Akademik Veri Yönetim Sistemi
ISI BILIMI VE TEKNIGI DERGISI-JOURNAL OF THERMAL SCIENCE AND TECHNOLOGY, cilt.33, sa.1, ss.111-118, 2013 (SCI-Expanded)
In this study; heat transfer, friction factor and thermal performance factor characteristics are numerically investigated in a plain tube inserted the curvilinear converging rings (CCRs). Three different pitch ratios are considered as p/D = 1, 2 and 3. The study is conducted in the range of Reynolds number 5000 -20000. Air is accepted as the working fluid (Pr=0.7). The governing equations are solved using the Simple algorithm and Standard k-epsilon turbulence model with Fluent 6.1.22 programme. To validate the applied numerical method, the results obtained from the plain tube with CCRs are compared with the empirical results presented in literature. The values of Nusselt number, friction factor and thermal performance factor for the plain tube with CCRs are presented depending on Reynolds number and pitch ratios studied. The thermal performance results for the studied cases are also compared with results given in previous studies related to the conical rings. Consequently, the average Nusselt number and friction factor for all the pitch ratios are found to be about 68- 109 % and 412-635 % over the plain tube at the same pumping power, respectively. The best enhancement of 7.5 % was obtained for Re = 5000 and p/D = 1. The cases of p/D =2 and 3 are thermodynamically advantageous only for Re<10000.