Thermal hydraulic modelling is needed for describing processes that use
water for cooling. Simulator codes solve conservation equations of coolant
mass, momentum and energy using numerical methods. Additionally, correlation
based models are needed for describing, among others, heat transfer and
friction between the structures and the coolant. In two-phase flow the
correlations for interfacial heat transfer and friction are used for
exchanging of mass, momentum and energy between liquid and gas phases.
Typical applications are various boiler processes and nuclear reactors. Some
modern boilers operate in supercritical water conditions as well as a new
nuclear reactor concept SCWR (Super Critical Water Cooled Reactor). Water
properties change fast around the critical point (220.64 bar, 374.15 C) and
heat transfer in supercritical state is not fully understood, which makes
modelling challenging and is typically beyond normal operation regime of the
analysis codes. At the moment VTT is modifying two of its code packages,
APROS and TRAB-SMABRE to adapt for supercritical conditions. APROS is a
general purpose simulation code both for nuclear and non-nuclear
applications, while TRAB-SMABRE is used solely for nuclear reactor analysis.
The models for water properties, such as density, specific heat capacity and
heat conductivity, have already been developed. The homogeneous water model
of APROS (3 conservation equations) has already been tested in supercritical
boiler conditions and operates in principle. The more sophisticated
operation mode of APROS (6 conservation equations) operates in supercritical
state but the transition from supercritical to subcritical two-phase state
has not yet been tested. The correlation package of heat transfer and
friction has to be tested and possibly modified in supercritical conditions.
The testing of the TRAB-SMABRE code (5 conservation equations) is to be
started soon. TRAB-SMABRE and possibly also APROS are to be applied for
reactivity transient analysis of the European development version of the
supercritical water reactor in the Euratom 6th Framework Programme project
High Performance Light Water Reactor, HPLWR Phase 2.
|BALTICA VII - International Conference on Life Management and Main-tenance for Power Plants
|12/06/07 → 14/06/07