Experimental investigation of heat transfer and friction factor characteristics of surfactant solutions
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Tarih
2023
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Yayıncı
Bursa Teknik Üniversitesi, Lisansüstü Eğitim Enstitüsü
Erişim Hakkı
info:eu-repo/semantics/openAccess
Özet
Optimum sonuçlara ulaşma çabaları, modern ısı transferi biliminin daha küçük ama daha verimli cihazlar yapmaya odaklanmasına neden oldu. Çift borulu ısı değiştirici (DPHE), endüstriyel sektörlerde yaygın olarak kullanılmaktadır. DPHE'nin etkinliğini artırmak için araştırmacılar, ısı transferi yeteneklerini geliştirmeye yönelik çeşitli yaklaşımlar geliştirdiler. Bu stratejilerden biri, daha iyi termal özelliklere sahip alternatif bir temel ısıl akışkan elde etmeye yönelik uygulamaları içerir. Bununla birlikte, bilim insanları türbülanslı boru akışlarında sürtünmeyi azaltan katkı maddelerinin sürtünmeyi azaltma özelliklerini keşfetmekle ilgilendiler. Bu katkı maddelerinin boru sistemlerindeki akışkan sürtünmesini azaltmada neyin etkili olduğuna dair daha fazla fikir edinmeye yönelik çok sayıda teorik ve deneysel çalışma bulunmaktadır. Uzmanlar, bu benzersiz fiziksel davranışları açıklayabilecek çeşitli senaryolar önermektedir. Bu çalışma, sürtünmeyi azaltan maddeler olarak sürfaktan çözeltileri kullanan bir ters akışlı çift borulu ısı değiştiricideki (DPHE) basınç düşüşünü azaltmayı amaçlamaktadır. Bu amaçla sodyum dodesil sülfat (SDS), nonilfenol etoksilat (NP-10) ve polisorbat 80 (Tween 80) olmak üzere üç farklı sürfaktan suya ayrı ayrı ağırlıkça % 0,2 katı konsantrasyonlarında eklenerek sürfaktan çözeltileri hazırlandı. Isıtıcı, soğutucu, depolama tankı, pompa ve çift borulu ısı değiştiriciden oluşan bir test deneyi düzeneği kuruldu. Soğuk akışkan olarak kullanılan sürfaktan çözeltileri ısı değiştiricinin iç borusundan farklı debilerde (3, 4, 5, 6, 7, 8 L/dk) geçerken, sıcak akışkan, saf su debisi deney boyunca 5L/dk da sabit tutulmuştur. Çalışma türbülanslı akış rejimlerinde gerçekleştirilmiştir. Basınç düşüsü ölçümleri ve ısı transferi ölçümleri eş zamanlı gerçekleştirildi. Basınç düşüşü verilerinden sürtünme faktörü hesaplanarak literatürle karşılaştırıldı. Basınç düşüşü ölçümlerinden, sürtünme azalması belirledi. Sürfaktan çözeltileri için sabit akış hızında hesaplanan sürtünme azalması sonuçlarına göre, maksimum sürtünme azalması NP-10 sürfaktan çözeltisi kullanıldığında %15 oranında elde edildi. En az sürtünme azalması ise Tween 80 çözeltisi için % 1.10 olarak elde edildi. Sürtünme azalması SDS ve NP-10 çözeltileri için akış hızı ile artmakta ve bir maksimumdan geçtikten sonra azalmaktadır. Ancak Twee80 çözeltisi için akış hızı ile azalan bir sürtünme azalma davranışı gözlenmiştir. Basınç düsüşü ölçümleri ile eş zamanlı aynı sürfaktan çözeltileri için ısı transferi ölçümleri yapıldı ve saf su ile elde edilen sonuçlar ile karşılaştırıldı. Tüm ısı katsayısı yardımı ile konvektif ısı transferi katsayıları hesaplandı. Konvektif ısı transferi katsayıları hesaplamalarında hem Wilson plot yöntemi hemde klasik iç akış ısı transfer korelasyonu, Dittus Boelter korelasyonu, kullanıldı. Elde edilen sonuçlar karşılaştırıldı. Saf su için elde edilen sonuçlar klasik ısı transfer korelasyonları ile karşılaştırıldı. Buna göre, Dittus Boelter korelasyonu, deneysel sonuçlarla en yakın uyumu gösterdiği gözlemlenmiştir, maksimum sapma % 6 gösterilmiştir. Sabit akış hızında su ile karşılaştırıldığında SDS çözeltisi için suya yakın Nusselt sayıları elde edilirken, NP10 ve Tween80 çözelitleri için ise daha düşük Nusselt sayıları elde edilmiştir. Surfakatan ilavesi sabit basınçta suya göre basınç düşüşünde bir azalmaya sebep olması yanında ısı transferinde de bir azalmaya sebep olduğu görülmüştür.
Efforts to achieve optimal results have led modern heat transfer science to focus on creating smaller yet more efficient devices. The double-pipe heat exchanger (DPHE) is widely used across industrial sectors. To elevate DPHE's effectiveness, investigators have introduced diverse approaches for enhancing heat transfer capabilities. These strategies include implementing a chemical compound, including a surfactant and alternative base fluids with better thermal specifications. Nonetheless, scientists were interested in exploring the drag-reduction properties of drag-reducing additives in turbulent pipe flows. Numerous research has advanced our understanding of this topic. Theoretical and experimental studies abound as we seek greater insight into what makes these additives effective at reducing fluidic friction within piping systems by examining changes along the conduits' wall where molecular momentum is transferred between fluids. Experts propose various scenarios that could explain these unique physical behaviors. This study aims to decrease pressure drop in a counterflow double-pipe heat exchanger (DPHE) using surfactant solutions as drag-reducing agents. For this purpose, surfactant solutions were prepared by adding three different surfactants, including sodium dodecyl sulfate (SDS), nonylphenol ethoxylate (NP-10), and polysorbate 80 (Tween 80) at weight concentrations of 0.2% to water, separately. The test rig consisting of a heater, cooler, storage tank, pump, and the test section of a double pipe heat exchanger was set up. While surfactant solutions used as cold fluid passed through the inner tube of the heat exchanger at several flow rates (3, 4, 5, 6, 7, 8 LPM), the flow rate of the hot fluid, distilled water was kept constant at 5 LPM throughout the experiment. The study was conducted in turbulent flow regimes. Pressure drop measurements and heat transfer measurements were carried out simultaneously. The friction factor was calculated from the pressure drop data and compared with the literature. According to the results, the maximum drag reduction was achieved by approximately 15% when using an NP-10 surfactant solution, while Tween 80 surfactant solution yielded the most negligible reduction in drag at 1.10%. In the case of SDS and NP10 solutions, drag reduction increases with the Reynold number until reaching a peak, after which it decreases. However, with the Tween 80 surfactant solution, a decrease in drag was observed as the fluid flow got turbulently. Heat transfer measurements were made for the same surfactant solutions simultaneously with the pressure drop measurements and compared with the results obtained with distilled water. Convective heat transfer coefficients were calculated with the help of the overall heat transfer coefficient. The Wilson plot method and classical internal flow heat transfer correlation, Dittus Boelter correlation, were used to calculate convective heat transfer coefficients. Obtained results were compared to each other. The results obtained for pure water were compared with classical heat transfer correlations. Accordingly, it was observed that the Dittus Boelter correlation showed the closest agreement with the experimental results, with a maximum deviation of 6%. Compared to water at a constant flow rate, Nusselt numbers close to the water were obtained for the SDS solution, while lower Nusselt numbers were obtained for the NP10 and Tween80 solutions. It was observed that the addition of surfactant caused a decrease in pressure drop compared to water at constant pressure and showed a reduced heat transfer.
Efforts to achieve optimal results have led modern heat transfer science to focus on creating smaller yet more efficient devices. The double-pipe heat exchanger (DPHE) is widely used across industrial sectors. To elevate DPHE's effectiveness, investigators have introduced diverse approaches for enhancing heat transfer capabilities. These strategies include implementing a chemical compound, including a surfactant and alternative base fluids with better thermal specifications. Nonetheless, scientists were interested in exploring the drag-reduction properties of drag-reducing additives in turbulent pipe flows. Numerous research has advanced our understanding of this topic. Theoretical and experimental studies abound as we seek greater insight into what makes these additives effective at reducing fluidic friction within piping systems by examining changes along the conduits' wall where molecular momentum is transferred between fluids. Experts propose various scenarios that could explain these unique physical behaviors. This study aims to decrease pressure drop in a counterflow double-pipe heat exchanger (DPHE) using surfactant solutions as drag-reducing agents. For this purpose, surfactant solutions were prepared by adding three different surfactants, including sodium dodecyl sulfate (SDS), nonylphenol ethoxylate (NP-10), and polysorbate 80 (Tween 80) at weight concentrations of 0.2% to water, separately. The test rig consisting of a heater, cooler, storage tank, pump, and the test section of a double pipe heat exchanger was set up. While surfactant solutions used as cold fluid passed through the inner tube of the heat exchanger at several flow rates (3, 4, 5, 6, 7, 8 LPM), the flow rate of the hot fluid, distilled water was kept constant at 5 LPM throughout the experiment. The study was conducted in turbulent flow regimes. Pressure drop measurements and heat transfer measurements were carried out simultaneously. The friction factor was calculated from the pressure drop data and compared with the literature. According to the results, the maximum drag reduction was achieved by approximately 15% when using an NP-10 surfactant solution, while Tween 80 surfactant solution yielded the most negligible reduction in drag at 1.10%. In the case of SDS and NP10 solutions, drag reduction increases with the Reynold number until reaching a peak, after which it decreases. However, with the Tween 80 surfactant solution, a decrease in drag was observed as the fluid flow got turbulently. Heat transfer measurements were made for the same surfactant solutions simultaneously with the pressure drop measurements and compared with the results obtained with distilled water. Convective heat transfer coefficients were calculated with the help of the overall heat transfer coefficient. The Wilson plot method and classical internal flow heat transfer correlation, Dittus Boelter correlation, were used to calculate convective heat transfer coefficients. Obtained results were compared to each other. The results obtained for pure water were compared with classical heat transfer correlations. Accordingly, it was observed that the Dittus Boelter correlation showed the closest agreement with the experimental results, with a maximum deviation of 6%. Compared to water at a constant flow rate, Nusselt numbers close to the water were obtained for the SDS solution, while lower Nusselt numbers were obtained for the NP10 and Tween80 solutions. It was observed that the addition of surfactant caused a decrease in pressure drop compared to water at constant pressure and showed a reduced heat transfer.
Açıklama
Anahtar Kelimeler
Kimya Mühendisliği, Chemical Engineering
