Buildings.Fluid.DataCenters.Racks.Hybrid

Package with hybrid liquid and air-cooled IT racks

Information

This package contains models for hybrid IT racks that combine liquid cooling and air cooling technologies.

Extends from Modelica.Icons.VariantsPackage (Icon for package containing variants).

Package Content

Name	Description
AirLiquid	Hybrid rack model combining liquid-cooled and air-cooled components
AirLiquidRearDoorHexActive	Hybrid rack model combining liquid-cooled and air-cooled components with an active rear door heat exchanger
AirLiquidRearDoorHexPassive	Hybrid rack model combining liquid-cooled and air-cooled components with a rear door heat exchanger
AirRearDoorHexActive	Air-cooled rack model with an active rear door heat exchanger
AirRearDoorHexPassive	Air-cooled rack model with a passive rear door heat exchanger
Data	Package with performance data for hybrid racks
Examples	Collection of models that illustrate model use and test models
BaseClasses	Package with base classes for Buildings.Fluid.DataCenters.Racks.Hybrid

Buildings.Fluid.DataCenters.Racks.Hybrid.AirLiquid

Hybrid rack model combining liquid-cooled and air-cooled components

Buildings.Fluid.DataCenters.Racks.Hybrid.AirLiquid

Information

Model of a hybrid IT rack that combines liquid-cooled and air-cooled components. This model integrates two separate cooling technologies in a single rack. The liquid cooling component uses cold plates and is based on Buildings.Fluid.DataCenters.Racks.Liquid.ColdPlateR_P, while the air cooling component with integrated fans is based on Buildings.Fluid.DataCenters.Racks.Air.Rack_P.

The model has separate fluid ports for each cooling loop. For liquid cooling, portLiq_a and portLiq_b serve as the inlet and outlet ports. For air cooling, portAir_a and portAir_b serve as the inlet and outlet ports. Each cooling system has its own input for the electrical power consumption by the IT equipment. The input PLiq specifies the power consumption for the liquid-cooled IT equipment, and the input PAir specifies the power consumption for the air-cooled IT equipment. Note that PAir does not include the power to operate the fan, as this is an output of the model.

The model provides three power consumption outputs on the right side. The output PLiqTot is the electric power consumed by liquid-cooled IT. The output PAirTot is the total electric power consumed by air-cooled IT, including fan energy. The output PAirFan is the electric power consumed by the fan for air-cooled IT.

Extends from Buildings.Fluid.DataCenters.Racks.Hybrid.BaseClasses.AirLiquid (Partial hybrid rack model combining liquid-cooled and air-cooled components).

Parameters

Type	Name	Default	Description
replaceable package MediumLiq		PartialMedium	Medium for liquid cooling loop
replaceable package MediumAir		PartialMedium	Medium for air cooling loop
Performance data
Generic	dat	redeclare parameter Building...	Performance data
Liquid cooling
VolumeFlowRate	VColPla_flow_nominal	sum(dat.liq.theRes.V_flow)/s...	Design flow rate of one cold plate for liquid cooling [m3/s]
Real	nColPla	dat.liq.PIT_nominal/(VColPla...	Number of cold plates for liquid cooling
Fan controller
Strategy	fanControl	Buildings.Fluid.DataCenters....	Type of fan control strategy
Real	fanSpeed[:, :]	[0.0, 0.0; 1.0, 1.0]	Load and fan speed matrix (1st column normalized IT load, 2nd fan speed), e.g., fanSpeed=[0, 0; 0.5, 0.7; 1, 1])
Temperature	TAirOut_set	dat.air.TOut_nominal	Set point temperature for rack outlet air [K]
Real	k	1	Gain of fan PI controller
Time	Ti	60	Integrator time constant of fan PI controller [s]
Dynamics
Liquid cooling
Dynamics	energyDynamicsLiq	Modelica.Fluid.Types.Dynamic...	Type of energy balance for liquid-cooled component: dynamic (3 initialization options) or steady state
Time	tauLiq	2	Time constant of liquid outlet temperature at nominal flow [s]
Air cooling
Dynamics	energyDynamicsAir	Modelica.Fluid.Types.Dynamic...	Type of energy balance for air-cooled component: dynamic (3 initialization options) or steady state
Time	tauAir	2	Time constant of air outlet temperature at nominal flow [s]
Initialization
Liquid cooling
Temperature	TLiq_start	293.15	Start value of liquid temperature [K]
Air cooling
Temperature	TAir_start	293.15	Start value of air temperature [K]
Advanced
Liquid cooling
Boolean	linearizedLiq	false	= true, use linear relation between m_flow and dp for liquid cooling
Assumptions
Boolean	allowFlowReversalAir	true	= false to simplify equations, assuming, but not enforcing, no flow reversal for air loop
Boolean	allowFlowReversalLiq	true	= false to simplify equations, assuming, but not enforcing, no flow reversal for liquid loop

Connectors

Type	Name	Description
FluidPort_a	portLiq_a	Liquid cooling inlet port
FluidPort_b	portLiq_b	Liquid cooling outlet port
FluidPort_a	portAir_a	Air cooling inlet port
FluidPort_b	portAir_b	Air cooling outlet port
input RealInput	PLiq	Power consumed by for liquid-cooled IT [W]
input RealInput	PAir	Power consumed by air-cooled IT [W]
output RealOutput	PLiqTot	Electric power consumed by liquid-cooled IT [W]
output RealOutput	PAirTot	Electric power consumed by air-cooled IT, including fan energy [W]
output RealOutput	PAirFan	Electric power consumed by fan for air-cooled IT [W]

Modelica definition

model AirLiquid "Hybrid rack model combining liquid-cooled and air-cooled components" extends Buildings.Fluid.DataCenters.Racks.Hybrid.BaseClasses.AirLiquid; equation connect(air.port_b, portAir_b); end AirLiquid;

Buildings.Fluid.DataCenters.Racks.Hybrid.AirLiquidRearDoorHexActive

Hybrid rack model combining liquid-cooled and air-cooled components with an active rear door heat exchanger

Buildings.Fluid.DataCenters.Racks.Hybrid.AirLiquidRearDoorHexActive

Information

Model of a hybrid IT rack that combines liquid-cooled and air-cooled components with an active rear door heat exchanger. This model extends Buildings.Fluid.DataCenters.Racks.Hybrid.BaseClasses.AirLiquid and adds an active rear door heat exchanger using Buildings.Fluid.DataCenters.Racks.RearDoorHeatExchangers.Active.

Unlike Buildings.Fluid.DataCenters.Racks.Hybrid.AirLiquidRearDoorHexPassive, this model includes a dedicated fan that actively drives air flow through the heat exchanger. The fan speed is modulated by a PI controller to maintain zero back pressure. The fan power is reported through the output PReaDooHexFan.

The fan is part of the rear door heat exchanger model and positioned downstream of the heat exchanger. The rear door heat exchanger cools the warm rack exhaust air using a coolant loop connected through portReaDooHex_a (inlet) and portReaDooHex_b (outlet).

The medium for the rear door heat exchanger coolant is MediumReaDooHex, which is separate from the liquid cooling medium MediumLiq used by the cold plate components.

If the fan of the air-cooled IT is controlled based on the rack outlet temperature, then the temperature between the rack and the rear door heat exchanger is used as the measurement signal; otherwise, the IT load is used as an input for the fan controller. The fan of the rear door heat exchanger is controlled to have zero back pressure. Therefore, if the CPU fan speed increases, it will build up back pressure, and the rear door heat exchanger then increases its speed as well.

Extends from Buildings.Fluid.DataCenters.Racks.Hybrid.BaseClasses.PartialAirLiquidRearDoorHex (Partial model for hybrid rack combining liquid-cooled and air-cooled components with a rear door heat exchanger).

Parameters

Type	Name	Default	Description
replaceable package MediumLiq		PartialMedium	Medium for liquid cooling loop
replaceable package MediumAir		PartialMedium	Medium for air cooling loop
replaceable package MediumReaDooHex		PartialMedium	Medium for rear door heat exchanger coolant loop
Liquid cooling
VolumeFlowRate	VColPla_flow_nominal	sum(dat.liq.theRes.V_flow)/s...	Design flow rate of one cold plate for liquid cooling [m3/s]
Real	nColPla	dat.liq.PIT_nominal/(VColPla...	Number of cold plates for liquid cooling
Fan controller
Strategy	fanControl	Buildings.Fluid.DataCenters....	Type of fan control strategy
Real	fanSpeed[:, :]	[0.0, 0.0; 1.0, 1.0]	Load and fan speed matrix (1st column normalized IT load, 2nd fan speed), e.g., fanSpeed=[0, 0; 0.5, 0.7; 1, 1])
Temperature	TAirOut_set	dat.air.TOut_nominal	Set point temperature for rack outlet air [K]
Real	k	1	Gain of fan PI controller
Time	Ti	60	Integrator time constant of fan PI controller [s]
Rear door heat exchanger fan controller
Real	kReaDooHex	1	Gain of PI controller
Time	TiReaDooHex	10	Integrator time constant of PI controller [s]
Dynamics
Liquid cooling
Dynamics	energyDynamicsLiq	Modelica.Fluid.Types.Dynamic...	Type of energy balance for liquid-cooled component: dynamic (3 initialization options) or steady state
Time	tauLiq	2	Time constant of liquid outlet temperature at nominal flow [s]
Air cooling
Dynamics	energyDynamicsAir	Modelica.Fluid.Types.Dynamic...	Type of energy balance for air-cooled component: dynamic (3 initialization options) or steady state
Time	tauAir	2	Time constant of air outlet temperature at nominal flow [s]
Initialization
Liquid cooling
Temperature	TLiq_start	293.15	Start value of liquid temperature [K]
Air cooling
Temperature	TAir_start	293.15	Start value of air temperature [K]
Advanced
Liquid cooling
Boolean	linearizedLiq	false	= true, use linear relation between m_flow and dp for liquid cooling
Assumptions
Boolean	allowFlowReversalAir	true	= false to simplify equations, assuming, but not enforcing, no flow reversal for air loop
Boolean	allowFlowReversalLiq	true	= false to simplify equations, assuming, but not enforcing, no flow reversal for liquid loop
Boolean	allowFlowReversalCoo	true	= false to simplify equations, assuming, but not enforcing, no flow reversal for rear door heat exchanger coolant

Connectors

Type	Name	Description
FluidPort_a	portLiq_a	Liquid cooling inlet port
FluidPort_b	portLiq_b	Liquid cooling outlet port
FluidPort_a	portAir_a	Air cooling inlet port
FluidPort_b	portAir_b	Air cooling outlet port
input RealInput	PLiq	Power consumed by for liquid-cooled IT [W]
input RealInput	PAir	Power consumed by air-cooled IT [W]
output RealOutput	PLiqTot	Electric power consumed by liquid-cooled IT [W]
output RealOutput	PAirTot	Electric power consumed by air-cooled IT, including fan energy [W]
output RealOutput	PAirFan	Electric power consumed by fan for air-cooled IT [W]
FluidPort_a	portReaDooHex_a	Rear door heat exchanger coolant inlet port
FluidPort_b	portReaDooHex_b	Rear door heat exchanger coolant outlet port
output RealOutput	PReaDooHexFan	Power consumed by rear door heat exchanger fan [W]

Modelica definition

model AirLiquidRearDoorHexActive "Hybrid rack model combining liquid-cooled and air-cooled components with an active rear door heat exchanger" extends Buildings.Fluid.DataCenters.Racks.Hybrid.BaseClasses.PartialAirLiquidRearDoorHex( redeclare parameter Buildings.Fluid.DataCenters.Racks.Hybrid.Data.AirLiquidRearDoorHexActive.Generic dat, redeclare final Buildings.Fluid.DataCenters.Racks.RearDoorHeatExchangers.Active reaDooHex( final k=kReaDooHex, final Ti=TiReaDooHex)); parameter Real kReaDooHex=1 "Gain of PI controller"; parameter Modelica.Units.SI.Time TiReaDooHex=10 "Integrator time constant of PI controller"; Modelica.Blocks.Interfaces.RealOutput PReaDooHexFan( final quantity="Power", final unit="W") "Power consumed by rear door heat exchanger fan"; equation connect(reaDooHex.PFan, PReaDooHexFan); end AirLiquidRearDoorHexActive;

Buildings.Fluid.DataCenters.Racks.Hybrid.AirLiquidRearDoorHexPassive

Hybrid rack model combining liquid-cooled and air-cooled components with a rear door heat exchanger

Buildings.Fluid.DataCenters.Racks.Hybrid.AirLiquidRearDoorHexPassive

Information

Model of a hybrid IT rack that combines liquid-cooled and air-cooled components with a rear door heat exchanger.

This model extends Buildings.Fluid.DataCenters.Racks.Hybrid.BaseClasses.AirLiquid and adds a rear door heat exchanger using Buildings.Fluid.DataCenters.Racks.RearDoorHeatExchangers.Passive.

The rear door heat exchanger is connected between the air outlet of the air-cooled rack component air.port_b and the top-level air outlet port portAir_b. It cools the warm rack exhaust air using a liquid coolant loop connected through portReaDooHex_a (inlet) and portReaDooHex_b (outlet).

The medium for the rear door heat exchanger coolant is MediumReaDooHex, which is separate from the liquid cooling medium MediumLiq used to cool the cold plate components.

The model has separate fluid ports for each cooling loop. For liquid cooling, portLiq_a and portLiq_b serve as the inlet and outlet ports. For air cooling, portAir_a and portAir_b serve as the inlet and outlet ports. For the rear door heat exchanger coolant, portReaDooHex_a and portReaDooHex_b serve as the inlet and outlet ports.

Parameters

Type	Name	Default	Description
replaceable package MediumLiq		PartialMedium	Medium for liquid cooling loop
replaceable package MediumAir		PartialMedium	Medium for air cooling loop
replaceable package MediumReaDooHex		PartialMedium	Medium for rear door heat exchanger coolant loop
Performance data
Generic	dat	redeclare replaceable parame...	Performance data
Liquid cooling
VolumeFlowRate	VColPla_flow_nominal	sum(dat.liq.theRes.V_flow)/s...	Design flow rate of one cold plate for liquid cooling [m3/s]
Real	nColPla	dat.liq.PIT_nominal/(VColPla...	Number of cold plates for liquid cooling
Fan controller
Strategy	fanControl	Buildings.Fluid.DataCenters....	Type of fan control strategy
Real	fanSpeed[:, :]	[0.0, 0.0; 1.0, 1.0]	Load and fan speed matrix (1st column normalized IT load, 2nd fan speed), e.g., fanSpeed=[0, 0; 0.5, 0.7; 1, 1])
Temperature	TAirOut_set	dat.air.TOut_nominal	Set point temperature for rack outlet air [K]
Real	k	1	Gain of fan PI controller
Time	Ti	60	Integrator time constant of fan PI controller [s]
Dynamics
Liquid cooling
Dynamics	energyDynamicsLiq	Modelica.Fluid.Types.Dynamic...	Type of energy balance for liquid-cooled component: dynamic (3 initialization options) or steady state
Time	tauLiq	2	Time constant of liquid outlet temperature at nominal flow [s]
Air cooling
Dynamics	energyDynamicsAir	Modelica.Fluid.Types.Dynamic...	Type of energy balance for air-cooled component: dynamic (3 initialization options) or steady state
Time	tauAir	2	Time constant of air outlet temperature at nominal flow [s]
Initialization
Liquid cooling
Temperature	TLiq_start	293.15	Start value of liquid temperature [K]
Air cooling
Temperature	TAir_start	293.15	Start value of air temperature [K]
Advanced
Liquid cooling
Boolean	linearizedLiq	false	= true, use linear relation between m_flow and dp for liquid cooling
Assumptions
Boolean	allowFlowReversalAir	true	= false to simplify equations, assuming, but not enforcing, no flow reversal for air loop
Boolean	allowFlowReversalLiq	true	= false to simplify equations, assuming, but not enforcing, no flow reversal for liquid loop
Boolean	allowFlowReversalCoo	true	= false to simplify equations, assuming, but not enforcing, no flow reversal for rear door heat exchanger coolant

Connectors

Type	Name	Description
FluidPort_a	portLiq_a	Liquid cooling inlet port
FluidPort_b	portLiq_b	Liquid cooling outlet port
FluidPort_a	portAir_a	Air cooling inlet port
FluidPort_b	portAir_b	Air cooling outlet port
input RealInput	PLiq	Power consumed by for liquid-cooled IT [W]
input RealInput	PAir	Power consumed by air-cooled IT [W]
output RealOutput	PLiqTot	Electric power consumed by liquid-cooled IT [W]
output RealOutput	PAirTot	Electric power consumed by air-cooled IT, including fan energy [W]
output RealOutput	PAirFan	Electric power consumed by fan for air-cooled IT [W]
FluidPort_a	portReaDooHex_a	Rear door heat exchanger coolant inlet port
FluidPort_b	portReaDooHex_b	Rear door heat exchanger coolant outlet port

Modelica definition

model AirLiquidRearDoorHexPassive "Hybrid rack model combining liquid-cooled and air-cooled components with a rear door heat exchanger" extends Buildings.Fluid.DataCenters.Racks.Hybrid.BaseClasses.PartialAirLiquidRearDoorHex( redeclare final Buildings.Fluid.DataCenters.Racks.RearDoorHeatExchangers.Passive reaDooHex); end AirLiquidRearDoorHexPassive;

Buildings.Fluid.DataCenters.Racks.Hybrid.AirRearDoorHexActive

Air-cooled rack model with an active rear door heat exchanger

Buildings.Fluid.DataCenters.Racks.Hybrid.AirRearDoorHexActive

Information

Model of an air-cooled IT rack with an active rear door heat exchanger.

This model extends Buildings.Fluid.DataCenters.Racks.Hybrid.BaseClasses.PartialAirRearDoorHex and adds an active rear door heat exchanger using Buildings.Fluid.DataCenters.Racks.RearDoorHeatExchangers.Active.

Unlike Buildings.Fluid.DataCenters.Racks.Hybrid.AirRearDoorHexPassive, this model includes a dedicated fan that actively drives air flow through the heat exchanger. The fan speed is modulated by a PI controller to maintain zero back pressure. The fan power is reported through the output PReaDooHexFan.

The medium for the rear door heat exchanger coolant is MediumReaDooHex.

Extends from Buildings.Fluid.DataCenters.Racks.Hybrid.BaseClasses.PartialAirRearDoorHex (Partial model for air-cooled rack with a rear door heat exchanger).

Parameters

Type	Name	Default	Description
replaceable package MediumAir		PartialMedium	Medium for air cooling loop
replaceable package MediumReaDooHex		PartialMedium	Medium for rear door heat exchanger coolant loop
Fan controller
Strategy	fanControl	Buildings.Fluid.DataCenters....	Type of fan control strategy
Real	fanSpeed[:, :]	[0.0, 0.0; 1.0, 1.0]	Load and fan speed matrix (1st column normalized IT load, 2nd fan speed), e.g., fanSpeed=[0, 0; 0.5, 0.7; 1, 1])
Temperature	TAirOut_set	dat.air.TOut_nominal	Set point temperature for rack outlet air [K]
Real	k	1	Gain of fan PI controller
Time	Ti	60	Integrator time constant of fan PI controller [s]
Rear door heat exchanger fan controller
Real	kReaDooHex	1	Gain of PI controller
Time	TiReaDooHex	10	Integrator time constant of PI controller [s]
Dynamics
Air cooling
Dynamics	energyDynamicsAir	Modelica.Fluid.Types.Dynamic...	Type of energy balance for air-cooled component: dynamic (3 initialization options) or steady state
Time	tauAir	2	Time constant of air outlet temperature at nominal flow [s]
Initialization
Air cooling
Temperature	TAir_start	293.15	Start value of air temperature [K]
Assumptions
Boolean	allowFlowReversal	true	= false to simplify equations, assuming, but not enforcing, no flow reversal
Boolean	allowFlowReversalCoo	true	= false to simplify equations, assuming, but not enforcing, no flow reversal for rear door heat exchanger coolant

Connectors

Type	Name	Description
FluidPort_a	portAir_a	Air cooling inlet port
FluidPort_b	portAir_b	Air cooling outlet port
input RealInput	PAir	Power consumed by air-cooled IT [W]
output RealOutput	PAirTot	Electric power consumed by air-cooled IT, including fan energy [W]
output RealOutput	PAirFan	Electric power consumed by fan for air-cooled IT [W]
FluidPort_a	portReaDooHex_a	Rear door heat exchanger coolant inlet port
FluidPort_b	portReaDooHex_b	Rear door heat exchanger coolant outlet port
output RealOutput	PReaDooHexFan	Power consumed by rear door heat exchanger fan [W]

Modelica definition

model AirRearDoorHexActive "Air-cooled rack model with an active rear door heat exchanger" extends Buildings.Fluid.DataCenters.Racks.Hybrid.BaseClasses.PartialAirRearDoorHex( redeclare parameter Buildings.Fluid.DataCenters.Racks.Hybrid.Data.AirRearDoorHexActive.Generic dat, redeclare final Buildings.Fluid.DataCenters.Racks.RearDoorHeatExchangers.Active reaDooHex( final k=kReaDooHex, final Ti=TiReaDooHex)); parameter Real kReaDooHex=1 "Gain of PI controller"; parameter Modelica.Units.SI.Time TiReaDooHex=10 "Integrator time constant of PI controller"; Modelica.Blocks.Interfaces.RealOutput PReaDooHexFan( final quantity="Power", final unit="W") "Power consumed by rear door heat exchanger fan"; equation connect(reaDooHex.PFan, PReaDooHexFan); end AirRearDoorHexActive;

Buildings.Fluid.DataCenters.Racks.Hybrid.AirRearDoorHexPassive

Air-cooled rack model with a passive rear door heat exchanger

Buildings.Fluid.DataCenters.Racks.Hybrid.AirRearDoorHexPassive

Information

Model of an air-cooled IT rack with a passive rear door heat exchanger.

This model extends Buildings.Fluid.DataCenters.Racks.Hybrid.BaseClasses.PartialAirRearDoorHex and adds a rear door heat exchanger using Buildings.Fluid.DataCenters.Racks.RearDoorHeatExchangers.Passive.

The medium for the rear door heat exchanger coolant is MediumReaDooHex.

The model has separate fluid ports for each cooling loop. For the rear door heat exchanger coolant, portReaDooHex_a and portReaDooHex_b serve as the inlet and outlet ports.

Extends from Buildings.Fluid.DataCenters.Racks.Hybrid.BaseClasses.PartialAirRearDoorHex (Partial model for air-cooled rack with a rear door heat exchanger).

Parameters

Type	Name	Default	Description
replaceable package MediumAir		PartialMedium	Medium for air cooling loop
replaceable package MediumReaDooHex		PartialMedium	Medium for rear door heat exchanger coolant loop
Performance data
Generic	dat	redeclare replaceable parame...	Performance data
Fan controller
Strategy	fanControl	Buildings.Fluid.DataCenters....	Type of fan control strategy
Real	fanSpeed[:, :]	[0.0, 0.0; 1.0, 1.0]	Load and fan speed matrix (1st column normalized IT load, 2nd fan speed), e.g., fanSpeed=[0, 0; 0.5, 0.7; 1, 1])
Temperature	TAirOut_set	dat.air.TOut_nominal	Set point temperature for rack outlet air [K]
Real	k	1	Gain of fan PI controller
Time	Ti	60	Integrator time constant of fan PI controller [s]
Dynamics
Air cooling
Dynamics	energyDynamicsAir	Modelica.Fluid.Types.Dynamic...	Type of energy balance for air-cooled component: dynamic (3 initialization options) or steady state
Time	tauAir	2	Time constant of air outlet temperature at nominal flow [s]
Initialization
Air cooling
Temperature	TAir_start	293.15	Start value of air temperature [K]
Assumptions
Boolean	allowFlowReversal	true	= false to simplify equations, assuming, but not enforcing, no flow reversal
Boolean	allowFlowReversalCoo	true	= false to simplify equations, assuming, but not enforcing, no flow reversal for rear door heat exchanger coolant

Connectors

Type	Name	Description
FluidPort_a	portAir_a	Air cooling inlet port
FluidPort_b	portAir_b	Air cooling outlet port
input RealInput	PAir	Power consumed by air-cooled IT [W]
output RealOutput	PAirTot	Electric power consumed by air-cooled IT, including fan energy [W]
output RealOutput	PAirFan	Electric power consumed by fan for air-cooled IT [W]
FluidPort_a	portReaDooHex_a	Rear door heat exchanger coolant inlet port
FluidPort_b	portReaDooHex_b	Rear door heat exchanger coolant outlet port

Modelica definition

model AirRearDoorHexPassive "Air-cooled rack model with a passive rear door heat exchanger" extends Buildings.Fluid.DataCenters.Racks.Hybrid.BaseClasses.PartialAirRearDoorHex( redeclare final Buildings.Fluid.DataCenters.Racks.RearDoorHeatExchangers.Passive reaDooHex); end AirRearDoorHexPassive;