atw 2018-04v6

atw Vol. 63 (2018) | Issue 4 ı April
Heat Transfer Systems for Novel Nuclear
Power Plant Designs
Sebastian Vlach, Christoph Fischer and Herman van Antwerpen
This article focuses on work that involves designing or modifying heat exchangers that usually can be found in the auxiliary
systems of any power plant. The basic premise of the article is to show that the software provides a one-stop solution for
designing many types of heat transfer systems, where the interaction between various loops connected by heat exchangers can
be assessed. This article especially addresses the audience among nuclear power plants as the quality control in the development
of the software makes it most suitable for nuclear related work. Moreover, the software discussed in this article has the
capability to do contaminant tracing, which could be very useful for nuclear contamination studies in designing specialized
ventilation systems. To highlight the versatility of the software network approach it will be shown how to model any setup and
kind of heat exchanger such as plate, tube-in-tube, liquid/gas, finned tube etc. Additionally, the Koeberg pressurized water
reactor (PWR) steam generator comparison and the Hamm-Uentrop thorium high temperature reactor (THTR) steam
generator comparison are shown as practical examples.
Introduction “Every type of technology benefits from advances inspired by new knowledge and understanding.
Although nuclear energy has operated mostly safely in the past, nuclear engineers do continue to devise new ideas for
making nuclear energy even safer and more secure. The future of reliable nuclear energy requires scientific research to
verify that new types of advanced nuclear fuels and materials are robust enough to withstand the conditions inside a
nuclear reactor during normal and abnormal conditions.” (Idaho National Laboratory).
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OPERATION AND NEW BUILD
Based on the laws of thermodynamics 1D system
simulation is extremely robust, fast, and reliable. One
software package for 1D system simulation that gains
more and more attention recently was developed in the
early 1990ies by a South African company, namely M-Tech
Industrial. Initially, Flownex® Simulation Environment
was developed for aerospace applications and the energy
sector. Moreover, nuclear validation and verification were
supervised by the governmental ESKOM institution
through its subsidiary PBMR Ltd., who developed a
high-temperature gas-cooled (pebble-bed) reactor in
cooperation with Jülich Research Centre at that time.
Specifically for the nuclear safety analyses required by
PBMR, the software has Nuclear Quality Assurance
( NQA-1) Certification and its development process is
based on ISO 9001.
System simulation programmes provide engineers and
designers a fast and efficient way to set up simulation
models for simple as well as complex fluid dynamic
networks. Such networks commonly contain several
components such as fans, pumps, heat exchangers etc. that
can be computed almost instantly. Furthermore, dynamics
and the control of such networks can be investigated by
running different operation scenarios, such as start-up,
shut down, and various loading conditions, where steady
state and transient effects are taken into account. Thus,
weak spots within a system can be eliminated during the
design process prior to manufacturing as literally any
modification can be tested virtually.
Subsequently, the user is able to analyse the results very
quickly.
Material data that the software supports can be
gaseous, gas mixtures, as well as incompressible pure
fluids and two-phase pure fluids. The user is able to access
a vast library based on the NIST data base. Hence, complex
flows can be modelled using temperature and pressure
dependent material data as well as multiphase effects like
conden sation, evaporation, and cavitation.
The software is equipped with a vast array of components
that cover most required simulation scenarios.
Those components can be used as single components or as
building blocks of components found in thermal fluid
systems or subsystems.
Building blocks, with various levels of detail are
available to model heat transfer phenomena as shown in
Figure 1. Some of the simple heat exchanger models
utilises the Number of Transfer Units (NTU) Method while
other more complex versions employ a fully discretised
approach to heat exchanger modelling. The heat exchanger
types range from tube to plate heat exchangers that can be
modelled as parallel, counter, or cross flow types. Other
components can be vessels, reactors, tube systems, valves,
pumps, fans, compressors, seals etc. Moreover, a whole
library of com ponents for dynamics and control is available
within the software.
1D System Simulation
Flownex® Simulation Environment includes all the
necessary numerical formulations for solving all important
thermo-fluid physical phenomena and moreover, a modern
Windows-GUI that enables an intuitive and easy interaction
for the user. Therefore, the user can concentrate on
design and optimisation rather than on the complexities
usually associated with operating such calculation software.
Typical simulations are run in real time or in the
order of seconds, which makes parameter studies and
optimisation loops extremely fast and very efficient.
| | Fig. 1.
Library for heat exchangers [1].
| | Fig. 2.
Heat transfer library [1].
Operation and New Build
Heat Transfer Systems for Novel Nuclear Power Plant Designs ı Sebastian Vlach, Christoph Fischer and Herman van Antwerpen