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清华大学学报(自然科学版)  2015, Vol. 55 Issue (1): 14-20    
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能源桩热响应测试的模拟及适用性评价
郭红仙(),李翔宇,程晓辉
Simulation and applicability of thermal response tests in energy piles
Hongxian GUO(),Xiangyu LI,Xiaohui CHENG
Department of Civil Engineering, Tsinghua University,Beijing 100084, China
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摘要 

该文旨在分析基于钻孔埋管换热器的热响应测试(thermal response tests, TRT)测试用于桩基埋管换热器时的通用性与局限性。首先选用不同的分析模型进行温度响应的计算与比较,并选用包含流体对流换热的有限元模型(FEM),模拟了不同桩径、不同埋管形式以及不同加热功率的能源桩TRT。计算表明:用于钻孔埋管的TRT测试同样适用于能源桩,但随着桩径的增大,测试所需的最短时间变长;桩内埋管数量的增加和加热功率的提高也不能缩短测试时间。通过模拟北京CFG(cement fly-ash gravel)桩的TRT测试,有限元模型得到了验证。该试验表明:能源桩TRT测试的加热功率不宜过大。对直径大于400 mm的能源桩,TRT测试时长>100 h,测试条件不易保证,建议采用原位钻孔取样后实验室测试的方法获取岩土热物性参数。

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关键词 地源热泵(GSHP)能源桩热响应测试(TRT)传热模型测试时长    
Abstract

Thermal response tests (TRT) are used to investigate the thermal properties of the ground for dimensioning borehole heat exchangers. This study analyzes the versatility and limitations of TRT in energy piles. Several analytical solutions are presented for the temperature response of the borehole system with a finite element model (FEM) used to study the effect of convection for different pile diameters, different types of pipes and different heating powers. The results show that the TRT tests can be used in energy piles but the minimum duration of the tests increases with increasing pile diameter, while the types of pipes and the heating power have no effects. The accuracy of the FEM model was verified by simulations of Beijing TRT tests on CFG (cement fly-ash gravel) piles with the results indicating that the high heating power is not appropriate. TRT tests may take hundreds of hours for large diameter piles (larger than 400 mm); thus, lab tests for the thermal parameters are suggested using undisturbed borehole samples.

Key wordsground source heat pumps (GSHP)    energy piles    thermal response test (TRT)    heat transfer model    test duration
收稿日期: 2014-03-20      出版日期: 2015-05-15
基金资助:清华-MIT-剑桥三校低碳大学联盟基金资助项目(300907001)
引用本文:   
郭红仙,李翔宇,程晓辉. 能源桩热响应测试的模拟及适用性评价[J]. 清华大学学报(自然科学版), 2015, 55(1): 14-20.
Hongxian GUO,Xiangyu LI,Xiaohui CHENG. Simulation and applicability of thermal response tests in energy piles. Journal of Tsinghua University(Science and Technology), 2015, 55(1): 14-20.
链接本文:  
http://jst.tsinghuajournals.com/CN/  或          http://jst.tsinghuajournals.com/CN/Y2015/V55/I1/14
  不同热源解析模型的温度响应计算
  TRT测试的有限元模型示意图
  桩基埋管截面示意图
算例 几何参数
l/m d/mm D/mm dout/mm din/mm
1 30 150 120 25 20
2 30 600 400 25 20
3 30 800 600 25 20
  桩基埋管几何参数

参数
热导率/(W·m-1·K-1) 密度/(kg·m-3) 热容/(kJ·kg-1·K-1) 流量/(m3·h-1) 加热功率/(W·m-1)
λs λc ρs ρc cs cc Q q
取值 2.0 1.5 2 000 2 400 1.0 0.96 0.6 70
  桩基埋管换热数值模拟参数取值
  不同桩径的能源桩TRT测试进出口平均水温模拟结果
  埋管布置示意图
  不同埋管形式的能源桩TRT测试模拟结果
时间/h 计算综合热导率/(W·m-1·K-1)
1U埋管 2U埋管 3U埋管
3D FEM 2D FEM ILS 3D FEM 2D FEM ILS 3D FEM 2D FEM ILS
10 48 2.69 3.80 3.19 3.10 3.80 3.19 3.16 3.80 3.19
120 240 2.08 2.14 2.13 2.17 2.14 2.13 2.10 2.14 2.13
222 322 2.06 2.08 2.08 2.11 2.08 2.08 2.06 2.08 2.08
222 422 2.06 2.07 2.07 2.10 2.07 2.07 2.07 2.07 2.07
  不同埋管形式的桩基TRT测试取不同时段计算的综合热导率
  不同加热功率的能源桩TRT测试模拟结果
时间/h 计算综合热导率/(W·m-1·K-1)
q=
70 W·m-1
q=
117 W·m-1
q=
210 W·m-1
48 222 2.18 2.18 2.18
222 422 2.07 2.07 2.07
  3D FEM中不同加热功率计算的综合热导率
  北京CFG桩埋管位置图
深度 各土层
土样
描述
热物参数
m 密度 热容 热导率
g·cm-3 J·kg-1·K-1 W·m-1·K-1
0~1.3 素填土层 2.00 2.00 1.50
1.3~3.9 砂质粉土 1.93 1.21 1.67
3.9~4.4 粉质粘土 1.92 1.37 1.58
4.4~6.3 砂质粉土 1.97 1.21 1.67
6.3~14.2 卵石 2.50 0.78 2.20
14.2~16.3 粉质粘土 2.04 1.37 1.58
16.3~18.1 砂质粉土 2.03 1.17 1.64
18.1~20.0 卵石 2.50 0.78 2.20
  原状土样热物参数测定结果
  北京CFG桩TRT测试模拟结果(直角坐标)
  北京CFG桩TRT测试模拟结果(对数坐标)
时间/h 数据
来源
计算综合热导率/(W·m-1·K-1)
q=
97 W·m-1
q=
120 W·m-1
q=
194 W·m-1
77 96 3D
FEM
1.72 1.72 1.72
试验 1.08 1.88 4.67
77 120 3D
FEM
1.57 1.57 1.57
试验 1.71 8.86
  北京CFG桩TRT测试的热导率计算
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