Thermally Stratified Tank Model Type38
by G. Morrison (TRNAUS)
The temperature distribution in the storage tank of a thermosyphon or
low flow rate pumped solar water heater has a major effect on system
performance. The modelling approach used in the TRNSYS stratified tank
component is based on the SOLSYS model [10]. Energy balances are formulated
for moving segments of fluid such that the convection terms do not appear. The
advantage of this technique is that the components of the fixed node energy
balance equation that have long time constants are seperated from the the
components that may have short time constants. The energy balance equation that
includes only heat loss and conduction can then be readily solved with time
steps up to one hour, without the numerical accuracy problems that may be
present when there is a convection term in the energy balance equation.
Convection is analyzed by a record keeping process on segments of fluid passing
in and out of the tank.
The follwing features are added in this TRNAUS version of the component.
1) Heat Pipe Coupling between the collector and the tank.
2) Thermal Dump Valve
3) Two Position Auxiliary Input
4) Computation Sequence
5) Load Energy Binning
REF: TRNSYS Extensions for Australian Solar Products(TRNAUS) by G. Morrison
Univ. of New South Wales Report No 1991/FMT/2