Condensation inside tubes; pressure drop in straight tubes with vertical downflow
Abstract
This Data Item 90024, an addition to the Heat Transfer Subseries, develops a prediction procedure for pressure drop in annular/dispersed flow. It does not apply at the bottom of a condenser, where there is slug flow or the condensate flows as a falling film. However, the pressure drop in this region is small. The method used is to predict the pressure drop using existing correlations for twophase diabatic flow (Friedel with a roughness correction for the frictional component, Premoli et al to establish the vapor density/liquid density ratio and hence the gravitational component, and homogeneous theory for the momentum component). Correction factors on that prediction are developed by comparing the results with experimental data extracted from the literature covering a wide range of diameter, pressure, quality, mass and heat fluxes, and density ratio. Values are tabulated of the correction factor applying for given ranges of density ratio, quality and condensation number (heat flux divided by the product of mass flux times latent heat of vaporization). Also tabulated with each value are the number of points used and the standard deviation. A stepbystep calculation process is set out and illustrated with a worked example. In practice, the pressure drop at inlet to the tubes of a condenser dominates, and it is shown how it may be estimated using ESDU 89012.
 Publication:

Abstract Only ESDU International Ltd
 Pub Date:
 November 1990
 Bibcode:
 1990esdu.reptS.....
 Keywords:

 Condensates;
 Drop Towers;
 Estimating;
 Heat Flux;
 Heat Transfer;
 Surface Roughness;
 Two Phase Flow;
 Heat Of Vaporization;
 Latent Heat;
 Momentum;
 Standard Deviation;
 Vapors;
 Fluid Mechanics and Heat Transfer