Re: [TRNSYS-users] GSHP-suystem

["Jeff Thornton" <thornton@tess-inc.com>]

<Type 31b: the loss coeffcient has a default value of 20 kJ/hr.m^2.K
but I think that common values are about of 6000 kJ/hr.m^2.K: does
anyone know exact formula to determinate this parameter?>

It had better not be 6000 kJ/h.m2.K!  There won't be any energy left in
your system at all.  The loss coefficient accounts for the internal fluid
resistance (convection), the resistance due to conduction through the pipe
wall (and possibly insulation), and the resistances due to convective and
radiative exchange from the outer pipe surface.  If you're not comfortable
calculating these yourself then I would suggest that you use one of the
newer pipe models - there are versions from TESS available for buried and
exposed pipes.

<Type 556: does anyone know exact formula to determinate the flow
convection coefficient and the no-flow convection coefficient?>

Type 556 has been shown to have some problems recently.  This model is not
part of TRNSYS 17 and has been replaced by the TESS model described
earlier.

<Type 557a: wich is the value of "reference temperature" (PAR 20)? does
anyone know exact formula to determinate it?>

There is no formula to determine it.  It should be set to the expected
average temperature of the fluid in the bores over the course of the
simulation.

<When is the "Initial thermal gradient" different to zero? And how
could I know an exact value? >

When the ground temperature is not uniform with depth.  Many times this
number is found when a thermal response test is done on the soil.

<Finally I need to know the meaning of the parameter 32 and its
maximum and minimum temperature.>

If you are modeling a system that has been operating for years, you can
use the preheat function to drive the ground heat exchanger with a
sin-wave forcing function with the prescribed minimum and maximum
temperatures.  Otherwise leave the preheating years to zero.

Jeff



Jeff Thornton
President - TESS, LLC

22 North Carroll Street - Suite 370
Madison WI 53703 USA

Phone: 608-274-2577
Fax: 608-278-1475
E-mail: thornton@tess-inc.com
Web: www.tess-inc.com