T H E R M O D Y N A M I C S

The default Density (SI unit: kg/m3), Heat capacity at constant pressure CP (SI unit: J/ (kg·K)), and Ratio of specific heats (unitless) for a general gas or liquid use values From

material. Select User defined to enter other values or expressions.

Select a Fluid type:

•Select Gas/liquid to specify the density, the heat capacity at constant pressure, and the ratio of specific heats for a general gas or liquid. The default settings are to use data from the material. Select User defined to enter another value for the density, heat capacity, or ratio of specific heats.

•Select Ideal gas to use the ideal gas law to describe the fluid. In this case, specify the thermodynamics properties by selecting a gas constant type and selecting between entering the heat capacity at constant pressure or the ration of specific heats:

From the list under Gas constant type, select Specific gas constant to specify the

specific gas constant Rs, or select Mean molar mass to specify the mean molar mass

Mn. If Mean molar mass is selected, the software uses the universal gas constant

R 8.314 J/(mol·K), which is a built-in physical constant. For both properties, the default setting is to use the property value from the material. Select User defined to define another value for either of these material properties.

From the list under Specify Cp or , select Heat capacity at constant pressure to specify

the heat capacity at constant pressure Cp, or select Ratio of specific heats to specify the ratio of specific heats . For both properties, the default setting is to use the

property value from the material. Select User defined to define another value for either of these material properties.

For an ideal gas, specify either Cp or the ratio of specific heats, , but not

both since these, in that case, are dependent.

Tip

Viscous Heating

The Viscous Heating node adds the following term to the right-hand side of the Heat Transfer in Fluids equation:

where is the viscous stress tensor and S is the strain-rate tensor. Equation 13-4 represents the heating caused by viscous friction within the fluid.

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