Abstract
The cooling performance of jet impinging hybrid nanofluid on a rotating hot circular cylinder was numerically assessed under the effects of multiple magnetic fields via finite element method. The numerical study was conducted for different values of Reynolds number (100≤Re≤300), rotational Reynolds number (0≤Rew≤800), lower and upper domain magnetic field strength (0≤Ha≤20), size of the rotating cylinder (2 w ≤r≤ 6 w) and distance between the jets (6 w ≤ H ≤ 16 w). In the presence of rotation at the highest speed, the Nu value was increased by about 5% when Re was increased from Re = 100 to Re = 300. This value was 48.5% for the configuration with the motionless cylinder. However, the rotations of the cylinder resulted in significant heat transfer enhancements in the absence or presence of magnetic field effects in the upper domain. At Ha1 = 0, the average Nu rose by about 175%, and the value was 249% at Ha1 = 20 when cases with the cylinder rotating at the highest speed were compared to the motionless cylinder case. When magnetic field strengths of the upper and lower domains are reduced, the average Nu decreases. The size of the cylinder is influential on the flow dynamics and heat transfer when the cylinder is rotating. An optimum value of the distance between the jets was obtained at H = 14 w, where the Nu value was highest for the rotating cylinder case. A modal analysis of the heat transfer dynamics was performed with the POD technique. As diverse applications of energy system technologies with impinging jets are available, considering the rotations of the cooled surface under the combined effects of using magnetic field and nanoparticle loading in heat transfer fluid is a novel contribution. The outcomes of the present work will be helpful in the initial design and optimization studies in applications from electronic cooling to convective drying, solar power and many other systems.
Highlights
Jet impinging heat transfer (j-imp HT) applications arise in different thermal engineering systems
The upper and lower domains of the were exposed to uniform magnetic field (MaF) of different strengths while double jets of hybrid N-F were used for different parts of the rotating cylinder
Convective HT performance for impinging jets onto a rotating hot circular cylinder was numerically assessed under multiple MaF effects
Summary
Jet impinging heat transfer (j-imp HT) applications arise in different thermal engineering systems. In a review Mohammadpour and Lee [16], the effects of using N-Fs on the HT improvements for conventional and swirl type impinging jets were analyzed Some challenges, such as nanoparticle agglomeration and pressure drop, were mentioned with future trends and applications. Naphon and Wiriyasart [18] experimentally analyzed the nano j-imp HT in a micro channel heat sink by using TiO2 nanoparticles They observed convective HT incrementation by about 18.56% at a nanofluid concentration of 0.015%, and no additional pressure drop was obtained. The present study deals with the confined slot j-imp HT and flow features for a rotating surface located in between the domains that are under the effects of MaF of different strengthens. As there are many applications of impinging jets in different energy system technologies, the use of multiple MaF effects for a jet impinging on a hot rotating surface is a novel contribution. Modal analysis was used for exploring the heat transfer dynamics of the j-imp system under multiple MaF effects, and the details are explained in the following subsection of the manuscript
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