blockPrimaryVariableFlow

Ideal control of condenser or evaporator variable flow rate

Information

This block implements an ideal control of the evaporator (or condenser) water mass flow rate. The control intent aims to maintain a constant water temperature difference dT_nominal across the heat exchanger, within the limit of a minimum mass flow rate ratio ratFloMin. For computational performance and to avoid the use of a PI controller, the required mass flow rate is computed based on a signal representative of the load.

Parameters

Type	Name	Default	Description
Real	cp	Buildings.Utilities.Psychrometrics.Constants.cpWatLiq	Specific heat capacity
Real	Q_flow_nominal		Heat flow rate at nominal conditions (>0 for condenser)
Real	dT_nominal		DeltaT at nominal conditions (>0 for condenser)
Real	ratFloMin	0.3	Minimum mass flow rate (ratio to nominal)
Real	m_flow_nominal	Q_flow_nominal/cp/dT_nominal	Mass flow rate at nominal conditions

Connectors

Type	Name	Default	Description
Buildings.Controls.OBC.CDL.Interfaces.RealInput	loa		Signal approximating the load on condenser or evaporator
Buildings.Controls.OBC.CDL.Interfaces.RealOutput	m_flow		Mass flow rate

Components

Type	Name	Description
Buildings.Controls.OBC.CDL.Reals.Sources.Constant	masFloMin	Minimum mass flow rate
Buildings.Controls.OBC.CDL.Reals.MultiplyByParameter	masFlo_dT	Mass flow rate for constant DeltaT
Buildings.Controls.OBC.CDL.Reals.Max	masFlo	Mass flow rate
Buildings.Controls.OBC.CDL.Reals.Abs	abs1	Absolute value

Revisions

February 23, 2021, by Antoine Gautier:
First implementation.