Conductivity Testing

What is a Thermal Conductivity Test?

Formation thermal conductivity is a very important design variable that should be known before attempting to design a commercial geothermal system. Major Geothermal can provide design engineers and other individuals this value by performing a simple 48 hour in-situ thermal conductivity test. The test requires a test bore with a unicoil that has been backfilled appropriately (preferably bentonite grout) and a drill log of the test bore. The test can commence 5-7 days after test bore has been completed. After the 40-48 hour test is complete, data will be analyzed, and a report will be supplied containing the measured formation thermal conductivity, estimated thermal diffusivity, and the undisturbed deep earth temperature. This testing method follows ASHRAE recommended procedures as found in the 2003 ASHRAE Handbook, HVAC Applications, page 32.14.

How the Test is Performed

A borehole is drilled on-site and a test loop is installed using polyethylene pipe and grout. The test borehole and pipe installation are done to full installation standards so they may be used as part of your finished ground source heat exchanger when you decide to proceed with the project.

A detailed drill log is kept to assist in the proper estimating of drill costs as well as conductivity heat transfer. For a specific period of time usually 48 hours, water is pumped through the loop. While water is being pumped, a test measuring water flow and rejected heat is conducted.

The test will provide information about:

Drilling Conditions

The types of soil present

Thermal properties of the soil

Deep earth temperatures

At the end of the testing period, the data collected is analyzed by a team of professionals and a state of the art technical report is generated.