Use of an open photoacoustic cell for the thermal characterisation of liquid crystals

Abstract

In this paper, we describe the use of an open cell photoacoustic configuration for the evaluation of the thermal effusivity of liquid crystals. The feasibility, precision and reliability of the method are initially established by measuring the thermal effusivities of water and glycerol, for which the effusivity values are known accurately. In order to demonstrate the use of the present method in the thermal characterization of liquid crystals, we have measured the thermal effusivity values in various mesophases of 4-cyano-4octyloxybiphenyl (8OCB) and 4-cyano-4-heptyloxybiphenyl (7OCB) liquid crystals using a variable temperature open photoacoustic cell. A comparison of the measured values for the two liquid crystals shows that the thermal effusivities of 7OCB in the nematic and isotropic phases are slightly less than those of 8OCB in the corresponding phases.

Photoacoustic Method for Measurement of Thermal Effusivity of Fe3O4 Nanofluid

“…Photoacoustic methods are known to be useful tools for investigation of thermal parameters for gases, liquids, thin films, and powder materials [4][5][6][7][8][9][10][11]. There has been considerable amount of work based on experimental techniques related to PA spectroscopy [12][13][14][15]. For NPs dispersions at very low concentrations or solid particle loading the sample were effectively treated as transparent one, and Rosencwaig-Gersho (RG) theory could be applied [16].…”

Thermal Effusivity Measurement of Virgin Coconut Oil-Methanol Mixtures using Photoacoustic Technique

“…1. Both the virgin coconut oil and methanol are optically non-absorbers at The photoacoustic signals was detected using an electret microphone and was processed using a lock-in amplifier [7][8][9][10][11][12][13][14] . The amplitude and phase signals were recorded as a function of laser beam modulation frequency for both, empty cell and after filling the cell with the liquid sample.…”

“…Therefore, one can expect that any change in one of these parameters should result in change of the thermal effusivity value [1] . The utility of the photoacoustic (PA) technique for measuring thermal diffusivity or thermal effusivity of materials has been well reported in the literatures [1,2,[7][8][9][10][11][12][13][14] . Among them the open photoacoustic cell detection is easy and simple to construct for measuring the thermal effusivity of liquid sample.…”

Numerical Determination of Thermal-Diffusivity Coefficients of Some Nematic Liquid Crystals in Situ

“…Based on the results obtained from these studies, the technological use of liquid crystals has increased [3,4]. Liquid crystal displays (LCDs) for calculators, computers, watches, and thermometers are common examples of liquid-crystal uses in various applications.…”