Simulation of novel bionic tree-shaped ground heat exchanger to mitigate thermal short-circuiting

doi:10.11949/0438-1157.20201572

Abstract

Abstract:

The thermal short-circuiting problem between adjacent buried pipes is the key factor to restrain the efficient and sustainable operation of ground heat exchanger (GHE). In this paper, based on the constructal theory, a novel bionic tree-shaped GHE is proposed to solve the thermal short-circuiting problem and improve performance of GHE. The thermal performance and comprehensive performance of the bionic tree-shaped GHE were simulated by Fluent, and a comparison between the bionic tree-shaped GHE and serpentine GHE was conducted. The feasibility of the bionic tree-shaped GHE for solving the thermal interference problem of adjacent buried pipes and improving the system efficiency was analyzed. The results indicated that the new bionic tree-shaped GHE can effectively mitigate the thermal short-circuiting problem of adjacent buried pipe and avoid local heat accumulation. Meanwhile, the uniformity of soil temperature was improved. Furthermore, when the inlet velocity is in the range of 0.4—1.2 m/s, the comprehensive performance of bionic tree-shaped GHE is obviously better than that of serpentine GHE, with a value of 33.4%—38.3%.

Key words: thermal short-circuiting, fractals, bionic tree-shaped ground heat exchanger, thermos-fluidic performance, numerical simulation, CFD

摘要：

抑制相邻地埋管热短路问题是提升其换热性能和保持可持续运行的关键。针对地埋管换热器运行过程中相邻管路热短路问题，借鉴构型理论与仿生学理论，提出新型仿生树状结构地埋管换热器。利用Fluent模拟仿生树状地埋管换热器的换热和综合性能，并与传统蛇形地埋管换热器性能对比，分析仿生树状地埋管换热器对于解决相邻地埋管热干扰问题和提高系统效能的可行性。研究结果表明：新型仿生树状地埋管换热器可有效改善相邻埋管热短路问题，避免局部热量堆积，提高土壤温度的均匀性。同时，在进口流速0.4～1.2 m/s范围内，仿生树状地埋管换热器的综合性能明显优于蛇形管地埋管换热器，高33.4%～38.3%。

关键词: 热短路, 分形, 仿生树状地埋管换热器, 流动换热性能, 数值模拟, CFD

CLC Number:

TQ 028.8

XU Lingling, PU Liang. Simulation of novel bionic tree-shaped ground heat exchanger to mitigate thermal short-circuiting[J]. CIESC Journal, 2021, 72(S1): 134-139.

徐玲玲, 蒲亮. 基于热短路问题的仿生地埋管换热器模拟[J]. 化工学报, 2021, 72(S1): 134-139.

Figures/Tables 6

Fig.1 Schematic diagram of novel bionic tree-shaped GSHP system

Table 1 Thermophysical properties of material

材料

密度/(kg/m³)

比热容/

(J/(kg·K))

热导率/

(W/(m·K))

Fig.2 Comparison of experimental and numerical simulation results of horizontal serpentine GHE

Table 2 Thermal influence range of different GHEs along x/y/z direction

换热器	S_x/m	S_y /m	S_z /m
仿生树状地埋管换热器	5	2.6	5.3
蛇形管地埋管换热器	1.6	2.5	4.8

Fig.3 Variations of Nusselt number and comprehensive performance factor with increase of inlet velocity with two GHE这a—仿生树状地埋管换热器;b—蛇形管地埋管换热器

Fig.4 Variations of comprehensive performance factor and Nusselt number with the increase of bifurcation number

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