EDYPHiCE

The work proposed in this project focuses on the manipulation i) of fluids in single-phase liquid state and ii) of liquid- vapor interfaces using electro-hydrodynamic effects with the aim of pumping and/or enhancing heat transfers at the interface between a fluid and a solid wall. In the current state of knowledge, the questions must primarily been addressed from a scientific point of view. Indeed, models published in the open literature are not able to describe quantitatively the experimental results available. The main objective is thus to increase the level of maturity of this multidisciplinary topic to open and/or enlarge the application fields it can concern. To this end, fundamental studies will be developed to determine the theoretical electrical, fluidic and thermal models of phenomena occurring when an electric field is applied in a liquid with and without a liquid-vapor interface. A specific study on different fluids will also be conducted to determine their EHD performances according to their thermal factors merit. Simultaneously to these fundamental studies, two specific applications will be explored. The first one consists in the development of an electro-hydrodynamic pump for hybridizing capillary two-phase cooling systems. The aim is to improve the reliability and performance of such systems for space applications on the one hand, and to broad their field of application to the terrestrial environment without loss of performance on the other hand. The methodology adopted follows a logic of increasing complexity: the study will focus initially on the analysis of pumping capacity depending on the type of fluid, of the applied electric field and of the electrodes design. The aim of this part of the study is to design and to realize an optimized basic module of an EHD pump. To this end, the test bench developed during the preliminary study that the partners have already done will be used. Depending on the desired pumping capacity, this basic module will be repeated n times. Both fluidic and electrical architectures of these n modules will then be defined to design a high capacity EHD pump to be implemented in a two-phase capillary pumped loop operating in ground environment. The robustness of the EHD pumping will be analyzed as a function of vibration stresses to validate the potentiality of uses of such devices in embedded systems (land, air, space). The second application that will be explored consists in coupling the electro-hydrodynamic phenomena, the convective effects and the liquid-vapor phase-change. This part of the project aims to establish the means for the control of liquid-gas interfaces necessary (especially) for the design of enhanced and innovative heat exchangers. Considered situations will cover a static configuration (induced by a dielectric strength of a liquid-vapor interface versus the hydrostatic pressure), a quasi-static situation (same as above but with evaporation at the liquid-vapor interface) and the case of a two-phase flow generated by an imposed pressure gradient or by capillary forces. At the end of the project, thanks to the results obtained, research and development activities will be initiated in the framework of the Technological Research Institute Saint Exupéry in Toulouse. It is therefore planned to develop a hybrid capillary two-phase loop capable to transfer high heat fluxes. This loop will include a EHD pumping system in addition of the capillary pumping. A demonstrator will be realized. It is also planned to realize an optimized evaporator prototype using dielectric strength.