Heat transfer in nanofluid spray cooling of a solid heated surface for cooling systems in civil and military applications

Abstract

Interest in spray cooling has been increasing as an efficient thermal management technique for high power load systems such as electronics, e.g. in UAV's (Unmanned Aerial Vehicles), which have an important application in both civil and military applications. This work aimed to study the use of nanofluids as a way of improving sprays thermal performance. Nanofluids were prepared using, as base solution, distilled water with 0.05% (m/m) cetyltrimethylammonium bromide. Alumina nanoparticles were mixed at different concentrations: 0.5%, 1% and 2% (m/m). The effect of the shape of the nanoparticles was inferred using two different silver nanofluids, with 1% (m/m) concentration, one using spherical and the other using triangular particles. These nanofluids were sprayed using a hollow-cone atomizer, at two different heights from an AISI 304 stainless steel foil, heated by Joule effect. Thermal footprints of the sprays were acquired using infrared thermography and dissipated heat fluxes were calculated. When comparing the performance of silver nanofluids, the one with spherical particles resulted in slightly lower surface temperatures than the fluid with triangular particles. Heat transfer coefficients decreased with increasing thermal conductivity and dynamic viscosity of the nanofluids. On the other hand, a strong positive correlation was revealed with the specific heat capacity of the nanofluids. For the range of experimental conditions covered here, nanofluids have proven to increase the thermal performance of the spray.

Numerical Solution of Heat Transfer Flow of Casson Hybrid Nanofluid over Vertical Stretching Sheet with Magnetic Field Effect

“…To achieve the desired heat exchange rate, appropriate nanoparticle types with specific weight percent are employed. The hybrid nanofluids found large applications in different aspects of human life such as transportation [5], defense [6], microfluidics [7], etc. ; in this way, the concept of hybrid nanofluids has been the subject of numerous numerical and experimental investigations.…”