Kare Kesitteki Helisel Tellerin Kenar Uzunluğunun Isı Transferi ve Basınç Düşümüne Etkisinin Sayısal İncelenmesi

Isı transferi uygulamaları endüstrinin en önemli araştırma konuları arasındadır. Sunulan makalede incelenen en önemli faktör, daha az enerji ile yüksek ısı transferi elde etmektir. Isı eşanjörlerinde ısı transferini iyileştirme çabaları da buna örnektir. Bu çalışmada dairesel boru içerisine yerleştirilen kare kesitteki helisel tellerin kenar uzunluğunun ısı transferi ve basınç düşüşüne etkisi sayısal olarak incelenmiştir. Analizler ANSYS FLUENT modülünde k-ℇ türbülans modeli kullanılarak elde edilmiştir. Doğrulamada kullanılan denklemler, türbülanslı rejimdeki kullanılan Dittus-Boelter denklemiyle Nusselt sayısı ve türbülanslı rejimde kullanılan sürtünme faktörü ile sayısal sonuçlarla karşılaştırılmıştır. Sayısal olarak elde edilen boş boru sonuçları ile ampirik ilişkilerin sonuçlarının birbirine oldukça yakın olduğu görülmüştür. Yerleştirilen sarmal/helisel tellerin kesit uzunluğu 3, 4 ve 5 mm'dir. Yerleştirilen sarmal tellerin hatve oranı 1'dir. Reynolds sayısı araştırma aralığı 5175 ila 24,575 arasındadır. Elde edilen sonuçlara göre kenar uzunluğu arttıkça hem Nusselt sayısı hem de sürtünme faktörü artmaktadır. Ayrıca termo-hidrolik olarak ele alanan termal performans kriterine (PEC) göre düşük Reynolds sayısında daha yüksek verim elde edilmiştir. En yüksek PEC, 1,25 değeri ile 3 mm kesit uzunluğuna sahip sarmal telde görüldü. Ancak artan Reynolds sayısı ile kesit uzunluğu 5 mm'nin PEC'nin 4 ve 3'ten büyük olduğu görülmektedir.

Anahtar Kelimeler:

Isı Transfer İyileştirmesi, FLUENT, Helisel Tel, PEC, Kesit geometrisi.

Numerical Investigation of the Effect of Edge Length of Square Helical Wires on Heat Transfer and Pressure Drop

Heat transfer and applications are among the most important research topics of the industry. The most important factor investigated in this paper is to achieve high heat transfer with less energy. Efforts to improve heat transfer in heat exchangers are an example of this. In this study, the effect of the length of the square helical wires placed in the circular pipe on the heat transfer and pressure drop was investigated numerically. All results were obtained using the k-ℇ turbulence model in the ANSYS FLUENT module. The equations used in the verification were compared with the Dittus-Boelter equation and the Nusselt number friction factor in the turbulent regime with numerical results. It has been observed that the results of the smooth pipe obtained numerically and the results of the empirical relations are quite close to each other. The cross-sectional length of the inserted helical wires is 3, 4, and 5 mm. The pitch ratio of the placed helical wires is 1. The Reynolds number research range is between 5175 and 24,575. According to the obtained results, both the Nusselt number and the friction factor increase with increasing edge length. In addition, higher efficiency is obtained at a low Reynolds number according to the thermo-hydraulic thermal performance criterion (PEC). The highest PEC was seen in the helical wire with a cross-section length of 3 mm, with a value of 1.25. However, it is observed that the PEC of 5 is greater than 4 and 3 with increasing Reynolds number.

Keywords:

Heat transfer enhancement, FLUENT, Helical coil, Cross-section, PEC,

PDF

___

García, A., Vicente, P. G., & Viedma, A. (2005). Experimental study of heat transfer enhancement with wire coil inserts in laminar-transition-turbulent regimes at different Prandtl numbers. International Journal of Heat and Mass Transfer, 48(21–22), 4640–4651. https://doi.org/10.1016/j.ijheatmasstransfer.2005.04.024
Göksu, T. T., & Yilmaz, İ. H. (2019). Enhancement of heat transfer using twisted tape insert in a plain tube. 10.
Gunes, S., Ozceyhan, V., & Buyukalaca, O. (2010). Heat transfer enhancement in a tube with equilateral triangle cross sectioned coiled wire inserts. Experimental Thermal and Fluid Science, 34(6), 684–691. https://doi.org/10.1016/j.expthermflusci.2009.12.010
Murugesan, P., Mayilsamy, K., & Suresh, S. (2010). Heat Transfer and Friction Factor Studies in a Circular Tube Fitted with Twisted Tape Consisting of Wire-nails. Chinese Journal of Chemical Engineering, 18(6), 1038–1042. https://doi.org/10.1016/S1004-9541(09)60166-X
Muthusamy, C., & Srithar, K. (2015). Energy and exergy analysis for a humidification–dehumidification desalination system integrated with multiple inserts. Desalination, 367, 49–59. https://doi.org/10.1016/j.desal.2015.03.032
Özceyhan, V. (2005). Conjugate heat transfer and thermal stress analysis of wire coil inserted tubes that are heated externally with uniform heat flux. Energy Conversion and Management, 46(9–10), 1543–1559. https://doi.org/10.1016/j.enconman.2004.08.003
Promvonge, P., & Eiamsa-ard, S. (2006). Heat transfer enhancement in a tube with combined conical-nozzle inserts and swirl generator. Energy Conversion and Management, 47(18–19), 2867–2882. https://doi.org/10.1016/j.enconman.2006.03.034
Promvonge, P., & Eiamsa-ard, S. (2007). Heat transfer in a circular tube fitted with free-spacing snail entry and conical-nozzle turbulators. International Communications in Heat and Mass Transfer, 34(7), 838–848. https://doi.org/10.1016/j.icheatmasstransfer.2007.03.020
Promvonge, P., Skullong, S., Kwankaomeng, S., & Thiangpong, C. (2012). Heat transfer in square duct fitted diagonally with angle-finned tape—Part 1: Experimental study. International Communications in Heat and Mass Transfer, 39(5), 617–624. https://doi.org/10.1016/j.icheatmasstransfer.2012.03.007
Wang, L., & Sundén, B. (2002). Performance comparison of some tube inserts. International Communications in Heat and Mass Transfer, 29(1), 45–56. https://doi.org/10.1016/S0735-1933(01)00323-2
Yakut, K., & Sahin, B. (2004). Flow-induced vibration analysis of conical rings used for heat transfer enhancement in heat exchangers. Applied Energy, 78(3), 273–288. https://doi.org/10.1016/j.apenergy.2003.09.001
Yun, R., Hwang, J.-S., Chung, J. T., & Kim, Y. (2007). Flow boiling heat transfer characteristics of nitrogen in plain and wire coil inserted tubes. International Journal of Heat and Mass Transfer, 50(11–12), 2339–2345. https://doi.org/10.1016/j.ijheatmasstransfer.2006.10.038