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Program EWS, Ver. 4.7
Huber Energietechnik AG
3.11 The sheet “Parameter”
Select the sheet “Parameter” from the pull-down menu “Windows” in the menu (see Fig. 3.37). The
simulation grid, the simulation time steps and the stop criterion for the iteration can be defined in
the sheet “Parameter”. The time step for the calculation of the thermal borehole resistance Rb can
be defined in field 7.15. Field 7.15 is set to “no” in the default setting. In this case, Rb is calculated
with the given design mass flow rate (field 2.7) at the beginning of a simulation and it remains
constant for the rest of the simulation period. If field 7.15 is set to “yes”, Rb is recalculated in each
time step (hourly). Thereby, the computing time increases, but the result can get more accurate.
Additionally, the design of the output file can be set on the sheet “Parameter”.
Normally, the user has not to fill in the sheet “Parameter”, since it can be calculated with the default
values for most cases.
1
4
6
5
7
7.1
7.2
7.3
7.4
7.5
7.6
7.7
7.8
7.9
7.10
7.11
7.12
7.13
7.14
7.15
Fig. 3.37:
The sheet “Parameter”.
In field 7.15 is defined whether the thermal borehole resistance Rb is recalculated for each
calculation step. The borehole resistance Rb (thermal resistance between borehole and fluid) is
basically a parameter which is influenced by geometrical factors of the borehole, by the properties
of the filling material and by the pipes. Additionally, it includes the heat transfer coefficient α (from
the piping wall to the fluid) which depends on the mass flow rate in the pipes. Since the program
EWS offers the option to simulate a variable mass flow rate, the user gets two options: Either the
heat transfer coefficient α (and thereby the thermal borehole resistance Rb) is recalculated for each
calculation step or Rb is kept constant for the hole simulation. If the field 7.15 is left on the default
setting (“no”), Rb is calculated at the beginning of the simulation on the basis of the design mass
flow rate (field 2.7).
Bed_EWS47_En.doc
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Huber Energietechnik AG