A Technique for Measuring an Unsteady Temperature Distribution in a Liquid using Holographic Interferometry

Abstract

An application of a holographic interferometry technique was demonstrated for measuring the steady and unsteady state temperature distributions in two liquids, water and n-propanol. The deflection and temperature errors caused by refraction, which is the most important source of errors within a steep temperature gradient field such as the thermal boundary layer, were discussed and estimated. Estimated errors in the measured temperature of the liquid phase under spreading flame conditions for a 0.5cm path length of n-propanol with 250°C/cm temperature gradient are within 2%. The technique required : (1) transparency of the liquid and (2) availability of the relation for the thermooptic coefficient of the liquid with temperature. If these requirements are satisfied, the temperature distribution within the liquid phase can be measured with a spatial resolution of as high as 20μm.