WOLFRAM SYSTEM MODELER

ValveDiscrete

Valve for water/steam flows with linear pressure drop

Wolfram Language

In[1]:=

SystemModel["Modelica.Fluid.Valves.ValveDiscrete"]

Out[1]:=

Information

This information is part of the Modelica Standard Library maintained by the Modelica Association.

This very simple model provides a (small) pressure drop which is proportional to the flowrate if the Boolean open signal is true. Otherwise, the mass flow rate is zero. If opening_min > 0, a small leakage mass flow rate occurs when open = false.

This model can be used for simplified modelling of on-off valves, when it is not important to accurately describe the pressure loss when the valve is open. Although the medium model is not used to determine the pressure loss, it must be nevertheless be specified, so that the fluid ports can be connected to other components using the same medium model.

The model is adiabatic (no heat losses to the ambient) and neglects changes in kinetic energy from the inlet to the outlet.

In a diagram animation, the valve is shown in "green", when it is open.

Parameters (10)

allowFlowReversal	Value: system.allowFlowReversal Type: Boolean Description: = true to allow flow reversal, false restricts to design direction (port_a -> port_b)
dp_start	Value: 0.01 * system.p_start Type: AbsolutePressure (Pa) Description: Guess value of dp = port_a.p - port_b.p
m_flow_start	Value: system.m_flow_start Type: MassFlowRate (kg/s) Description: Guess value of m_flow = port_a.m_flow
m_flow_small	Value: if system.use_eps_Re then system.eps_m_flow * system.m_flow_nominal else system.m_flow_small Type: MassFlowRate (kg/s) Description: Small mass flow rate for regularization of zero flow
show_T	Value: true Type: Boolean Description: = true, if temperatures at port_a and port_b are computed
show_V_flow	Value: true Type: Boolean Description: = true, if volume flow rate at inflowing port is computed
dp_nominal	Value: Type: AbsolutePressure (Pa) Description: Nominal pressure drop at full opening=1
m_flow_nominal	Value: Type: MassFlowRate (kg/s) Description: Nominal mass flowrate at full opening=1
k	Value: m_flow_nominal / dp_nominal Type: HydraulicConductance (kg/(s⋅Pa)) Description: Hydraulic conductance at full opening=1
opening_min	Value: 0 Type: Real Description: Remaining opening if closed, causing small leakage flow

Connectors (3)

	port_a	Type: FluidPort_a Description: Fluid connector a (positive design flow direction is from port_a to port_b)
	port_b	Type: FluidPort_b Description: Fluid connector b (positive design flow direction is from port_a to port_b)
	open	Type: BooleanInput Description: 'input Boolean' as connector

port_a

Type: FluidPort_a

Description: Fluid connector a (positive design flow direction is from port_a to port_b)

port_b

Type: FluidPort_b

Description: Fluid connector b (positive design flow direction is from port_a to port_b)

open

Type: BooleanInput

Description: 'input Boolean' as connector

Components (3)

	system	Type: System Description: System wide properties
	state_a	Type: ThermodynamicState Description: State for medium inflowing through port_a
	state_b	Type: ThermodynamicState Description: State for medium inflowing through port_b