[Bldg-sim] [Equest-users] Roof Conduction Load

Dru.Crawley at bentley.com Dru.Crawley at bentley.com
Tue Aug 20 01:47:50 PDT 2013


DOE-2 does not simulate radiation.
________________________________
From: Jeremiah Crossett<mailto:jcrossett at phasechange.com>
Sent: ‎8/‎20/‎2013 6:58 AM
To: Joe Huang<mailto:yjhuang at whiteboxtechnologies.com>
Cc: <equest-users at lists.onebuilding.org><mailto:equest-users at lists.onebuilding.org>; Bldg-sim2 (Bldg-sim at lists.onebuilding.org)<mailto:bldg-sim at lists.onebuilding.org>; Bhartendu Awasthi<mailto:bhartendu.awasthi90 at gmail.com>
Subject: Re: [Bldg-sim] [Equest-users] Roof Conduction Load

Joe, Just wondering,  given your expertise how would you compare this to the heat balance method.., and what do you think is more realistic?



Jeremiah D. Crossett  | Senior Analyst  |  Phase Change Energy Solutions
120 E. Pritchard St.  | Asheboro, NC 27203  | Mobile 503-688-8951<tel:503-688-8951>
www.phasechange.com<http://www.phasechange.com>
  [http://i.imgur.com/Sldxf.jpg]





On Mon, Aug 19, 2013 at 6:14 PM, Joe Huang <yjhuang at whiteboxtechnologies.com<mailto:yjhuang at whiteboxtechnologies.com>> wrote:
Just to repeat what David and Rodrigo have already sad, DOE-2 calculates conduction loads in a two step process. In LOADS, a constant reference temperature is specified, which DOE-2 uses to calculate the amount of heat flow through the surfaces. This is the LOADS loads summarized in the LS-E and LS-F reports.  In SYSTEMS, DOE-2 calculates the true temperature of the zone based on the loads passed from LOADS, as well as the actions of the HVAC system.  In the course of this calculation, the heat flows ("loads") from LOADS are adjusted, but this is not done surface by surface, but in total using the so-called "Zone Conductance" times the difference between the actual zone temperature and the reference temperature used in LOADS.  At this point, heat flows through internal walls are also considered, using the  difference between this hour's zone temperature and the previous hour's zone temperature of the adjacent space, e.g., the Attic or Plenum.  If you are interested in this number, I believe it can be extracted in an hourly report.

In reference to Rodrigo's question, I don't see any benefit in forcing a heat flow between the room and the attic by using different reference temperatures.   You will simply get a constant heat flow at that temperature difference throughout the simulation. In reality, attics are generally colder than the room in the winter and warmer than the room in the summer, so the derived heat flow with this temperature difference doesn't get you any closer to reality, in my opinion.

Joe

Joe Huang
White Box Technologies, Inc.
346 Rheem Blvd., Suite 108D
Moraga CA 94556
yjhuang at whiteboxtechnologies.com<mailto:yjhuang at whiteboxtechnologies.com>
http://weather.whiteboxtechnologies.com for simulation-ready weather data
(o) (925)388-0265<tel:%28925%29388-0265>
(c) (510)928-2683<tel:%28510%29928-2683>
"building energy simulations at your fingertips"


On 8/19/2013 12:05 PM, David Wood wrote:
Hi All,

The LS-C report comes from the LOADS simulation portion of DOE 2.2. The plenum reference temperature used in LOADS is adjusted in the SYSTEMS portion of the program and the loads in the spaces adjacent to the plenum are corrected
correspondingly.

Dave Wood


On Thu, Aug 8, 2013 at 8:58 AM, Rodrigo Cerqueira <rodrigo.cerqueira at mra.qc.ca<mailto:rodrigo.cerqueira at mra.qc.ca>> wrote:

Hi,

This happens because the load calculation is made with a fixed temperature (see picture). All the spaces, include plenum zones, have the same temperature by default (70°F). So, all roof load appears in the plenum spaces. To considerate the roof load, you have to change this temperature in plenum spaces and a part of roof load will appear like "internal surface conduction". But I'm not sure if this is a good practice. Maybe someone else has an opinion about that.



[X]



Rodrigo Cerqueira, ing. jr, M.Ing.

Simulation énergétique



[signatureCouriel]







De : equest-users-bounces at lists.onebuilding.org<mailto:equest-users-bounces at lists.onebuilding.org> [mailto:equest-users-bounces at lists.onebuilding.org<mailto:equest-users-bounces at lists.onebuilding.org>] De la part de Bhartendu Awasthi
Envoyé : 8 août 2013 06:35
À : equest-users at lists.onebuilding.org<mailto:equest-users at lists.onebuilding.org>; bldg-sim at lists.onebuilding.org<mailto:bldg-sim at lists.onebuilding.org>
Objet : [Equest-users] Roof Conduction Load



Hi All,



I am doing an energy simulation model in eQuest. I noticed that the load through roof conduction in LS-C is zero where as in LS-B (for plenum space) it is showing some load.



As per my understanding this load should appear in LS-C also.

Also, if I reduce the U value of the roof, the load through roof reduces and can be accounted in LS-B only (plenum space).



Refer attached LS-C and LS-B reports.

Any help will be appreciated.





Thanks & Regards



Bhartendu Awasthi

_______________________________________________
Bldg-sim mailing list
http://lists.onebuilding.org/listinfo.cgi/bldg-sim-onebuilding.org
To unsubscribe from this mailing list send  a blank message to BLDG-SIM-UNSUBSCRIBE at ONEBUILDING.ORG<mailto:BLDG-SIM-UNSUBSCRIBE at ONEBUILDING.ORG>




--
Regards,

David S. Wood
Principal
Wood, Byk & Associates
office:    610.347.0710<tel:610.347.0710>
mobile:  610.247.1208<tel:610.247.1208>


_______________________________________________
Bldg-sim mailing list
http://lists.onebuilding.org/listinfo.cgi/bldg-sim-onebuilding.org
To unsubscribe from this mailing list send  a blank message to BLDG-SIM-UNSUBSCRIBE at ONEBUILDING.ORG<mailto:BLDG-SIM-UNSUBSCRIBE at ONEBUILDING.ORG>


_______________________________________________
Bldg-sim mailing list
http://lists.onebuilding.org/listinfo.cgi/bldg-sim-onebuilding.org
To unsubscribe from this mailing list send  a blank message to BLDG-SIM-UNSUBSCRIBE at ONEBUILDING.ORG<mailto:BLDG-SIM-UNSUBSCRIBE at ONEBUILDING.ORG>




More information about the Bldg-sim mailing list