Desiccant Wheel with both sides in the Supply Flow

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Fabulous, I think moving the fan shouldn't be too much of an issue. Is there any chance I can do this with a chilled water coil? A second issue I have is to look at the load on the chiller I have two units and both have had their DX coils replaced by chilled water coils. I think I can find a work around for this later on, but it would be great to do it in one fell swoop! Thanks again!

Unfortunately, the HX used with water coils (CoilSystem:Cooling:Water:HeatExchangerAssisted) does not include the desiccant wheel as a "Heat Exchanger Object Type". No reason why not except that the original model development was for the Cromer Cycle DEAC model. It should be easy enough to add in.

@Annie Marston@rraustad Have any of you been able to model a desiccant heat exchanger that uses the same air stream on both the regeneration and process side in Energyplus? When I tried to do what has been suggested in this question, I have problems specifying the inlet/outlet nodes of regeneration and process air in the HeatExchanger:Desiccant:BalancedFlow object. Apparently, Energyplus does not allow to specify the same air stream for regeneration and process sides. Any help on how to solve this issue would be greatly appreciated.

The picture above is how this model is intended to be used. The air steam into the desiccant HX then passes through a coil (not the fan, directly to the coil). The coil outlet then passes through the desiccant HX. Is this what you mean by the "same air stream"?

@rraustad thank you for your answer. What I want to model is basically a series desiccant wheel in a dedicated outdoor-air application (a separate regeneration air stream is not necessary). I think this model will help me to model what I want but I am getting Node connection errors. Can you please explain how to properly setup the inlet/outlet nodes of regeneration and process air in the HeatExchanger:Desiccant:BalancedFlow object? Also, I cannot find the CoilSystem:Cooling:DX:HeatExchangerAssisted object type when I tried to include this component in my air loop main branch.

@rraustad I would be very grateful if you can take a look at my .idf file to see what is the problem with my model. You can find the idf file here:

https://drive.google.com/file/d/1GDow...

Thanks in advance for your help.

In the OA System the HX OA node (HX supply air inlet) is Node 48 yet in the OA Mixer, Node 56 (HX supply air outlet) is the OA Node. I changed the OA Mixer OA node to 48. For the desiccant system, I don't see that CoilSystem:Cooling:DX:HeatExchangerAssisted is allowed on the main branch, not sure why. I do see that HeatExchanger:Desiccant:BalancedFlow is allowed on the main branch. So you will have to wrap the desiccant HX around the CoilSystem:Cooling:DX object (HX process side, then CoilSystem, then HX regen side). Not sure that will work since you would have to include the ....

... desiccant HX type and name in the main branch equipment list twice, each with different node name. That too should through a node connection error.

The source code says:

 //        HX Assisted coils are not allowed on a branch at this time
 //        CASE('COILSYSTEM:COOLING:DX:HEATEXCHANGERASSISTED')

Not sure if it's still true or not, but for sure you'll get a warning if you try:

** Severe  ** GetAirPathData: AirLoopHVAC = "AEDG AIR LOOP HVAC BUILDING STORY 1".
**   ~~~   ** ..Invalid Air Loop Component Type = "COILSYSTEM:COOLING:DX:HEATEXCHANGERASSISTED".
**   ~~~   ** ..Air Loop Component Name = "COIL SYSTEM HX ASSISTED".
**   ~~~   ** ..reference Branch = "AEDG AIR LOOP HVAC BUILDING STORY 1 MAIN BRANCH"

OK, put the CoilSystem:Cooling:DX:HeatExchangerAssisted inside the CoilSystem:Cooling:DX object and then put the CoilSystem:Cooling:DX object on the main branch. That is supposed to work.

From the IDD file:

CoilSystem:Cooling:DX,
 A6,  \field Cooling Coil Object Type
    \type choice
    \required-field
    \key Coil:Cooling:DX:SingleSpeed
    \key CoilSystem:Cooling:DX:HeatExchangerAssisted
    \key Coil:Cooling:DX:TwoSpeed
    \key Coil:Cooling:DX:TwoStageWithHumidityControlMode
    \key Coil:Cooling:DX:VariableSpeed
    \key Coil:Cooling:DX:SingleSpeed:ThermalStorage

I will try that. Thank you very much for your help.

@rraustad I managed to run the file without any severe errors by implementing your last suggestion. Apparently it is working, as the dew-point temperature in most zones has reduced approximately by 1 - 2 C. The only problem now is that I still get some warnings related to the performance data of the desiccant wheel and it may be affecting the performance of the system specially in one specific zone (perimeter zone 1 with south orientation), which seems to not be affected at all by the desiccant-based dehumidification. Any idea of why the system is not working only in one zone?

Here is a link to the fixed idf: https://drive.google.com/file/d/1V2sn...

@rraustad I wanted to ask you one last thing regarding the heat exchanger assisted cooling coil. How do I control the operation of the desiccant wheel? I see that the HeatExchanger:Desiccant:BalancedFlow has an availability schedule as input, so should I use the same availability schedule as the cooling coil? , that is, whenever my DOAS is working, the desiccant dehumidifier works too? how does that work?

Also, what would be the appropriate selection for the last inputs of CoilSystem:Cooling:DX object, considering that I am using the CoilSystem:Cooling:DX:HeatExchangerAssisted inside the CoilSystem:Cooling:DX object. Specifically, what should I select for:

Dehumidification control type Run on sensible load Run on latent load Use outdoor air DX Cooling Coil Outdoor air DX Cooling Coil Leaving Minimum Air Temperature

For control of the desiccant wheel the availability schedule can turn off the HX when needed. If you want it to operate the same time as the coil, use the same schedule. The HX schedule could be more restrictive and turn off the HX at times when the coil can operate but I can't think of why that might happen in the real world. Since the HX is not in the OA system, Use OA DX cooling coil = No. Run on sensible load = true for temperature control. Run on latent load = true for humidity control.