半円形断面円環状粗さ要素による人工粗面坑道の平均熱伝達率について

坑道壁面から通気への熱伝達率に関する研究 (第5報)

抄録

In this paper, we present the results of the experimental investigation of the relation between average heat transfer coefficient and friction coefficient in rough model circular airway having ring type roughness elements with semicircular cross-section, as a series of previous reports.
Measurements were carried out under the condition of heating air in the airway which was heated in its whole length by isothermal hot water.
Results were obtained for Reynolds number Re from 4.0×10³ to 9.0×10⁴ at a Prandtl number P_r equal to 0.71 and roughness-height-to-diameter ratio h/D from 0.0408 to 0.122.
The following experimental formula was also obtained for circular airway as well as the cases having ring type roughness elements with isosceles triangular cross-section and rectangular one as reported in the previous papers: N_um=CR_e*^m P_r^0.5
In the above expression Num is Nusselt number based on effective heat transfer area A_m, R_e* is modified Reynolds number defiened by friction velocity, and further C and m are constants related to the roughness ratio h/D and the shape of the roughness element as given in Fig. 15.