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Re: [EnergyPlus_Support] Help
This is a nice discussion, because it brings home the fact that "there is no wall"...it's all just computer code. If you don't tell it that it "belongs" to zone 1, then there's no reason why it should. And it doesn't care how far away it is from the zone in its geometeric location (it doesn't even have to be inside the building). It with interact with two things
1) the zone air node via convection
2) other surfaces via radiation exchange
For convection calcs perhaps only its orientation is a parameter relating to its geometric description location.
And for radiation exchange, this is exactly the sticky point. Here it does matter.
While that is true, and usefull, you need to understand the "how" slightly. For example, I've often defined a surface object miles away from my building, being sure to make it adiabatic with nosun nowind boundry conditions but assigning it to a zone...with the purpose of assigning a fan:zoneexhaust object to it with the required AirFlowNetwork objects. This way I don't have to subdivide the zone roof (or other zone surface) just to mount the fan and it makes modular copy paste efforts far easier. Since the pseudo-area is minimally small, of the same construction mass wise and the boundry conditions are appropriate, I expect negligable error in the heatbalance.
Mit freundlichen Grü�en- Sent from my iPhone (excuse the brevity)
i. A.
Jean Marais
b.i.g. bechtold
Tel. +49 30 6706662-23
On 22.02.2014, at 22:44, Jim Dirkes <<mailto:jim@xxxxxxxxxxxxxxxxxxxxxxxxxxx>jim@xxxxxxxxxxxxxxxxxxxxxxxxxxx> wrote:
>
> Jeremiah,
> Please be sure to post the response! The ASHRAE / IBPSA energy modeling workshop slides tell the story that the walls and roof do not need to be contiguous as long as they are associated with a proper zone. I took that at face value, but would like confirmation, especially since the slide developers (RMI) are more familiar with eQuest, I think.
>
> Joe,
> If everyone on the world was â??confrontationalâ?? in as gracious and constructive a manner as you, weâ??d all be way ahead! Keep it up!
>
> James V Dirkes II, PE, BEMP, LEED AP
> <http://www.buildingperformanceteam.com/>> www.buildingperformanceteam.com
> Energy Analysis, Commissioning & Training Services
> 1631 Acacia Drive, Grand Rapids, MI 49504 USA
> 616 450 8653
>
> From: <mailto:EnergyPlus_Support@xxxxxxxxxxxxxxx>EnergyPlus_Support@xxxxxxxxxxxxxxx [mailto:EnergyPlus_Support@xxxxxxxxxxxxxxx] On Behalf Of Jeremiah Crossett
> Sent: Saturday, February 22, 2014 4:29 PM
> To: <mailto:EnergyPlus_Support@xxxxxxxxxxxxxxx><mailto:EnergyPlus_Support@xxxxxxxxxxxxxxx>EnergyPlus_Support@xxxxxxxxxxxxxxx
> Subject: Re: [EnergyPlus_Support] Help
>
>
> Joe,
> Thanks for your critical thought on the matter. I will submit a help desk request for clarification and report back. I am not opposed to having walls, just that the goal of the paticular method is to model only the parts of the building relevant to the application of the PCM..
>
>
>
>
> Jeremiah D. Crossett | Senior Analyst | Phase Change Energy Solutions
> 120 E. Pritchard St. | Asheboro, NC 27203
> | Mobile 503-688-8951
> <http://www.phasechange.com/>> www.phasechange.com
> <http://i.imgur.com/Sldxf.jpg>
>
>
>
>
> On Sat, Feb 22, 2014 at 1:04 PM, Joe Huang <<mailto:YJHuang@xxxxxxxxxxxxxxxxxxxxxxxx><mailto:YJHuang@xxxxxxxxxxxxxxxxxxxxxxxx>YJHuang@xxxxxxxxxxxxxxxxxxxxxxxx> wrote:
>
> Just a note of caution. Not meaning to be confrontational in any way, but I'd like to know why Adil feels not having closure "doesn't matter"?
> I haven't looked at this aspect of EnergyPlus, but from what I know of the heat balance method, the view factors should add up to 1.0. If you tell me that the Simple Model simply (:-)) prorates view factors by the surface areas in that zone, adding up to 1.0, then that's fine, but if not, you might be having some "heat leak".
>
> Joe
>
>
>
> On 2/22/2014 11:33 AM, Jeremiah Crossett wrote:
>>
>> Adil,
>> Thank you much for taking a look and shearing your insight. Great to know that my simplified modeling approach is reasonable and that the warnings can be safely ignored.
>> The concept of modeling only roof or wall is really useful for initial studies, and I hope will be useful for exemplary calculations for LEED models that have been generated in other software that can not model PCM's. The idea is to model only the building elements of interest with an idealized HVAC system so that analysis and post processing are as simple as possible..
>>
>> For the original users question, I agree with Joe, Jean and Niraj that unless you are intending to model a part of a building such as I have that you should enclose your zones, but just mentioned my model to give an example how E+ could be used in this way..
>>
>>
>>
>> Kind regards
>>
>>
>>
>> Jeremiah D. Crossett | Senior Analyst | Phase Change Energy Solutions
>> 120 E. Pritchard St. | Asheboro, NC 27203
>> | Mobile 503-688-8951
>> <http://www.phasechange.com/>>> <http://www.phasechange.com>>> www.phasechange.com
>>
>>
>>
>>
>>
>> On Sat, Feb 22, 2014 at 11:23 AM, Adil <<mailto:smhadil78@xxxxxxxxx><mailto:smhadil78@xxxxxxxxx>smhadil78@xxxxxxxxx> wrote:
>>
>> Jermiah,
>> These warnings might have been put in EP for geometry integrity testing. Any cube or energy plus zone enclosure must have atleast 6 surface provided that you have define the zone by using buildingsurface:detailed object (this is default surface with many geometry export). In my opinion it dosent really matter for your model. You can safely ignore it. May be ep development team can note it and instigate this warning only incase of Buildingsurface detailed objects and not in surface objects that you have used.
>>
>> Adil
>> <http://www.geedindia.org>>> <http://www.geedindia.org>>> www.geedindia.org
>> From: <mailto:jcrossett@xxxxxxxxxxxxxxx>Jeremiah Crossett
>> Sent: 20-02-2014 03:01
>> To: <mailto:EnergyPlus_Support@xxxxxxxxxxxxxxx><mailto:EnergyPlus_Support@xxxxxxxxxxxxxxx>EnergyPlus_Support@xxxxxxxxxxxxxxx
>> Subject: Re: [EnergyPlus_Support] Help [1 Attachment]
>>
>> Yea, it is quite useful to be able to do a simple model with the roof simple object-- so now I am a bit concerned-- if anyone has further opinions on the attached model that uses only a roof, zone area and ceiling height to calculate volume I would like to hear.. The model uses loads and schedules from the commercial reference primary school, but with a roof of an actual school. The goal of the model is to evaluate roof PCM capacity, SRI and U value and nothing more- so a surface model is used. The file will open in open studio, but has some "Material Property Phase Change Dual Curve" objects from a custom version of E+ I use.
>>
>> The specific error I get from the attached file is:
>>
>> Program Version,EnergyPlus, Version 8.1, YMD=<tel:2014.02.18%2022>2014.02.18 22:51,IDD_Version 8.1.0.008
>> ************* Beginning Zone Sizing Calculations
>> ** Warning ** GetSurfaceData: The total number of floors, walls, roofs and internal mass surfaces in Zone GYMNASIUM
>> ** ~~~ ** is < 6. This may cause an inaccurate zone heat balance calculation.
>> ** Warning ** GetSurfaceData: The total number of floors, walls, roofs and internal mass surfaces in Zone CAFETERIA
>> ** ~~~ ** is < 6. This may cause an inaccurate zone heat balance calculation.
>> ** Warning ** GetSurfaceData: The total number of floors, walls, roofs and internal mass surfaces in Zone CLASSROOM
>> ** ~~~ ** is < 6. This may cause an inaccurate zone heat balance calculation.
>> ** Warning ** GetSurfaceData: The total number of floors, walls, roofs and internal mass surfaces in Zone CORRIDOR & OTHER
>> ** ~~~ ** is < 6. This may cause an inaccurate zone heat balance calculation.
>> ** Warning ** Surfaces in Zone="GYMNASIUM" do not define an enclosure.
>> ** ~~~ ** Number of surfaces <= 3, view factors are set to force reciprocity.
>> ** Warning ** Surfaces in Zone="CAFETERIA" do not define an enclosure.
>> ** ~~~ ** Number of surfaces <= 3, view factors are set to force reciprocity.
>> ************* Testing Individual Branch Integrity
>> ************* All Branches passed integrity testing
>> ************* Testing Individual Supply Air Path Integrity
>> ************* All Supply Air Paths passed integrity testing
>> ************* Testing Individual Return Air Path Integrity
>> ************* All Return Air Paths passed integrity testing
>> ************* No node connection errors were found.
>> ************* Beginning Simulation
>> ************* Simulation Error Summary *************
>> ************* EnergyPlus Warmup Error Summary. During Warmup: 0 Warning; 0 Severe Errors.
>> ************* EnergyPlus Sizing Error Summary. During Sizing: 6 Warning; 0 Severe Errors.
>> ************* EnergyPlus Completed Successfully-- 6 Warning; 0 Severe Errors; Elapsed Time=00hr 01min 46.73sec
>>
>>
>>
>>
>>
>>
>>
>>
>> Jeremiah D. Crossett | Senior Analyst | Phase Change Energy Solutions
>> 120 E. Pritchard St. | Asheboro, NC 27203 | Mobile 503-688-8951
>> <http://www.phasechange.com/>>> <http://www.phasechange.com>>> www.phasechange.com
>>
>>
>>
>>
>>
>> On Wed, Feb 19, 2014 at 1:06 PM, Niraj Poudel <<mailto:nirajpdl@xxxxxxxxx><mailto:nirajpdl@xxxxxxxxx>nirajpdl@xxxxxxxxx> wrote:
>>
>> The view factor for the roof probably assumes an infinite plane. Hence a 0.5 value. Is what my guess would be.
>>
>> Niraj
>>
>> On Wed, Feb 19, 2014 at 3:04 PM, Jeremiah Crossett <<mailto:jcrossett@xxxxxxxxxxxxxxx><mailto:jcrossett@xxxxxxxxxxxxxxx>jcrossett@xxxxxxxxxxxxxxx> wrote:
>>
>> Possibly, but the very quick tests I did showed no noticeable difference when adding a zone with walls and a floor, compared to a roof surface and zone area x height.
>> The benefit is a quick model of a roof, and it seems alright, but may look further given your opinion..
>>
>>
>>
>> Jeremiah D. Crossett | Senior Analyst | Phase Change Energy Solutions
>> 120 E. Pritchard St. | Asheboro, NC 27203 | Mobile 503-688-8951
>> <http://www.phasechange.com/>>> <http://www.phasechange.com>>> www.phasechange.com
>>
>>
>>
>>
>>
>> On Wed, Feb 19, 2014 at 12:42 PM, Joe Huang <<mailto:YJHuang@xxxxxxxxxxxxxxxxxxxxxxxx><mailto:YJHuang@xxxxxxxxxxxxxxxxxxxxxxxx>YJHuang@xxxxxxxxxxxxxxxxxxxxxxxx> wrote:
>>
>> Wouldn't that foul up the zone heat balance that depends on knowing the view factor or at least the area of each surface ?
>>
>> Joe
>>
>>
>> On 2/19/2014 12:37 PM, Jeremiah Crossett wrote:
>>>
>>> Depending on what you are doing, you might just as well ignore it-- for example if you want the surface to be fully adiabatic then you could remove it, and would get this warning.
>>> I have some models that are just roofs with zone area, ceiling height and internal loads per square foot-- and it seems to work as expected, but also produces this warning-
>>>
>>>
>>>
>>> Jeremiah D. Crossett | Senior Analyst | Phase Change Energy Solutions
>>> 120 E. Pritchard St. | Asheboro, NC 27203 | Mobile 503-688-8951
>>> <http://www.phasechange.com/>>>> <http://www.phasechange.com>>>> www.phasechange.com
>>>
>>>
>>>
>>>
>>>
>>> On Wed, Feb 19, 2014 at 12:33 PM, Joe Huang <<mailto:YJHuang@xxxxxxxxxxxxxxxxxxxxxxxx><mailto:YJHuang@xxxxxxxxxxxxxxxxxxxxxxxx>YJHuang@xxxxxxxxxxxxxxxxxxxxxxxx> wrote:
>>>
>>> "Degenerate surfaces" sound terrible! Maybe you should go see a psychologist (just joking :-) )
>>>
>>> Seriously, I suggest you search through your IDF, find the seven surfaces with less than two vertices (which only define a line and not a surface), and add the missing vertices.
>>>
>>> Joe
>>>
>>>
>>>
>>>
>>> On 2/19/2014 11:58 AM, Oswaldo alonso Guzmán villalobos wrote:
>>>>
>>>> Hellow, I try to simulate a building, when I simulate it, the energy plus gives the following message,
>>>>
>>>> GetSurfaceData: There are 7 degenerate surfaces; Degenerate surfaces are those with number of sides < 3.
>>>>
>>>> How fix this error?
>>>> Thanks.
>>>>
>>>> Att. Oswaldo Alonso Guzmán Villalobos
>>
>> [The entire original message is not included.]
>>
>
>
>
>
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