Boiling coefficients

Boiling Coefficients For the nucleate oiling coefficient the Mostinsld equation [Teplenergetika, 4, 66 (1963)] may be used ... 

A well-recognized and often-used equation for determining a reasonable, even if preliminary, nucleate boiling coefficient is represented by the McNelly equation for boiling outside of tubes ... 

Palen and Taborek proposed as the best choice for circular tube bundles (as compared to square) the following film boiling coefficient after analyzing available data (their... 

The following is a calculation procedure suggested by Paien and SmalP for the required boiling coefficient for a horizontal tube bundle ... 

Due to the development of the data, the method requires the use of a single tube boiling film coefficient. Using this to reach the overall bundle transfer The overall U value is determined for a theoretical boiling coefficient of an unfouled tube (single) (this is an iterative procedure). See reference 90 also. 

U(j) = single tube overall heat transfer coefficient hj = nucleate boiling coefficient for single tube, outside Btu/hr (ft) (°F)... 

For the entire bundle, the film boiling coefficient (assumes all tubes boiling, no liquid head effect so that some tubes are not boiling) ... 

Read boiling coefficient, h, from Figure 10-108 using... 

Figure 10-107A. First physical property factor for boiling coefficient. (Used by permission Chen, Ning Hsing. Chemical Engineering V. 66 No. 5, 1959. McGraw-Hill, Inc. All rights reserved.)...

This method for vertical thermosiphon reboilers is based on semi-empirical correlations of experimental data and is stated to predict heat transfer coefficients 30 percent, which is about the same range of accuracy for most boiling coefficient data. The advantage of this method is that it has had significant design experience in the industry to support it. It is also adaptable to other types of reboilers used in the industry. See Figures 10-110 and 10-111. 

Figure 10-115—1/Xjj values for use in Figure 10-118. Figure 10-118—a for correcting the nucleate boiling coefficient.

Boiling coefficient, hg (Table 10-30 or other source, or Equation 10-185). 

Material Press. (psia) Equation Terms Max. At ( F) Boiling Coefficient at Designated At Heating Device... 

Figure 10-118 a from Equation 10-184. d. Nucleate boiling coefficient, h, from Table 10-30 or other source. (An estimate of the film temperature drop is required.)... 

Boiling coefficients Determine from the McNelly, Gilmour, Kem, or Yilmaz equations previously given, or Fair s suggestion of the Bliss or Levy equations, which were not given due to constants not being available. 

Figure 10-150. Boiling coefficients for low-finned tubes. (Used by permission Katz, D. L, Meyers, J. E., Young, E. H., and Balekjian, G. Petroleum Refiner, V. 34, No. 2, 1955. Gulf Publishing Company. All rights reserved.)...

Bp = coefficient in Levy boiling coefficient equation, Figure 10-99. 

In the absence of experimental data, the correlation given by Forster and Zuber<86) may be used to estimate pool boiling coefficients, although the following reduced pressure correlation given by M()STlNSKl(9ri) is much simpler to use and gives reliable results for h (in W/m2 K) ... 

A comprehensive review of the methods available for predicting convective boiling coefficients is given by Webb and Gupte (1992). The methods proposed by Chen (1966) and Shah (1976) are convenient to use in manual calculations and are accurate enough for preliminary design work. Chen s method is outlined below and illustrated in Example 12.9. 

The convective boiling coefficient lijc can be estimated using the equations for singlephase forced-convection heat transfer modified by a factor fc to account for the effects of two-phase flow ... 

The nucleate boiling coefficient can be calculated using correlations for nucleate pool boiling modified by a factor fs to account for the fact that nucleate boiling is more difficult in a flowing liquid. 

The forced-convective boiling coefficient will be estimated using Chen s method. 

As the heat flux is known and only a rough estimate of the coefficient is required, use Mostinski s equation to estimate the nucleate boiling coefficient Section 12.11.2. 

When only a low rate of vaporisation is required a vertical cylindrical vessel with a heating jacket or coils should be considered. The boiling coefficients for internal submerged coils can be estimated using the equations for nucleate pool boiling. 

The equations for estimating nucleate boiling coefficients given in Section 12.11.1 can be used for close boiling mixtures, say less than 5°C, but will overestimate the coefficient if used for mixtures with a wide boiling range. Palen and Small (1964) give an empirical correction factor for mixtures which can be used to estimate the heat-transfer coefficient in the absence of experimental data ... 

Proposed layout gives 26 U-tubes, tube outer limit diameter 420 mm. Boiling coefficient... 

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