Re: Vertical U-Tube Ground Heat Exchanger and Ground source heat pump model

[Jeff Thornton <thornton@xxxxxxxxxxxx>]

At 01:34 AM 3/15/2004 +0800, kenyym@xxxxxxxxxxxxx wrote:

> I am using Type 504 (Ground source heat pump model) and type 557a (Vertical
> U-tube ground heat exchanger) and I have got some questions regarding 
> these two
> components.

> In type 557a, there is a parameter called initial surface temperature and its
> default value is 20 deg C. I am interested in studying the ground temperature
> variation in the storage volume and I found that this parameter will 
> affect the
> temp. in the storage volume. I would like to know what does this parameter 
> mean
> and is the default value valid for application in Hong Kong. If it is not
> valid, how can I find the corresponding value for my application.

You are correct in that the surface temperature parameter will affect the 
temperature of the storage volume.  An excellent estimate for this 
parameter is the average annual air temperature for the location you wish 
to study.

> In type 504, the external files contain the heat pump performance data. I 
> would
> like to know if those data are standard for geothermal heat pump or I have to
> find the heat pump performance data relative to my own design condition. And
> for my own design conditions, the total cooling capacity is 234 tons of
> refrigeration, how could I enter this into the component for simulation.

The catalog data files provided with this model are for a "typical" 
geothermal heat pump - I believe the size is in the 2 to 3 ton range.  You 
should find manufacturers catalog data for the heat pump you will be using 
for the project and create a data file following the format provided in the 
provided sample files.  I'm doubting that there is an available machine 
capable of producing 234 tons of cooling so you'll have to use multiple 
units of Type 504 or you could scale the data in the catalog files up to 
250 tons - but this approach can neglect some of the advantages of using 
heat pumps in commercial applications; namely the thermal benefit of having 
some heat pumps in heating mode and some heat pumps in cooling mode.

> Finally, I would be very grateful if you could send me more information about
> this two modules, as well as any other modules or information related to
> geothermal heat pump system for air conditioning application.

We have published quite a few articles and technical reports on modeling 
heat pump systems with TRNSYS.  I can send you the links if you are 
interested.  There is also a new technical description manual for both Type 
504 and Type 557 that will be released with Version 2 of the TESS libraries 
(Spring 04 with the release of TRNSYS 16).  While the 
parameters/inputs/outputs will be slightly different from the version you 
are using, the technical description could provide some helpful 
information.  E-mail if you'd like an early version of these documents.

With kindest regards,

Jeff Thornton
TESS

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