Valve
Navigation: Models ➔ Pressure Changing Models ➔ Valve 1
| Valve 1 in Steady State and Dynamic Transfer Push Mode | Valve 1 in Dynamic Transfer Pull Mode |
|---|
Related Links: Setting up Transfer Pull Network, Dynamic Transfer Simulation Mode
General Description
The valve model will add pressure drop to the stream or operates at a specified pressure.
Diagram
The diagram shows the default drawing of the Valve, with the required connecting streams. The unit will not operate unless all of the above streams are connected.
The physical location of the connections is not important; the user may connect the streams to any position on the drawing.
Inputs and Outputs
| Label | Required Optional |
Input Output |
Number of Connections | Description | |
| Min | Max | ||||
| Input | Required | In | 1 | 1 | Input stream to valve. |
| Output | Requered | Out | 1 | 1 | Output stream from valve. |
Model Theory
The valve is a constant enthalpy process.
Step 1) Enthalpy can be calculated from the inlet conditions.
Step 2) Outlet temperature can be calculated from enthalpy and outlet pressure.
Data Sections
Summary of Data Sections
- Valve-1 tab - Contains general information relating to the unit.
- VLE - Optional tab, only visible if the VLEquilibrium is enabled in the Evaluation Block.
- Info tab - Contains general settings for the unit and allows the user to include documentation about the unit and create Hyperlinks to external documents.
- Links tab, contains a summary table for all the input and output streams.
- Audit tab - Contains summary information required for Mass and Energy balance. See Model Examples for enthalpy calculation Examples.
Valve Page
Unit Type: Valve-1 - The first tab page in the access window will have this name.
| Tag (Long/Short) | Input / Calc | Description/Calculated Variables / Options |
| Tag | Display | This name tag may be modified with the change tag option. |
| Condition | Display | OK if no errors/warnings, otherwise lists errors/warnings. |
| ConditionCount | Display | The current number of errors/warnings. If condition is OK, returns 0. |
| GeneralDescription / GenDesc | Display | This is an automatically generated description for the unit. If the user has entered text in the 'EqpDesc' field on the Info tab (see below), this will be displayed here. If this field is blank, then SysCAD will display the UnitType or SubClass. |
Requirements | ||
| PressMethod | None | No pressure change across the unit. |
| Drop | The user specifies a pressure drop. Therefore, Pout = Pin - Pdrop | |
| Fixed | The user specifies a fixed outlet pressure from the unit. | |
| Atmos | The outlet pressure from the unit is set to atmospheric pressure. | |
| PressDropReqd / PDropReqd | Input | The required pressure drop. Visible if the Drop method is selected. |
| PressureReqd / P_Reqd | Input | The required outlet pressure. Visible if the Fixed method is selected. |
| VLEquilibrium | Off | Vapour Liquid Equilibrium is off. |
| On | Vapour Liquid Equilibrium (VLE) is enabled. The associated section, VLE becomes visible and may be configured. Note: This option may automatically adjust the species make-up in Qo. | |
Results | ||
| MassFlow / Qm | Calc | The total mass of material flowing through the valve. |
| TemperatureIn / Ti | Calc | The temperature of material at the inlet of the valve. |
| TemperatureOut / To | Calc | The temperature of material at the outlet of the valve. |
| PressureIn / Pi | Calc | The actual pressure at the inlet of the valve. |
| PressChange / dP | Calc | The pressure change in the valve. |
| PressureOut / Po | Calc | The actual pressure at the outlet of the valve. |
| DensityIn / Rhoi | Calc | The density of material at the inlet of the valve. |
| DensityOut / Rhoo | Calc | The density of material at the outlet of the valve. |
| VapourFracIn / Vfi | Calc | Vapour Mass Fraction at the inlet of the valve. |
| VapourFracOut / Vfo | Calc | Vapour Mass Fraction at the outlet of the valve. |
Adding this Model to a Project
Add to Configuration File
Sort either by DLL or Group:
| DLL: | Piping1.dll |
→ | Units/Links | → | Piping: Valve(1) | |
| or | Group: | Mass Transfer |
→ | Units/Links | → | Piping: Valve(1) |
See Model Selection for more information on adding models to the configuration file.
Insert into Project Flowsheet
| Insert Unit | → | Piping | → | Valve(1) |
See Insert Unit for general information on inserting units.