Experimental and numerical study on heat transfer, flow resistance, and compactness of alternating flattened tubes

Sajadi, Ahmad Reza; Kowsary, Farshad; Bijarchi, Mohamad Ali; Sorkhabi, Sami Yamani Douzi

doi:10.1016/j.applthermaleng.2016.07.033

Cited by 29 publications

(6 citation statements)

References 26 publications

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“…Wang et al [13] Twisted square duct Air 10,000-100,000 The twisting brings about a special variation pattern of the spanwise distribution of the local heat transfer coefficient Sajadi et al [14] Alternating flattened tube Oil 500-2000…”

Section: Continuity Equationmentioning

confidence: 99%

“…Sajadi et al [14] proposed a new alternating flattened tube and studied the heat transfer and flow resistance of alternating flattened tubes used experimental and numerical methods. Their experimental and numerical results indicated that the alternating flattened tube had a better performance enhancement ratio compared to the traditional smooth tubes.…”

Section: Introductionmentioning

confidence: 99%

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Numerical study of heat transfer and flow characteristic of twisted tube with different cross section shapes

et al. 2018

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In the present work, three dimensional numerical study is conducted to investigate the heat transfer and flow characteristics of twisted tubes of different cross section shapes with the Reynolds number ranging from 50 to 2000. The constant wall temperature condition is used in the simulation analysis. The numerical results of twisted square tube are compared with the available previous experimental data. The results indicate that the heat transfer performance of twisted tube is enhanced compared with the smooth tube, while the pressure drop increases as well. One of the key findings is that the transition point of twisted square tube from laminar flow to turbulent flow is identified and located at Re = 500. It is also found that the cross section shape has little effect on the heat transfer of twisted tubes, while it has great influence on the flow pattern. The results also reveal that the twist pitch has remarkable effects on the heat transfer performance of twisted tubes. In addition, the maximum value of PEC of 2.69 is obtained in twisted pentagon tube with twist pitch ratio of 0.17, and the Reynolds number of 350. These results are significant because it will contribute to the development of compact twisted tube heat exchangers.

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Section: Continuity Equationmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Numerical study of heat transfer and flow characteristic of twisted tube with different cross section shapes

et al. 2018

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“…It is evident that the friction factor and average Nusselt number calculated by the k-e turbulence models were much closer to the experimental results than the other models. Considering these results and those of previous studies [16,17,22,23], the standard k-e turbulence model was employed for numerical simulation of turbulent flow and heat transfer of AEA tubes. The friction factor and average Nusselt number can be written as:…”

Section: Governing Equationmentioning

confidence: 89%

Investigation of heat transfer and pressure drop of turbulent flow in tubes with successive alternating wall deformation under constant wall temperature boundary conditions

Khaboshan

2018

J Braz. Soc. Mech. Sci. Eng.

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In this study, the effects of the presence of multi-longitudinal vortex and various rotation angles between the pitches of alternating elliptical axis (AEA) tubes on heat transfer and pressure drop of turbulent flow were numerically investigated. Turbulent flow of water fluid was simulated at Reynolds numbers of 10,000-60,000. The turbulent flow and heat transfer in the tubes were discussed in terms of parameters such as static pressure, velocity magnitude, wall shear stress, turbulent intensity, performance evaluation criterion and the field synergy principle. The results demonstrate that most heat transfer occurs in the transition zone, but this also caused a high rate of pressure drop. Increasing the rotation angle between pitches from 60°to 80°increased the heat transfer, which increased the number of the multi-longitudinal vortices from four to eight and better mixed the cold fluid with the hot fluid near the tube wall on more paths. The friction factor decreased and the average Nusselt number increased as the Reynolds number increased. Both parameters increased as the angle of the pitch rotation increased. The performance evaluation criteria for all AEA tubes at a constant pumping power showed that the highest value (1.09) was achieved at a low Reynolds number (Re = 10,000) in the AEA 90°tube.

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“…The results established that convex corrugated inner tube and concave corrugated outer tube give maximum effectiveness. In another study, Sajadi et al 17 also investigated numerically and experimentally the heat transfer and flow performance using an alternating flattened tube. They realized that the alternating flattened tubes produce better performance in comparison to conventional circular tubes.…”

Section: Introductionmentioning

confidence: 99%

Experimental investigation of heat transfer enhancement in a double pipe heat exchanger with a twisted inner pipe

Ali

Jalal

2021

Heat Trans

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In the present work, an experimental investigation is conducted to address the influence of inner pipe twisting on the overall performance of a double pipe heat exchanger. With the fluid to fluid heat exchange, both parallel and counter flow directions are examined as well. In addition to the original elliptical pipe, three pipes with different numbers of twisting (3, 5, and 7 twists per unit length) constructed from the elliptical pipe are considered where the heat transfer rate and pressure drop are addressed. All tests are carried out in the turbulent flow regime where the Reynolds number (Re) ranging from 5000 to 26,000 and water is used as the working medium. The obtained outcomes show that for both flow directions, there is an enhancement in the heat exchanger overall performance with all considered twisting pipes. The maximum enhancement in the Nusselt number is found to be 1.8 for the parallel flow and around 2.2 for the counter flow compared with the original pipe. The inner pipe with 7 twists, however, improves the overall performance the most, where a maximum performance enhancement factor of 1.63 and 1.9 are observed at Reynolds number of 26,000 in the parallel and counter flow configurations, respectively.

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Experimental and numerical study on heat transfer, flow resistance, and compactness of alternating flattened tubes

Cited by 29 publications

References 26 publications

Numerical study of heat transfer and flow characteristic of twisted tube with different cross section shapes

Numerical study of heat transfer and flow characteristic of twisted tube with different cross section shapes

Investigation of heat transfer and pressure drop of turbulent flow in tubes with successive alternating wall deformation under constant wall temperature boundary conditions

Experimental investigation of heat transfer enhancement in a double pipe heat exchanger with a twisted inner pipe

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