KARAKUS, Taha Resul; FIRAT, Ilker; YILDIRIM, Orhan; SONMEZ, Fatin; KOCALI, Sevinc Sevgi CICEK; YILDIZ, Abdussamed; KARAGOZ, Sendogan; COMAKLI, Omer

In this study, the effects of different numbers of sphere turbulators placed in a cir-cular-shaped test pipe under turbulent flow conditions on heat transfer, friction factor, thermal performance factor and entropy production were experimentally investigated. Water was used as the working fluid in the experiments carried out in the number range Re = 8379-16701. Initially, plain pipe and supported plain pipe experiments were carried out by keeping the fluid inlet temperature and test pipe surface temperature constant. Then, 1, 2, and 3 sphere turbulator experiments were carried out under the same conditions, respectively. According to the find-ings, the maximum Nusselt number increase compared to the supported plain pipe was 83.34% for the test pipe with 3 sphere turbulators. The minimum and maxi-mum Nu number increase rates of 3 sphere turbulators compared to 1 and 2 sphere turbulators were obtained as 42.61%-46.93% and 13.99%-17.11%, respectively. The increase rates of maximum friction factors of 1, 2, and 3 sphere turbulators compared to the supported plain pipe were 174.42%, 226.70%, and 306.53%, re-spectively. In addition, the maximum total entropy rate for sphere turbulators was obtained as 0.058 W/mK for 1 sphere turbulator at Re = 8379. In terms of the sec-ond law, the maximum entropy generation of sphere turbulators compared to the supported plain pipe decreased by 79.39% for 3 sphere turbulators at Re = 8379. As a result, it was concluded that the optimum number of sphere turbulators is 3 sphere turbulators with the lowest entropy production number and the highest ther-mal performance factor value (1.28).

Tasyurdu, Yasemin

In this paper, we define five parameters generalization of Fibonacci numbers that generalizes Fibonacci, Pell, Modified Pell, Jacobsthal, Narayana, Padovan, k-Fibonacci, k-Pell, Modified k-Pell, k-Jacobsthal numbers and Fibonacci p-numbers, distance Fibonacci numbers, (2, k)-distance Fibonacci numbers, gen-eralized (k, r)-Fibonacci numbers in the distance sense by extending the defini-tion of a distance in the recurrence relation with two parameters and adding three parameters in the definition of this distance, simultaneously. Tiling and combinatorial interpretations of generalized Fibonacci numbers are presented, and explicit formulas that allow us to calculate the nth number are given. Also generating functions and some identities for these numbers are obtained.

Kiziltug, Sezai; Cakmak, Ali; Erisir, Tulay; Mumcu, Gokhan

In this study, we give the curves and tubular surfaces in Galilean space G3 with modified orthogonal frame. Firstly, we consider any curve in G3and we obtain derivative formulas of modified orthogonal frame of any curve in G3. Therefore, we get tubular surface with modified orthogonal frame in Galilean space G3. Consequently, we give some examples and figures.

Karagoz, Sendogan; Erzincanli, Semih; Yildirim, Orhan; Firat, Ilker; Kaya, Mehmet; Comakli, Omer; Omeroglu, Gokhan

This experimental study deals with the heat transfer and friction effects of sinus-oidal part turbulators for single-phase flows occurring in a circular shaped pipe. Turbulators with three different radius values are placed in the pipe to make the flow turbulent. In this way, changes in Nusselt number and friction coefficient are examined. As a result of the experiments made with Reynolds numbers in the range of 6614-20710, the increase rates of the Nusselt numbers of turbulators with 20 mm, 110 mm, and 220 mm radius compared to the empty pipe were ob-tained as 153.49%, 85.36%, and 52.09%, respectively. As a result of the decrease in the radius, there was an increase in the Nusselt number and the friction factor. Parallel to the Nusselt number, the highest friction factor was obtained in the smallest radius turbulator. It was found that the thermal enhancement factors of 110 mm and 220 mm radius turbulators increased by 179.54% and 132.95%, re-spectively, compared to the 20 mm radius turbulator. Similarly, it was deter-mined that the thermal enhancement factor of the 110 mm radius turbulator in-creased by 20% compared to the 220 mm radius turbulator.