Fluid Library

AFT xStream provides a fluid library for numerous common fluids. If the working fluid you wish to model is not in this library, you may elect to enter the fluid properties in a custom library for later recall using the Edit Fluids panel in the Library Manager.

You can open the Edit Fluids panel from the Library menu or from the Edit Fluid list button in the Fluid panel in Analysis Setup. The Edit Fluids panel allows you to review currently defined AFT Standard and custom fluids, to change the data for custom fluids, and to enter new fluids. All AFT Standard fluid properties are assumed to be a function of temperature. Custom fluids can be a function of temperature or solids concentration.

Once you have entered a custom fluid, it will appear in the Fluids Available in Library list of the Fluid panel when AFT Standard is selected.

You can add new fluids in the Library Manager Edit Fluids panel by clicking the Add New Fluid button. A number of fluid properties are required for a compressible flow analysis. There are also several optional properties. The required properties are dynamic viscosity, specific heat at constant pressure, enthalpy, and molecular weight. Other entries for critical property data are used for some of the equation of state and enthalpy models. A constant compressibility factor can be assigned. The thermal conductivity is optional if pipe heat transfer is being modeled as adiabatic or isothermal.

Except for the constants, density, and enthalpy, all properties are assumed to be functions of temperature only. The assumption can break down in systems with very large temperature changes, and should be checked by the user. These properties are modeled with fourth order polynomials, and features for creating curve fits from raw data are provided.

The enthalpy is a strong function of temperature but a weaker function of pressure. Frequently the pressure dependence of enthalpy can be ignored. The three enthalpy models offered by AFT Arrow allow you to choose different ways of handling the pressure dependence.

The Fluid Library window also allows you to open the Change Fluid Data window which is essentially the same window as the Add New Fluid window. For easy editing, data for the fluid you wish to change is entered for you in the appropriate areas. The original curve fit data you entered is also displayed.

The Add New Fluid/Change Fluid Data windows offer cross-plotting of your custom curves against the curve fit data points. You can also import data from text files into these windows.