Empirical Correlations/Models

DOE-HDBK-3010-94

3.0 Liquids; Aqueous Solutions

= 0.33 (MFg)0.91

ARF

(3-7)

= mole fraction of pressurizing gas or water vapor flashed.

where: MFg

The mole fraction of pressurizing gas is computed using the method described in

Appendix B of Ballinger, Sutter and Hodgson (May 1987) and is equal to the fraction

of liquid flashed at release. The enthalpy and volume of vapor and liquid before and

directly at release are used to calculate the fraction flashed.

The mass of vapor "flashed" at release is determined by an energy balance for the

two phases after the initial pressure is vented. As an initial step, nomenclature must

be defined. Temperature T1 and pressure P1 are the liquid temperature and pressure

before release (i.e., superheated, pressurized liquid). Temperature T2 is the saturation

temperature of the remaining liquid and generated vapor immediately after release to

a lower pressure (P2, typically atmospheric pressure).

A simple, conservative energy balance can equate the enthalpies of the saturated vapor

and liquid directly after the release to the enthalpy of the superheated liquid just

before release. This energy balance, where the total mass, volume of container, and

initial time are known, is as follows:

masssh(Hsh)

massv(Hv) + massl(Hl)

(3-8)

where:

masssh =

mass of superheated liquid present (g),

enthalpy of superheated liquid at T1 and P1 (cal/g),

Hsh

massv =

mass of saturated vapor generated by flashing during

depressurization (g),

enthalpy of saturated vapor (e.g., vapor at saturation

temperature T2 for pressure P2 ) (cal/g),

massl =

mass of saturated liquid remaining after depressurization

(g), and

enthalpy of saturated liquid (e.g., liquid at saturation

temperature T2 for pressure P2 ) (cal/g).

The simple mass balance for the flashing system would be:

masssh =

massv + massl

(3-9)

The mass balance can be rearranged to

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