EFFECT OF TEMPERATURE GRADIENTS ON CALORIMETRIC MEASUREMENTS IN FLUIDS

点击翻译按钮获取中文摘要

Due to the dynamic nature of the scanning process, a temperature gradient exists throughout the fluid samples during scanning calorimeter measurements. As a result, when a scanning calorimeter is used to make heat-capacity measurements, the effect of the lagging temperature gradient in the sample distorts the output when a phase transition occurs. Over the years, several schemes have been developed to correct this distortion; to date, however, no one has attempted to quantitate the temperature gradient in the sample and determine its actual relationship to the measured output. We have developed detailed, two-dimensional RC models of several calorimeter designs, and have evaluated the dynamic temperature gradients in the fluid samples during the measurement process, using a commercial circuit-simulation (SPICE) program. These analyses have both revealed the source of several temperature gradient-induced errors in the measurements, and allowed us to redesign and re-evaluate new calorimeter designs in software before they are constructed, in order to reduce the magnitude of these errors.