Aspiration Effect on the Convection of a Rotating Hot Rod Covered by an Eccentric Porous Annular Layer

Abstract

Low-energy consumption cooling systems can be accomplished through coolant aspiration rather than forced convection. This paper examines the impact of inlet port locations $(X_L, X_M, \text{and\hspace{0.05em}}{X}_R)$, porous layer (PL) eccentricity $\left(0\le \delta /D\le 0.175\right),$ Darcy number $\left(10^{-5}\le \mathrm{Da}\le 10^{-1}\right)$, and Richardson number $\left(0.01\le \mathrm{Ri}\le 10\right)$ on fluid flow and HT characteristics in an aspirated cavity containing a hot rotating cylinder $\left(0\le \Omega \le 50\right)$ immersed in a porous medium. The cavity walls are thermally insulated, while the varying inlet port positions are subjected to a fixed cold temperature $\left(T_c\right).$ The centrally positioned cylindrical rod is subjected to a uniform heat flux $\left(q^{″}\right)$, and submerged in an annular porous medium. The region between the PL and the heated cylinder consists of the fluid-porous matrix, while the region external to the porous-layer-hot-cylinder arrangement contains clear fluid with $(\text{Pr}=0.7)$. The relevant dimensionless equations were solved using the Finite element method. The results show, for the parameter combination of $\mathrm{Ri}=1.0, \mathrm{Da}=10^{-1} \mathrm{and} \delta /D=0$, different roles of the lower port positions that are: (i) for motionless cylinder ($\Omega =0$), the middle position exhibits the best Nu_av values, about 8% more than that the left and right positions, while for a relatively low speed, $\Omega =10$, the middle and right positions produce an Nu_av that is 11% higher than the left position. For higher rotational speed $\Omega \ge 30$, the position of the lower port becomes ineffective on the Nu_av. Darcy number enhances the heat transfer. The results of this investigation have applications in thermal stress management in steel rod production, nuclear reactor technology, and other fields such as the utilization of geothermal energy.