D3.2 – Ground Source Heat Exchanger design framework

The goal of WP3 is to develop a design framework for novel ground (slinky/earth basket) type shallow heat exchangers. This design framework, based on developing theoretical models of heat transfer and on experimental data, will be implemented in a design- and engineering calculation tool to support the implementation of these new technologies in the market.

The design framework defines the goals of the (thermal and hydraulic) design (especially sizing) of the ground source heat exchanger, as a function of different boundary conditions (building energy demand, soil thermal parameters, required system performance etc.). Moreover, an engineering tool it is aimed at the overall system design and will support the engineer in the choices of heat exchanger technology (vertical, horizontal or earth basket/slinky) and other design parameterizations.

This deliverable describes the overall design process and provides information and procedures for data collection and evaluation. The detailed description of the design process for different types of Ground Heat Exchangers is based on the design of the actual GHEX systems implemented in the demo sites of the Geofit project and includes vertical borehole heat exchangers, shallow slinky heat exchangers and earth basket type heat exchangers.

This deliverable is suited to be implemented in a design handbook or procedure that can be part of an integrated quality control system.

D3.1 – Design methodologies strengths and weaknesses

In this deliverable the main fundamental processes of heat transport relevant to the ground heat exchangers have been described. For the purpose of the project, only heat transport due to conduction will be considered in detail.

There is abundant literature concerning methods to calculate the thermal response of ground heat exchangers and design. Using a few selected references an introduction to analytical and numerical methods is presented. A description of the different implementations of analytical and numerical modeling and design software codes is presented as well.

The different methods are classified for strengths and weaknesses based on criteria including methodology, complexity, number of input parameters required, processes considered, flexibility with regard to geology and parameters relating to the actual ground heat exchanger. The aim has not been to arrive at a ranking, but only at an overview of the capabilities of the codes and the ease or complexity of use. Cost is of course also an important aspect but is currently not included.

Based on the overview of different methodologies and implementations a roadmap for the development of the GHEX engineering tool within the work package has been defined. This roadmap is based on the expertise of the different partners and works from a detailed level, using the results to derive simplified models that can be integrated into a final engineering design tool.

GEOFIT: Poster for the Experiment on GHEX characterization (WP3)

GEOFIT is optimizing compact geothermal heat exchangers systems (GHEX) with a more compact design based on a helix. To help establish heat transfer behavior, experiments are being conducted by consortium partner AIT. This poster shows the objective, approach and set-up for this experiment, which belongs to WP3. The subsequent CFD-simulations based on this experimental data will help establish a reliable engineering design tool for the helically based GHEX systems.