modelAirLiquid
Information
This is a partial 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.
This is a partial model because it does not connect the outlet port air.port_b
of the air-cooled component to the model output portAir_b.
This connection must be made by the model that extends this partial model.
Parameters
| Type | Name | Default | Description |
|---|---|---|---|
| Performance data | |||
| Buildings.Fluid.DataCenters.Racks.Hybrid.Data.AirLiquid.Generic | dat | Performance data | |
| Dynamics › Liquid cooling | |||
| Modelica.Fluid.Types.Dynamics | energyDynamicsLiq | 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 | 2 | Time constant of liquid outlet temperature at nominal flow |
| Initialization › Liquid cooling | |||
| Modelica.Units.SI.Temperature | TLiq_start | 293.15 | Start value of liquid temperature |
| Liquid cooling | |||
| Modelica.Units.SI.VolumeFlowRate | VColPla_flow_nominal | 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 | 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 | false | = true, use linear relation between m_flow and dp for liquid cooling |
| Dynamics › Air cooling | |||
| Modelica.Fluid.Types.Dynamics | energyDynamicsAir | 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 | 2 | Time constant of air outlet temperature at nominal flow |
| Initialization › Air cooling | |||
| Modelica.Units.SI.Temperature | TAir_start | 293.15 | Start value of air temperature |
| Fan controller | |||
| Buildings.Fluid.DataCenters.Racks.FanControllers.Types.Strategy | fanControl | Buildings.Fluid.DataCenters.Racks.FanControllers.Types.Strategy.Load | 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]) |
| Modelica.Units.SI.Temperature | TAirOut_set | dat.air.TOut_nominal | Set point temperature for rack outlet air |
| Real | k | 1 | Gain of fan PI controller |
| Modelica.Units.SI.Time | Ti | 60 | Integrator time constant of fan PI controller |
| 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 | Default | Description |
|---|---|---|---|
| Modelica.Fluid.Interfaces.FluidPort_a | portLiq_a | Liquid cooling inlet port | |
| Modelica.Fluid.Interfaces.FluidPort_b | portLiq_b | Liquid cooling outlet port | |
| Modelica.Fluid.Interfaces.FluidPort_a | portAir_a | Air cooling inlet port | |
| Modelica.Fluid.Interfaces.FluidPort_b | portAir_b | Air cooling outlet port | |
| Modelica.Blocks.Interfaces.RealInput | PLiq | Power consumed by for liquid-cooled IT | |
| Modelica.Blocks.Interfaces.RealInput | PAir | Power consumed by air-cooled IT | |
| Modelica.Blocks.Interfaces.RealOutput | PLiqTot | Electric power consumed by liquid-cooled IT | |
| Modelica.Blocks.Interfaces.RealOutput | PAirTot | Electric power consumed by air-cooled IT, including fan energy | |
| Modelica.Blocks.Interfaces.RealOutput | PAirFan | Electric power consumed by fan for air-cooled IT |
Components
| Type | Name | Default | Description |
|---|---|---|---|
| Buildings.Fluid.DataCenters.Racks.Liquid.ColdPlateR_P | liq | Liquid-cooled rack component | |
| Buildings.Fluid.DataCenters.Racks.Air.Rack_P | air | Air-cooled rack component |
Contents
| Name | Description |
|---|---|
 MediumLiq | Medium for liquid cooling loop |
| MediumAir | Medium for air cooling loop |
Revisions
-
August 22, 2026, by Michael Wetter:
First implementation.