三类随机分形结构下干土壤有效热导率的介观研究

doi:10.11949/j.issn.0438-1157.20181504

摘要/Abstract

摘要：

地埋管换热器的换热能力是设计地源热泵系统的关键，而环境土壤的有效热导率是影响地下传热量的重要参数。为探究土壤的介观结构参数对有效热导率的影响，提出三类随机分形结构，并结合格子玻尔兹曼方法，对土壤类多孔材料的传热特性进行了基础研究。通过对热探针实验结果和三类重构结构下模拟结果的对比分析，发现孔隙率仍然是影响干土壤有效热导率的主要因素，分形维度数和粒径比的影响则较小；干土壤介观结构的随机性对有效热导率有较大的影响，随机颗粒分布的微小变化会导致差异高达到24.5%。

关键词: 多孔介质, 分形, 热导率, 热传导, 格子玻尔兹曼方法, 热探针

Abstract:

The heat transfer capacity of the ground heat exchanger is the key to designing the ground source heat pump system, and the effective thermal conductivity of the environmental soil is an important parameter affecting the underground heat transfer. To further investigate the impacts of mesoscopic structural parameters on the effective thermal conductivity of soil, this paper proposes three random fractal structures and applys lattice Boltzmann method to simulate the heat transfer procedure in the soil-like porous materials. By comparing and analyzing the simulation results with the experimental findings which are derived from thermal probe tests, it is found that porosity is still the dominant factor that affects the effective thermal conductivity of dry soil, while the impacts of fractal dimension and size ratio are minor. The randomness of phase distribution in the dry soil does have considerable effect on the variations of effective thermal conductivity. A slight change of the particle distribution can lead to a difference up to 24.5%.

Key words: porous media, fractal, thermal conductivity, heat conduction, lattice Boltzmann method, thermal probe

中图分类号:

TK 521.2

徐国稳, 李坤, 蒋祎璠, 黄明骏, 房东旭, 蔡姗姗. 三类随机分形结构下干土壤有效热导率的介观研究[J]. 化工学报, 2019, 70(7): 2496-2502.

Guowen XU, Kun LI, Yifan JIANG, Mingjun HUANG, Dongxu FANG, Shanshan CAI. Mesoscopic study on effective thermal conductivity of dry soil under three types of random fractal structures[J]. CIESC Journal, 2019, 70(7): 2496-2502.

图/表 6

参考文献 31

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组别	粒径/mm
组别	0.6~0.8	0.8~1.0	1.0~1.5	1.5~2.0	2.0~2.5	2.5~3.0	3.0~3.55	3.55~4
1	218.5	48.6	117.6	113.7	110.8	108.6	117.4	94.7
2	415.9	49.1	104.5	88.1	77.6	70.1	70.7	53.9
3	573.8	39.7	79.4	62.5	52.3	45.4	44.2	32.7

组别	粒径/mm
组别	0.6~0.8	0.8~1.0	1.0~1.5	1.5~2.0	2.0~2.5	2.5~3.0	3.0~3.55	3.55~4
1	218.5	48.6	117.6	113.7	110.8	108.6	117.4	94.7
2	415.9	49.1	104.5	88.1	77.6	70.1	70.7	53.9
3	573.8	39.7	79.4	62.5	52.3	45.4	44.2	32.7

组别	密度/(kg?m^-3)	孔隙率	分形维度数	粒径比
1	1125	0.370，0.414，0.433	2.1	5
2	1125	0.370，0.414，0.433	2.5	5
3	1125	0.370，0.414，0.433	2.7	5

组别	密度/(kg?m^-3)	孔隙率	分形维度数	粒径比
1	1125	0.370，0.414，0.433	2.1	5
2	1125	0.370，0.414，0.433	2.5	5
3	1125	0.370，0.414，0.433	2.7	5

组别	孔隙率	实验结果/ (W?(m?K)^-1)	数值结果/(W?(m?K)^-1)			相对误差/%
组别	孔隙率	实验结果/ (W?(m?K)^-1)	MCF多边形	MCF圆形	QSGS&MCF	MCF多边形	MCF圆形	QSGS&MCF
1	0.370	0.1573	0.1466	0.1447	0.1754	6.80	8.03	-11.51
	0.414	0.1472	0.1238	0.1181	0.1440	15.87	19.79	2.17
	0.433	0.1480	0.1126	0.1115	0.1296	23.91	24.66	12.43
2	0.370	0.1574	0.1489	0.1462	0.1794	5.38	7.11	-13.98
	0.414	0.1544	0.1232	0.1222	0.1514	20.18	20.86	1.94
	0.433	0.1521	0.1167	0.1164	0.1296	23.28	23.44	14.79
3	0.370	0.1673	0.1444	0.1486	0.1825	13.68	11.17	-9.09
	0.414	0.1563	0.1236	0.1259	0.1468	20.93	19.42	6.08
	0.433	0.1558	0.1168	0.1122	0.1388	25.01	27.98	10.91