Buildings.Fluid.DataCenters.Racks.RearDoorHeatExchangers

Package with models for rear door heat exchangers

Information

Package with standalone models for rear door heat exchangers used in IT racks. A rear door heat exchanger is mounted at the back of the rack and removes heat from the warm server exhaust air using a liquid coolant loop.

Two variants are provided:

Buildings.Fluid.DataCenters.Racks.RearDoorHeatExchangers.Passive: the air is driven through the heat exchanger by the server fans inside the rack. No additional fan is required.
Buildings.Fluid.DataCenters.Racks.RearDoorHeatExchangers.Active: an integrated fan drives the air through the heat exchanger, allowing independent control of the air flow rate. A PI controller regulates the fan speed to maintain a target air outlet temperature.

Extends from Modelica.Icons.Package (Icon for standard packages).

Package Content

Name	Description
Active	Active rear door heat exchanger with integrated temperature controlled fan
Passive	Passive rear door heat exchanger — air driven by fans in server
Data	Data records for rear door heat exchangers
Examples	Example models for rear door heat exchangers
BaseClasses	Base classes for rear door heat exchanger models

Buildings.Fluid.DataCenters.Racks.RearDoorHeatExchangers.Active

Active rear door heat exchanger with integrated temperature controlled fan

Buildings.Fluid.DataCenters.Racks.RearDoorHeatExchangers.Active

Information

Model of an active rear door heat exchanger (RDHx) for IT racks.

In this configuration, an integrated fan drives the warm server exhaust air through the heat exchanger mounted at the rear door of the rack. The fan speed is modulated by a PI controller to maintain zero back pressure. The fan power is reported through the output PFan.

The liquid coolant enters through portCoo_a and exits through portCoo_b. The air enters through portAir_a (warm server exhaust), passes through the fan and then through the heat exchanger, and exits through portAir_b (cooled air leaving the rack).

The performance data are provided through the record dat of type Buildings.Fluid.DataCenters.Racks.RearDoorHeatExchangers.Data.Active.Generic.

Extends from Buildings.Fluid.DataCenters.Racks.RearDoorHeatExchangers.BaseClasses.PartialRearDoorHeatExchanger (Partial model of a rear door heat exchanger with coolant and air ports).

Parameters

Type	Name	Default	Description
replaceable package MediumCoo		PartialMedium	Medium for rear door heat exchanger coolant loop
replaceable package MediumAir		PartialMedium	Medium for air side
Fan controller
Real	k	1	Gain of PI controller
Time	Ti	10	Integrator time constant of PI controller [s]
Assumptions
Boolean	allowFlowReversalCoo	true	= false to simplify equations on coolant side, assuming, but not enforcing, no flow reversal
Boolean	allowFlowReversalAir	true	= false to simplify equations on air side, assuming, but not enforcing, no flow reversal
Dynamics
Conservation equations
Dynamics	energyDynamics	Modelica.Fluid.Types.Dynamic...	Type of energy balance for fan

Connectors

Type	Name	Description
FluidPort_a	portCoo_a	Coolant inlet port
FluidPort_b	portCoo_b	Coolant outlet port
FluidPort_a	portAir_a	Air inlet port
FluidPort_b	portAir_b	Air outlet port
output RealOutput	PFan	Power consumed by rear door heat exchanger fan [W]

Modelica definition

model Active "Active rear door heat exchanger with integrated temperature controlled fan" extends Buildings.Fluid.DataCenters.Racks.RearDoorHeatExchangers.BaseClasses.PartialRearDoorHeatExchanger( redeclare replaceable parameter Buildings.Fluid.DataCenters.Racks.RearDoorHeatExchangers.Data.Active.Generic dat constrainedby Buildings.Fluid.DataCenters.Racks.RearDoorHeatExchangers.Data.Active.Generic); parameter Modelica.Fluid.Types.Dynamics energyDynamics= Modelica.Fluid.Types.Dynamics.SteadyState "Type of energy balance for fan"; parameter Real k=1 "Gain of PI controller"; parameter Modelica.Units.SI.Time Ti=10 "Integrator time constant of PI controller"; Modelica.Blocks.Interfaces.RealOutput PFan( final quantity="Power", final unit="W") "Power consumed by rear door heat exchanger fan"; Buildings.Fluid.DataCenters.Racks.BaseClasses.Fan fan( redeclare final package Medium = MediumAir, final inputType=Buildings.Fluid.Types.InputType.Continuous, final allowFlowReversal=allowFlowReversalAir, final m_flow_nominal=dat.mAir_flow_nominal, final PFan_nominal=dat.PFan_nominal, final eta_nominal=dat.eta_nominal, final energyDynamics=energyDynamics, addPowerToMedium=true) "Rear door heat exchanger fan"; Buildings.Fluid.Sensors.TemperatureTwoPort senTAirOut( redeclare final package Medium = MediumAir, final m_flow_nominal=dat.mAir_flow_nominal, final tau=0, final allowFlowReversal=allowFlowReversalAir) "Air temperature leaving rear door heat exchanger"; Buildings.Fluid.DataCenters.Racks.FanControllers.BackPressure con( final k=k, final Ti=Ti) "Controller for fan"; Sensors.Pressure senPreIn(redeclare package Medium = MediumAir) "Inlet pressure"; Sensors.Pressure senPreOut(redeclare package Medium = MediumAir) "Outlet pressure"; Sensors.TemperatureTwoPort senTAirReaDooHexOut( redeclare package Medium = MediumAir, final allowFlowReversal=allowFlowReversalAir, m_flow_nominal=dat.mAir_flow_nominal) "Air temperature exiting rear door heat exchanger"; equation connect(senTAirOut.port_b, portAir_b); connect(fan.P, PFan); connect(senPreOut.port, portAir_b); connect(con.pSet, senPreOut.p); connect(con.pMea, senPreIn.p); connect(senPreIn.port, senTAirReaDooHexIn.port_a); connect(con.y, fan.y); connect(senTAirReaDooHexIn.port_b, reaDooHex.port_a2); connect(fan.port_b, senTAirOut.port_a); connect(reaDooHex.port_b2, senTAirReaDooHexOut.port_a); connect(senTAirReaDooHexOut.port_b, fan.port_a); end Active;

Buildings.Fluid.DataCenters.Racks.RearDoorHeatExchangers.Passive

Passive rear door heat exchanger — air driven by fans in server

Buildings.Fluid.DataCenters.Racks.RearDoorHeatExchangers.Passive

Information

Model of a passive rear door heat exchanger (RDHx) for IT racks.

In this configuration, the server fans inside the rack drive the warm exhaust air through the heat exchanger mounted at the rear door. No dedicated fan is added; the air-side pressure drop is overcome by the server fans.

The liquid coolant enters through portCoo_a and exits through portCoo_b. The air enters through portAir_a (warm server exhaust) and exits through portAir_b (cooled air leaving the rack).

The performance data are provided through the record dat of type Buildings.Fluid.DataCenters.Racks.RearDoorHeatExchangers.Data.Passive.Generic.

Extends from Buildings.Fluid.DataCenters.Racks.RearDoorHeatExchangers.BaseClasses.PartialRearDoorHeatExchanger (Partial model of a rear door heat exchanger with coolant and air ports).

Parameters

Type	Name	Default	Description
replaceable package MediumCoo		PartialMedium	Medium for rear door heat exchanger coolant loop
replaceable package MediumAir		PartialMedium	Medium for air side
Nominal condition
Generic	dat	redeclare parameter Building...	Heat exchanger performance data
Assumptions
Boolean	allowFlowReversalCoo	true	= false to simplify equations on coolant side, assuming, but not enforcing, no flow reversal
Boolean	allowFlowReversalAir	true	= false to simplify equations on air side, assuming, but not enforcing, no flow reversal

Connectors

Type	Name	Description
FluidPort_a	portCoo_a	Coolant inlet port
FluidPort_b	portCoo_b	Coolant outlet port
FluidPort_a	portAir_a	Air inlet port
FluidPort_b	portAir_b	Air outlet port

Modelica definition

model Passive "Passive rear door heat exchanger — air driven by fans in server" extends Buildings.Fluid.DataCenters.Racks.RearDoorHeatExchangers.BaseClasses.PartialRearDoorHeatExchanger; equation connect(reaDooHex.port_b2, portAir_b); connect(senTAirReaDooHexIn.port_b, reaDooHex.port_a2); end Passive;