Isothermal Flow Calorimeter
Two flow calorimeters are used to measure enthalpies of mixing under isothermal (0 to 150°C) and isobaric (up to 150 bar) conditions. The principle of measurement is to compensate the heat effects and to measure the required power. Two calibrated flow pumps (ISCO) allow to alter the mixture composition. A back pressure regulator provides the opportunity to perform the measurements at higher pressure to prevent evaporation. The accuracy of hE is estimated to be better than 1%. One of the calorimeters additionally provides the possibility to measure heats of mixing for systems composed from high melting substances (Tm < 125 °C). Typical Results are shown in Figure 3 and 4.
Scheme of the device
Fig. 3: Typical hE-results compared with data from literature
Fig. 4: hE-data for a system with miscibility gap at 90 and 50 °C
compared with the mod. UNIFAC (Do) prediction