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Re: heat transfer with water-bearing stratum of the soil
- Date: Thu, 11 Mar 2004 12:40:12 +0100
- From: henkwitte <henk.witte@xxxxxxxxxxxxxxx>
- Subject: Re: heat transfer with water-bearing stratum of the soil
Dear Adriana,
With "interacting" do you mean ground water movement? In any case, ground
water effects are not easy to incorporate. We try to take into account two
effects: natural ground water flow (advection) and thermally induced
convection. Both may affect operation of a ground loop system especially in
cooling operation. We use a numerical model (HST3D) developed by the USGS
to estimate effects of ground water on the system. The disadvantage is that
it is not possible to model the heatpump - heatexchanger - borehole with
this model, only a heat flux can be specified and the temperature response
to different ground water regimes can be compared.
This model can not be used with TRNSYS however! For relatively simple
(small) systems the effect of ground water flow can be incorporated by
changing the soil thermal conductivity. Using HST3D and a line source
approach you can estimate the '"apparent" conductivity from the temperature
response to a specified heat flux (given the real conductivity of the
ground and ground water flow). This conductivity can than be used in the
TRNSYS ground heat exchanger model. that should give you a good idea about
the order of magnitude of the effect.
I have some results of experimental measurements we carried out, so if you
are interested please send me your email address and I can send you the PDF's.
Best wishes,
Henk Witte
Dear trnsys users,
I'm working on ground coling.
Does anybody know if there is a type for modelling ground heat exchangers
interacting with the
water-bearing stratum of the soil? Such interaction is not taken into
account in the Duct Storage Model
type.
Thank you
Adriana
----------
Adriana Angelotti
PhD student
eErg end-use Efficiency Research Group
Politecnico di Milano, Dipartimento di Energetica
Piazza Leonardo da Vinci 32
20133 Milano
Italy
ph +39.02.2399.3859
fax +39.02.2399.3940
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