Abstract:

In the application of the deep borehole heat exchanger (DBHE), the pipe array is composed of multiple DBHEs and used for the building heating. In order to study the heat transfer performance of the coaxial DBHE array, a numerical model was established based on the typical geological distribution in Xixian New Area. The influence of the distance between the DBHEs and their distribution patterns was investigated on the thermal interaction and the attenuation of outlet-water temperature during the long-term heating period. The results showed that the ‘cold accumulation’ of rock and soil around the DBHE was the main reason for the decline of the heating capacity of the DBHE array year by year. When the distance between the DBHEs increases from 5m to 25m, the average outlet-water temperature of the DBHE and the heat extraction power increased by 3.86% and 11.5%, respectively. Considering the geological distribution in Xixian New Area, the distance between the DBHEs should be kept above 15m. In the four types of DBHE array distributions (cross, circular, polyline, linear), the straight-line distribution exhibited the smallest attenuation in outlet-water temperature and heat extraction power. The outlet-water temperature of the central DBHE only decreased by 5.74%. In the engineering applications, it is necessary to avoid the overlapping arrangement of DBHEs and ensure that they are arranged in a straight line.

Key words: middle-deep geothermal energy, coaxial deep borehole heat exchanger, pipe array, heat exchange, cold accumulation

摘要：

在中深层地热地埋管（DBHE）供热技术应用中，主要使用多个地埋管构成管群为建筑供暖。为了研究中深层同轴地埋管管群换热性能，本文基于西安市西咸新区典型地质分布，构建了中深层同轴地埋管管群数值模型，研究了不同间距、不同分布下各地埋管换热器间热交互作用以及长期取热期水温衰减规律。结果表明，多井集群供暖过程中周围岩土所形成的“冷堆积”现象是导致地埋管集群供暖能力逐年下降的主要原因；当地埋管间距从5m增至25m，平均出口水温和取热功率分别提升3.86%和11.5%；在西咸新区典型地质条件分布下，地埋管间间距应保持在15m以上；本文提出的四种管群分布中，地埋管呈直线分布时各地埋管出口水温和取热功率衰减最小，其中心地埋管出口水温仅衰减5.74%。在工程设计中，中深层地埋管管群应尽可能直线排布，避免重叠排布。

关键词: 中深层地热, 同轴地埋管, 管群, 换热, 冷堆积