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Öğe Second Law analysis in concentric heat exchangers with vortex flow generators(Energy Education Science and Technology, 2011) Argunhan, Zeki; Çakmak, Gülşah; Yıldız, Cengiz; Behçet, RasimIn the present study, the experimental results of heat transfer of a concentric tube heat exchanger were analyzed with respect to Second Law of Thermodynamics to reach the geometric optimal design of the heat exchangers. In order to increase the heat transfer, the vortex generators were placed in the entrance of the inner pipe of the heat exchanger. These vortex generators are 60 mm in diameter having six angled (55°, 65°, 75°, 90°) winglets. The winglets have one rectangular slot in each and are 2×7 mm in dimensions. Experiments were carried out with different Reynolds Numbers. Air as hot fluid and water as cold fluid were passed through the inner pipe and outer pipe of the concentric tube heat exchanger, respectively. The variations of the efficiency and Entropy Generation Number with respect to Reynolds Number are shown in graphics, and the results were discussed.Öğe The effect of rotary type turbulator placed in entrance of heat exchanger on heat transfer and frictional loss(Energy Education Science and Technology, 2011) Argunhan, Zeki; Behçet, Rasim; Yakut, Ali KemalIn this study, improving heat transfer in heat exchangers with paralel flow is gained by using swirl flow. For this purpose, a propeller type of turbulator was placed in the entrance of interior pipe of heat exchanger with paralel flow and the effect of turbulator on the heat transfer and friction losses in steady conditions was experimentally investigated. The effect of production of turbulance for improvement of heat transfer in interior pipe flows and the effects of turbulator on heat transfer and pressure drop are experimentally researched by placing a propeller type of turbulator at the entrance of heat exchanger to produce swirl air flow. In experiment setup, water was used as the fluid on which the heat was transferred and air was used as the fluid from which heat was transferred to the water. By usage of datas obtained from experimental measurements were calculated for Reynolds number ranging from 8000 to 24000 necessary relationships effet on heat transfer and pressure drop. In comparison with empty pipe it was seen that the heat transfer increased at range between 25,5%- 50,3% and the friction losses increased 5 times. Besides, by analyzing the system exergy, the dependence of non-dimensional exergy loss on Reynolds number was drawn to investigate whether this improvement technique is advantageous thermodynamically or not. When comparing the exergy losses in empty pipe and the pipe with a turbulator at approximately same Reynolds numbers, it was seen that exergy loss is 15% higher for empty pipe than that for the pipe with the turbulator. As a result of that information, the improvement technique was proved to be advantageous in thermodynamic manner too. By the usage of turbulator that results in the partial recovery of loss energy, it was proven that the improvement technique was thermodynamically advantageousÖğe Isı değiştiricisine yerleştirilen pervane tipi türbülatörün ısı transferi üzerindeki etkisi(Karabük Üniversitesi, 2009) Aydın, Hüseyin; İlkılıç, Cumali; Behçet, Rasim
