{"title":"Experimental and numerical study of turbulent fluid flow of jet impingement on a solid block in a confined duct with baffles","authors":"A. Abdel-Fattah, E. Wahba, A.-F. Mahrous","doi":"10.1016/j.icheatmasstransfer.2024.108294","DOIUrl":null,"url":null,"abstract":"<div><div>This study investigates the heat transfer and fluid flow characteristics of turbulent flow resulting from jet impingement on a heated solid block positioned on the lower wall of a duct with baffles. Both experimental and numerical methods were employed in this research. The flow was presumed to be three-dimensional, steady, incompressible, and turbulent. The study involved the installation of one baffle on the lower wall and another one on the upper wall. Three variants of the k-ε turbulence model (the standard, the RNG, and the realizable) were numerically compared. The realizable k-ε model has shown the most reliable results compared to the other models, and thus is utilized in all calculations.</div><div>The flow characteristics were experimentally and numerically studied by varying jet Reynolds number (38,957 ≤ Re ≤ 77,315), baffle height (h<sub>b</sub> /d = 0.6,0.8 and 1.0), baffles' locations arrangement [(L<sub>1</sub>/d with L<sub>2</sub>/d) as (3 with 4), (4 with 6), (6 with 8) and (6 with 4)], solid block temperature (333 <sup>o</sup> K ≤ T<sub>b</sub> ≤ 363 <sup>o</sup> K) at an aspect ratio (w/a) of 5.25.</div><div>The results showed that several vortices were formed: a main vortex close to the upper wall, a smaller one above the hot solid block, a vortex adjacent to the solid block, and additional vortex zones both in front of and behind the lower and upper baffles. The vortices intensity increases as the Reynolds number grows up. When the baffle locations change downstream, the sizes of these generated vortices increase, the height of the recirculation zone behind the lower baffle is slightly higher than that behind the upper baffle, and the primary vortex diminishes. Besides, all recirculation zones grow up in sizes when swapping the baffle locations.</div><div>The study also revealed that the pressure is higher when the baffle is presented in the domain than the case of no baffle. The pressure value at the stagnation point, peak sub-atmospheric pressure value and maximum pressure value increase as the Reynolds number increases. They also increase with the increase of baffle height. However, it was found that the pressure values decay when the positions of the baffles get changed in the downstream direction.</div><div>In addition, the results showed that the maximum deviation in temperature between the experimental and theoretical results was about 3 %. Besides, the increase in the maximum temperature value in the presence of baffles was about 10.8 % as compared to the case without baffles. Furthermore, the temperature increases as the Reynolds number decreases while it increases with the increase of solid block temperature and/or baffles height and location.</div></div>","PeriodicalId":332,"journal":{"name":"International Communications in Heat and Mass Transfer","volume":"160 ","pages":"Article 108294"},"PeriodicalIF":6.4000,"publicationDate":"2024-12-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":"0","resultStr":null,"platform":"Semanticscholar","paperid":null,"PeriodicalName":"International Communications in Heat and Mass Transfer","FirstCategoryId":"5","ListUrlMain":"https://www.sciencedirect.com/science/article/pii/S073519332401056X","RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"Q1","JCRName":"MECHANICS","Score":null,"Total":0}
引用次数: 0
Abstract
This study investigates the heat transfer and fluid flow characteristics of turbulent flow resulting from jet impingement on a heated solid block positioned on the lower wall of a duct with baffles. Both experimental and numerical methods were employed in this research. The flow was presumed to be three-dimensional, steady, incompressible, and turbulent. The study involved the installation of one baffle on the lower wall and another one on the upper wall. Three variants of the k-ε turbulence model (the standard, the RNG, and the realizable) were numerically compared. The realizable k-ε model has shown the most reliable results compared to the other models, and thus is utilized in all calculations.
The flow characteristics were experimentally and numerically studied by varying jet Reynolds number (38,957 ≤ Re ≤ 77,315), baffle height (hb /d = 0.6,0.8 and 1.0), baffles' locations arrangement [(L1/d with L2/d) as (3 with 4), (4 with 6), (6 with 8) and (6 with 4)], solid block temperature (333 o K ≤ Tb ≤ 363 o K) at an aspect ratio (w/a) of 5.25.
The results showed that several vortices were formed: a main vortex close to the upper wall, a smaller one above the hot solid block, a vortex adjacent to the solid block, and additional vortex zones both in front of and behind the lower and upper baffles. The vortices intensity increases as the Reynolds number grows up. When the baffle locations change downstream, the sizes of these generated vortices increase, the height of the recirculation zone behind the lower baffle is slightly higher than that behind the upper baffle, and the primary vortex diminishes. Besides, all recirculation zones grow up in sizes when swapping the baffle locations.
The study also revealed that the pressure is higher when the baffle is presented in the domain than the case of no baffle. The pressure value at the stagnation point, peak sub-atmospheric pressure value and maximum pressure value increase as the Reynolds number increases. They also increase with the increase of baffle height. However, it was found that the pressure values decay when the positions of the baffles get changed in the downstream direction.
In addition, the results showed that the maximum deviation in temperature between the experimental and theoretical results was about 3 %. Besides, the increase in the maximum temperature value in the presence of baffles was about 10.8 % as compared to the case without baffles. Furthermore, the temperature increases as the Reynolds number decreases while it increases with the increase of solid block temperature and/or baffles height and location.
本文研究了射流冲击位于有挡板的管道下壁上的加热固体块所产生的湍流的传热和流体流动特性。本研究采用了实验和数值相结合的方法。流动被假定为三维的、稳定的、不可压缩的和湍流的。这项研究包括在下墙上安装一个挡板,在上墙上安装另一个挡板。对三种k-ε湍流模型(标准模型、RNG模型和可实现模型)进行了数值比较。与其他模型相比,可实现的k-ε模型显示出最可靠的结果,因此在所有计算中都得到了应用。在展长比(w/a)为5.25的条件下,通过改变射流雷诺数(38,957≤Re≤77,315)、挡板高度(hb /d = 0.6、0.8和1.0)、挡板位置排列[(L1/d与L2/d)分别为(3与4)、(4与6)、(6与8)和(6与4)]、固体块温度(333 o K≤Tb≤363 o K),对流动特性进行了实验和数值研究。结果表明:在上部壁面附近形成了一个主涡,在热固体块上方形成了一个较小的涡,在固体块附近形成了一个涡,在上下挡板前后形成了附加涡区。旋涡强度随雷诺数的增大而增大。当下游挡板位置改变时,这些涡的大小增大,下挡板后的再循环区高度略高于上挡板后的再循环区高度,一次涡减小。此外,当交换挡板位置时,所有再循环区域的大小都会增大。研究还发现,当挡板出现在区域内时,压力比没有挡板的情况下要高。滞止点压力值、峰值亚大气压值和最大压力值随雷诺数的增加而增大。它们也随挡板高度的增加而增加。然而,当沿下游方向改变挡板位置时,压力值有所衰减。结果表明,实验温度与理论温度的最大偏差约为3%。此外,与没有挡板的情况相比,有挡板时最高温度值升高约10.8%。温度随雷诺数的减小而升高,随固体块体温度和挡板高度及位置的增加而升高。
期刊介绍:
International Communications in Heat and Mass Transfer serves as a world forum for the rapid dissemination of new ideas, new measurement techniques, preliminary findings of ongoing investigations, discussions, and criticisms in the field of heat and mass transfer. Two types of manuscript will be considered for publication: communications (short reports of new work or discussions of work which has already been published) and summaries (abstracts of reports, theses or manuscripts which are too long for publication in full). Together with its companion publication, International Journal of Heat and Mass Transfer, with which it shares the same Board of Editors, this journal is read by research workers and engineers throughout the world.