Boelter

The mathematical formulation of forced convection heat transfer from fuel rods is well described in the Hterature. Notable are the Dittus-Boelter correlation (26,31) for pressurized water reactors (PWRs) and gases, and the Jens-Lottes correlation (32) for boiling water reactors (BWRs) in nucleate boiling. 

In the macroscopic heat-transfer term of equation 9, the first group in brackets represents the usual Dittus-Boelter equation for heat-transfer coefficients. The second bracket is the ratio of frictional pressure drop per unit length for two-phase flow to that for Hquid phase alone. The Prandd-number function is an empirical correction term. The final bracket is the ratio of the binary macroscopic heat-transfer coefficient to the heat-transfer coefficient that would be calculated for a pure fluid with properties identical to those of the fluid mixture. This term is built on the postulate that mass transfer does not affect the boiling mechanism itself but does affect the driving force. 

Proc. Heat Tran.sfer Fluid Mech. Jn.st., ASME, pp. 89-98, June 22-24 [1949]) and Cleeves and Boelter Chem. Eng. Prog., 43, 123-134 [1947]). 

Najjar, Bell, and Maddox studied the influence of physical property data on calculated heat transfer film coefficients and concluded that accurate fluid property data is extremely important when calculating heat transfer coefficients using the relationships offered by Dittus-Boelter, Sieder-Tate, and Petukhov. Therefore, the designer must strive to arrive at good consistent physical/thermal property data for these calculations. 

E. For heating and cooling turbulent gases and other low viscosity fluids at DG/p > 8,000 the Dittus-Boelter relation is used. See Figures 10-46, 10-51, and 10-52. 

The convection heat transfer rate inside the tubes is expressed by the Dittus-Boelter equation ... 

Data on thermal performance are not readily available on all heat exchangers because of the proprietary nature of the machines. To exemplify typical thermal data, heat transfer can best be described by a Dittus-Boelter type equation ... 

The values of /"fh and ffc (the film resistances for the hot and cold fluids, respectively) can be calculated from the Dittus-Boelter equations previously described and the wall metal resistance / from the average metal thickness and thermal conductivity. The fouling resistances of the hot and cold fluids /"dh and are often based on experience, but a more detailed discussion of this will be presented later in this chapter. 

The results of a number of workers who have used a variety of gases such as air, carbon dioxide, and steam and of others who have used liquids such as water, acetone, kerosene, and benzene have been correlated by Dnrus and BOELTER-13 who used mixed units for their variables. On converting their relations using consistent (SI, for example) units, they become ... 

Wtnterton"5 has looked into the origins of the Dittus and Boelter equation and has found that there is considerable confusion in the literature concerning the origin of equation 9.61 which is generally referred to as the Dittus-Boelter equation in the literature on heat transfer. 

Dittos, F.W. and Boelter, L.M.K. Univ. of California, Berkeley, Pubns in Engineering 2 (1930) 443. Heal, transfer in automobile radiators of the tubular type. Reprinted Inti Cnmm. Heat Mast Transfer 12 (.1985) 3. 

Winterton. R.H.S. Inti. Jl. Heat Mass Transfer 41 (1998) 809. Where did the Dittos and Boelter equation come from ... 

Displacement thickness of boundary layer 673, 677 Distillation columns, mass transfer 576 Distributors for water cooling towers 762 Ditius-Boelter equation 417 Di ttos, F. W. 417.563... 

Dittus FW, Boelter LMK (1930) Heat transfer in automobile radiators of tubular type. University of California, Berkley. Publ Eng 2(13) 443 61... 

Heat fluxes in fire conditions have commonly been measured by steady state (fast time response) devices namely a Schmidt-Boelter heat flux meter or a Gordon heat flux meter. The former uses a thermopile over a thin film of known conductivity, with a controlled back-face temperature the latter uses a suspended foil with a fixed edge temperature. The temperature difference between the center of the foil and its edge is directly proportional to an imposed uniform heat flux. Because the Gordon meter does not have a uniform temperature over its surface, convective heat flux may not be accurately measured. 

Medtherm 64 Series Heat Flux Sensor (Schmidt-Boelter type)... 

For the case of turbulent flow the Dittus-Boelter(9) correlation given in Volume 1, Chapters 9 and 10, is used ... 

The thermodynamic approach does not make explicit the effects of concentration at the membrane. A good deal of the analysis of concentration polarisation given for ultrafiltration also applies to reverse osmosis. The control of the boundary layer is just as important. The main effects of concentration polarisation in this case are, however, a reduced value of solvent permeation rate as a result of an increased osmotic pressure at the membrane surface given in equation 8.37, and a decrease in solute rejection given in equation 8.38. In many applications it is usual to pretreat feeds in order to remove colloidal material before reverse osmosis. The components which must then be retained by reverse osmosis have higher diffusion coefficients than those encountered in ultrafiltration. Hence, the polarisation modulus given in equation 8.14 is lower, and the concentration of solutes at the membrane seldom results in the formation of a gel. For the case of turbulent flow the Dittus-Boelter correlation may be used, as was the case for ultrafiltration giving a polarisation modulus of ... 

To Professor Llewellyn Boelter, deceased, who had overall cognizance of the UCLA effort, as Dean of Engineering, and who also contributed, in ray opinion, by virtue of his qualities as a real human being. 

The procedure of taking a ratio of two coefficients, as done in equations (91) and (92), using a Dittus-Boelter equation for the hypothetical liquid-only case, leads to the relation ... 

D9. Drake, R. M., Smith, C. G., and Stathakis, G. J., in Heat Transfer, Thermodynamics and Education Boelter Anniversary Volume (H. A. Johnson, ed.). McGraw-Hill, New York,... 

Application of dimensional analysis to Eq. (42) leads to the dimensionless groups of the Dittus-Boelter equation for Eq. (43), one obtains... 

Although at first glance the solution in Eq. (184) would seem to be more realistic than that in Eq. (182), it has been found that the solution for the flat velocity profile agrees better with experiment than does that for the parabolic. This discrepancy has been explained by Boelter (B14,... 

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