[esp-r] Re: convective heat transfer coefficients in ESP -r

[Burek, Stas]

Dear Gunter

I presume that you're looking at a solar chimney or some sort of passive solar collector? We're doing work on exactly that. We have a paper recently published in Energy and Buildings, and we're doing some more work on the how height affects the flow rate and heat transfer.

If you look at the literature, there's plenty of it for buoyancy driven flow in a vertical channel. The problem is that there is very little that specifically reflects the conditions in a solar system - a lot of it refers to systems with symmetrical heating, or with an adiabatic 'cold' wall, or with a uniform wall temperature - none of these conditions occur in a solar system.

Also, if you're looking at flow within a channel, with the temperature rising both for the fluid and the channel walls, it's difficult to define a heat transfer coefficient. So far, we've analysed our (experimental) data to give a result for bulk flow and thermal efficiency, as a function of channel depth and heat input. Coming soon will be these as a function of the channel height, as well. Then we'll take a look at how the heat transfer coefficient varies over the height of the system.

Check out:

Air flow and thermal efficiency characteristics in solar chimneys and Trombe Walls  * 
Energy and Buildings, In Press, Corrected Proof, Available online 17 August 2006, 
S. A.M. Burek and A. Habeb

There are references to lots of previous work there as well.

Hope this might be useful

Thanks

Stas Burek


Dr. Stas Burek
School of the Built and Natural Environment
Glasgow Caledonian University
Cowcaddens Road
Glasgow G4 0BA
Scotland, UK
Tel: (+44) (0)141 331 3897
Fax: (+44) (0)141 331 3370

-----Original Message-----
From: esp-r-bounces at lists.strath.ac.uk [mailto:esp-r-bounces at lists.strath.ac.uk] On Behalf Of Pueltz, Gunter
Sent: 15 September 2006 10:45
To: 'esp-r at lists.strath.ac.uk'
Subject: [esp-r] convective heat transfer coefficients in ESP -r

To the ESP-r fan club:

Can anyone provide some informations about the Bar-Cohen and Rosenhow
correlation
for convective heat transfer coefficients in an open, vertical channel (only
buoyancy driven air flow) ?

Does this correlation take the air velocity within a channel into account ?
Is the air velocity calculated according to the results of the
air-flow-network ?
The channel itself is a zone, which is linked with an air flow node ....

What is the best approach for the htc in an open, vertical channel with
intensive
air flow (one side of the channel is very hot: it is the wall of a turbine)
...?

Any comments are appreciated !

Best regards,
Gunter 

--
Gunter Pültz

Müller-BBM GmbH
Robert-Koch-Straße 11
82152 Planegg
Telefon +49 (0)89 85602 - 336
Telefax +49 (0)89 85602 - 111
http://www.MuellerBBM.de 

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