Cylinders horizontal, boiling

Film boiling on horizontal cylinders. In his pioneering work on film boiling on a horizontal cylinder, Bromley proposed a classical theoretical equation in dimensionless form ... 

Effect of reduced temperature Tr Clements and Colver (1964), based on data with many liquids over a wide range of diameters for boiling on horizontal cylinders, achieved a considerable improvement in Eq. (2-152) by modifying it empirically to... 

Elkassabgi, Y., and J. H. Licnhard, 1988, The Peak Pool Boiling Heat Fluxes from Horizontal Cylinders in Subcooled Liquids, Trans. ASME, J. Heat Transfer /70 479—496. (2)... 

Sun and Lienhard (34] have presented a relation for the peak boiling heat flux on horizontal cylinders which is in good agreement with experimental data. The relation is... 

Calculate the peak heat flux for boiling water at atmospheric pressure on a horizontal cylinder of 1.25-cm OD. Use the L.ienhard relation. 

Disodium perfluorohexanedioate (5 g, 0.015 mol) was spread in a thin layer in a horizontal open cylinder of platinum foil which was then inserted into a horizontal nickel furnace tube of 2.5-cm diameter and scaled at one end. The tube was evacuated to 0.01 Torr and than heated stepwise to 450 C. Two glass traps connected in series between the furnace tube and the pump were examined periodically appreciable reaction occurred below 300 C and there was little sign of further reaction at temperatures above 370 C. The combined volatile products were transferred into a vacuum system where they were separated into fractions boiling above or below 10 C. The more volatile fraction was washed with 2M NaOH and refractionated in vacuo yield 0.73 g (30%) bp 5-7 C. 

Using an analysis similar to Nusselt s theory on filmwisc condensation presented in the next section, Bromley developed a theory for the prediction of heat flux for stable film boiling on the outside of a horizontal cylinder. The heat Ilux for film boiling on a horizontal cylinder or sphere of diameter D is given by... 

The heat flux for stable film boiling on the outside of a horizontal cylinder or sphere of diameter D is given by... 

FIGURE 15.60 Effect of pressure and cylinder diameter on burnout heat flux for saturated pool boiling of water from horizontal cylinders (from Hewitt [147], with permission from The McGraw-Hill Companies). 

Correlations for CHF in Pool Boiling. Most correlations for critical heat flux in pool boiling have been of the form indicated in Eq. 15.128. Although this equation was introduced in the context of the hydrodynamic instability model of Zuber [159,160], the form of the equation was derived some years earlier by Kutateladze [166], Thus, the use of the equation is not necessarily associated with any physical model. In the following text, equations will be given for the most usual practical cases of horizontal flat plates and horizontal cylinders relationships for other shapes are discussed by Lienhard and Dhir [155,161],... 

FIGURE 15.70 Minimum film boiling temperature for boiling of water from horizontal cylinders as a function of system pressure (from Sakurai and Shiotsu [180], with permission from ASME). 

FIGURE 15.76 Modes of film boiling, (a) vertical flat plate (b) sphere or cylinder (c) horizontal plate. 

An extension of this model to take account of turbulence is described by Klimenko [194], Horizontal Cylinders. The horizontal cylinder has been the most widely studied case of film boiling. Again, there is a strong analogy with condensation (see Fig. 15.76ft) and the classical expression for this case is that due to Bromley [190] as follows ... 

K. H. Sun and J. H. Lienhard, The Peak Pbol Boiling Heat Flux on Horizontal Cylinders, Int. J. Heat Mass Transfer (13) 1425-1439,1970. 

J. H. Lienhard and P. T. Y. Wong, The Dominant Unstable Wavelength and Minimum Heat Flux During Film Boiling on a Horizontal Cylinder, J. Heat Transfer (86) 220-226,1964. 

Fig. 42.10 Variation of Sauter mean diameter ( >32) and mean streamwise velocity (U) with streamwise position (Z) for different high-boiling-point chemical agents (the horizontal bar and vertical dashed lines represent the location of the cylinder) [1]...

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