Design, Construction and Commissioning of an Apparatus for Measuring the Thermal Conductivity of Geothermal Grouting Materials Based on the Transient Hot Wire Method

Abstract

The aim of the present study is to develop an apparatus for the measurement of the thermal conductivity of geothermal grouting materials. The apparatus, named MCT, is designed and constructed as a direct application of a mathematical model of heat transference for conduction in an infinite homogeneous isotropic medium using a linear heat source of infinite length, infinitesimal radius and radial heat flow. This application is known as the transient hot wire method. The apparatus mainly consists of a hot wire, a power supply, a temperature sensor and a datalogger. The commissioning of the developed apparatus is carried out by means of the calibration of the temperature sensor, as well as measurements of thermal conductivity using four reference samples whose thermal conductivity is known. Each of the reference samples is formed of two solid rectangular prisms of the same material and of the same dimensions. MCT is precise and accurate. In good experimental conditions the uncertainty of the measurements is within 10%. In addition, the MCT apparatus is light and with reduced dimensions.

Keywords

• transient hot wire method
• thermal conductivity
• geothermal grout