Valve

Navigation: Main Page -> Models -> Pressure Changing Models

Related Topics: Valve 1 in dynamic with Simple flow calculation mode

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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

1. Valve-1 tab - Contains general information relating to the unit.
2. VLE - Optional tab, only visible if the VLEquilibrium is enabled in the Evaluation Block.
3. Info tab - Contains general settings for the unit and allows the user to include documentation about the unit and create Hyperlinks to external documents.
4. Links tab, only visible in SysCAD 9.2, contains a summary table for all the input and output streams.
5. Audit tab - Contains summary information required for Mass and Energy balance. See Model Examples for enthalpy calculation Examples.

Valve Page

Class: Valve-1

Tag / Symbol	Input / Calc	Options	Description/Calculated Variables
Common First Data Section
Requirements
PressureMethod	List Box	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.
PDrop	Input		The required pressure drop. Visible if the Drop method is selected.
PRqd	Input		The required outlet pressure. Visible if the Fixed method is selected.
VLEquilibrium	List Box	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
Qm	Calc		The mass flow rate through the unit.
Ti	Calc		The inlet temperature to the unit.
To	Calc		The outlet temperature from the unit.
Pi	Calc		The inlet pressure to the unit.
dP	Calc		The pressure change across the unit.
Po	Calc		The outlet pressure from the unit.
Vfi	Calc		The Inlet vapour fraction.
Vfo	Calc		The outlet vapour fraction.

Adding this Model to a Project

Insert into Configuration file

Sort either by DLL or Group.

	DLL:	Basic1.dll	→	Units/Links	→	Process: Piping: Valve(1)
or	Group:	Mass Transfer	→	Units/Links	→	Process: Piping: Valve(1)

See Project Configuration for more information on adding models to the configuration file.

Insert into Project

Insert Unit

→

Process

→

Piping

→

Valve(1)

See Insert Unit for general information on inserting units.