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<small><font face="Arial">Hello everyone,<br>
<br>
I am trying to model Earth-Air tunnels in eQUEST located in a
tropical,composite climate (New Delhi). Following the last two threads
on this issue dated Nov. 2003 and Oct, 2006 (shown below) nothing else
seems to have been discussed, especially relating to modeling this
strategy in eQUEST? If anyone has had any experience with it then
please share. I'd appreciate your feedback. Meanwhile, let me try and
explain the system that I am trying to model and how I am approaching
it --<br>
<br>
Earth-air (horizontal) tunnels utilize 100% outside air as it is blown
through them. This brings down the temperature as the air is sensibly
pre-cooled for the air handling unit. In the hot-dry months the air is
either delivered or is subjected to direct-indirect evap-cooling. For
warm-humid periods a small portion of the pre-cooled air stream is
subjected to DX coil where it drops most of its moisture and is mixed
with the rest of the air stream In principle my strategy will be to
model ground-source heat exchanger (GSHX) wherein a fluid (water)
rejects or gains heat and transfers the benefit to the air handling
unit using 100% OA. I am guessing that the transfer of heat between
water-earth via the GSHX and then water-air in the AHU has to be very
efficient to diminish losses incurred and model this system fairly
accurately. I will finally subtract the pumping energy from the total.
Here is the crux, and the questions --<br>
</font></small>
<ol>
<li><small><font face="Arial">Am I thinking in the right direction?</font></small></li>
<li><small><font face="Arial">How does one increase the efficiency of
the GSHX process to best reflect earth-air heat exchange? The aim as I
said earlier is to diminish the losses incurred due to the water-earth
and water-air processes of the GSHX?<br>
</font></small></li>
</ol>
<small><font face="Arial">For now, I am tied to eQUEST to solve this
problem because a large time-consuming part of the model is already
accomplished. However if there is a better way to address this with any
other tool then please do not shy from sharing your knowledge. Many
thanks for helping in the past and in advance on this one.<br>
<br>
sincerely,<br>
Neeraj<br>
<br>
Neeraj Kapoor<br>
t: +91-99581.70018<br>
Kalpakrit Sustainable Environments Pvt. Ltd.<br>
New Delhi<br>
<br>
---------------<br>
</font></small>
<pre wrap="">Victor Hanby wrote:
</pre>
<blockquote type="cite">
<pre wrap=""><span class="moz-txt-citetags">></span>
<span class="moz-txt-citetags">> </span>On 31 Oct 2006, at 10:07, Yatin Choudhary wrote:
<span class="moz-txt-citetags">></span>
</pre>
<blockquote type="cite">
<pre wrap=""><span class="moz-txt-citetags">>></span>
<span class="moz-txt-citetags">>> </span>hi every one
<span class="moz-txt-citetags">>> </span>i am trying to simulate a type 56 with earth air tunnel hypocast
</pre>
</blockquote>
</blockquote>
<pre wrap=""><!---->,...
</pre>
<blockquote type="cite">
<blockquote type="cite">
<pre wrap=""><span class="moz-txt-citetags">>> </span>want
<span class="moz-txt-citetags">>> </span>to compare with a 1.5 TR window unit ac
<span class="moz-txt-citetags">>> </span>please advise
<span class="moz-txt-citetags">>></span>
<span class="moz-txt-citetags">>></span>
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</pre>
</blockquote>
<pre wrap=""><span class="moz-txt-citetags">></span>
<span class="moz-txt-citetags">> </span>Dr Farraj Al-Ajmi pretty much did this for his PhD studies at
<span class="moz-txt-citetags">> </span>Loughborough University (UK). It's described in
<span class="moz-txt-citetags">></span>
<span class="moz-txt-citetags">> </span>Al-Ajmi, F., D.L.Loveday and V.I.Hanby 2006 ``The cooling potential
</pre>
</blockquote>
<pre wrap=""><!---->of
</pre>
<blockquote type="cite">
<pre wrap=""><span class="moz-txt-citetags">> </span>earth-air heat exchangers for domestic buildings in a desert
</pre>
</blockquote>
<pre wrap=""><!---->climate''
</pre>
<blockquote type="cite">
<pre wrap=""><span class="moz-txt-citetags">> </span>Building and Environment 41:235--244.
<span class="moz-txt-citetags">></span>
<span class="moz-txt-citetags">> </span>and
<span class="moz-txt-citetags">></span>
<span class="moz-txt-citetags">> </span>Hanby, V.I., F.Al-Ajmi and D.L.Loveday 2004 ``The optimal design for
</pre>
</blockquote>
<pre wrap=""><!---->a
</pre>
<blockquote type="cite">
<pre wrap=""><span class="moz-txt-citetags">> </span>ground cooling tube in a hot, arid climate'' Building Services
<span class="moz-txt-citetags">> </span>Engineering Research and Technology 26(1):1--10.
<span class="moz-txt-citetags">></span>
<span class="moz-txt-citetags">> </span>Farraj wrote TYPES for the ground cooling tube and the subsoil
<span class="moz-txt-citetags">> </span>environment. I've lost touch with him but I think he has posted here
<span class="moz-txt-citetags">> </span>in the past. He might be able to help you with some code. I modeled
<span class="moz-txt-citetags">> </span>the ac unit sing a fixed temperature approach for each coil
<span class="moz-txt-citetags">> </span>(evaporator and condenser) then assumed a fixed fraction of Carnot to
</pre>
</blockquote>
<pre wrap=""><!---->
</pre>
<blockquote type="cite">
<pre wrap=""><span class="moz-txt-citetags">> </span>get the energy consumption.
<span class="moz-txt-citetags">></span>
<span class="moz-txt-citetags">> </span>Vic Hanby
<span class="moz-txt-citetags">></span>
<span class="moz-txt-citetags">> </span>-----------------------------------------------
<span class="moz-txt-citetags">> </span>Professor V I Hanby
<span class="moz-txt-citetags">> </span>Institute of Energy and Sustainable Development
<span class="moz-txt-citetags">> </span>De Montfort University
<span class="moz-txt-citetags">> </span>The Gateway
<span class="moz-txt-citetags">> </span>Leicester LE1 9BH
<span class="moz-txt-citetags">> </span>UK
<span class="moz-txt-citetags">> </span>------------------------------------------------
<span class="moz-txt-citetags">></span>
<span class="moz-txt-citetags">></span>
<span class="moz-txt-citetags">> </span>======================================================
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<pre wrap=""><!---->
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* <i class="moz-txt-slash"><span class="moz-txt-tag">/</span>Subject<span
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* <i class="moz-txt-slash"><span class="moz-txt-tag">/</span>From<span
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------------------------------------------------------------------------
Bonjour Hugues,
I'm unaware of any single program that automatically sets this up. A
very discrete finite-... 3D conduction model would be desirable, but
depending on your specific needs, ESP-r would be a very good candidate
as an annual assessment tool. I've used ESP-r for underground air
culvert assessment in the past and a couple of graduate students have
used ESP-r for similar studies (Y. Jeong, a grad student at Concordia,
and another student in Norway (a PhD student I believe) have both used
ESP-r for assessing the Media School in Norway, which has an
underground
air culvert).
In Jeong's case, the culvert is modeled as one zone, but it is fairly
straightfoward in ESP-r to subdivide this in, let's say, 10 zones
(e.g.,
a 40m culvert could be made up of ten 4m segments) - that's what I do.
This will give you a more detailed assessment, e.g., of culvert surface
temperatures along the airflow path (useful for condensation assessment
or to see just how effective the first segments of the culvert are in
relation to the last ones). ESP-r also allows you to set up an airflow
network, but 'scheduled' airflows might be OK for your needs.
The main challenge is setting up the surface boundary
conditions. Without setting up a 3D conduction model in ESP-r
(available, but not for the faint-hearted), you'll have to specify
boundary conditions for each surface. If the culvert is deep enough,
you
can just feed it monthly ground profiles for ~¾ of the surfaces, with
harmonics calculated with standard models (see Maitos and Argiriou) -
the same models used for ground-coupled heat pump simulation. If it's
deep enough, the daily variations will be minor (~ ±1°C during the
course of a month). The remaining ~¼ of the surfaces will more likely
feel the effect of the nearby ground surface, so ambient air might be
more suitable as a surface boundary condition. If the culvert is very
close to the ground surface, then it's a bit more tricky - maybe ~½ of
the surfaces need ambient air as a boundary condition. You can of
course
'tweak' the model to see just how sensible it is to variable changes.
Another point is setting up the right surface element 'constructions'
so
on one hand it remains numerically stable, and on the other the
constructions remain 'thick' enough so that using monthly profiles
remains valid (at least conceptually).
Transsolar have modeled culverts for other energy consultants in the
past - maybe they've set up some basic modeling approach in TRNSYS (?).
Simpler empirical approaches are available: Argiriou and Maitos give an
overview of existing models found in the literature.
Good luck,
----
Some references:
Jeong, Y., and Haghighat, F. (2002) "Modeling of a hybrid ventilated
building, Grong School" /Proceedings of the 4th International Forum on
Hybrid Ventilation: An Integrated Solution for Ventilation, Health and
Energy/, Montreal pp.198-207.
Maitos, A. (1999) "Cooling with underground air ducts" MSc Thesis.
University of Strathclyde: Glasgow. 68p.
Argiriou, A.A. (1996) "Ground cooling" in /Passive Cooling of
Buildings/. M.J. Santamouris and D.N. Asimakopoulos, eds., James &
James: London. pp.360-403.
Kumar, R., Ramesh, S., and Kaushik, S.C. (2003) "Performance evaluation
and energy conservation potential of earth-air-tunnel system coupled
with non-air-conditioned building" <i class="moz-txt-slash"><span
class="moz-txt-tag">/</span>Building and Environment<span
class="moz-txt-tag">/</span></i> 38
pp.807-813.
Lay, R.M. (2003) "Earth Rangers Wildlife Centre - case study of
concrete
use for energy efficiency" /Proceedings of the 8th Environmental and
Sustainable Engineering Specialty Conference of the Canadian Society
for
Civil Engineering/, Moncton.
Sawhney, R.L., Buddhi, D., and Thanu, N.M. (1999) "An experimental
study
of summer performance of a recirculation type underground airpipe air
conditioning system" <i class="moz-txt-slash"><span class="moz-txt-tag">/</span>Building and Environment<span
class="moz-txt-tag">/</span></i> 34(2) pp.189-196.
----
Denis Bourgeois
PhD student/doctorant
École d'architecture, Université Laval
denis.bourgeois@xxxxxxxxxxxxx <a class="moz-txt-link-rfc2396E"
href="mailto:denis.bourgeois@xxxxxxxxxxxxx"><mailto:denis.bourgeois@xxxxxxxxxxxxx></a>
----
----- Original Message -----
*From:* Hugues Boivin <a class="moz-txt-link-rfc2396E"
href="mailto:huguesboivin@xxxxxxxxxxxx"><mailto:huguesboivin@xxxxxxxxxxxx></a>
*To:* BLDG-SIM@xxxxxxxx <a class="moz-txt-link-rfc2396E"
href="mailto:BLDG-SIM@xxxxxxxx"><mailto:BLDG-SIM@xxxxxxxx></a>
*Sent:* Friday, November 21, 2003 1:11 PM
*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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