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).



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


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

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