modelStorageTankWithExternalHeatExchanger

A model of a storage tank with external heat exchanger to produce hot water

Information

This model implements a heating hot water tank with external heat exchanger that heats domestic hot water.

It is based on Fig. 3 in Evaluations of different domestic hot water preparing methods with ultra-low-temperature district heating by X. Yang, H. Li, and S. Svendsen at doi.org/10.1016/j.energy.2016.04.109, as well as the Advanced Energy Design Guide for Multifamily Buildings-Achieving Zero Energy published by ASHRAE in 2022 at https://www.ashrae.org/technical-resources/aedgs/zero-energy-aedg-free-download.

For a model that connects this hot water system to a heat pump, see Buildings.DHC.ETS.Combined.Subsystems.HeatPumpDHWTank.

Type	Name	Default	Description
Buildings.DHC.Loads.HotWater.Data.GenericDomesticHotWaterWithHeatExchanger	dat		Performance data
Real	k	0.1	Proportional gain of circulation pump controller
Real	Ti	60	Integrator time constant of circulation pump controller
Assumptions
Boolean	allowFlowReversalDom (from PartialFourPortDHW)	true	= false to simplify equations, assuming, but not enforcing, no flow reversal for domestic water
Boolean	allowFlowReversalHea (from PartialFourPortDHW)	true	= false to simplify equations, assuming, but not enforcing, no flow reversal for heating water
Initialization
Modelica.Media.Interfaces.Types.Temperature	TTan_start	323.15	Start value of tank temperature
Advanced
Real	eps	dat.QHex_flow_nominal/CMin_flow_nominal/(dat.TDom_nominal + dat.dTHexApp_nominal - dat.TCol_nominal)	Heat exchanger effectiveness

Type	Name	Description
Modelica.Fluid.Interfaces.FluidPort_a	port_aDom (from PartialFourPortDHW)	Fluid connector for cold water (or recirculation water)
Modelica.Fluid.Interfaces.FluidPort_b	port_bDom (from PartialFourPortDHW)	Fluid connector for heated domestic hot water
Modelica.Fluid.Interfaces.FluidPort_a	port_aHea (from PartialFourPortDHW)	Fluid connector for heating water (positive design flow direction is from port_a to port_b)
Modelica.Fluid.Interfaces.FluidPort_b	port_bHea (from PartialFourPortDHW)	Fluid connector b for heating water (positive design flow direction is from port_a to port_b)
Buildings.Controls.OBC.CDL.Interfaces.RealInput	TDomSet (from PartialFourPortDHW)	Temperature setpoint for heated domestic water
Modelica.Blocks.Interfaces.RealOutput	PEle	Electric power required for pumping equipment
Buildings.Controls.OBC.CDL.Interfaces.BooleanOutput	charge	Output true if tank needs to be charged, false if it is sufficiently charged

Type	Name	Description
Buildings.Fluid.Movers.Preconfigured.FlowControlled_dp	pumHex	Pump with head as input
Buildings.Fluid.Storage.Stratified	tan	Heating water tank
Buildings.Fluid.Sensors.TemperatureTwoPort	senTemHot	Temperature sensor for hot water supply
Buildings.Fluid.HeatExchangers.ConstantEffectiveness	hex
Buildings.Fluid.FixedResistances.Junction	junTop	Flow junction at top of tank
Buildings.Fluid.Sensors.MassFlowRate	senMasFlo	Mass flow rate of domestic hot water
Modelica.Thermal.HeatTransfer.Sensors.TemperatureSensor	TTanTop	Fluid temperature at the top of the tank
Modelica.Thermal.HeatTransfer.Sensors.TemperatureSensor	TTanBot	Fluid temperature at the bottom of the tank
Buildings.DHC.Loads.HotWater.BaseClasses.HeatExchangerPumpController	conPum	Controller for pump of heat exchanger
Buildings.DHC.Loads.HotWater.BaseClasses.TankChargingController	conCha	Controller for tank charge signal
Buildings.Fluid.Actuators.Valves.ThreeWayLinear	divVal	Diversion valve to reduce mixing in tank
Buildings.Fluid.Sensors.TemperatureTwoPort	senTemRet	Temperature sensor for return heating water from heat exchanger
Buildings.DHC.Loads.HotWater.BaseClasses.TankValveController	conVal	Diversion valve controller
Buildings.Controls.OBC.CDL.Reals.AddParameter	dTHexApp	Offset for heat exchanger approach temperature