An experimental study of local heat transfer using high Prandtl number liquid jets

Clément Renon (1) , Matthieu Fénot (1) , Manuel Girault (1) , Stéphane Guilain (2) , Bassel Assaad (2)

1 PPrime [Poitiers] - Institut Pprime [UPR 3346]
2 Technocentre Renault [Guyancourt]

An experimental investigation was performed to determine the local value of heat transfer coefficient with a free-surface axisymmetric downward jet of lubricating oil impinging on a fixed plate. A large range of Prandtl numbers was considered (148 < < 925) in order to fill a data gap on highly viscous fluids, especially regarding local measurements. In the range of Reynolds numbers considered (170 < < 2225), dependencies similar to the literature were identified for laminar and turbulent regimes. A significant influence of the injector diameter (1, 2 and 4 mm) on exchanges was found, but nozzle-to-target distances (5 < / < 20) showed no particular effect. Local and mean values of the Nusselt number were correlated by taking into account the above-mentioned parameters. Nevertheless, data exploitation showed that the warming of the thin liquid film over the plate, which is dependent on the heating flux to evacuate, should be taken into account for viscous fluids such as oils; the induced changes of viscosity lead to divergencies in measured heat exchanges. A methodology based on empirical observation was developed to take this phenomenon into consideration.

Mots clés: Impinging liquid jet; Local heat transfer; High Prandtl number fluid; Oil; Infrared thermography; Electric machine cooling

Domaines: Thermique [physics.class-ph]; Mécanique des fluides [physics.class-ph]

Clément Renon, Matthieu Fénot, Manuel Girault, Stéphane Guilain, Bassel Assaad. An experimental study of local heat transfer using high Prandtl number liquid jets. International Journal of Heat and Mass Transfer, 2021, 180, pp.121727. ⟨10.1016/j.ijheatmasstransfer.2021.121727⟩. ⟨hal-03435681⟩