Design, fabrication and analysis of an instrument to measure thermal conductivity of liquids and phase change materials using a thermoelectric device

Abstract

The determination of the thermal properties of liquids is very important in many fields of engineering (energy industry, refrigeration, pharmaceuticals, etc). The aim of this work is to develop a measurement system to determine thermal conductivity, thermal diffusivity, and specific heat of materials in liquid state. This instrument uses a thermoelectric device and impedance spectroscopy measurements. The apparatus aims to be able to determine that three thermal parameters in only one measurement without being too much expensive and not using very complex components. It consists of an small container attached to the upper ceramic part of a thermoelectric device in which the liquid sample is placed. The lower part of the device is soldered to a heat sink. The thermal properties of liquids (water, luzar antifreezer and diethylene glycol) were determined by impedance spectroscopic measurements. Total uncertainties of <8.6% for thermal conductivity, <6.3% for thermal diffusivity and <6.1% for specific heat capacity were obtained, which positions the new instrument as a good alternative to the currently used methods. Subsequently it is extended to phase change materials. First, the behaviour of the material in liquid state is studied by obtaining its properties. Later it has been observed what happens to the material when it changes from a liquid to a solid state by using the same device.