[Bldg-sim] IES VE: Radiant, hollow-core ceiling

[Timothy Moore]

Rebecca,
 
Regarding your particular evaporatively cooled hollow-core system in a mixed-mode building:
 
As you are not planning to naturally ventilate the hollow core itself, you will need to use MacroFlo (the dynamically coupled bulk airflow modeling application within the VE) a bit differently than I had described in my more general email on the topic. Rather than coupling operable opening to the hollow core, you will need to use MacroFlo to model the dynamic performance of the space associated with the operable windows in the building, any controls interlocks you may be planning, and to look at the building performance if these were to overlap (i.e., if there are no control interlocks).
 
While you may find the MicroFlo CFD module useful for looking at the potential for natural ventilation under specific conditions, it is the MacroFlo dynamic bulk airflow modeler you will need to use to control and assess the role of natural ventilation within the dynamic thermal simulations.
 
As you are planning to couple the floor cavities to a fan-driven mechanical HVAC system using evaporative cooling, you will need to set up this system in ApacheHVAC. If indirect-evap, you will use spray chamber upstream on the exhaust side of a heat exchanger. If direct evap, just the spray chamber. Obviously you can also use both of these. Indeed, the air-handler can be configured however you wish, including IDDE + DX dehum + Desiccant wheel regenerated by the condenser for the DX, or other unconventional configuration. 
 
The VE is very well suited to modeling mixed-mode systems, evaporative cooling, and the radiant heat transfer that are involved in what you are looking at. 
 
Timothy Moore 
Senior Consultant - Special Projects 

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________________________________


From: Rebecca Butler [mailto:Rebecca.Leigh.Butler at gmail.com] 
Sent: Thursday, March 05, 2009 8:50 AM
To: bldg-sim at lists.onebuilding.org
Subject: [Bldg-sim] IES VE: Radiant, hollow core ceiling

 

I have a question regarding the capabilities of IES VE and its CFD package and I was hoping someone might have some experience or insight to help get me started on the following problem.  We have a concept cooling design which includes a radiant hollow core concrete ceiling through which evaporatively cooled air is routed.  The air which is routed through the radiant ceiling comes from a central evaporative cooler and is then exhausted at the exterior of each room after it has passed through the airflow passages in the ceiling.  Just to be clear, this is not a typical radiant system in that electricity is being used to cool the slab but instead evaporatively cooled outdoor air is being used in its place.  We also want to couple these effects with natural ventilation which occurs because of the use of operable windows.  

We are trying to analyze the effects of these techniques in a cooling season in Colorado (hence the benefit of the evaporative cooler).  We have conducted rough calculations of the benefits of using such a system using standard ASHRAE energy transfer techniques and we want to verify our results.  Have you ever heard of this type of system being modeled in IES VE and/or is it capable of modeling such a system?  Is there a way to modify the "radiant ceiling" option in IES to take into account the saving which would occur by using evaporatively cooled air in the place of electricity?  If not, is there a way to manually create such a system from the ground up?

Any help would be greatly appreciated.  Thank you.

Rebecca Butler
LEED AP
Enermodal Engineering
(303) 861-2070 

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