Dataset supporting publication: "Geofit: Experimental Investigations and Numerical Validation of Shallow Spiral Collectors as a Basis for Development of a Design Tool for Geothermal Retrofitting of Existing Buildings"

Dataset supporting publication: “Geofit: Experimental Investigations and Numerical Validation of Shallow Spiral Collectors as a Basis for Development of a Design Tool for Geothermal Retrofitting of Existing Buildings” (publication available in GEOFIT Zenodo)

The H2020 GEOFIT (grant no. 792210) project will implement and demonstrate easy-to-install and economical geothermal systems in combination with heat pumps for energy-efficient building retrofits at five pilot sites across Europe - a historic building (ITA), a school (ESP), an indoor swimming pool (IRL), an office building (FRA) and a single-family house (IRL) (GEOFIT,2018). Heat pump tests and experimental laboratory tests with shallow geothermal heat collector types are carried out in climate chambers at the AIT. Material data of different soil types are determined in the thermophysics laboratory. Furthermore, CFD simulations of the conducted experiments are calculated with ANSYS Fluent. All this provides data and know-how for the development of a design tool for ground collector configurations such as helices and slinky loops, which are particularly relevant for building retrofits in GEOFIT. Experimental work focused on near-surface spiral geothermal heat exchanger configurations that can be installed at a maximum depth of five metres. Real-scale experiments were carried out for vertically oriented spiral collectors (helix) in real soil. One objective was to develop a measurement concept in the laboratory environment to create the framework for a reliable database. This database is used as a basis for the further development or new development of engineering design tools. Distributed resistance temperature sensors and a fibre-optic temperature measurement system (DTS) were used. The moisture content of the soil was recorded using soil moisture sensors. A heat flow was conditioned by means of a helix shaped electric heating cable in a 1m³ cuboid soil container. The measurements were carried out in a climate chamber at a defined constant temperature of 10 °C. The evaluation of the transient response behaviour is spatially resolved. This results in coordinate-related temperature points, which describe temperature gradients in all axes of the container over time. Three different types of soil were investigated. The temperature behaviour of humus soil, sand and a mixture of these was investigated experimentally in smaller experiments and the material data such as heat capacity, thermal conductivity and density were determined thermophysically in the laboratory. Based on this data, a CFD model was developed which can be used to modify the geometry parameters of the helix.

本数据集支撑发表论文《Geofit：作为既有建筑地热改造设计工具开发基础的浅层螺旋集热器实验研究与数值验证》，该论文可于GEOFIT Zenodo平台获取。

H2020框架下的GEOFIT项目（项目编号792210）将在欧洲五处试点场地推广并验证易于安装且经济高效的地热系统与热泵组合方案，用于既有建筑节能改造。试点场地分别为：历史建筑（ITA）、学校（ESP）、室内游泳馆（IRL）、办公楼（FRA）以及独栋住宅（IRL）（GEOFIT,2018）。

奥地利技术研究院（AIT）的气候舱内开展了热泵测试与浅层地热集热器类型的实验室实验。研究团队在热物理实验室中测定了多种土壤类型的材料参数；此外，采用ANSYS Fluent对所开展的实验进行计算流体动力学（CFD）仿真。上述工作均为开发螺旋盘管（helix）、弹簧状环路（slinky loops）等地热集热器构型的设计工具提供了数据与技术诀窍，此类集热器构型正是GEOFIT项目既有建筑改造场景中的核心应用对象。

本实验研究聚焦于最大安装深度可达5米的近地表螺旋式地热换热器构型。团队在真实土壤环境中开展了垂直螺旋集热器（helix）的足尺实验。本研究的目标之一是在实验室环境中构建标准化测量方案，为建立可靠的数据库奠定基础；该数据库将作为工程设计工具进一步开发或全新开发的核心依据。

实验中采用了分布式电阻温度传感器与光纤测温系统（DTS, Distributed Temperature Sensing），并利用土壤湿度传感器记录土壤含水率。通过安装于1立方米长方体土壤容器内的螺旋形电加热电缆调控热流，实验全程在设定恒定温度为10℃的气候舱内开展。

对瞬态响应特性的评估采用空间解析方法，可得到与坐标相关的温度点，进而能够随时间推移描述容器各坐标轴方向的温度梯度。本研究共针对三种不同类型的土壤开展实验：腐殖土、砂土以及二者的混合土体。通过小型预实验分别测定了三类土壤的温度特性，并在热物理实验室中测定了其热容、热导率与密度等材料参数。基于上述数据，研究团队开发了可用于调整螺旋盘管几何参数的CFD仿真模型。