Publikationsrepositorium - Helmholtz-Zentrum Dresden-Rossendorf

As a part of my graduation in engineering school in France and master’s degree, I am doing
my 6-month internship/master thesis in the Helmholtz-Zentrum Dresden-Rossendorf in the Institute
of Fluid Dynamics. The team comprised of my supervisor and PhD student, Mrs. Malini Bangalore
Mohankumar, Dr. Sebastian Unger, PhD student Alexandre Guille Bourdas, and I, is working on a
project of Thermal Energy Storage (TES). This system would store the surplus of electricity when
the production is higher than the demand. The electricity is used in order to heat a storage material.
Indeed, an electrical heater heats a CO2 flow, which will through a tank heating the storage material.
The electrical heater is the subject of my work and thesis.
The choice of the fluid was already determined: the CO2 at atmospheric pressure, as it is non
toxic, non inflammable, low corrosive and has advantageous thermodynamic properties.
Nevertheless, other fluids will be studied in the future. Furthermore, the mass flow rate and the
temperatures are fixed by the process of the other systems, such as the thermal storage cycle and the
power cycle. The mass flow rate is 5 kg/s and the inlet/outlet temperatures are 400°C/1000°C. These
are the only constraints for designing the heater. Then different sizes, geometries of the heater will
be studied in order to determine the configuration of the heater.
In this aim, a review of heaters and heat transfer in the shell part of shell-and-tube heat
exchangers is developed. In fact, few articles are available on the operation of electrical heaters at
high temperature. Moreover, shell-and-tube heat exchangers work in the same way as the heater.
However, the range of temperatures differs, so some work has to be done in order to model the heat
transfer in the heater.
With this in mind, an analytical work is developed, in order to have an order of magnitude of
the heat transfer. In this part, different models and correlations are used, to have a first estimation of
the heater length.
Then, a simulation approach applying numerical methods, such as Computational Fluid
Dynamics (CFD) is done. This approach, allows to determine more accurate results, which include
radiation. However, a focus is necessary on the validity of the model of resolution/radiation on the
software.
Finally, to optimize the heat transfer performance in the heater, the results of different designs
are compared,