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[EnergyPlus_Support] Fwd: VRV VRF

---------- Mensaje reenviado ----------
De: francisco minoyetti <fminoyetti@xxxxxxxxx>
Fecha: 25 de enero de 2011 14:05
Asunto: VRV VRF
Para: EnergyPlus_Support@xxxxxxxxxxxxxxx

Hi, I would highly appreciate any help or advice on how to input the following systems in an IDF Editor, even approximately
1. One-to-one air-to-air VRV systems and Multi-split air-to-air VRV systems.   
2. Does anyone have any experience submitting an approximate Multi-Split-Air-to-air-VRV for LEED EA Credit 1?
3. How can I assure I am properly accounting for fan energy consumption when each system has outdoor unit fans, indoor unit fans and OA injection fans connected to the mixing box? 
4. How is Delta Pressure Rise modelled in a split system which has OA injection connected to the mixing box where OA and recirculated air are mixed? 

I?m trying to model a 600m2 building with: 
(14) 1-to-1 air-to-air VRV systems
(3) multi-split air-to-air VRV systems
(1) gas fired rooftop
(4) ventilators for mechanical extraction (restrooms)
(3) ventilators for mechanical OA injection into (most of, but not all of) the indoor units' mixing boxes 

E+ helpserve Team already told me the VRV module is going in now and will be available on the next release, which is great news. 
Nonetheless, I need to see some approximate results ASAP. 
I am attaching all the information I have collected for each component. 
I'm new to EnergyPlus and would appreciate any advice as to how to model these systems.  

For the research I've done on previous YahooGroup entries, I found this one referring to air-to-air VRV. 
I don't quite understand what "adjustment" would refer toor how it could be done in the IDF Editor:
07-08-2005 Michael J. Witte - I have not seen performance data for these systems, so I cannot say for sure how they differ. My understanding of these systems is that the only difference between this type of system and several individual DX units would be the efficiency at various part-load conditions. So, it may be quite reasonable to model this as multiple single-zone units with some adjustment to the part-load curve or the nominal efficiency to approximate the VRV performance.

On Green Building Genie I found this which in turn the E+ helpserve Team's opinion is that it wouldn't be accepted for LEED certification.  

?I think the closest you could get on the cooling side would be to use an AirloopHVAC: UnitaryCoolOnly with AirTerminal: SingleDuct: VAV:NoReheat air distribution units. The power side of the VRF would have to be modeled using a squared curve on PLR where Power is proportional to the square of speed (or PLR). However, with this configuration the fan power will be low since VRF systems typically use constant volume fans. You can modify the fan power in a spreadsheet after the simulation is complete. Sorry if the jpg doesn't come through but it just shows the squared power law of power vs speed. For heating it is much harder. Using the AirloopHVAC: UnitaryHeatPump: AirToAir with AirTerminal: SingleDuct: Uncontrolled will model both cooling and heating, however, the compressor control is limited to a single zone. If the zone loads are balanced (flow through air distribution units are balanced based on load) this will be a fair approximation, at least with what is available in EnergyPlus. You could still use the squared curve for power in this object. So there is no simple answer, you would have to pick a system and review the results to see how close you are to manufacturer?s performance data. Then modify the input to more closely model the system using different configurations. There are many EnergyPlus users that would be interested in your findings. ? 
Greenbuildinggenie is providing this information to comprehensively collect information on this tip. We neither recommend nor endorse these methods. Some of the software may start supporting VRV modeling in near future. Please check the software before concluding.

Thank you all.

Francisco Minoyetti
Bovis Lend Lease Argentina


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