Number：

81

Download

PDF

Name：

Tzer-Ming Jeng,

Titles：

Author：

Tzer-Ming Jeng, Sheng-Chung Tzeng, Hung-Ming Su, Chi-Shan Hsiao,Yu-Chi Wei

Paper name：

Thermal Behaviors Of A Rotating Al-Foam Cylinder Under The ConfinedUnconfined Impinging Jet

Name of activity：

Keywords：Heat transfer, Rotating porous cylinder, Impinging jet, Confined/Unconfined conditions.

Abstract：This work experimentally investigated the heat transfer of a rotating porous cylinder under a circular impinging jet at the confined/unconfined conditions. The 0.93-porosity/40 PPI aluminum foams were used. The dimensions of the Al-foam cylinder were 40 mm in diameter (D) and 20 mm in height (H) excepting the 4 mm-thickness spreader. Air was employed as the coolant. The diameter (d) of the circular nozzle was 20 mm. Relevant parameters included the rotational Reynolds number (Rer=788~3163), the jet Reynolds number (Rej=3325~16690) and the relative impinging height (C/d=0.05~9). As shown in Fig. 1,the results indicated that, for the pure rotating condition the average Nusselt number (Nur) of the unconfined system was higher than that of the confined system at C/d=0.05, but there were few differences between these both systems at other values of C/d. For the pure jet-flow condition, on the contrary, the average Nusselt number (Nuj) of the unconfined system was smaller than that of the confined system at C/d=0.05, while there were also few differences in Nuj between these both systems for c/d=1~9. Besides, the Nur generally increased from C/d=0.05 to C/d=1, but changed little as C/d=1~9. However, the Nuj declined with increasing C/d, especially for the smaller Rej. For the combined condition of the rotation and jet flow, the unconfined system had higher average Nusselt number (Nurj) than the confined one at C/d=0.05, especially for the bigger Rer and Rej. When the C/d increased, the difference of Nurj between the confined/unconfined systems would decline. Besides, the rotational effect on the Nurj was more substantial at the smaller C/d and the unconfined condition. Finally, according to all the experimental data, this work proposed the empirical relationships between average Nusselt number and Reynolds number for the confined/unconfined systems with various C/d.

Back