 170 in the pellet bed, jd should vary from 0.5 to 0.1, which yields a Nusselt number from 4.4 to 16.1. The heat and mass transfer to wire meshes has received much less attention (110,116). The correlation available shows that the /-factor varies as (Re)-0-41, so that the Nusselt number varies as (Re)0-69. In the range of the Reynolds number from 20 to 420, the j-factor varies from 0.2 to 0.05, so that the Nusselt number varies from 3.6 to 18.6. The Sherwood number for CO is equal to 1.05 Nu, but the Sherwood number for benzene is 1.31 Nu. 

Results of experimental studies of heat transfer may be conveniently represented by means of the j- factor method developed by COLBURN4341 and by CHILTON arid COLBURN 35 for representing data on heat transfer between a turbulent fluid and the wall of a pipe. From equation 9.64 ... 

The proposals made for calculating transfer coefficients from physical data of the system and the liquid and vapour rates are all related to conditions existing in a simpler unit in the form of a wetted-wall column. In the wetted-wall column, discussed in Chapter 12, vapour rising from the boiler passes up the column which is lagged to prevent heat loss. The liquid flows down the walls, and it thus provides the simplest form of equipment giving countercurrent flow. The mass transfer in the unit may be expressed by means of the j-factor of Chilton and Colburn which is discussed in Volume 1, Chapter 10. Thus ... 

At high values of Reynolds number, such as may pertain to model droplets, the value of the constant 2 becomes less significant (102), and Equations 3 and 4 may be converted to the j-factor equations of Chilton and Colburn (12, 14). Maisel and Sherwood (82, 83) employed the j-factor equations in their data presentation, but the same data were applied successfully by Ranz and Marshall in their own analysis in support of the Froessling equation. 

Chilton-Colbum Analogy On occasion one will find that heat-transfer-rate data are available for a system in which mass-transfer-rate data are not readily available. The Chilton-Colburn analogy [90,53] (see Tables 5-17-G and 5-19-T) provides a procedure for developing estimates of the mass-transfer rates based on heat-transfer data. Extrapolation of experimental jM or data obtained with gases to predict liquid systems (and vice versa) should be approached with caution, however. When pressure-drop or friction-factor data are available, one may be able to place an upper bound on the rates of heat and mass transfer of f/2. The Chilton-Colburn analogy can be used for simultaneous heat and mass transfer as long as the concentration and temperature fields are independent [Venkatesan and Fogler, AlChE J. 50,1623 (2004)]. 

The heat transfer coefficient can be calculated from the mass transfer coefficient by means of the Chilton-Colburn analogy, also called the j factor analogy. The factors are defined as ... 

One of the most extensively ured and successful analogies—the j factor of Chilton and Colburn 10—was proposed as an empirical relationship based on available expurimantal data al that time ... 

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

J-factor A dimensionless factor used in heat and mass transfer of fluids with turbulent flowin pipes. It isafunctionofReynolds number, geometry, and boundary conditions from which the friction factor can be obtained and agrees well with convective heat transfer correlations orfor detemiiningheattransfercoefficients.lt was proposed by Americanchemi-cal engineer Allan P. Colburn (1904-55) and forms part of the Chilton-Colbum analogy, which is used in heat, momentum, and mass transfer. 

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