Thermal Diffusivity of Liquids Determined by Flash Heating of a Three-Layered Cell. Report No. 79-10

摘要

An investigation of the applicability of the flash method and a three-layered cell for determining the thermal diffusivity of liquids at temperatures between their melting and boiling points is described. Two different cell designs were developed for containing a liquid as the central layer - one involving brazing and the other bolted flanges. Test units were fabricated from stainless steel 304. Experiments were conducted with water and a high temperature heat transfer salt known as Hitec. Thermal diffusivity values were calculated by comparison of rear surface temperature measurements with the one-dimensional transient temperature variation in a three-layered cell subjected to an exponential heat pulse at the front surface. This procedure requires accurately known thermal properties of the cell walls. Thermal diffusivity results for water obtained with two brazed cells and one bolted cell were all within +- 1.0% of standard reference values. Results at the same temperature obtained for Hitec with two brazed cells were within +- 2.5% of each other over the temperature range of 149 to 427 exp 0 C. Although lower by about 16% at 149 exp 0 C, experimental values approached those given by the manufacturer at the upper end of the temperature range. (ERA citation 05:006033)