A FLOW CALORIMETER FOR THE MEASUREMENT OF THE ISOTHERMAL JOULE-THOMSON COEFFICIENT OF GASES AT ELEVATED-TEMPERATURES AND PRESSURES - RESULTS FOR NITROGEN AT TEMPERATURES UP TO 473 K AND PRESSURES UP TO 10 MPA AND FOR CARBON-DIOXIDE AT TEMPERATURES UP TO 500 K AND PRESSURES UP TO5 MBA

A new isothermal flow calorimeter for gases at high temperatures and p ressures is described. The calorimeter employs a throttling-capillary tube to provide both the pressure drop and the heating element. Consid erable care was taken to operate the calorimeter in an isothermal envi ronment by use of a fluidized-bed thermostat. The instrument has been used to make measurements of the molar isothermal Joule-Thomson coeffi cient of N-2 at temperatures in the range 295 K to 473 K and at pressu res in the range of 1.0 MPa to 10.0 MPa and also of CO2 at temperature s in the range 300 K to 500 K and at pressures in the range 3.0 MPa to 5.0 MPa. The molar isothermal Joule-Thomson coefficient for NI has be en measured to +/-1 J . MPa(-1). mol(-1) and that for CO2 to +/- 4 J . MPa(-1). mol(-1). Agreement is found with other available experimenta l results and with the predictions made by the IUPAC-approved equation s of state. (C) 1995 Academic Press Limited