Jean-Antoine Gruss

Extruded Microchannel-Structured Heat Exchangers

Abstract In the search for more compact air/liquid heat exchangers, one possibility is to increase the heat transfer coefficient and surface area by a decrease of the size of the fluid channels. A practical example could be seen in the air/water cross-flow heat exchangers used in cars. For such exchangers, minimization of the total volume leads to a very thin structure, with a lot of small and short air channels. We have designed and patented a cross-flow heat transfer surface with microchannels that has such a structure and can be manufactured industrially at a reasonable cost by extrusion either in aluminum or in polymers. The thermo-hydraulic performance of the structure has been simulated using standard correlations and CFD codes, and prototypic structures are under investigation to validate simulations. Compared to classical heat exchangers, our design is superior in flexibility and compactness for air/liquid applications.

Experimental study of convective heat transfer and pressure loss of SiO 2 /water nanofluids Part 1: Nanofluid characterization - Imposed wall temperature

This paper describes an experimental study on the convective heat transfer of SiO 2 /water nanofluids inside a circular tube with imposed wall temperature. To our knowledge, very few papers have been published with temperature boundary conditions and none in cooling conditions. The experimental apparatus is described which allows us to measure local wall temperatures as well as fluid inlet/outlet temperatures. The flow regimes range from laminar to turbulent. The Reynolds and Nusselt numbers are deduced by using thermal conductivity and viscosity values measured with the same temperature conditions as those in the tests. The shear rate influence is also taken into account in the viscosity determination.The results indicate that the general trend of standard correlations is respected. However, the heat transfer coefficient values are higher than observed with pure water. An explanation is proposed.