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

[Neeraj Kapoor]

Hello everyone,

I am trying to model Earth-Air tunnels in eQUEST located in atropical,composite climate (New Delhi). Following the last two threadson this issue dated Nov. 2003 and Oct, 2006 (shown below) nothing elseseems to have been discussed, especially relating to modeling thisstrategy in eQUEST? If anyone has had any experience with it thenplease share. I'd appreciate your feedback. Meanwhile, let me try andexplain the system that I am trying to model and how I am approachingit --

Earth-air (horizontal) tunnels utilize 100% outside air as it is blownthrough them. This brings down the temperature as the air is sensiblypre-cooled for the air handling unit. In the hot-dry months the air iseither delivered or is subjected to direct-indirect evap-cooling. Forwarm-humid periods a small portion of the pre-cooled air stream issubjected to DX coil where it drops most of its moisture and is mixedwith the rest of the air stream In principle my strategy will be tomodel ground-source heat exchanger (GSHX) wherein a fluid (water)rejects or gains heat and transfers the benefit to the air handlingunit using 100% OA. I am guessing that the transfer of heat betweenwater-earth via the GSHX and then water-air in the AHU has to be veryefficient to diminish losses incurred and model this system fairlyaccurately. I will finally subtract the pumping energy from the total.Here is the crux, and the questions --
  
   Am I thinking in the right direction?  
   How does one increase the efficiency ofthe GSHX process to best reflect earth-air heat exchange? The aim as Isaid earlier is to diminish the losses incurred due to the water-earthand water-air processes of the GSHX?
    
For now, I am tied to eQUEST to solve thisproblem because a large time-consuming part of the model is alreadyaccomplished. However if there is a better way to address this with anyother tool then please do not shy from sharing your knowledge. Manythanks for helping in the past and in advance on this one.

sincerely,
Neeraj

Neeraj Kapoor
t: +91-99581.70018
Kalpakrit Sustainable Environments Pvt. Ltd.
New Delhi

---------------

Victor Hanby wrote:
  
>> On 31 Oct 2006, at 10:07, Yatin Choudhary wrote:>  
      
>>>> hi every one>> i am trying to simulate a type 56 with earth air tunnel hypocast    
  
,... 
      
>> want>> to compare with a 1.5 TR window unit ac>> please advise>>>>>> ======================================================>> You received this e-mail because you are subscribed>> to the BLDG-SIM at GARD.COM mailing list.  To unsubscribe>> from this mailing list send a blank message to>> BLDG-SIM-UNSUBSCRIBE at GARD.COM>>    
    
>> Dr Farraj Al-Ajmi pretty much did this for his PhD studies at > Loughborough University (UK). It's described in>> Al-Ajmi, F., D.L.Loveday and V.I.Hanby 2006 ``The cooling potential  

of 
  
> earth-air heat exchangers for domestic buildings in a desert  

climate'' 
  
> Building and Environment 41:235--244.>> and>> Hanby, V.I., F.Al-Ajmi and D.L.Loveday 2004 ``The optimal design for  

a 
  
> ground cooling tube in a hot, arid climate''  Building Services > Engineering Research and Technology 26(1):1--10.>> Farraj wrote TYPES for the ground cooling tube and the subsoil > environment. I've lost touch with him but I think he has posted here > in the past. He might be able to help you with some code. I modeled > the ac unit sing a fixed temperature approach for each coil > (evaporator and condenser) then assumed a fixed fraction of Carnot to  


  
> get the energy consumption.>> Vic Hanby>> -----------------------------------------------> Professor V I Hanby> Institute of Energy and Sustainable Development> De Montfort University> The Gateway> Leicester LE1 9BH> UK> ------------------------------------------------>>> ======================================================> You received this e-mail because you are subscribed to the > BLDG-SIM at GARD.COM mailing list.  To unsubscribe from this mailing  

list 
  
> send a blank message to BLDG-SIM-UNSUBSCRIBE at GARD.COM  

    * /To/: <BLDG-SIM at xxxxxxxx <mailto:BLDG-SIM at DOMAIN.HIDDEN>>    * /Subject/: [BLDG-SIM] earth-air exchanger (earth channels)    * /From/: Denis Bourgeois <denis.bourgeois at xxxxxxxxxxxxx      <mailto:denis.bourgeois at DOMAIN.HIDDEN>>    * /Date/: Fri, 21 Nov 2003 15:27:36 -0500    * /List-unsubscribe/: <mailto:BLDG-SIM-Unsubscribe at gard.com>    * /References/:      <MDAEMON-F200311201548.AA4849171pd80000629044 at xxxxxxxx     <mailto:MDAEMON-F200311201548.AA4849171pd80000629044 at DOMAIN.HIDDEN>>      <MDAEMON-F200311211204.AA0424687pd80000630311 at xxxxxxxx     <mailto:MDAEMON-F200311211204.AA0424687pd80000630311 at DOMAIN.HIDDEN>>    * /Reply-to/: denis.bourgeois at xxxxxxxxxxxxx      <mailto:denis.bourgeois at DOMAIN.HIDDEN>    * /Sender/: postman at xxxxxxxx <mailto:postman at DOMAIN.HIDDEN>------------------------------------------------------------------------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 anunderground 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 surfacetemperatures along the airflow path (useful for condensation assessmentor 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 ~&frac34; 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 ~&frac14; 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 ~&frac12; of the surfaces need ambient air as a boundary condition. You can ofcourse '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 anoverview 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 evaluationand energy conservation potential of earth-air-tunnel system coupled with non-air-conditioned building" /Building and Environment/ 38pp.807-813.Lay, R.M. (2003) "Earth Rangers Wildlife Centre - case study ofconcrete use for energy efficiency" /Proceedings of the 8th Environmental and Sustainable Engineering Specialty Conference of the Canadian Societyfor Civil Engineering/, Moncton.Sawhney, R.L., Buddhi, D., and Thanu, N.M. (1999) "An experimentalstudy of summer performance of a recirculation type underground airpipe air conditioning system" /Building and Environment/ 34(2) pp.189-196.----Denis BourgeoisPhD student/doctorantÉcole d'architecture, Université Lavaldenis.bourgeois at xxxxxxxxxxxxx <mailto:denis.bourgeois at xxxxxxxxxxxxx> ----    ----- Original Message -----    *From:* Hugues Boivin
 <mailto:huguesboivin at xxxxxxxxxxxx>    *To:* BLDG-SIM at xxxxxxxx <mailto:BLDG-SIM at xxxxxxxx>    *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)    ==================    You received this e-mail because you are subscribed     to the BLDG-SIM at xxxxxxxx <mailto:BLDG-SIM at xxxxxxxx> mailing list. To unsubscribe     from this mailing list send a blank message to     BLDG-SIM-UNSUBSCRIBE at xxxxxxxx

       
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