Experimental study of opto-thermal parameters of glycerol and ethylene glycol at various temperatures using laser thermal lens spectroscopy

Abstract

One of the important applications of the photothermal effect is laser thermal lens spectroscopy. Using this technique, some opto-thermal parameters of materials such as thermal diffusivity, thermo-optic coefficient (TOC), thermal conductivity, etc. can be accurately measured. In this experimental study the thermal diffusivity of butanol and propanol were measured. The accuracy of our experimental setup was confirmed by comparing with the reference. Then, the experiments were repeated for glycerol and ethylene glycol and measured the thermal diffusivity and thermal conductivity of these samples. A reliable agreement between these results and reference values was observed. Finally, thermal conductivity of glycerol and ethylene glycol at various temperatures was studied. These results show that thermal conductivity increases (from 0.2805 to 0.2865 W/mK for glycerol and from 0.246 to 0.275 W/mK for ethylene glycol) with increasing temperature (from 25°C to 90°C). Also, TOC and \(\frac{dn}{dQ}\) of these samples were measured at the beam waist of 25 µm and laser energy of 100 mJ.