Experimental and numerical study of slightly loaded water alumina nanofluids in the developing region of a 1.1 mm in diameter pipe and convective enhancement evaluation

摘要: Abstract The reported investigation studies, both experimentally and numerically, the convective heat transfer process in single-phase laminar flow of water alumina nanofluids. Two different nanoparticles size intervals, 20–30 40–60 nm, three loads, 0.001%, 0.010% 0.100%, are tested inside an electrically heated cylindrical channel. main aim present is to explore determine enhancement for several nanofluids a 1.1 mm. inner diameter pipe. It proposed systematic approach order clearly considering same working conditions under which each pair case (water/nanofluid) modeled. These flux applied wall, inlet section temperature mass rate. test comprised non region followed by uniformly comparative influence self-diffusion thermodiffusion particular case. experimental results have shown growth trend fully developed with maximum Nusselt number 8%. In addition, generalized enhancements been found near attaining values up 30% depending on load operating conditions. A reduction 13% also detected, mainly, central part tube observed trends accentuated increasing nanofluid load. attained cannot be explained, only, terms concentration field. Numerical much smaller than data and, therefore, it foreseeable that there some other intensifying or enhancing mechanism. mechanism apparently linked leading opinion thermophoresis effects do not suffice explain detected enhancement. More investigations needed this direction.