[BLDG-SIM] earth-air exchanger (earth channels)

[Simon Rees]

I am doing some modelling work on an earth coupled duct at the moment. I
have used CFD (CFX 4) to model the duct in 3D, including the concrete
wall. It has shown that the duct surface temperature does vary
significantly along its length. This variation in the driving
temperature difference is more significant than variations in fluid
temperature would be in a hydronic system, as this temp. diff. is
smaller. I have also done some 2D finite volume calcs that include about
10m depth of soil. As it is a 2D model it has been possible to run with
weather data for multiple years. This has shown that the temp.
distribution does not reach steady-periodic conditions until several
years have past (about 10 years in my case).  The long term rise/fall in
temp depends on the annual balance of heating/cooling loads. This
characteristic is well known in the geothermal heat pump community but
it appears often neglected in air coupled designs.
 
I am keen to hear of the experience of others. I can suggest another
reference: F. Al-Ajmi (2002). Potential cooling of the subsoil
environment in dry desert climate implicated by means of Earth-Air Heat
exchanger in domestic dwellings. PhD Thesis, Loughborough University
(UK).
 
Simon Rees,
De Montfort University, UK.

-----Original Message-----
From: postman at gard.com [mailto:postman at gard.com] On Behalf Of Hugues
Boivin
Sent: 21 November 2003 18:11
To: BLDG-SIM at gard.com
Subject: [BLDG-SIM] earth-air exchanger (earth channels)


Does anyone knows a simulation tool to evaluate energy savings by
earth-to-air exchanger (earth channels) ?
 
Thank you.
 
 
 
Hugues Boivin
Mechanical Engineer
Laval University
GRAP (Groupe de recherche en ambiance physique)


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