Description

If we want to reduce greenhouse gas emissions, we must address heating and cooling systems by using renewable or recovered energy and heat sources, which are then distributed to consumers through a district heating network. In this context, Le Havre Seine Métropole is building a district heating network spanning over 60 km, powered by three main sources: the BioSynErgy plant (which uses biomass) for 65% of the heat, heat recovery from industrial waste for 15%, and a gas-fired boiler in Caucriauville for the remaining 20% as a backup or emergency source.

A district heating network uses pumps to circulate a heat transfer fluid through a network of pipes. One of the sources of energy loss identified for these systems is friction between the fluid and the pipe walls. It is therefore clear that one way to save energy is to reduce friction or drag, and numerous methods for doing so have been studied. The use of surfactant solutions is one such method.

Despite the abundance of literature on the subject, our understanding of the mechanisms responsible for drag reduction through the use of surfactant solutions remains incomplete. The same is true for the mechanisms underlying heat transfer reduction. Furthermore, a joint study of these two phenomena is necessary to evaluate the energy efficiency of district heating networks.

With this thesis, we aim to provide new insights into the mechanisms of drag and heat transfer reduction through the addition of surfactants in the context of heat transfer. To this end, we propose to study the different flow regimes, drag reduction, and heat transfer of surfactant solutions in Hagen-Poiseuille flow—flow through a pipe with a circular cross-section—by varying the concentration and temperature. Hagen-Poiseuille flow belongs to the class of wall-shear flows, which are characterized by an identical subcritical transition scenario to turbulence—a topic currently under study at LOMC. The effects of the Reynolds number and temperature will be considered jointly to assess their mutual influence. Specifically, our objective is to describe how the addition of a surfactant modifies the various instability patterns and the transition to turbulence in Hagen-Poiseuille flow, as a function of its concentration and temperature. We will also estimate heat and momentum transfer in the flow. And, in parallel with the Hagen-Poiseuille flow experiments, we will study the physical properties of the solution as a function of concentration and temperature, using, in particular, our rheometers.