Determination of thermal conductivity, thermal diffusivity, and specific heat of liquids using a thermoelectric module

Abstract

Managing heat through working fluids is essential in many applications, as well as the development of new fluids with improved properties. Therefore, the characterization of their thermal properties, which is usually a laborious task, is necessary to design and model new thermal systems. In this study, we show the proof of concept of a new method capable of determining the thermal conductivity, thermal diffusivity, and specific heat capacity of liquids from a single simple measurement, provided their density is known (a property easy to measure). The method is based on the use of a thermoelectric module, which is soldered to a large copper block at one side (heat sink). At the other side, the liquid is added on top of the ceramic external layer of the module. By means of impedance spectroscopy measurements, it is demonstrated for three liquids (water, Luzar, and diethylene glycol) that their thermal properties of can be obtained. In order to do this, a new equivalent circuit was developed to account for the new boundary conditions of the measuring setup. Random and systematic errors were calculated and combined to obtain a total uncertainty <8.6% for the thermal conductivity, <6.3% for the thermal diffusivity, and <6.1% for the specific heat capacity. The reasonably low uncertainties obtained position the new method as a low-cost alternative able to provide the three key thermal properties of liquids from one single measurement and only using a single setup.