Thermal Conductivity of Room Temperature Deep Eutectic Solvents

As deep eutectic solvents (DESs) became a prevalent category of materials, reporting their physical and chemical properties turned to be urgent. In this work, a database of the thermal conductivity of 39 DESs was experimentally investigated in a temperature range of 25 degrees C to 60 degrees C, since this property was not broadly reported yet. Knowing the thermal conductivity is a significant approach to obtain the fluids' heat transfer coefficients, which are essential for fluid heat transfer applications and equipment design. The selection of the reported DESs was based on their liquid phase status at room temperature and commonness. Herein, the thermal conductivity was studied as a function of temperature and compositions. Also, the data were fit with the conventional equations to predict the thermal conductivity value at a certain temperature. The highest R-2 was selected to identify the best behavior with the common types of equations. It was found that the thermal conductivity reduced by raising the temperature, which was attributed to the enhancement that occurred in electrons' randomness and reduction in electrons' free motion. Furthermore, as the temperature rises up, the density decreases, and molecular distance increases. DESs contained choline chloride showed higher thermal conductivity stability than other DESs. While an opposite scenario was noticed for glycerol and ethylene glycol DESs due to the possibility of generating water.