PHOTOTHERMAL TECHNIQUE FOR MEASURING THERMAL CONDUCTIVITY AND DIFFUSIVITY OF NANOFLUIDS: A NEW APPROACH

Nanofluids have become nowadays of special importance because of their different uses in industry, therefore, to propose methods to calculate their thermal properties would be useful. In this work, a new variant for the calculation of thermal conductivity and diffusivity of nanofluids is proposed; the possibilities and limitations of this non-stationary method, which uses light radiation as the heat source, are studied. Here, the light is homogenously incident on one of the end surfaces of a cylinder that has a thermally insulated side surface, setting the temperature at the other end to a constant value, then the temperature distribution is obtained as a function of the coordinate and time; adjusting the theoretical model, parabolic heat diffusion equation, to the experimental data obtained. The conditions of validity of the method to measure thermal diffusivity and thermal conductivity of fluids are analyzed; as well as, the way in which it could be used to verify the validity of the Hamilton and Crosser (HC) model in the case of nanofluids. Currently, nanofluids are used to exchange heat, as they have been found to exceed the potential of conventional refrigerants; however, the calculation of thermal properties still does not offer definitive values.

Thermal Lens Microscopy: Characterization and Optimization

Thermal lens microscopy (TLM) is a highly sensitive photothermal technique, and has found various applications in chemical analysis, especially when it is combined with lab-on-a-chip chemistry. In this paper, we analyze a couple of key characteristics of TLM, and give suggestions for optimization of the system for higher detection sensitivity, lower noise, lower irradiation density and/or better temporal and spatial resolutions. This will advance the development of TLM instrument for different chemical and biochemical analyses.