How to model Dry Cooler with Spray

asked 2024-08-01 04:41:46 -0500

Keigo
3931 ●1 ●45 ●21 https://www.linkedin.c...

updated 2024-08-01 10:37:24 -0500

Aaron Boranian

13965 ●80 ●24 http://bigladdersoftware.com/

I want to model a dry cooler with spray in front of the outdoor air inlet to precool the outdoor air as shown below.

image description

If the dry cooler does not have the spray, I think FluidCooler:SingleSpeed or FluidCooler:TwoSpeed is appropriate, but these object do not have a input field for water spray.

It's great if there is a way to change the air condition at the Outdoor Air Inlet Node. We can also apply it to other equipment. This kind of spray is often used in various equipment such as air-cooled chillers and air-cooled VRF outdoor units to improve cooling efficiency.

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answered 2024-08-01 10:24:43 -0500

Aaron Boranian

13965 ●80 ●24 http://bigladdersoftware.com/

updated 2024-08-01 14:12:16 -0500

@Keigo it looks like DX cooling coils have a condenser type input that can be set to "EvaporativelyCooled". Is this what you're hoping to do for chillers and VRF outdoor units? If so, then this evap-cooled condenser capability is currently available in EnergyPlus, but only for certain object types:

Chillers

VRF Outdoor Units

EDIT

I see now that you were just mentioning chillers and VRF outdoor units as examples of evaporatively cooling condensers, but want to do the same thing for fluid coolers -- apologies.

Since this isn't an option for fluid cooler object types in EnergyPlus, your best option will likely be to use EMS. You would create an EMS program that calculates how the outdoor air inlet node should have its conditions modified to account for the pre-cooling sprayer. You would then use the outdoor air system node conditions actuators to override the outdoor air drybulb and/or wetbulb at a specific OutdoorAir:Node object name, which is referenced as the fluid cooler's outdoor air node field.

If evaporatively-cooled fluid coolers is common practice, then you can create a feature request on the EnergyPlus Github site for developers to add it to future versions.

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Thanks for your prompt response. EvaporativelyCooledCondenser Type looks what I expect for Chiller:Electric:EIR and AirConditioner:VariableRefrigerantFlow.

For FluidCooler:TwoSpeed, I wrote an EMS script to override the System Node Temperature of the Outdoor Air Inlet Node with Actuated Component Type - System Node Setpoint and Actuated Component Control Type - Temperature Setpoint, but it did not work. Is there any other way to override the temperature of the Outdoor Air Inlet Node?

Keigo ( 2024-08-01 11:22:26 -0500 )edit

@Keigo you wouldn't use an actuator to override a setpoint, but instead to override the outdoor air condition at a specific node (outdoor air conditions are still taken from the EPW file for other outdoor air nodes not affected by the actuator). I've updated my answer above for this.