Pump

This pump unit model is a class of pressure changer which is based on the IDAES pressure changer and makes the following assumptions:

  • supports a single liquid phase only

  • supports steady-state only

  • supports isothermal pump only

Degrees of Freedom

Pump units generally have two or more degrees of freedom, depending on the pump efficiency model used.

Typical fixed variables are:

  • outlet pressure, \(P_{out}\) or pressure difference across the inlet and outlet,:math:Delta P

  • pump efficiency

Model Structure

The pump unit model consists of a single ControlVolume0D (named control_volume) with one Inlet Port (named inlet) and one Outlet Port (named outlet).

Sets

Description

Symbol

Indices

Time

\(t\)

[0]

Phases

\(p\)

[‘Liq’]

Components

\(j\)

[‘H2O’, ‘NaCl’]*

*Solute depends on the imported property model; example shown here is for the NaCl property model.

Variables

When the configuration option variable_efficiency is set to its default of VariableEfficiency.none (indicating constant efficiency), the variables are the same as those listed in the “Variable” tab of IDAES pressure changer.

When the configuration variable_efficiency is not VariableEfficiency.none, then there are three additional variables to account for variable pump efficiency:

Description

Symbol

Variable Name

Index

Units

Best efficiency point flowrate of the centrifugal pump

\(F_{bep}\)

bep_flow

None

\(\text{m}^3/\text{s}\)

Best efficiency of the centrifugal pump

\(\eta_{bep}\)

bep_eta

None

dimensionless

Ratio of pump flowrate to best efficiency point flowrate

\(r_{bep, t}\)

flow_ratio

[t]

dimensionless

Equations and Relationships

When the configuration variable_efficiency is set to default VariableEfficiency.none, the constraints are the same as those listed in IDAES pressure changer.

When the configuration variable_efficiency is not VariableEfficiency.none, there are two additional constraints:

Description

Equation

Pump flow ratio

\(F_{in, t} = r_{bp, t} * F_{bp}\)

Actual pump efficiency

\(\eta_{pump, t} = \eta_{bep} * r_{bep, t}\)

When the configuration variable_efficiency is set to VariableEfficiency.flow, then the pump efficiency is assumed to depend only on flow (Kuritza et al., 2017):

\[\begin{split}\eta_{pump, t}= \begin{cases} 0.4 & \text{for } r_{bp, t} < 0.6\\ -0.995 * r_{bp, t}^{2} + 1.977 * r_{bp, t} + 0.018 & \text{for } 0.6 \le r_{bp, t} \le 1.4\\ 0.4 & \text{for } r_{bp, t} > 1.4 \end{cases}\end{split}\]

NOTE: this option for centrifugal pumps has been used in modeling but not validated for high pressure applications

Class Documentation

class watertap.unit_models.pressure_changer.Pump(*args, **kwds)
Parameters:

  • rule (function) – A rule function or None. Default rule calls build().

  • concrete (bool) – If True, make this a toplevel model. Default - False.

  • ctype (class) –

    Pyomo ctype of the block. Default - pyomo.environ.Block

    Config args

    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: { useDefault - get flag from parent (default = False), 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.}

    support_isentropic_performance_curves

    Include a block for performance curves, configure via isentropic_performance_curves.

    isentropic_performance_curves

    Configuration dictionary for the performance curve block.

    isentropic_performance_curves
    build_callback

    Optional callback to add performance curve constraints

    build_head_expressions

    If true add expressions for ‘head’ and ‘head_isentropic’. These expressions can be used in performance curve constraints.

    variable_efficiency

    Indicates the relationship used to define pump efficiency VariableEfficiency.none - uses default pump efficiency at BEP VariableEfficiency.flow - uses an efficiency correlation scaled to the BEP flow rate VariableEfficiency.flow_head - uses an efficiency correlation scaled to the BEP flow rate and head

  • initialize (dict) – ProcessBlockData config for individual elements. Keys are BlockData indexes and values are dictionaries with config arguments as keys.

  • 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 override the default behavior of matching the BlockData index exactly to the index in initialize.

Returns:

(Pump) New instance

References

Kuritza, J. C., Camponogara, G., Marques, M. G., Sanagiotto, D. G., & Battiston, C. (2017). Dimensionless curves of centrifugal pumps for water supply systems: development and case study. Rbrh, 22, e45. https://www.scielo.br/j/rbrh/a/GpYnSMFgwbm6WWcksDTXq6z/?format=html&lang=en