Calculation of radiation heat transfer in staggered drop-shaped tubes bundle

The purpose of this study is to clarify heat transfer and fluid flow behavior across six-row mixed tube bundles. The tube bundle consists of circular and drop-shaped cross sections in a staggered arrangement. The Reynolds number Re for the flow is varied from 1.78 × 103 to 18.72 × 103. Six cases of the mixed tube bundle were considered. The results of the mixed tube bundles were compared with those of the circular (case I) and drop-shaped ones (case II). The Ansys Fluent software package was utilized to predict the flow pattern over the tube bundles. The results of the numerical simulation showed that the cross-sectional shape of the tubes and their location in the bundle significantly affect the heat transfer and pressure drop in the bundle. Case IV (circular tubes in the first, third, and fifth rows and drop-shaped tubes in the second, fourth, and sixth rows) increases the average Nusselt number [Formula: see text] by about 1.11%–8.10% and 47.86%–49.04% compared to that of the circular and drop-shaped tube bundles, respectively. Case VII (drop-shaped tubes in the first, second, fourth, and sixth rows and circular tubes in the third and fourth rows) has the lowest friction factor [Formula: see text] compared to the other cases of circular and mixed tube bundles. Moreover, the maximum values of the thermal–hydraulic performance [Formula: see text] were achieved for case IV at Re = 1.78 × 103 and the case VII at Re >1.78 × 103, which were about 14.55% and (2.08–4.49)%, respectively, higher than those obtained for the drop-shaped tube bundle. Generalized correlations of [Formula: see text], [Formula: see text], and [Formula: see text] for the studied mixed tube bundles were predicted.

Flow and heat transfer characteristics of staggered mixed circular and drop-shaped tube bundle

Deeb

2022

Enhancing heat exchanger performance through hybrid angle of attack control for drop-shaped tubes

Deeb

2023

In this study, a numerical investigation was conducted to explore the potential improvement in the overall performance of heat exchangers comprising drop-shaped tubes through the control of the angle of attack. A comprehensive analysis was conducted, evaluating eight distinct configurations of 20-row bundles consisting of drop-shaped tubes in both staggered and in-line arrangements. A thorough comparison was made against corresponding bundles with circular tubes. The study covered a range of Reynolds numbers Re = 1.78 × 103–1.87 × 104 and angles of attack θi−j = 0°–360°. Two methods were employed to evaluate the thermal-hydraulic performance. The findings indicated that the friction factor of case 6 of drop-shaped tube bundle (θ1−5 = 0°, θ6−10 = 330°, θ11−15 = 30°, θ16−20 = 0°) exhibited a reduction of approximately 27%–43% and 42%–46% compared to the staggered (case 3) and in-line (case 1) configurations of drop-shaped tube bundles at zero angles of attack, respectively. Additionally, case 6 achieved the highest thermal-hydraulic performance, surpassing the staggered bundles of circular tubes (case 3) by 1.4–1.8 times and the in-line bundles of circular tubes (case 1) by 2.9–3.5 times. Novel equations were derived to estimate the mean Nusselt number, effectiveness, and friction factor for case 6, exhibiting a maximum deviation of 0.74%, 0.48%, and 0.73% correspondingly.

The impact of drop-shaped pin-fins on the thermal and hydraulic characteristics of a finned tube

Deeb

2024

In this study, circular and drop-shaped pin-fins were employed to investigate the influence of pin-fins on the thermal behavior and flow characteristics of finned tubes using a combination of experimental and numerical methods. The configuration of in-line pin-fins was analyzed and compared with that of a smooth tube. The analysis covered Reynolds numbers spanning from Re = 7.03 × 103 to 35.17 × 103. Thermal and hydraulic contours were depicted. Two methodologies were utilized to assess the overall performance. The outcomes demonstrated that the average Nusselt number for the finned tubes equipped with drop and circular pin-fins rose by approximately 50.03%–93.1% and 59.59%–77.08%, respectively, in comparison to the smooth circular tube. Moreover, the drop-shaped pin-fins on the tube displayed a reduced friction factor, leading to a reduction of 1.36%–7.95% in comparison to the circular counterpart. Furthermore, both drop and circular pin-fins on the tubes exhibited approximately 2.93%–54.89% and 7.33%–37.1% higher efficiency, respectively, compared to the smooth tube. Generalized correlations were developed to compute the Nusselt number, friction factor, and effectiveness in relation to the Reynolds number, with the aim of providing guidance for future research and design efforts in heat exchangers incorporating pin-fin tubes. The utilization of tubes featuring drop-shaped pin-fins plays a significant role in energy conservation.