[Bldg-sim] eQuest: changing inside film resistance on schedule?

[Joe Huang]

Brent,

This was something I looked at about 15 years ago in a LBNL project for
the California Institute for Energy Efficiency to design a 
compressorless house for California transition climates, using the 
DOE-2.1E program. There was a paper that I wrote with Fred Winkelmann 
called "the Story of h", that I believe got turned into an LBNL report, 
circa 1993. Since eQUEST uses the same modeling as DOE-2.1E,
what I found should also apply.

Unfortunately, it is difficult to vary the inside air film coefficient
in DOE-2, since it is used in calculating the response factor of each 
layer, and ultimately in the weighting factor of each space. Making the
response factora changeable during a simulation would require major 
mathematical surgery of the room model used in DOE-2 and possibly 
invalidate the whole weighting factor approach.

What I did do, which was not very satisfactory, was to do multiple runs
varying the h (inside air film coefficient) in order to bound the 
effect. I based the value of h depending on the air flow rate on work
done by Jeff Spitler at Oklahoma State University on an ASHRAE project,
but I don't recall the exact values.  I do recall that beyond a certain 
amount of air changes, ~ 20 ?, there was little change in h.

Joe Huang
White Box Technologies
346 Rheem Blvd, Suite 108D
(925)388-0265
yjhuang at whiteboxtechnologies.com

Brent Eubanks wrote:
> 
> 
> (Got no responses from eQuest users list, reposting here)
>   
> 
> Another question related to my thermal mass passive cooling project:  
> Part of this project is to use ceiling fans for comfort cooling during 
> the day.  We also are considering using the ceiling fans (under EMS 
> control) to run at night to improve the efficiency of the heat transfer 
> to walls during the precooling phase.
> 
>  
> 
> It seems like the easiest way to simulate this would be to adjust the 
> inside film resistance downward during the times the ceiling fans are 
> running.  To wit:
> 
> 1)      Is there any way to vary the inside film resistance e.g. on a 
> schedule?
> 
> 2)      Does anyone have a sense of the relationship between inside film 
> resistance and air velocity, to establish a good value for the times 
> that the fans are running?  We’re expecting air velocities of ~100-200 
> FPM near the walls.
> 
> 3)      Can anyone think of a different approach to simulating this 
> effect, other than manipulating the inside film resistance values?  
> 
> Thanks, once again.  
> 
> Brent Eubanks
> 
> Mechanical Designer, Taylor Engineering, LLC
> 
> 1080 Marina Village Parkway, Suite 501, Alameda CA 94501
> 
> (510) 473-1164 direct, (510) 749-9135 office
> 
> (510) 749-9136 fax
> 
>  
> 
> beubanks at taylor-engineering.com
> 
> www.taylor-engineering.com
> 
>  
> 
> 
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