Three-Way Valves in Polysun Fluid Loop Design
Three-way valves play a crucial role when it comes to the analysis of fluid loops. Three-way valves share the inflowing fluid-flow in a fixed proportion. The position of the mixing valve is adjusted by the controller. Based on the situation in the schematic system diagram the three-way valve alternatively distributes inflowing fluid-flows or brings together two separate fluid flows. The adjusted output is marked with x. If the signal of the controller is logically one the x output will be completely open. Both situations are schematically outlined in the following graph:
Function of the Three-Way Valve in Polysun
The three-way valve is an important hydraulic component in Polysun that is used in a variety of ways in fluid circuits. Depending on the system layout, it performs one or both of the following tasks:
- Splitting an incoming fluid flow: A three-way valve can split a single inlet into two outlets. The split ratio (e.g. how much fluid goes to path A vs. path B) is determined by the valve’s control.
- Mixing two fluid flows: Conversely, it can take two flows and combine them into one outlet to achieve a desired mixing temperature.
The valve position (i.e. how wide the valve is open) is controlled by a control system. When the control signal (e.g. an analogue output signal or a logical state) is activated (i.e. set to 1), fluid flows in the x direction as shown in the three-way valve diagram. In other positions, partial opening occurs in accordance with the control behaviour.
Use cases and configuration
The three-way valve is often combined with a mixing valve controlller. This control monitors temperature variables (e.g. supply vs. return or two supplies) and controls the three-way valve so that a specific target temperature is reached at the outlet.
In Polysun, the valve position can be designed as an analogue signal. Depending on how the system model is created, the three-way valve can also be used as part of a switching concept (e.g. for switchover functions) or can function dynamically via the control system with temperature regulation.