Dittus-Boelter correlation

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. 

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 ... 

The heat transfer coefficient for the fluid in the pipe is estimated using the Dittus-Boelter correlation ... 

For fully-developed laminar forced convection in microchannels, Nu is proportional to Re° , while for the fully-developed turbulent heat transfer Nu is predicted by the Dittus-Boelter correlation by modif3ung only the empirical constant coefficient from 0.023 to 0.00805. 

Turbulent Flow. Perhaps the best known heat-transfer correlation for fully developed turbulent flow is that owing to Dittus and Boelter.27 The mass transfer analogy based on the Dittus-Boelter correlation is ... 

A widely used correlation in turbulent regime is the Dittus- Boelter correlation 115] ... 

The current analysis of several well-known heat transfer correlations for supercritical fluids showed that the Dittus—Boelter correlation (1930) significantly overestimates experimental HTC values within the pseudocritical range. The Bishop et al. (1965) and Jackson (2002) correlations tend also to deviate substantially from the experimental data within the pseudocritical range. The Swenson et al. (1965) correlation provided a better fit for the experimental data than the previous three correlations within some flow conditions, but does not follow up closely the experimental data within others. 

Dittus-Boelter correlation A dimensionless equation used in heat transfer for forced convection. For a fluid with turbulent flow in a pipe of circular cross section ... 

Forced convection in subcooled liquid Dittus-Boelter correlation... 

The uncertainty of heat transfer correlation can be treated in two ways one is to use a corresponding engineering hot channel factor, the other is to treat this uncertainty separately with parametric uncertainties. The latter is applied to this study as is done for the Super LWR in Chap. 2. The uncertainty of the heat transfer correlation is evaluated by comparing with the Oka-Koshizuka correlation and the Dittus-Boelter correlation in the high coolant enthalpy region. The uncertainty is evaluated as 6.33°C. It is taken as the correlation uncertainty because the hot spot is always in the high coolant enthalpy region. 

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