Thermal Diffusivity of Isooctane from (298.15–583.15) K and up to 7.5 MPa in the Near-Critical Region by Dynamic Light Scattering

Isooctane is an ideal gasoline component with a high octane number and low volatility. However, there is a lack of research on the thermal properties of isooctane, especially near the critical point. This work uses dynamic light scattering to measure the thermal diffusivity of isooctane in the temperature range of (298.15–583.15) K, along 8 isobaric lines p = (0.1, 2.0, 2.5, 2.7, 3.0, 3.5, 5.0, 7.5) MPa, and analyzes the trend of thermal diffusivity with temperature and pressure. The average relative combined expanded uncertainty of the thermal diffusivity is 0.0214. Meanwhile, the experimental data were compared with the calculated values from thermal conductivity, and the absolute average values of the relative deviation and maximum deviation were 2.88 and 8.22%, respectively.