Jeffrey D. Spitler
C.M. Leonard Professor
Current and Recent Research
Simulation of Ground Source Heat Pump Systems
For several years, we have been
developing models for ground loop heat exchangers, heat pumps, and other related
components. These models are aimed at being used in component-based modular
simulation environments such as TRNSYS or HVACSIM+.
The ground loop heat exchanger model
(Yavuzturk
and Spitler 1999) is capable of accounting for short (1 hour or less)
time-step effects, while also accounting for very long-term (30 years+) borehole
interactions.
Ongoing work is funded by the U.S.
Department of Energy. Six-page summaries of work done in
1998
and 1999
are available.
Determination of the ground's
thermal conductivity is a significant challenge facing designers of Ground
Source Heat Pump (GSHP) systems applied in commercial buildings. The number of
boreholes and the depth and cost of each borehole are highly dependent on the
ground thermal properties. Hence, depending on the geographic location and the
local drilling costs, the ground thermal properties strongly influence the
initial cost to install a GSHP system. In order to be able to predict ground
thermal properties, an experimental apparatus has been built capable of imposing
a heat flux on a test borehole, and measuring its temperature response.
Parameter estimation techniques in conjunction with a two-dimensional numerical
model are used to determine the thermal conductivity of the surrounding ground.
The initial development of the
apparatus and analysis techniques are described in an
M.S.
thesis written by Trey Austin. A more refined version of the analysis
procedures and some validation efforts are described in a paper
(Austin,
et al. 2000) published in the ASHRAE Transactions. Ongoing research is aimed
at reducing the amount of time required to make an in situ measurement, reducing
the amount of time required to analyze the results, and further validating the
methodology. The initial work was funded by the National Rural Electric
Cooperative Association. Additional work was funded by the U.S. Department of
Energy. Six page summaries of work done in
1998
and 1999
are available here.
Evaluation of the Effects of Groundwater Flow on Closed Loop
Ground Source Heat Pump Systems
Aquifer flows are widely thought to
have a beneficial effect on closed loop ground source heat pump systems.
However, there has been little, if any work done to quantify the effects of the
groundwater flow. We performed a study of the effects of groundwater flow on
both in situ ground properties estimation and on the operation of the ground
loop heat exchanger. The results are soon to be submitted for publication. This
work is funded by the U.S. Department of Energy. A six page summary of work done
in 1998 is available here.
Research into the geothermal smart
bridge is ongoing at Oklahoma State University, with the close cooperation of
the Oklahoma Department of Transportation. The project is aimed at the
development of a bridge deck heating system to eliminate preferential icing. The
proposed bridge deck heating system
-
Is hydronic, i.e. a heated
fluid is circulated through tubes embedded in the bridge deck,
-
Makes use of a ground source
heat pump system, which recovers energy stored in the earth, and uses it to
heat the fluid circulated through the bridge deck,
-
Is automatic, and makes use of
local and remote weather stations to forecast potential icing conditions,
(the automatic nature of the controls has given rise to the informal name
"Smart Bridge")
-
Is expected to enhance both
safety, by eliminating preferential icing conditions, and bridge deck life,
by eliminating the application of salt on the bridge deck, and reducing
corrosion of the reinforcing steel.
Initial research was funded by the
Oklahoma Department of Transportation. Initial research was done on a very
small-scale (3' by 10') test bridge deck, along with an experimentally
calibrated numerical model. More recently, the U.S. Department of Transportation
has funded a much larger research project.
Additional work is aimed at deploying the technology at a
bridge on Interstate 40, just East of Weatherford.
Weatherford
Smartbridge Site
The Bank of Oklahoma Tower, part of
the Williams Center, a 52 story multipurpose building located in downtown Tulsa,
Oklahoma. It is approximately 160 ft by 160 ft by 1360 ft tall. It houses about
1500 employees in nearly 1.2 million square feet. The goal of this project is to
investigate system modifications that would be economically feasible and result
in lower energy costs. This project was funded by the Williams Headquarters
Building Company.
ASHRAE 1052-RP Development of an
Analytical Verification Test Suite for Whole Building Energy Simulation Programs - Building Fabric
This project involves the
development of an analytical test suite, covering a variety of heat transfer
mechanisms, for use in validating building simulation programs. There are some
building heat transfer scenarios for which an analytical solution can be
devised. E.g. steady-state conduction in walls; transient conduction in walls
with either periodic boundary conditions or a unit step boundary condition. The
test suite will consist of a variety of analytical solutions, weather files
which create the necessary boundary conditions, and sufficient auxiliary
information so that users and developers of building simulation programs can
create input files and compare results to the analytical solutions.
ASHRAE 1090-RP Development of a
Two-Dimensional Transient Model of Snow-Melting Systems, and Use of the Model
for Analysis of Design Alternatives
The objective of this project is to
develop a 2-D transient model of a snow-melting system; develop a library of
storms; use the model with both steady-state data and actual storms to perform a
parametric analysis of heat input requirements for various configurations,
weather conditions, and free area ratios.
ASHRAE 1119-RP R & D Studies
Applied to Standing Column Well Design
Standing
column wells are used for direct (i.e. open-loop) heat exchange with the
earth. The objectives of this project include studying the characteristics of
standing column wells for the purposes of establishing firm guidelines for their
siting and design; developing analysis tools to strengthen these guidelines and
to provide the basis for computer codes which can supply ready prediction of
required well depth; and outline field tests which can provide monitoring data
to verify the codes. The
information may become a part of the ASHRAE handbook and an instruction manual
for the design and installation of standing column wells that will serve the
geothermal and HVAC communities.
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