Case studies

Thermal conductivity probe: what it is and use

The thermal conductivity probe, also known as a thermal needle probe, is one of the most widely used tools to determine the soil’s ability to transfer heat.

The operating principle is simple and effective: the probe, inserted into the ground, acts simultaneously as a heat source and a sensor. By analyzing the rate of heat diffusion in the soil, it is possible to calculate the thermal conductivity, a key parameter for many engineering and environmental applications.

Why measuring thermal conductivity is important

Thermal conductivity represents a material’s ability to transfer heat. It is a key property in the design of underground infrastructures, as it directly affects heat dissipation.

This measurement is particularly relevant in several fields:

• installation of underground cable ducts;
• design of geothermal systems;
• environmental and geotechnical assessments;
• photovoltaic systems, especially in installations involving underground components or soil thermal management.

The value is expressed in W/(m·K), a unit that describes the amount of heat transferred through a material.

Measurement methods in field and laboratory

Measurements can be performed directly in situ up to approximately 120 cm depth. Installation is quick: a small-diameter hole is made, the probe is inserted, and the automatic data acquisition procedure is started, lasting only a few minutes.

For deeper investigations, soil samples can be collected and analyzed in the laboratory, still ensuring high accuracy.

Results are displayed immediately in both numerical and graphical form and stored for further processing.

A key parameter for design

The propagation of heat in materials occurs without movement of matter, through energy transfer between areas at different temperatures. This phenomenon depends on several factors, including:

• material properties;
• temperature and pressure;
• geometry and boundary conditions.

Understanding these aspects makes it possible to optimize the design of systems and infrastructures, improving efficiency and safety.