Colburn analogy

Chilled surface drying ChiUproofing Chilton-Colburn analogy Chimeramycins Chimeras... 

The penetration theory predicts that should vary by the square root of the molecular difriisivity, as compared with film theoiy, which predicts a first-power dependency on D. Various investigators have reported experimental powers of D ranging from 0.5 to 0.75, and the Chilton-Colburn analogy suggests a 2/3 power. 

Chilton-Colburn analogies, Ns = 1-0, (gases), f = drag coefficient. Corresponds to item 5-21-F and refers to same conditions. 8000 < Nr < 300,000. Can apply analogy, jo =//2, to entire plate (including laminar portion) if average values are used. 

U. Tubes, turbulent, smooth tubes, Chilton-Colburn 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 provides a procedure for developing estimates of the mass-transfer rates based on heat-transfer data. Extrapolation of experimental or Jh data obtained with gases to predict hquid 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, according to Eq. (5-308). 

For systems other than air-water vapor, the value of h /k c, may differ appreciably from unity, and the wet-bulb and adiabatic-saturation temperatures are no longer equal. For these systems the psychrometric ratio may be obtained by determining h /k from heat- and mass-transfer an ogies such as the Chilton-Colburn analogy [Ind. Eng. Chem., 26, 1183 (1934)]. For low humidities this analogy gives... 

Equations (13-115) to (13-117) contain terms, for rates of heat transfer from the vapor phase to the hquid phase. These rates are estimated from convective and bulk-flow contributions, where the former are based on interfacial area, average-temperature driving forces, and convective heat-transfer coefficients, which are determined from the Chilton-Colburn analogy for the vapor phase and from the penetration theoiy for the liquid phase. 

Several analytical studies have sought to extend the application of the basic method of Chen. For fluids of Prandtl number different from unity, Bennett and Chen (1980) extended the analysis by a modified Chilton-Colburn analogy to give... 

For turbulent flow, we shall use the Chilton-Colburn analogy [12] to derive an expression for mass transfer to the spherical surface. This analogy is based on an investigation of heat and mass transfer to a flat plate situated in a uniform flow stream. At high Schmidt numbers, the local mass transfer rate is related to the local wall shear stress by... 

The Chilton-Colburn analogy can be also used to estimate the local mass transfer rate in laminar flow where the wall shear stress is related to the azimuthal velocity gradient by... 

For the conditions cited, it was shown that jD was 0.235 and, by the Chilton-Colburn analogy Jh = 0.235. From the definition of the heat transfer factor jH, it follows that... 

Chili peppers, 23 163, 164 Chili powder, 23 164 adulterated, 23 163 Chilled castings, tellurium in, 24 424 Chilled surface drying, in bar soap manufacture, 22 750-751 Chill proofing enzymes, 10 294 Chilton-Colburn analogy, 1 47 Chimeric embryos, 12 458... 

The (Ta - Ts)/8 term is the temperature gradient, which correlates (dTIdy through the boundary layer thickness. The fact that 8 can be correlated with the Reynolds number and that the Colburn analogy can be applied leads to the correlation of the form... 

In some kinds of equipment, data only on mass transfer rates may be known. From these, on the basis of the Chilton-Colburn analogy, corresponding values of heat transfer rates can be estimated. 

This method takes advantage of the rough proportionality between heat and mass transfer coefficients according to the Chilton-Colburn analogy, and employs only heat transfer coefficients for the process of condensation from a mixture. The sensible heat of the vapor is transferred through the gas film... 

Data of heat transfer between particle and fluid usually arc not measured directly because of the experimental difficulties, but are deduced from measurements of mass transfer coefficients assuming the Colburn analogy to apply,... 

Equation (5-56), called the Reynolds-Colburn analogy, expresses the relation between fluid friction and heat transfer for laminar flow on a flat plate. The heat-transfer coefficient thus could be determined by making measurements of the frictional drag on a plate under conditions in which no heat transfer is involved. 

Various analyses, similar to the one for the universal velocity profile above, have been performed to predict turbulent-boundary-layer heat transfer. The analyses have met with good success, but for our purposes the Colburn analogy between fluid friction and heat transfer is easier to apply and yields results which are in agreement with experiment and of simpler form. 

The drag coefficient for a sphere at Reynolds numbers less than 100 may be approximated by CD - b Re 1, where b is a constant. Assuming that the Colburn analogy between heat transfer and fluid friction applies, derive an expression for the heat loss from a sphere of diameter d and temperature T released from rest and allowed to fall in a fluid of temperature T.. (Obtain an expression for the heat lost between the time the sphere is released and the time it reaches some velocity v. Assume that the Reynolds number is less than 100 during this time and that the sphere remains at a constant temperature.)... 

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

In case of perfect Chilton-Colburn analogy, both factors are equal ... 

The two major modelling approaches based on either boundary layer approximations or well developed laminar flow have also been applied to the barrel reactor. Dittman (11) used a Chilton-Colburn analogy for flow over a flat plate to predict Si growth... 

Another concept sometimes used as a basis for comparison and correlation of mass transfer data in columns is the Chilton-Colburn analogy (35). This semi-empirical relationship was developed for correlating mass- and heat-transfer data in pipes and is based on the turbulent boundary layer model... 

Vb /(1 — x )> to be taken at liquid feed temperature yB/yB = saturation of solvent in feed gas ff0G ffG q the height of a gas phase heat transfer unit. (The FfOGs are computed from equation 54 the individual heights of a transfer unit for the solvent and for heat may be estimated from HGA and fiLA using the Chilton-Colburn analogy. The m in equation 54 is to be evaluated at the temperature of the liquid feed.) Reprinted by permission (45). 

For a sphere, the mass transfer coefficient can be obtained from Ihe Colburn analogy for the Nusselt number ... 

Colburn Analogy Nu = JhRlkjf = 2.0 + 0.6 Re Pr, where Nu is the Nusselt number, Pr is the Prandlt number, and Ajyis the thermal conductivity of the fluid. 

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