Phase Coupled Fluid Energy Model Reference

The enthalpy field can be of interest in some applications, especially those involving phase change. In such applications, it is recommended that you also set the Heat of Formation and Standard State Temperature properties for each phase material. These two parameters, along with the specific heat of the phase, allow the enthalpy for a particular phase to be fully defined. Consistent definitions of phase enthalpies (that is with phase reference enthalpies defined against a reference temperature that is common for all phases) also correctly defines the magnitude and sign of enthalpy of phase.

These reference condition inputs have been named Heat of Formation and Standard State Temperature as commonly used in reacting flows. However, any other consistent set of reference data can be used instead.

For phase change calculations, a typical usage is to specify phase enthalpies at the saturation temperature corresponding to the system pressure. Example values for two-phase boiling water systems operating at 101,325 Pa are:

Enthalpy reference temperature: 373.12 K
Enthalpy reference value (liquid): 417436 J/kg
Enthalpy reference value (vapor): 2674950 J/kg

The enthalpy results that are computed for this system can then be compared directly with steam table values.

Table 1. Phase Coupled Fluid Energy Model Reference
Theory	See Energy Equation.
Provided By	[physics continuum] > Models > Optional Models
Example Node Path	Continua > Physics 1 > Models > Phase Coupled Fluid Energy
Requires	Material:Multiphase Multiphase Model: Eulerian Multiphase (EMP)
Properties	None.
Activates	Physics Models	In each Eulerian phase: Energy. The available models are: Segregated Fluid Enthalpy Segregated Fluid Temperature
	Materials	Heat of Formation, Specific Heat, Standard State Temperature, Thermal Conductivity. See Material Properties.
	Reference Values	Minimum Allowable Temperature, Maximum Allowable Temperature. See Reference Values.
	Initial Conditions	Static Temperature See Initial Conditions.
	Boundary Inputs	For Inflow and Outflow boundaries: Static Temperature See Boundary Settings.
	Interface Inputs	See Interface Settings.
	Region Inputs	For phases with the Segregated Fluid Enthalpy model activated: Energy Source Option See Region Settings.
	Solvers	Segregated Energy See Segregated Energy Solver for Multiphase.
	Report Options	Phase Heat Transfer. See Reports.
	Field Functions	See Field Functions.

Material Properties

These properties can be set for each phase and for each component of multi-component phases:

Heat of Formation

See Using the Heat of Formation.

Specific Heat

Method	Corresponding Method Node
Gas Kinetics	Available for Multi-Component Gas components only. See Using the Gas Kinetics Method for Specific Heat.
Polynomial in T	Available for each phase, and for each component of multi-component phases. Enthalpy is calculated as the integral of specific heat over T in the interval between the specified Standard State Temperature and T, plus the heat of formation. The heat of formation defaults to zero if the corresponding material property value is not specified. See Using Polynomial in T.
Mass-Weighted Mixture	Available at the phase level for multi-component phases. Specify the Specific Heat for each component of the multi-component phase. See Using the Mass-Weighted Mixture.

Method

Corresponding Method Node

Gas Kinetics

Available for Multi-Component Gas components only.

See Using the Gas Kinetics Method for Specific Heat.

Polynomial in T

Available for each phase, and for each component of multi-component phases.

Enthalpy is calculated as the integral of specific heat over T in the interval between the specified Standard State Temperature and T, plus the heat of formation. The heat of formation defaults to zero if the corresponding material property value is not specified.

See Using Polynomial in T.

Mass-Weighted Mixture

Available at the phase level for multi-component phases.

Specify the Specific Heat for each component of the multi-component phase.

See Using the Mass-Weighted Mixture.

Standard State Temperature

See Using the Standard State Temperature.

Thermal Conductivity

See Using the Thermal Conductivity Method.

Reference Values

Minimum Allowable Temperature: The smallest temperature value that is permitted anywhere in the continuum. The default value is 100 K.
The Phase Coupled Fluid Energy model limits temperature corrections such that the corrected value does not go below this minimum. If this occurs, a message is printed to the Output window.
Maximum Allowable Temperature: The largest temperature value that is permitted anywhere in the continuum. The default value is 5000 K.
The Phase Coupled Fluid Energy model limits temperature corrections such that the corrected value does not exceed this maximum. If this occurs, a message is printed to the Output window.

Initial Conditions

Static Temperature: Activated for a phase when an Energy model (Segregated Fluid Enthalpy or Segregated Fluid Temperature) is activated.

Boundary Settings

Inflow and Outflow Boundaries

Static Temperature: Available in the Physics Values for each phase that has an Energy model (Segregated Fluid Enthalpy or Segregated Fluid Temperature) activated.

Interface Settings

Applies to Wall boundaries and Interface boundaries.

User Wall Heat Flux Coefficient Specification

Controls the heat flux relationship at walls and interfaces.

See Energy Source Option.

This setting is available in the Physics Conditions for each phase that has the Segregated Fluid Enthalpy model activated.

The User Wall Heat Flux Coefficient Specification in a multiphase simulation has some differences from the single-phase usage. You can implement your own wall contact models for the energy equation specifying user wall heat flux coefficients from internal wall heat flux coefficients.

The internal wall heat flux coefficients are defined per phase-wall contact area and the Net wall heat flux coefficients are defined against full geometric wall face area. For Eulerian Multiphase (EMP) simulations, this allows you to implement an alternative to the default model, using the volume fraction for the phase-wall contact area. You can implement this independently for the energy equation.

For more information, see Phase Heat Flux.

Method	Corresponding Physics Value Nodes
None	None
Specified	User Wall Heat Flux Coefficient A The user contribution to the constant coefficient of wall heat flux, A. User Wall Heat Flux Coefficient B The user contribution to the cell temperature coefficient of wall heat flux, B. User Wall Heat Flux Coefficient C The user contribution to the wall temperature coefficient of wall heat flux, C.
Specified Net Sets the net boundary heat flux coefficients equal to the user-specified heat flux coefficients, so that the net coefficients = user-defined coefficients. This method is available in Eulerian Multiphase (EMP) simulations only.	User Wall Heat Flux Coefficient A The user contribution to the constant coefficient of wall heat flux, A. User Wall Heat Flux Coefficient B The user contribution to the cell temperature coefficient of wall heat flux, B. User Wall Heat Flux Coefficient C The user contribution to the wall temperature coefficient of wall heat flux, C.

Region Settings

Applies to fluid regions.

Energy Source Option

Available in the Physics Conditions for each phase that has the Segregated Fluid Enthalpy model activated.

See Energy Source Option.

Reports

Phase Heat Transfer

Field Functions

Boundary Advection Heat Flux of [Phase]
Boundary Advection Heat Transfer of [Phase]
Boundary Conduction Heat Flux of [Phase]
Boundary Conduction Heat Transfer of [Phase]
Boundary Heat Flux
Boundary Heat Flux of [Phase]
Boundary Heat Flux on External Side
Boundary Heat Transfer of [Phase]
Effective Conductivity of [Phase]
External Ambient Temperature
External Heat Transfer Coefficient
Heat Transfer Coefficient
Heat Transfer Coefficient of [Phase]
Internal Wall Heat Flux Coefficient, A of [Phase]
Internal Wall Heat Flux Coefficient, B of [Phase]
Internal Wall Heat Flux Coefficient, C of [Phase]
Local Heat Transfer Coefficient
Local Heat Transfer Coefficient of [Phase]
Local Heat Transfer Reference Temperature
Local Heat Transfer Reference Temperature of [Phase]
Net Wall Heat Flux Coefficient, A of [Phase]
Net Wall Heat Flux Coefficient, B of [Phase]
Net Wall Heat Flux Coefficient, C of [Phase]
Porous Solid Conductivity of [Phase]
Relative Total Enthalpy of [Phase]
Relative Total Temperature of [Phase]
Rothalpy of [Phase]
Specific Heat of [Phase]
Static Enthalpy of [Phase]: When the Segregated Fluid Enthalpy model is activated in the phase.
Temperature Coefficient of [Phase]
Temperature of [Phase]
Temperature on External Side
Thermal Conductivity of [Phase]
Thermal Resistance
Total Energy of [Phase]
Total Enthalpy of [Phase]
Total Temperature of [Phase]