modelCDU_epsNTU
Example model of a CDU with varying load on the IT side
Extends from Modelica.Icons.Example (Icon for runnable examples).
Information
Example model of a CDU that serves liquid cooled racks.
The IT load is specified using a periodic pulse input. This load is cooled by a propylene glycol loop, which exchanges heat through the CDU with a chilled water supply. The chilled water is assumed to be delivered at constant temperature. A PI controller regulates the chilled water flow rate through the control valve in the CDU in order to track the propylene glycol temperature that is sent to the IT rack.
Parameters
| Type | Name | Default | Description |
|---|---|---|---|
| Modelica.Units.SI.Power | PRac | 48*132000 | Total rack design power |
| Modelica.Units.SI.Temperature | TRac_a | 273.15 + 42 | Supply coolant temperature to rack at design conditions |
| Modelica.Units.SI.Temperature | TRac_b | 273.15 + 47 | Return coolant temperature from rack at design conditions |
| Modelica.Units.SI.Temperature | TChi_a | 273.15 + 36 | Supply chilled water temperature to CDU at design conditions |
| Modelica.Units.SI.Temperature | TChi_b | 273.15 + 41 | Return chilled temperature from CDU at design conditions |
| Modelica.Units.SI.MassFlowRate | mRac_flow_nominal | PRac/(TRac_b - TRac_a)/MediumRac.cp_const | Rack mass flow rate at design conditions |
| Modelica.Units.SI.MassFlowRate | mChi_flow_nominal | PRac/(TChi_b - TChi_a)/MediumChi.cp_const | Chilled water mass flow rate at design conditions |
| Modelica.Units.SI.PressureDifference | dpRac_nominal | 60000 | Rack design pressure drop |
| Modelica.Units.SI.PressureDifference | dpHexChi_nominal | 80000 | Heat exchanger design pressure drop on chiller side |
| Buildings.Fluid.DataCenterEquipment.CDUs.LiquidToLiquid.Data.Generic_epsNTU | datCDU | Data performance record for CDU | |
| Buildings.Fluid.DataCenterEquipment.Racks.LiquidCooledSinglePhase.Data.OCP_1kW_OAM_PG25 | datRac | Rack performance data |
Components
| Type | Name | Default | Description |
|---|---|---|---|
| Buildings.Controls.OBC.CDL.Reals.Sources.Pulse | uti | Utilization of hardware | |
| Buildings.Fluid.DataCenterEquipment.Racks.LiquidCooledSinglePhase.ColdPlateR_P | rac | Rack with cold plate heat exchangers, modeled for simplicity as one large rack | |
| Buildings.Fluid.Sources.Boundary_pT | bou | Pressure boundary condition | |
| Buildings.Fluid.Sensors.TemperatureTwoPort | senTCDU_a | Chilled water supply temperature | |
| Buildings.Fluid.DataCenterEquipment.CDUs.LiquidToLiquid.CDU_epsNTU | cdu | CDU, modelled for simplicity as one large CDU | |
| Fluid.Sources.Boundary_pT | sou | Pressure boundary condition | |
| Fluid.Sensors.TemperatureTwoPort | senTCDU_b | Outlet temperature | |
| Fluid.Sensors.TemperatureTwoPort | senTRac_a | Rack inlet temperature | |
| Fluid.Sensors.TemperatureTwoPort | senTRac_b | Rack outlet temperature | |
| Controls.OBC.CDL.Reals.Sources.Constant | dpSet | Set point for head | |
| Controls.OBC.CDL.Reals.Sources.Constant | TSetRacIn | Set point for rack inlet temperature | |
| Modelica.Blocks.Math.Gain | PITAir | Power consumption by the air-cooled IT equipment |
Contents
| Name | Description |
|---|---|
 MediumChi | Medium for chilled water loop |
 MediumRac | Medium for rack |
Revisions
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December 23, 2025, by Michael Wetter:
First implementation.