An experimental setup for isobaric heat capacities for viscous fluids at high pressure: Squalane, bis(2-ethylhexyl) sebacate and bis(2-ethylhexyl) phthalate

A high-pressure flow calorimeter has been used to determine highly accurate isobaric heat capacities for different viscous fluids, squalane (SQN), bis(2-ethylhexyl) sebacate (DEHS) and bis(2-ethylhexyl) phthalate (DEHP) from T = (293.15 to 353.15) K and up to 30 MPa. The experimental device was adapted for viscous liquids at high pressure and it can measure heat capacities with an estimated total uncertainty better than 1%. The isobaric heat capacity values were analysed together with their temperature and pressure dependences. In addition, a fitting equation of the experimental molar isobaric heat capacity for these viscous fluids as a function of temperature and pressure was proposed.

► New setup to measure accurate heat capacities under pressure for viscous fluids. ► Highly accurate Cp up to 30 MPa for SQN, DEHS and DEHP are reported. ► A new fitting equation Cp(T, p) obtaining maximum deviations of 0.5% is presented. ► The highest Cp and the most pronounced decrease with pressure are shown for SQN.