Mechanical Engineering / Makine Mühendisliğihttp://openacccess.atu.edu.tr:8080/xmlui/handle/123456789/5172024-03-29T12:44:46Z2024-03-29T12:44:46ZKarışık taşınım ile olan ısı transferinin farklı geometrideki akış engelleri kullanılarak iyileştirilmesinin sayısal olarak incelenmesiOzdemir, SedatKilic, MustafaCalisir, TamerBaskaya, Senolhttp://openacccess.atu.edu.tr:8080/xmlui/handle/123456789/42262023-10-11T11:49:40Z2023-01-01T00:00:00ZKarışık taşınım ile olan ısı transferinin farklı geometrideki akış engelleri kullanılarak iyileştirilmesinin sayısal olarak incelenmesi
Ozdemir, Sedat; Kilic, Mustafa; Calisir, Tamer; Baskaya, Senol
Bu çalışmada; içinde ısı akısına sahip, farklı konum ve geometride engeller bulunan dik bir kanaldaki karışık konveksiyonun ısı transferine ve akış özelliklerine etkisi sayısal olarak incelenmiştir. Engellerin konumları, sayıları ve geometrileri değiştirilerek ısı transferine ve akış özelliklerine etkisi belirlenmeye çalışılmıştır. Çalışmada, alt alta bulunan iki yarı silindirik engelin, alt alta ve karşılıklı bulunan dört yarı silindirik engelin ve alt alta ve karşılıklı bulunan dört dikdörtgen engelin karışık konveksiyonla olan akış ve ısı transferine etkileri irdelenmiştir. Sonuç olarak; Nusselt sayısının, engellerin birbirine olan uzaklıklarının (L/D oranı) ve doğal taşınım etkilerinin (Ri sayısı) artmasıyla genel olarak arttığı tespit edilmiştir. Her iki engel geometrisinde (yarı silindirik engel ve dikdörtgen engel) L/D oranının ve değiştirilmiş Ri sayısının arttırılmasının Nusselt sayısına olan etkisinin benzer olduğu ve ısı transferini arttırdığı tespit edilmiştir. Yarı silindirik engeldeki Nusselt değerlerinin dikdörtgen engeldeki Nusselt değerlerine kıyasla daha büyük olduğu belirlenmiştir. Yarı silindirik engeldeki Nusselt değerlerinin dikdörtgen engeldeki Nusselt değerlerinden farkının; engeller arası mesafenin az olduğu (L/D=0,25) değer için; düşük Ri sayılarında (Ri=50) %72,5 iken yüksek Ri sayılarında (Ri=200) %19,6 olduğu tespit edilmiştir. Bu fark; engeller arası mesafenin çok olduğu (L/D=1,5) değer için; düşük Ri sayılarında (Ri=50) %58,6 iken yüksek Ri sayılarında (Ri=200) %39,1 olduğu tespit edilmiştir. Her iki engel geometrisinde de en yüksek Nu sayısının L/D= 1,5 ve Ri=200 olduğu durumda meydana geldiği belirlenmiştir. Ayrıca; çalışmada Nu sayısı için bir korelasyon elde edilmiştir. Sayısal çalışmanın sonuçları literatürde bulunan deneysel çalışmalarla da karşılaştırılarak; sıcaklık dağılımını ve akış özelliklerini iyi şekilde temsil edebildiği görülmüştür.; Purpose:In this study, it was aimed to numerically investigate the effects of the location, number and geometry of obstacles in a vertical channel on mixed convection heat transfer and flow properties for water as working fluid under different Re and Gr numbers.Theory and Methods:The FloEFD CFD code has been employed in this study to investigate the effects of semi-cylindrical and rectangular obstacle's location, number and geometry in a vertical channel of height of H=1.8 m and width of W=0.05 m on the mixed convection heat transfer and fluid flow (Figure.A). The effect of two semi -cylindrical obstacles located one under the other, four semi-cylindrical obstacles located one under the other on opposite sides, four rectangular obstacles located one under the other on opposite sides, on heat transfer and flow properties were investigated numerically. Analysis have been made for different Re numbers, Ri numbers, blockage ratios (BR) and L/D values where water was used as working fluid. The fluid enters the channel with a constant temperature (To) and velocity (uo) from the top of the channel.Results:In the present study, it was obtained that Nu number increases with increasing distance between obstacle (L/D) and natural convection effects (Ri number). For both obstacle geometries (two semi-cylindrical and rectangular obstacles), increasing L/D ratio and Ri number causes similar effect on Nu number and enhances heat transfer. It was determined that Nu numbers obtained for semi-cylindrical obstacles are bigger than the Nu numbers of rectangular obstacles. The highest Nu number can be obtained for L/D=1 and Ri=300 for both obstacle geometries.Conclusion:The mixed convection in a vertical channel with obstacles has been investigated numerically. It was observed that Nu number increases with increasing distance between obstacle (L/D) and natural convection effects (Ri number). It can be concluded that, the study could be further continued, and the effects of new types of fluids on heat transfer and flow properties, different channel and obstacle geometries on heat transfer and flow properties could be examined.
WOS indeksli yayınlar koleksiyonu. / WOS indexed publications collection.
2023-01-01T00:00:00ZEffect of adherend recessing on bi-adhesively bonded single-lap joints with spew filletCalik, AhmetYildirim, Sefahttp://openacccess.atu.edu.tr:8080/xmlui/handle/123456789/41732023-03-30T06:24:09Z2017-03-01T00:00:00ZEffect of adherend recessing on bi-adhesively bonded single-lap joints with spew fillet
Calik, Ahmet; Yildirim, Sefa
The effect of adherend recessing on the strength of full (spew)-fillet-formed bi-adhesively bonded single-lap joint (SLJ) was investigated using the finite-element (FE) method under pure tension (i.e., 20 dissimilar recess length and depth and two-type bi-adhesive bond). A three-dimensional (3D) FE model was developed for bi-adhesively bonded SLJ, which had fillet and recessed adherend, assuming that both adhesive and adherend have geometrical non-linearity and exhibit linear material behaviour. The novelty of present study is the application of recessing process on the fillet-formed bi-adhesively bonded SLJs. The bondline characteristics of bi-adhesively bonded joints with the effect of adherend recessing have been investigated by examining the distributions of the peel and maximum principle stresses (MPS) at the mid-plane of the bondline. The results from the FE simulations in which varying geometric parameters are used reveal that the combined effects of adherend recessing spew fillet and bi-adhesive bondline led to a major decrease in the peak values of the peel stress, which is the governing failure stress and MPS. A novel design that may be beneficial to improve the strength characteristics of aluminium SLJ is presented.
WOS indeksli yayınlar koleksiyonu. / WOS indexed publications collection.
2017-03-01T00:00:00ZNumerical analysis of the thermal and thermodynamic performance of a parabolic trough solar collector using SWCNTs-Therminol (R) VP-1 nanofluidMwesigye, AggreyYilmaz, Ibrahim HalilMeyer, Josua P.http://openacccess.atu.edu.tr:8080/xmlui/handle/123456789/41692023-03-24T12:07:08Z2018-04-01T00:00:00ZNumerical analysis of the thermal and thermodynamic performance of a parabolic trough solar collector using SWCNTs-Therminol (R) VP-1 nanofluid
Mwesigye, Aggrey; Yilmaz, Ibrahim Halil; Meyer, Josua P.
In this paper, energetic and exergetic performances of a parabolic trough solar collector using single walled carbon nanotubes (SWCNTs)-Therminol (R) VP-1 nanofluid were numerically investigated and presented. The main objective of this investigation was to determine the influence of high thermal conductivity SWCNTs suspended in the widely used heat transfer fluid, Therminol (R) VP-1 on the performance indicators of the parabolic trough solar collector. A parabolic trough system with a high concentration ratio of 113 was analyzed in this study. The thermo-physical properties of SWCNTs were taken as functions of nanotube length, nanotube diameter, and temperature, while the properties of Therminol (R) VP-1 were considered to be temperature dependent. The study involved determination of the actual heat flux profile through Monte Carlo ray tracing and the subsequent coupling of this heat flux profile to a computational fluid dynamics tool using user defined functions. The computational fluid dynamics tool was finite volume based, and the realizable k-epsilon model together with enhanced wall treatment were used for turbulence modeling. The entropy generation rates were obtained directly from the local velocity and temperature fields of the computed domain and later used in the exergy analysis. Results showed that although the heat transfer performance significantly improved with the use of SWCNTs, the increase in the thermal efficiency was not substantial. For the considered range of parameters, while the heat transfer performance increased up to 234%, the thermal efficiency increased around 4.4% as the volume fraction increased from 0 to 2.5%. The corresponding reduction in the entropy generation was about 70%.
WOS indeksli yayınlar koleksiyonu. / WOS indexed publications collection.
2018-04-01T00:00:00ZNUMERICAL INVESTIGATION OF COMBINED EFFECT OF NANOFLUIDS AND MULTIPLE IMPINGING JETS ON HEAT TRANSFERKilic, MustafaAli, Hafiz Muhammadhttp://openacccess.atu.edu.tr:8080/xmlui/handle/123456789/41612023-03-20T08:44:08Z2019-01-01T00:00:00ZNUMERICAL INVESTIGATION OF COMBINED EFFECT OF NANOFLUIDS AND MULTIPLE IMPINGING JETS ON HEAT TRANSFER
Kilic, Mustafa; Ali, Hafiz Muhammad
The present study is focused on numerical investigation of heat enhancement and fluid-flow from a heated surface by using nanofluids with three impinging jets. Effects of different volume ratio, different heat flux and different types of nanofluids (CuO-water, Al2O3-water, Cu-water, TiO-water, and pure water) on heat transfer and fluid-flow were studied numerically. The CuO-water nanofluid was used as a coolant in the other parameter. Three impinging jets were used to cool the surface. Low Reynolds number k-epsilon turbulent model of PHONEICS CFD code was used for numerical analysis. It is obtained that increasing volume ratio from phi=2% to 8% causes an increase of 10.4% on average Nusselt number. Increasing heat flux six times has not a significant effect on average Nusselt number. Using Cu-water nanofluid causes an increase of 2.2%, 5.1%, 4.6%, and 9.6% on average Nusselt number with respect to CuO-water, TiO-water, Al2O3-water, and pure water.
WOS indeksli yayınlar koleksiyonu. / WOS indexed publications collection.
2019-01-01T00:00:00Z