modelPumpBase

Base model for centrifugal pumps

Information

This is the base model for the Pump and PumpMech pump models.

The model describes a centrifugal pump, or a group of Np identical pumps in parallel. The pump model is based on the theory of kinematic similarity: the pump characteristics are given for nominal operating conditions (rotational speed and fluid density), and then adapted to actual operating condition, according to the similarity equations.

In order to avoid singularities in the computation of the outlet enthalpy at zero flowrate, the thermal capacity of the fluid inside the pump body can be taken into account.

The model can either support reverse flow conditions or include a built-in check valve to avoid flow reversal.

Modelling options

The nominal hydraulic characteristic (head vs. volume flow rate) is given by the the replaceable function flowCharacteristic.

The pump energy balance can be specified in two alternative ways:

usePowerCharacteristic = false (default option): the replaceable function efficiencyCharacteristic (efficiency vs. volume flow rate in nominal conditions) is used to determine the efficiency, and then the power consumption. The default is a constant efficiency of 0.8.
usePowerCharacteristic = true: the replaceable function powerCharacteristic (power consumption vs. volume flow rate in nominal conditions) is used to determine the power consumption, and then the efficiency.

Several functions are provided in the package Functions.PumpCharacteristics to specify the characteristics as a function of some operating points at nominal conditions.

Depending on the value of the checkValve parameter, the model either supports reverse flow conditions, or includes a built-in check valve to avoid flow reversal.

If the in_Np input connector is wired, it provides the number of pumps in parallel; otherwise, Np0 parallel pumps are assumed.

It is possible to take into account the heat capacity of the fluid inside the pump by specifying its volume V at nominal conditions; this is necessary to avoid singularities in the computation of the outlet enthalpy in case of zero flow rate. If zero flow rate conditions are always avoided, this dynamic effect can be neglected by leaving the default value V = 0, thus avoiding a fast state variable in the model.

The CheckValve parameter determines whether the pump has a built-in check valve or not.

If computeNPSHa = true, the available net positive suction head is also computed; this requires a two-phase medium model to provide the fluid saturation pressure.

Parameters

Type	Name	Default	Description
Integer	Np0	1	Nominal number of pumps in parallel
SI.Volume	V	0	Pump Internal Volume
Boolean	CheckValve	false	Reverse flow stopped
Boolean	allowFlowReversal	system.allowFlowReversal	= true to allow flow reversal, false restricts to design direction
SI.Acceleration	g	Modelica.Constants.g_n
SI.VolumeFlowRate	q_single0	w0/(Np0*rho0)	Nominal volume flow rate (single pump)
SI.Height	head0	dp0/(rho0*g)	Nominal pump head
Real	d_head_dq_0	(flowCharacteristic(q_single01.05) - flowCharacteristic(q_single00.95))/(q_single0*0.1)	Approximate derivative of flow characteristic w.r.t. volume flow
Real	d_head_dn_0	2/n0head0 - q_single0/n0d_head_dq_0	Approximate derivative of the flow characteristic w.r.t. rotational speed
SI.Power	W_eps	1e-8	Small coefficient to avoid numerical singularities
NonSI.AngularVelocity_rpm	n_eps	1e-6
Characteristics
Boolean	usePowerCharacteristic	false	Use powerCharacteristic (vs. efficiencyCharacteristic)
Units.LiquidDensity	rho0	1000	Nominal Liquid Density
NonSI.AngularVelocity_rpm	n0		Nominal rotational speed
Medium.MassFlowRate	w0		Nominal mass flow rate
SI.Pressure	dp0		Nominal pressure increase
External inputs
Boolean	use_in_Np	false	Use connector input for the pressure
Initialisation
Medium.MassFlowRate	wstart	w0	Mass Flow Rate Start Value
Medium.SpecificEnthalpy	hstart	1e5	Specific Enthalpy Start Value
Choices.Init.Options	initOpt	system.initOpt	Initialisation option
Boolean	noInitialPressure	false	Remove initial equation on pressure

Connectors

Type	Name	Description
FlangeA	infl
FlangeB	outfl
Modelica.Blocks.Interfaces.IntegerInput	in_Np	Number of parallel pumps

Components

Type	Name	Default	Description
Medium.ThermodynamicState	inletFluidState		Thermodynamic state of the fluid at the inlet
ThermoPower.System	system		System wide properties
Medium.MassFlowRate	w_single		Mass flow rate (single pump)
Medium.MassFlowRate	w	Np*w_single	Mass flow rate (total)
SI.VolumeFlowRate	q_single		Volume flow rate (single pump)
SI.VolumeFlowRate	q	Np*q_single	Volume flow rate (total)
SI.PressureDifference	dp		Outlet pressure minus inlet pressure
SI.Height	head		Pump head
Medium.SpecificEnthalpy	h		Fluid specific enthalpy
Medium.SpecificEnthalpy	hin		Enthalpy of entering fluid
Medium.SpecificEnthalpy	hout		Enthalpy of outgoing fluid
Units.LiquidDensity	rho		Liquid density
Medium.Temperature	Tin		Liquid inlet temperature
NonSI.AngularVelocity_rpm	n		Shaft r.p.m.
Integer	Np		Number of pumps in parallel
SI.Power	W_single		Power Consumption (single pump)
SI.Power	W	Np*W_single	Power Consumption (total)
SI.Power	Qloss	0	Heat loss (single pump)
SI.PerUnit	eta		Pump efficiency
SI.PerUnit	s		Auxiliary non-dimensional variable

Name	Description
Medium
flowCharacteristic	Head vs. q_flow characteristic at nominal speed and density
powerCharacteristic
efficiencyCharacteristic

Revisions

31 Oct 2006 by Francesco Casella:
Added initialisation parameter wstart.
5 Nov 2005 by Francesco Casella:
Model restructured according to kinematic similarity theory.
Characteristics now specified by replaceable functions.
6 Apr 2005 by Francesco Casella:
CharData substituted by OpPoints
16 Dec 2004 by Francesco Casella:
Standard medium definition added.
2 Aug 2004 by Francesco Casella:
Optional NPSHa computation added. Changed parameter names
5 Jul 2004 by Francesco Casella:
Model restructured by using inheritance. Adapted to Modelica.Media.
15 Jan 2004 by Francesco Schiavo:
ThermalCapacity and CheckValve added.
15 Dec 2003 by Francesco Schiavo:
First release.