[Bldg-sim] exterior convection coefficient for tilted roof
Luis Miguel Candanedo
luismiguel_78 at hotmail.com
Mon Feb 13 01:16:34 PST 2012
Hi Leen,
I did my PhD work on Building Integrated Photovoltaic/Thermal systems.
My
work was mostly focused at the interior convective heat transfer
coefficients in the cavity/gap between PV modules and the next layer of
building envelope in the roof where the air flowed.
However I looked numerically the influence of different wind correlations:
Test et al. (1981), Sharples and Charlesworth (1998), McAdams (McAdams, W.H.,
1954; Duffie, J.A. & Beckman, W.A.,
2006) as a function of the wind speed in m/s:
ho = 8.55
+ 2.56
⋅Vwind
ho =11.9+2.2⋅Vwind
h=5.7+3.8Vwind
and also I used a correction factor for the Wind speed at the height of my experimental setup.
(Hutcheon, Handegord, 1995)
Vwind=Vg(Z/Zg)^alphawind
In general I found that the Sharples and Charlesworth correlations gave me the best results.
You can look at my thesis and this paper
Candanedo, L. M., Athienitis, A., Candanedo, J., O’Brien, W., Chen, Y.,
(2010). Transient and Steady State Models for Open-Loop Air-Based BIPV/T
Systems. ASHRAE Transactions. Vol 116. P. 600-612.
I hope it helps,
Luis
Research Assistant
University of Mons
Belgium
From: luismiguel_78 at hotmail.com
To: bldg-sim at lists.onebuilding.org
Subject: RE: Bldg-sim Digest, Vol 51, Issue 10
Date: Mon, 13 Feb 2012 04:09:07 -0500
Hi Leen,
I did my PhD work on Building Integrated Photovoltaic/Thermal systems.
My work was mostly focused at the interior convective heat transfer coefficients in the cavity/gap between PV modules and the next layer of building envelope in the roof where the air flowed.
However I looked numerically the influence of different wind correlations:
From: bldg-sim-request at lists.onebuilding.org
Subject: Bldg-sim Digest, Vol 51, Issue 10
To: bldg-sim at lists.onebuilding.org
Date: Sun, 12 Feb 2012 13:30:46 -0800
Send Bldg-sim mailing list submissions to
bldg-sim at lists.onebuilding.org
To subscribe or unsubscribe via the World Wide Web, visit
http://lists.onebuilding.org/listinfo.cgi/bldg-sim-onebuilding.org
or, via email, send a message with subject or body 'help' to
bldg-sim-request at lists.onebuilding.org
You can reach the person managing the list at
bldg-sim-owner at lists.onebuilding.org
When replying, please edit your Subject line so it is more specific
than "Re: Contents of Bldg-sim digest..."
--Forwarded Message Attachment--
From: jhaberl at tamu.edu
To: l.f.r.peeters at gmail.com; bldg-sim at lists.onebuilding.org
Date: Sat, 11 Feb 2012 21:55:59 +0000
Subject: Re: [Bldg-sim] exterior convection coefficient for tilted roof
Leen,
This depends on whether or not the wind is blowing... or not. ASHRAE used to have tabluated values (still in some textbooks) of R = .17 Btu/ft2-hr-F for winter (15 mph wind) and .25 Btu/ft2-hr-F for summer (7 mph wind). Otherwise, for a vertical surface
it would be .68 for free convection, probably less for a tilted surface, .9 if horizontal heat flow down.
Also, radiation can be significant if the surface is facing a cloudless sky. I think Kreider's solar textbook has a equation for sky temperature...which is somewhat complicated by cloud cover, etc.
Jeff
8=! 8=) :=) 8=) ;=) 8=) 8=( 8=) 8=() 8=) 8=| 8=) :=') 8=)8=?
Jeff S. Haberl, Ph.D.,P.E., FASHRAE..............jhaberl at tamu.edu
Professor............................................................Office Ph: 979-845-6507
Department of Architecture.............................Lab Ph:979-845-6065
Energy Systems Laboratory.............................FAX: 979-862-2457
Texas A&M University.....................................77843-3581
College Station, Texas, USA, 77843..................URL:www.esl.tamu.edu
8=/ 8=) :=) 8=) ;=) 8=) 8=() 8=) :=) 8=) 8=! 8=) 8=? 8=)8=0
From: bldg-sim-bounces at lists.onebuilding.org [bldg-sim-bounces at lists.onebuilding.org] on behalf of leen peeters [l.f.r.peeters at gmail.com]
Sent: Saturday, February 11, 2012 1:59 PM
To: bldg-sim at lists.onebuilding.org
Subject: [Bldg-sim] exterior convection coefficient for tilted roof
Dear,
can anyone point me to some reference values for exterior convection coefficients for tilted surfaces like a roof?
Thanks
Leen
--Forwarded Message Attachment--
From: phcjam at yahoo.com
To: bldg-sim at lists.onebuilding.org
Date: Sat, 11 Feb 2012 14:40:27 -0800
Subject: [Bldg-sim] Fw: exterior convection coefficient for tilted roof
I've only seen reference values of interior convection coefficients for tilted surfaces, not exterior coefficients: which are available for summer & winter conditions, due to the difference in wind velocity.
Paul Hay MBA, BA(Arch)
Managing Partner
PAUL HAY Capital Projects
Caribbean Capital Project Management & Planning
P.O.Box 3367
Constant Springs, Kgn. 8
Jamaica, W.I.
tel: 1 (876) 756-0631cel: 1 (876) 324-4274fax: 1 (876)
756-0631 e-mail: paul.hay at phcjam.comskype name: phcjamtwitter: http://www.twitter.com/phcjamweb: http://www.phcjam.comprofile: http://www.linkedin.com/company/paul-hay-capital-projects
----- Forwarded Message -----
From: leen peeters <l.f.r.peeters at gmail.com>
To: bldg-sim at lists.onebuilding.org
Sent: Saturday, February 11, 2012 2:59 PM
Subject: [Bldg-sim] exterior convection coefficient for tilted roof
Dear,
can anyone point me to some reference values for exterior convection coefficients for tilted surfaces like a roof?
Thanks
Leen
_______________________________________________
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
--Forwarded Message Attachment--
From: chris.malcolm.yates at gmail.com
CC: bldg-sim at lists.onebuilding.org
To: phcjam at yahoo.com
Date: Sat, 11 Feb 2012 22:45:16 +0000
Subject: Re: [Bldg-sim] Fw: exterior convection coefficient for tilted roof
It's true wind does dominate external convection.
Cibse guide A will give you all the numbers that you're looking for
Chris
On 11 Feb 2012 22:40, "Paul Hay" <phcjam at yahoo.com> wrote:
I've only seen reference values of interior convection coefficients for tilted surfaces, not exterior coefficients: which are available for summer & winter conditions, due to the difference in wind velocity.
Paul Hay MBA, BA(Arch)
Managing Partner
PAUL HAY Capital Projects
Caribbean Capital Project Management & Planning
P.O.Box 3367
Constant Springs, Kgn. 8
Jamaica, W.I.
tel: 1 (876) 756-0631
cel: 1 (876) 324-4274fax: 1 (876)
756-0631 e-mail: paul.hay at phcjam.com
skype name: phcjamtwitter: http://www.twitter.com/phcjam
web: http://www.phcjam.comprofile: http://www.linkedin.com/company/paul-hay-capital-projects
----- Forwarded Message -----
From: leen peeters <l.f.r.peeters at gmail.com>
To: bldg-sim at lists.onebuilding.org
Sent: Saturday, February 11, 2012 2:59 PM
Subject: [Bldg-sim] exterior convection coefficient for tilted roof
Dear,
can anyone point me to some reference values for exterior convection coefficients for tilted surfaces like a roof?
Thanks
Leen
_______________________________________________
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
_______________________________________________
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
--Forwarded Message Attachment--
From: l.f.r.peeters at gmail.com
CC: bldg-sim at lists.onebuilding.org
To: chris.malcolm.yates at gmail.com
Date: Sat, 11 Feb 2012 23:51:33 +0100
Subject: Re: [Bldg-sim] Fw: exterior convection coefficient for tilted roof
Hi Chris,
CIBSE suggest to replace g with gcos(theta) in the Grasshof number. That means, it accounts for the roof being tilted in natural convection. When it comes to roofs, there is another aspects that starts to be important ... the roof finishing in tiles will have a 'detoriated' velocity underneath the tiles. It is mainly that one directing the convective losses ...
Am I correct on this?
Leen
On Sat, Feb 11, 2012 at 11:45 PM, Chris Yates <chris.malcolm.yates at gmail.com> wrote:
It's true wind does dominate external convection.
Cibse guide A will give you all the numbers that you're looking for
Chris
On 11 Feb 2012 22:40, "Paul Hay" <phcjam at yahoo.com> wrote:
I've only seen reference values of interior convection coefficients for tilted surfaces, not exterior coefficients: which are available for summer & winter conditions, due to the difference in wind velocity.
Paul Hay MBA, BA(Arch)
Managing Partner
PAUL HAY Capital Projects
Caribbean Capital Project Management & Planning
P.O.Box 3367
Constant Springs, Kgn. 8
Jamaica, W.I.
tel: 1 (876) 756-0631
cel: 1 (876) 324-4274
fax: 1 (876) 756-0631
e-mail: paul.hay at phcjam.com
skype name: phcjam
twitter: http://www.twitter.com/phcjam
web: http://www.phcjam.com
profile: http://www.linkedin.com/company/paul-hay-capital-projects
----- Forwarded Message -----
From: leen peeters <l.f.r.peeters at gmail.com>
To: bldg-sim at lists.onebuilding.org
Sent: Saturday, February 11, 2012 2:59 PM
Subject: [Bldg-sim] exterior convection coefficient for tilted roof
Dear,
can anyone point me to some reference values for exterior convection coefficients for tilted surfaces like a roof?
Thanks
Leen
_______________________________________________
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
_______________________________________________
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
_______________________________________________
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
--Forwarded Message Attachment--
From: chris.malcolm.yates at gmail.com
To: l.f.r.peeters at gmail.com; bldg-sim at lists.onebuilding.org
Date: Sun, 12 Feb 2012 12:54:41 +0000
Subject: Re: [Bldg-sim] Fw: exterior convection coefficient for tilted roof
Hi Leen,
I'm not familiar with the calculation involving the Grasshof number.
The formula given is hc= 4+4v, where hc is the convection
coefficient and v is the wind velocity. The formula is probably
derived empirically (don't know for certain). Are you definitely
talking about the convection element of heat transfer or are you
talking lw radiation?
Regards
Chris
On 11/02/2012 22:51, leen peeters wrote:
Hi Chris,
CIBSE suggest to replace g with gcos(theta) in the Grasshof
number. That means, it accounts for the roof being tilted in
natural convection. When it comes to roofs, there is another
aspects that starts to be important ... the roof finishing in
tiles will have a 'detoriated' velocity underneath the tiles. It
is mainly that one directing the convective losses ...
Am I correct on this?
Leen
On Sat, Feb 11, 2012 at 11:45 PM, Chris
Yates <chris.malcolm.yates at gmail.com>
wrote:
It's true wind does dominate external convection.
Cibse guide A will give you all the numbers that you're
looking for
Chris
On 11 Feb 2012 22:40, "Paul Hay"
<phcjam at yahoo.com>
wrote:
I've only seen reference values
of interior convection coefficients for tilted
surfaces, not exterior coefficients: which are
available for summer & winter conditions,
due to the difference in wind velocity.
Paul Hay MBA, BA(Arch)
Managing Partner
PAUL HAY Capital Projects
Caribbean
Capital Project Management & Planning
P.O.Box 3367
Constant Springs, Kgn. 8
Jamaica, W.I.
tel: 1
(876) 756-0631
cel: 1
(876) 324-4274
fax: 1 (876) 756-0631
e-mail: paul.hay at phcjam.com
skype name: phcjam
twitter: http://www.twitter.com/phcjam
web: http://www.phcjam.com
profile: http://www.linkedin.com/company/paul-hay-capital-projects
-----
Forwarded Message -----
From:
leen peeters <l.f.r.peeters at gmail.com>
To:
bldg-sim at lists.onebuilding.org
Sent:
Saturday, February 11, 2012 2:59 PM
Subject:
[Bldg-sim] exterior convection coefficient
for tilted roof
Dear,
can anyone point me to some reference
values for exterior convection
coefficients for tilted surfaces like a
roof?
Thanks
Leen
_______________________________________________
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
_______________________________________________
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
_______________________________________________
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
--
Chris Yates C Eng
MCIBSE
Building Physics Consultant
Tel: +447960731576
Email: chris.malcolm.yates at gmail.com
Skype: christopher.m.yates
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.onebuilding.org/pipermail/bldg-sim-onebuilding.org/attachments/20120213/90106903/attachment-0002.htm>
More information about the Bldg-sim
mailing list