Comparison of Simulated and Actual DSC Heat Flow Rate Measurements for First Order Transitions

摘要

A system of differential equations representing a heat flux DSC is solved and the resultsrnare compared with those obtained from DSC experiments. Two types of first order transitionsrnare investigated: melting of a pure substance and solidification of a pure substance with supercooling.rnThe conventional DSC heat flow rate measurement using only the temperaturerndifference between the sample and reference calorimeters is compared with the same modelrnmeasurement. The heat flow rate measurement method implemented in the TA InstrumentsrnQ1000TM DSC that includes the effects of imbalances and heating rate differences within thernDSC is compared with the model heat flow rate between the sample and pan. During bothrntransitions, the sample heat flow rate predicted by the model is quite different from that obtainedrnusing the conventional DSC heat flow rate measurement. It is shown that the differences are thernresult of simplifications implicit in the heat flow rate measurement based solely on the differencernbetween sample and reference calorimeter temperatures. Heat flow rates measured using thernimproved measurement of the Q1000 DSC agree very well with the model predictions.rnComparison of the model and experimental results and application of the principles of heatrnexchange explains the differences between these results and those of conventional DSC.