Variable Fluids Panel

AFT Impulse allows users to model constant or varying fluid properties.

• Constant Fluid Properties - All fluid properties are the same for every pipe and are as specified in the Fluid panel. Note that non-newtonian viscosity models will still cause the viscosity to vary if the constant fluid properties option is selected.

• Variable Fluid Properties - The values for density and viscosity in the Fluid panel are the default fluid properties for new pipes drawn on the Workspace, and you can then enter different fluid property values, if desired, for any pipe in the Fluid Properties tab of the Pipe Properties window. This does not mean that fluid properties can vary on their own in the model - they are constant in each pipe and must still be directly specified by the user.

  Note: Fluid properties from one pipe don't propagate through the system. Each pipe will only use it's assigned fluid properties regardless of flow direction.

  This option may be useful to model different pipes carrying different fluids, or to model changes in temperature across a component such as a heat exchanger. Impulse cannot perform heat transfer or dynamic mixing; however, fluid properties of pure components may be individually specified in upstream pipes, and the resulting mixture properties can be individually specified in downstream pipes. Or, cold fluid properties can be entered for pipes upstream of a heat exchanger, and hot fluid properties can be entered for pipes downstream of the heat exchanger.

  Note: Transient Forces cannot be reliably calculated if the density changes between pipes that are included within the length of the Force Set due to Variable Fluid Properties. There may be Warnings For Force Calculations displayed within the interface.