The Tank junction type allows you to connect up to twenty-five pipes. A minimum of one connecting pipe is required.

The Tank Properties window follows the second of the two basic Properties window formats.

Tank Model

There are two possible Tank Models available in the Tank junction, Infinite Tank and Finite Tank.

• Infinite Tank - Infinite tanks refer to a massive volume of gas whose pressure and temperature do not change appreciably as a result of gas inflow or outflow during the time frame of the simulation. An example is a large room or the atmosphere. The Infinite Tank model is convenient for specifying a fixed pressure in your system. This tank model applies a defined pressure at the junction location in the model. When solving a pipe flow system, an Infinite Tank causes the rest of the system to distribute the flow in a manner consistent with the defined pressure.

• Finite Tank - Finite tanks refer to a body of fluid which is small enough that its pressure and temperature change significantly during the time frame of the simulation as a result of gas inflow or outflow. An example is a tank which is pressurized by a compressor as the simulation progresses. Finite tanks require specification of tank geometry. Typically, the pressure and temperature are defined initially, and then calculated over time based on the tank geometry.

Both tank models will require the initial stagnation pressure and stagnation temperature/enthalpy to be defined.

If the Finite Tank option is chosen, then the volume and thermodynamic behavior of the tank become required inputs as discussed below.

Known Parameters Initially

For the Finite Open Tank option, the options become active to specify whether the pressure and temperature are defined by the user for the steady state.

• Initial Conditions Known - This option should always be chosen for tanks at the inlet or outlet of the system which are acting as boundaries, Or for tanks with a known operating temperature and pressure in the steady state.

• Initial Conditions Calculated From Steady State - This option should be used for tanks that are inline or at intermediate points in the system at which the pressure and temperature are not known.

Thermodynamic Process

The tank thermodynamics can be specified using one of three options:

• Adiabatic - The static enthalpy and volume in the tank will be fixed based on the user specified initial conditions in the tank. The variation in all other parameters will be calculated throughout the transient.

• Isothermal - The temperature and volume in the tank will be fixed based on the user specified initial conditions in the tank. The variation in all other parameters will be calculated throughout the transient.

• Known Heat and Volume vs. Time - The heat rate and volume are explicitly defined by the user throughout the transient. The variation in all other parameters will be calculated throughout the transient.