[Sbse] ASHRAE Lowdown Showdown Modeling Competition

Susan Roaf s.roaf at btinternet.com
Mon May 10 09:14:55 PDT 2021


Nathanial,

Really - I was talking about windows - not ducts, they are different you 
know?

How lose a grill do you need as a security feature on a window?  not 
that small..   umm has anyone papers on that?  A simple screwed in 
security on the no opening side of a window would work well on higher 
floors.  Of course sash windows are perfect.. but expensive.  Actually 
there has been some good work n the reduction in flow across a fly 
screen or door - c. roughly 50% I seem to remember - I will look the 
paper up.  Or anyone please send one they have for reference.

Re extreme winds - this is about loosing windows etc like the Austin 
Texas building or the Katrina hotel?   I have a fairly good paper i did 
on designing for high winds for the Scottish Architects if anyone wants 
a copy - the nice thing about windows is that you can shut them...so you 
can dictate the windspeeds they should operate in for everyday use. 
Like temperature - put the control back into the hands of the occupants. 
Noone designs HVAC buildings to work optimally in 100 klm windws?  the 
problem is different - trying to stop the windows flying out - 
especially in ever windier parts of america.

Anyone who pretends they have the correct answer to three decimal places 
is pretty well doomed to failure, but good clean common sens will get 
you a long way.   May the force be with you - wind driven of course.

Let me know if you want the paper ...

Sue


------ Original Message ------
From: "Nathaniel Jones" <nathanieljon at gmail.com>
To: "Matthias Haase" <mathaase at gmail.com>
Cc: "SBSE List" <sbse at uidaho.edu>; "Alexandra Rempel" 
<arempel at uoregon.edu>
Sent: Monday, 10 May, 21 At 15:49
Subject: Re: [Sbse] ASHRAE Lowdown Showdown Modeling Competition

Hi Sue and Matthias,

Of course ASHRAE has a method for calculating the pressure loss/speed 
reduction through screens and grills. It's in the ASHRAE Handbook of 
Fundamentals (in my 2009 edition it's chapter 21, tables CD6-1 and 
CR6-1). The chapter is on duct design, but since this is just physics 
we're talking about, it is applicable to other settings as well.


As for pressure distributions around buildings, ASCE has methods that 
can be applied to fairly normative building geometries for wind loading 
calculations. However, more complex geometries and surrounding 
structures result in unique wind pressure distributions that can only be 
analyzed with wind tunnel or CFD tests (although there are some 
promising results from reduced order models, i.e. machine learning). 
Matthias, if you are interested in adding buoyancy (i.e. convection) to 
outside pressure calculations, then I assume you are concerned with 
exhaust plume re-entrainment, as this is the only case I can think of 
where the temperature difference might be enough to counteract the force 
of wind. In that case, CFD is really the only option. Given the possible 
harm to occupants when exhaust is re-entrained into building air supply, 
I would be hesitant to use a simplified or generic model in such a case.


Nathaniel


On Mon, May 10, 2021 at 7:04 AM Matthias Haase <mathaase at gmail.com 
<mailto:mathaase at gmail.com> > wrote:

Dear all,

I agree that we need guidelines for pressure drops of screens and other 
devices (e.g.   shading). But we also need more research on pressure 
distribution around buildings and within districts. These have to be 
measured and calculated taking local solar radiation, absorption and 
convection into account. Many models I have seen are not detailed enough 
and often make simplifying assumptions. Measurements of airflow around 
buildings is often very generic and static. Any hint to work that has 
focused on this is much appreciated! UHI is going in the right direction 
but often asks for UHI mitigation instead of designing with pressure 
differences. Again, hints to promising work in this direction are most 
welcome.








best regards
Matthias Haase
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ZHAW Zurich University of Applied Sciences
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On Sun, May 9, 2021 at 11:28 PM Alexandra Rempel <arempel at uoregon.edu 
<mailto:arempel at uoregon.edu> > wrote:



Hi Sue,
It’s great to hear your thoughts on this! I sure hope you’re right that 
natural ventilation will be a prominent strategy here, supplemented by 
ceiling fans, of course! Passive heating and cooling have not been as 
popular in the past few  years as one might hope, but they’re gaining 
ground.

And no, I’m not aware of any ASHRAE strategy for calculating air speed 
reductions for screens and grills. We definitely need something like 
that!

Intriguingly, the teams are required to choose and defend their own 
indoor air temperature setpoints; in the past, the adaptive comfort zone 
has been used sporadically, and the air speed expansion to both standard 
and adaptive comfort zones  has not been fully exploited. I’m hoping 
this program is an irresistible invitation to do that this year, though!

I would love copies of all of the papers you mention; thank you so much. 
I’ll look at the HVLS website, as well.

Have you thought about coaching a team for this? There’s plenty of time!
Take care, and thank you again so much for your input!
Alex



---
Alexandra Rempel, Ph.D., M.Arch.
Assistant Professor of Environmental Design
Environmental Studies Program
University of Oregon, Eugene OR  97403




From: Susan Roaf <s.roaf at btinternet.com <mailto:s.roaf at btinternet.com> >
  Sent: Saturday, May 8, 2021 5:33 AM
  To: Alexandra Rempel <arempel at uoregon.edu <mailto:arempel at uoregon.edu> 
>; sbse at uidaho.edu <mailto:sbse at uidaho.edu>
  Subject: Re: [Sbse] ASHRAE Lowdown Showdown Modeling Competition




Dear All,


In that lovely climate there will be many who will want to run their 
building complexes for as much of the day and year as possible using 
natural ventilation which is the main way to reduce heating and cooling 
and ventilation costs in buildings (that is  obviously a no-brainer).

Question - Does ASHRAE have a standard methodology for calculating 
reductions in air movement due to insect screens and security grills?

Ceiling fans will also be key to genuinely low energy buildings.

This begs the question of what temperatures are inbuilt into the models 
use for acceptable temperatures for fan and natural ventilation use.

Fergus Nicol and I did a paper last November for the Dutch HVAC journal 
for acceptable temperature ranges for naturally ventilated building - I 
would be happy to send a copy to anyone interested.

I also have a great paper by Dick Aynsley on calculating fan power etc 
he did for a book I edited - I can send that too if you are interested. 
He was an early expert for Big Ass Fans who also have a great resource 
site on fan design:  HVLS Design Guide (bigassfans.com) 
<https://urldefense.com/v3/__https:/guide.bigassfans.com/__;!!C5qS4YX3!V41rAjKP6Hk9Rq1ESdqV4dV1e9n8wW_XSG8e9PrhE-JSCmsyeAeSunkm3yED2mIrFw$>

In that climate a great idea is to use simple roof space extract fans to 
pull air through the building from cooler / garden type places - where 
planting and water etc can lower temps by up to 5C - from a shiny hot 
sunny equivalent space with hard reflective  surfaces - if not more.

I have no doubt that such issues will dominate the submissions - or is 
this for high energy buildings that need energy 24/7/365 - that cant 
be....

Good luck with the interesting project.

Best wishes

Sue
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