Correlation 23

The following table lists the identification numbers of this correlation with respect to some well-known sources of thermodynamic data.

The equation has the following form:

You must use at least 4 coefficients with this correlation. The C4 coefficient cannot equal zero.

You can use up to 9 coefficients with this correlation.

You can use any temperature unit of measure (UOM) when you input data for this correlation. However, AVEVA Thermodynamic Data Manager converts temperatures to Kelvin (K) before it calculates the property value.

Modification for specific heat in AVEVA Process Simulation

In the Component Data section of the Fluid Editor, AVEVA Process Simulation shows temperature-dependent correlations for specific heat instead of enthalpy. When you enter correlation coefficients for specific heat in the Fluid Editor, you enter values for the derivative (specific heat) form of the correlation ().

However, AVEVA Thermodynamic Data Manager (TDM) shows temperature-dependant correlations for enthalpy, not specific heat. Therefore, when you specify the temperature-dependent properties in TDM, you see and enter the correlation coefficient values for the integrated (enthalpy) form of the equation (). When you specify the correlation coefficient values in TDM, you should take care to follow the correct coefficient mapping between the AVEVA Process Simulation coefficients () and the TDM coefficients (). See Example of coefficient mapping between AVEVA Thermodynamic Data Manager and AVEVA Process Simulation for more information.

Internally, AVEVA Process Simulation still uses the integrated (enthalpy) form of the equation to perform calculations. The coefficient in TDM is the constant of integration, and this term cancels out when performing calculations. Therefore, you can set the coefficient in TDM to any value without affecting the calculation results. When we specify the coefficient mapping for the correlation, we set the coefficient to zero, but you can use any value in TDM and still get matching calculation results in both AVEVA Process Simulation and TDM.

The following equation shows the derivative form of this correlation:

The following equations show the coefficient mapping between the integrated and derivative forms of the correlation:

You must use at least 3 coefficients with this correlation. The CCp3 coefficient cannot equal zero.

You can use up to 8 coefficients with this correlation.

Usage

We recommend that you use this correlation to calculate only the following properties:

• Ideal Vapor Enthalpy

• Ideal Gas Specific Heat Capacity