No abstract

Bu çalışmada, boru içerisine türbülans oluşturacak kanatçıklar yerleştirilerek boş boru ile kıyaslanmıştır. Üç farklı kanatçık arası mesafede (Sy=101, 216, 340) ve üç farklı kanatçık açısına(α=0 o , 45 o , 90 o ) sahip 9 türbülatör, üç farklı Reynolds sayısında (Re) kullanılmıştır. Bu türbülatörlerin ısı transfer performansı ve sürtünme karakteristikleri deneysel olarak incelenmiştir. En yüksek hız değerinde Nu sayısındaki en yüksek artış Sy =101mm kanatçık arası mesafede ve α = 90° kanatçık açısında elde edilmiştir. Kanatçık arası mesafenin artmasıyla Nu sayısında azalma olduğu görülmüştür. Sy mesafesi en az olan türbülatör bütün Re sayılarında en yüksek Nu sayısına sahiptir. Nu sayısı açısından sırama yapıldığında; Sy(10) > Sy(5) > Sy(3) olduğu gözlemlenmiştir. Bu türbülatörlerin kanatçık arası mesafesinin (Sy) ve kanatçık açılarının (α), Nu sayısına etkisi olduğu yapılan çalışmalarla görülmüştür.

This experimental study deals with the heat transfer and friction effects of sinusoidal 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 obtained 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%, respectively, compared to the 20 mm radius turbulator. Similarly, it was determined that the thermal enhancement factor of the 110 mm radius turbulator increased by 20% compared to the 220 mm radius turbulator.

Biomedical studies is among the multidisciplinary studies attracting most interest in recent years. Blood and vessel interactions and consequent hemodynamic effects cause cardiovascular diseases. A testing setup constituted by a peristaltic pump (similar to the heart mechanism) system was installed. The purpose of the experimental study presented is to investigate the effect, pressure drop, peristaltic pump inlet and outlet pressure and most importantly, the amount of power consumed by the peristaltic pump regarding arterial stenosis severity with varying areal stenosis percentages. The tests were performed for the pulse values from 54 to 168 bpm by setting up models with 0%, 60%, 70% and 80% symmetrical stenosis severities. In the study, the pressure difference in the test area increased concomitantly with elevated pulse value and increased stenosis severity. This situation revealed that as the intensity of narrowing increases in vessels, the narrowing space differential pressure increases, and this amount increases even more with increased exertion. The pressure at the peristaltic pump outlet increased concomitantly with elevated pulse value and increased stenosis severity. The peristaltic pump overworked to overcome the increased differential pressure related to the increased pulse value and stenosis severity. This result of the experimental data reveals the necessity to avoid activities requiring high pulse in human arteries similarly with a high percentage of stenosis.

No abstract