Measurements of isobaric heat capacity of liquid ethanol by using flow calorimetry

Abstract

The isobaric heat capacities of liquid ethanol are measured. Our group constructed a flow-calorimeter in 1996 for measuring specific heat-capacity at constant pressure of liquid refrigerants. The improvement of apparatus is continuously conducted. In 2008, Suzuki reconstructed the apparatus of a flow calorimetry and a stable mass flow rate became possible by introducing plastic accumulators. And isobaric heat capacities of ethanol are measured. The measurements were obtained at 8 points in the temperature range from 280 to 320 K and along a pressure of 500 kPa. The expanded uncertainty(coverage factor of k = 2) for heat capacity is estimated to be from 0.57 % to 0.91 % . We confirmed that the apparatus is able to measure without influence of heat loss and to get the repeatability within the uncertainty. For more careful consideration, we measured for two different samples of ethanol supplied from different manufacturers under the same conditions. Measured values for the different samples agree within the uncertainty each other. The measurements don’t perfectly agree with existing measurements reported by other researchers or derived specific-heat-capacity values from existing equation of state developed by Dillon and Penoncello within the uncertainty. Very careful assessment is requested for the isobaric heat capacity values of liquid ethanol.