Dear all,
Typ4a (Storage tank)
allows to model a stratified tank with several temperature
nodes. The problem I noticed is that the energy balance of
both sides on the tank can vary depending on the chosen
timestep :
In the attached file, a
simplified example, the tank is coupled to an energy
production and energy consumption model (very simple in an
equation). Thermal losses of the tank is set to zero.
When I run a simulation
with one node (1m height for 0.5m3) for the tank and a
timestep of 0.1hr, I get the same energy on both side (see
plotter “”Power&NRJ”, Esource = 2659kWh and Eload =
2666kWh), slight difference maybe explained by initial
charging period to setpoint temperature.
When I run it in the
same conditions but with 10 nodes (each 0.1m), these two
energy are different ! While I still have 2666kWh for Eload
I have 3146kWh !
When I run it again
reducing the timestep from 0.1hr to 0.001 hr, still with 10
nodes, I get 2666kWh, the energy balance is ok…
So, my question is : is
it necessary to check before every bigger simulation (that
can include lots of tank models) the energy balance of this
model for one defined timestep and boundary conditions to
the model or is there some rules to predefine adapted
discretisation for one given timestep ?
Kind regards,
Vincent PARTENAY
Energies
Renouvelables - Département ESE
Centre Scientifique et Technique du
Bâtiment
290
Route des Lucioles BP 209 – F 06904 Sophia Antipolis Cedex
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: +33-(0)4-93-95-67-21
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: +33-(0)4-93-95-64-31
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