Influence of diverter in cylinder array on its natural convection heat transfer

doi:10.11949/0438-1157.20201399

Abstract

Abstract:

For an array composed of 5 cylinders of the same specification in an infinite space, the natural convection heat transfer of diverters placed between the cylinders is numerically simulated. Considering the difference between the natural convection heat transfer when Ra is in the range of 10³—10⁴, the diverter's deflection angle is from 0° to 60°, and the cylinder spacing is from 2 to 4 cylinder diameters. The analysis of the local Nusselt number (Nu_loc) and the average Nusselt number (Nu_ave) of 5 cylinders shows that the natural convection heat transfer of the diverter to the array is reflected in two aspects. First, it is equivalent to an obstacle for the cylinders under the diverter to reduce the heat transfer, the second is to isolate the plume flow from the bottom of the cylinder above the diverter, thereby increasing the overall heat transfer of the array. In the case of large cylinder spacing, compared with the cylinder array without diverter, the heat transfer trend of C1—C4 cylinders has slowed down significantly, and the heat transfer trend of C4,C5 cylinders has increased, and the overall heat exchange of the system has been enhanced. The cylinder spacing S=2D, Ra=10³, the diverter mainly acts as an obstacle, weakening the heat transfer of the C1—C4 cylinders, resulting in a decrease in the overall heat transfer of the array. When the diverter deflection angle is 45°, the heat transfer of the array reaches its maximum value, which is up to 21% higher than that without the diverter.

Key words: cylinder, diverter, heat transfer, natural convection, numerical simulation

摘要：

对无限大空间中5根同规格圆管组成的圆管束在管间放置导流器的自然对流换热进行了数值模拟研究。考虑了Ra在10³～10⁴范围内，导流器偏转角为0°～60°，圆管间距为2～4倍圆管直径的自然对流换热，分析了5根圆管的局部Nusselt数（Nu_loc）和平均Nusselt数（Nu_ave）。研究结果表明，导流器对管束结构的自然对流换热影响体现在两方面：一是对导流器下方圆管而言相当于障碍物削弱其换热，二是对导流器上方圆管而言隔绝了下方羽状流的影响，从而增强系统的整体换热。在圆管间距较大时，与无导流器的圆管束相比，C1～C4各圆管换热下降趋势明显放缓，并且从C4、C5圆管换热趋势上升，系统整体换热增强。圆管间距S=2D，Ra=10³，导流器主要起障碍物的作用，削弱C1～C4各圆管换热，导致系统整体换热下降。当导流器偏转角度为45°时系统换热达到最大值，较无导流器时换热最多有着21%的提升。

关键词: 圆管, 导流器, 传热, 自然对流, 数值模拟

CLC Number:

TK 311

WANG Lingyue, ZHU Jinrong, WANG Congle, LYU Hui, CHENG Chunfu, ZHANG Jinye. Influence of diverter in cylinder array on its natural convection heat transfer[J]. CIESC Journal, 2021, 72(S1): 310-317.

王玲玥, 朱进容, 王从乐, 吕辉, 成纯富, 张金业. 圆管束中导流器对其自然对流换热的影响[J]. 化工学报, 2021, 72(S1): 310-317.

Figures/Tables 11

Fig.1 Sketch of physical model

Fig.2 Sketch of mesh generation

Table 1 Comparisons of simulated Nusselt number Nuˉ for different grids with experimental result of Ref. ［29］

网格数	$N u ˉ$
154184	9.119
218802	9.813
310166	9.998
412656	9.994
文献^[29]	10.109

Table 1 Comparisons of simulated Nusselt number Nuˉ for different grids with experimental result of Ref. ［29］

网格数	$N u ˉ$
154184	9.119
218802	9.813
310166	9.998
412656	9.994
文献^[29]	10.109

Table 2 Comparison of Nuloc for single cylinder and existing results

Ra		Nu_loc
Ra		θ=0°	θ=30°	θ=60°	θ=90°	θ=120°	θ=150°	θ=180°
10³	本文	3.822	3.795	3.687	3.501	2.894	1.974	1.258
	文献^[28]	3.798	3.755	3.640	3.376	2.841	1.958	1.210
	文献^[6]	3.813	3.772	3.640	3.374	2.866	1.975	1.218
10⁴	本文	6.159	6.138	5.869	5.561	4.903	3.326	1.577
	文献^[28]	5.986	5.931	5.756	5.406	4.716	3.293	1.532
	文献^[6]	5.995	5.935	5.750	5.410	4.764	3.308	1.534
10⁵	本文	9.715	9.652	9.318	8.791	7.992	5.833	2.107
	文献^[28]	9.694	9.595	9.297	8.749	7.871	5.848	1.989
	文献^[6]	9.675	9.557	9.278	8.765	7.946	5.891	1.987

Fig.3 Comparison of simulation results of Nuave of each cylinder in a vertical array of 5 cylinders and existing experimental results

Fig.4 Streamline diagram when diverters are placed at different deflection angle

Fig.5 Temperature diagram when diverters are placed at different deflection angles

Fig.6 Nuarrayand Nuave of each cylinder in array when diverters are placed at different deflection angles

Fig.7 Temperature diagram and streamline diagram with a cylinder spacing of S=2D ~4D

Fig.8 Nuave of each cylinder in array

Fig.9 Average Nu number of cylinders array

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