The Prawtech Terra FUTURA series geothermal probe forms a component of the ground heat source system for ground source heat pumps. The heat exchanger consists of a plastic geothermal head forming a monolithic unit with HDPE 100 RC pipes. The probe has been designed to optimise the installation process of the heat exchanger into the borehole and to increase the operational safety of the ground heat source installation. The modern probe manufacturing technology is based on the highest quality raw materials and continuous quality control of production and logistics processes.
The Terra FUTURA head has been designed to guarantee ergonomics and safety during installation. The external dimensions of the head reduce resistance when inserting the heat exchanger into the borehole, while the wedge-shaped front of the head facilitates the probe’s passage through individual soil layers and its safe placement at the designed depth, as well as the extraction of drilling fluid from the borehole. An integral part of each Prawtech head is a technical bore with an internal diameter of DN=30 mm, used for axial application of the heat exchanger into the borehole, parallel to the drilled hole. The probe head optionally enables bottom-up grouting and filling of the annular space of the borehole. The PRAWTECH probe head has a monolithic design and is produced entirely during an automated manufacturing process.
The Terra FUTURA geothermal probe is available as standard in two pressure series:
● Pn 12.5 (SDR 13.6): the maximum permissible depth of the borehole and heat exchanger installation must not exceed 120 metres;
● Pn 16 (SDR 11): the maximum permissible depth of the borehole and heat exchanger installation must not exceed 200 metres; in individual cases, the probe may be used for deeper boreholes following written consultation with a geologist, designer and the manufacturer.
and in two standard sizes:
● 2 x 40mm or 4 x 40mm: probe pipes are made of high-density polyethylene HDPE 100 RC, resistant to crack propagation (Crack Resistant), with an external diameter of 40mm each;
● 2 x 32mm or 4 x 32mm: probe pipes are made of high-density polyethylene HDPE 100 RC, resistant to crack propagation (Crack Resistant), with an external diameter of 32 mm each.
An alternative to the Terra FUTURA probe is the internally ribbed heat exchanger – the LAMELA probe.
The FUTURA Lamela geothermal probe has an internally ribbed design. The new heat exchanger structure provides increased hoop strength of the geothermal probe and improves the safety of heat exchanger installation in difficult hydrogeological conditions. The stable operation of the probe in the ground allows the declared service life of FUTURA probes to be achieved over a period of up to 100 years. Depending on the ground conditions (including the Lambda coefficient of the heat exchanger working medium) as well as the effectiveness of filling the annular space of the heat exchanger borehole, the internally ribbed probe may contribute to optimising the heat transfer process between the antifreeze fluid and the ground.
When designing and operating Terra FUTURA Lamela series vertical ground heat exchangers, it is recommended to familiarise oneself thoroughly with the product characteristics, and in particular the unit flow resistances given for internally ribbed probes (see: Terra FUTURA Lamela probe technical data sheet). The ribbing placed in the heat exchanger pipes effectively improves the heat transfer coefficient1, but may simultaneously increase hydraulic resistance for a certain range of fluid flow rates in the pipes (a phenomenon observed particularly in relation to antifreeze systems based on ethylene glycol).
1 Heat transfer (convection) refers to heat exchange between the probe wall and the antifreeze fluid flowing around it. Heat transfer depends on fluid velocity, type, shape and temperature of the heat transfer surface, and thermophysical properties of the glycol. Depending on the type of flow (laminar, turbulent, transitional), the Lamela probe is characterised by a high value of coefficient α compared to a standard heat exchanger with a smooth surface:
α2 ≥ 1.14 α1
where:
α1 – heat transfer coefficient for the FUTURA probe
α2 – heat transfer coefficient for the LAMELA probe.
All PRAWTECH geothermal probes are delivered to the customer only after successfully passing pressure and flow tests in accordance with the in-house quality control procedure.
Each heat exchanger has its own individual serial number.
