modelAirLiquidRearDoorHexActive
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).
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.
Parameters
| Type | Name | Default | Description |
|---|---|---|---|
| Performance data | |||
| Buildings.Fluid.DataCenters.Racks.Hybrid.Data.AirLiquid.Generic | dat (from AirLiquid) | Performance data | |
| Dynamics › Liquid cooling | |||
| Modelica.Fluid.Types.Dynamics | energyDynamicsLiq (from AirLiquid) | Modelica.Fluid.Types.Dynamics.DynamicFreeInitial | Type of energy balance for liquid-cooled component: dynamic (3 initialization options) or steady state |
| Modelica.Units.SI.Time | tauLiq (from AirLiquid) | 2 | Time constant of liquid outlet temperature at nominal flow |
| Initialization › Liquid cooling | |||
| Modelica.Units.SI.Temperature | TLiq_start (from AirLiquid) | 293.15 | Start value of liquid temperature |
| Liquid cooling | |||
| Modelica.Units.SI.VolumeFlowRate | VColPla_flow_nominal (from AirLiquid) | sum(dat.liq.theRes.V_flow)/size(dat.liq.theRes.V_flow, 1) | Design flow rate of one cold plate for liquid cooling |
| Real | nColPla (from AirLiquid) | dat.liq.PIT_nominal/(VColPla_flow_nominal*1000*4200*(dat.liq.PIT_nominal/(dat.liq.m_flow_nominal*4200))) | Number of cold plates for liquid cooling |
| Advanced › Liquid cooling | |||
| Boolean | linearizedLiq (from AirLiquid) | false | = true, use linear relation between m_flow and dp for liquid cooling |
| Dynamics › Air cooling | |||
| Modelica.Fluid.Types.Dynamics | energyDynamicsAir (from AirLiquid) | Modelica.Fluid.Types.Dynamics.DynamicFreeInitial | Type of energy balance for air-cooled component: dynamic (3 initialization options) or steady state |
| Modelica.Units.SI.Time | tauAir (from AirLiquid) | 2 | Time constant of air outlet temperature at nominal flow |
| Initialization › Air cooling | |||
| Modelica.Units.SI.Temperature | TAir_start (from AirLiquid) | 293.15 | Start value of air temperature |
| Fan controller | |||
| Buildings.Fluid.DataCenters.Racks.FanControllers.Types.Strategy | fanControl (from AirLiquid) | Buildings.Fluid.DataCenters.Racks.FanControllers.Types.Strategy.Load | Type of fan control strategy |
| Real[:,:] | fanSpeed (from AirLiquid) | [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]) |
| Modelica.Units.SI.Temperature | TAirOut_set (from AirLiquid) | dat.air.TOut_nominal | Set point temperature for rack outlet air |
| Real | k (from AirLiquid) | 1 | Gain of fan PI controller |
| Modelica.Units.SI.Time | Ti (from AirLiquid) | 60 | Integrator time constant of fan PI controller |
| Assumptions | |||
| Boolean | allowFlowReversalAir (from AirLiquid) | true | = false to simplify equations, assuming, but not enforcing, no flow reversal for air loop |
| Boolean | allowFlowReversalLiq (from AirLiquid) | true | = false to simplify equations, assuming, but not enforcing, no flow reversal for liquid loop |
| Boolean | allowFlowReversalCoo (from PartialAirLiquidRearDoorHex) | true | = false to simplify equations, assuming, but not enforcing, no flow reversal for rear door heat exchanger coolant |
| Rear door heat exchanger fan controller | |||
| Real | kReaDooHex | 1 | Gain of PI controller |
| Modelica.Units.SI.Time | TiReaDooHex | 10 | Integrator time constant of PI controller |
Connectors
Components
| Type | Name | Default | Description |
|---|---|---|---|
| Buildings.Fluid.DataCenters.Racks.Liquid.ColdPlateR_P | liq (from AirLiquid) | Liquid-cooled rack component | |
| Buildings.Fluid.DataCenters.Racks.Air.Rack_P | air (from AirLiquid) | Air-cooled rack component | |
| Buildings.Fluid.DataCenters.Racks.RearDoorHeatExchangers.BaseClasses.PartialRearDoorHeatExchanger | reaDooHex (from PartialAirLiquidRearDoorHex) |
Revisions
-
September 17, 2026, by Michael Wetter:
First implementation.