An optical absorption method to deduce the temperature dependence of gas viscosity

This paper demonstrates a method to quantify the viscosity dependence on temperature by using the technique of tunable diode laser absorption spectroscopy (TDLAS). A hollow core photonic crystal fiber (HC-PCF), used as a gas channel, is surrounded by a furnace for temperature adjustment. The path-integral absorbance of gas inside fiber as a function of time during transient is measured by using TDLAS. These measurements under non-isothermal conditions are correlated to the temperature dependence of viscosity, which can be used to infer the constant of the Power Law. The measurement sensitivity depends on the high-temperature length fraction of the fiber. It is shown that 5m fiber length (93% in the furnace) can provide a reasonable measurement resolution based on numerical simulations.