Automated high-temperature and high-pressure adiabatic calorimeter for measurements of the fundamental property ([formula omitted]) of fluids for scientific applications. Constant-volume heat capacity of compressed liquids and gases

Abstract

Isochoric heat capacity is a well-recognized tool for the study of internal energy, UV,T, which is directly related with the intermolecular potential function. Therefore, reliable isochoric heat capacity data provides a sensitive test of proposed models for the potential energy function. This paper describes a new automated high-temperature and high-pressure vacuum –type adiabatic calorimeter to precisely measurements of the isochoric heat capacity and phase transitions properties of compressed liquids and gases. New experimental high-temperature and high-pressure CV-apparatus includes automatic control of adiabaticity condition, real-time display of all experimental data obtained on the monitor, storage and processing of experimental results in various text and graphic formats, etc. Automated experimental apparatus under a computer-assisted control system makes it possible to significantly simplify the problem of correcting the measurement process and obtaining experimental information in a processed final form. Developed high-temperature CVV T apparatus capable to measure of the isochoric heat capacity of liquid and gases in the two- and single –phases over a temperature range of 293–453 K and at pressures up to 50 MPa with combined expanded uncertainty of the temperature, pressure, and heat capacity measurements at 0.95 confidence level with a coverage factor of k = 2 of 15 mK, 0.05%, and 1.5 % in the liquid and 2.5% in the vapor phases, respectively. The capability (accuracy and reliability) of the new CVV T apparatus is demonstrated by measuring the isochoric heat capacity of several reference fluids (propanol-1, propanol-2, and water) in the single and two-phase regions.