# Steam/Water Valve¶

This is a steam power generation turbine model for the stages between the inlet and outlet. This model inherits the PressureChanger model with the adiabatic options. Beyond the base pressure changer model this provides a pressure flow relation as a function of the valve opening fraction.

## Example¶

from pyomo.environ import ConcreteModel, SolverFactory, TransformationFactory

from idaes.core import FlowsheetBlock
from idaes.unit_models.power_generation import SteamValve
from idaes.property_models import iapws95
from idaes.ui.report import degrees_of_freedom, active_equalities

solver = SolverFactory('ipopt')
solver.options = {'tol': 1e-6}

m = ConcreteModel()
m.fs = FlowsheetBlock(default={"dynamic": False})
m.fs.properties = iapws95.Iapws95ParameterBlock()
m.fs.valve = SteamValve(default={"property_package": m.fs.properties})

hin = iapws95.htpx(T=880, P=2.4233e7)
# set inlet
m.fs.valve.inlet.enth_mol[0].fix(hin)
m.fs.valve.inlet.flow_mol[0].fix(26000/4.0)
m.fs.valve.inlet.pressure[0].fix(2.5e7)
m.fs.valve.Cv.fix(0.01)
m.fs.valve.valve_opening.fix(0.5)
m.fs.valve.initialize(outlvl=1)


## Parameters¶

Expression Symbol Index Sets Doc
flow_scale $$s_f$$ None Factor for scaling the pressure-flow equation, should be same magnitude as expected flow rate

## Variables¶

This model adds a variable to account for mechanical efficiency to the base PressureChanger model.

Variable Symbol Index Sets Doc
Cv $$C_v$$ None Valve coefficient for liquid [mol/s/Pa^0.5] for vapor [mol/s/Pa]
valve_opening $$x$$ time The fraction that the valve is open from 0 to 1

## Expressions¶

Currently this model provides two additional expressions, with are not available in the pressure changer model.

Expression Symbol Index Sets Doc
valve_function $$f(x)$$ time This is a valve function that describes how the fraction open affects flow.

## Constraints¶

The pressure flow relation is added to the inherited constraints from the PressureChanger model.

If the phase option is set to "Liq" the following equation describes the pressure-flow relation.

$\frac{1}{s_f^2}F^2 = \frac{1}{s_f^2}C_v^2\left(P_{in} - P_{out}\right)f(x)^2$

If the phase option is set to "Vap" the following equation describes the pressure-flow relation.

$\frac{1}{s_f^2}F^2 = \frac{1}{s_f^2}C_v^2\left(P_{in}^2 - P_{out}^2\right)f(x)^2$

## Initialization¶

This just calls the initialization routine from PressureChanger, but it is wrapped in a function to ensure the state after initialization is the same as before initialization. The arguments to the initialization method are the same as PressureChanger.

## SteamValve Class¶

class idaes.unit_models.power_generation.valve_steam.SteamValve(*args, **kwargs)

Basic steam valve models

Parameters: rule (function) – A rule function or None. Default rule calls build(). concrete (bool) – If True, make this a toplevel model. Default - False. ctype (str) – Pyomo ctype of the block. Default - “Block” default (dict) – Default ProcessBlockData config Keys dynamic Indicates whether this model will be dynamic or not, default = useDefault. Valid values: { useDefault - get flag from parent (default = False), True - set as a dynamic model, False - set as a steady-state model.} has_holdup Indicates whether holdup terms should be constructed or not. Must be True if dynamic = True, default - False. Valid values: { True - construct holdup terms, False - do not construct holdup terms} material_balance_type Indicates what type of mass balance should be constructed, default - MaterialBalanceType.useDefault. Valid values: { MaterialBalanceType.useDefault - refer to property package for default balance type **MaterialBalanceType.none - exclude material balances, MaterialBalanceType.componentPhase - use phase component balances, MaterialBalanceType.componentTotal - use total component balances, MaterialBalanceType.elementTotal - use total element balances, MaterialBalanceType.total - use total material balance.} energy_balance_type Indicates what type of energy balance should be constructed, default - EnergyBalanceType.useDefault. Valid values: { EnergyBalanceType.useDefault - refer to property package for default balance type **EnergyBalanceType.none - exclude energy balances, EnergyBalanceType.enthalpyTotal - single enthalpy balance for material, EnergyBalanceType.enthalpyPhase - enthalpy balances for each phase, EnergyBalanceType.energyTotal - single energy balance for material, EnergyBalanceType.energyPhase - energy balances for each phase.} momentum_balance_type Indicates what type of momentum balance should be constructed, default - MomentumBalanceType.pressureTotal. Valid values: { MomentumBalanceType.none - exclude momentum balances, MomentumBalanceType.pressureTotal - single pressure balance for material, MomentumBalanceType.pressurePhase - pressure balances for each phase, MomentumBalanceType.momentumTotal - single momentum balance for material, MomentumBalanceType.momentumPhase - momentum balances for each phase.} has_phase_equilibrium Indicates whether terms for phase equilibrium should be constructed, default = False. Valid values: { True - include phase equilibrium terms False - exclude phase equilibrium terms.} compressor Indicates whether this unit should be considered a compressor (True (default), pressure increase) or an expander (False, pressure decrease). thermodynamic_assumption Flag to set the thermodynamic assumption to use for the unit. - ThermodynamicAssumption.isothermal (default) - ThermodynamicAssumption.isentropic - ThermodynamicAssumption.pump - ThermodynamicAssumption.adiabatic property_package Property parameter object used to define property calculations, default - useDefault. Valid values: { useDefault - use default package from parent model or flowsheet, PropertyParameterObject - a PropertyParameterBlock object.} property_package_args A ConfigBlock with arguments to be passed to a property block(s) and used when constructing these, default - None. Valid values: { see property package for documentation.} valve_function The type of valve function, if custom provide an expression rule with the valve_function_rule argument. default - ValveFunctionType.linear Valid values - { ValveFunctionType.linear, ValveFunctionType.quick_opening, ValveFunctionType.equal_percentage, ValveFunctionType.custom} valve_function_rule This is a rule that returns a time indexed valve function expression. This is required only if valve_function==ValveFunctionType.custom phase Expected phase of fluid in valve in {“Liq”, “Vap”} initialize (dict) – ProcessBlockData config for individual elements. Keys are BlockData indexes and values are dictionaries described under the “default” argument above. idx_map (function) – Function to take the index of a BlockData element and return the index in the initialize dict from which to read arguments. This can be provided to overide the default behavior of matching the BlockData index exactly to the index in initialize. (SteamValve) New instance

## SteamValveData Class¶

class idaes.unit_models.power_generation.valve_steam.SteamValveData(component)[source]
build()[source]
Parameters: None – None
initialize(state_args={}, outlvl=6, solver='ipopt', optarg={'max_iter': 30, 'tol': 1e-06})[source]

Initialize the turbine stage model. This deactivates the specialized constraints, then does the isentropic turbine initialization, then reactivates the constraints and solves.

Parameters: state_args (dict) – Initial state for property initialization outlvl – sets output level of initialization routine * 0 = Use default idaes.init logger setting * 1 = Maximum output * 2 = Include solver output * 3 = Return solver state for each step in subroutines * 4 = Return solver state for each step in routine * 5 = Final initialization status and exceptions * 6 = No output solver (str) – Solver to use for initialization optarg (dict) – Solver arguments dictionary