Continuous Production of Biodiesel via Supercritical Methanol Transesterification in a Tubular Reactor. Part 1: Thermophysical and Transitive Properties of Supercritical Methanol

In the range of 520-600 K and 100-400 bar, the thermophysical properties of supercritical methanol, which includes density rho, viscosity eta, isobaric heat capacity C-P, and coefficient of thermal conductivity lambda, are calculated according to different methods and the effect of temperature and pressure is also discussed. On the basis of the thermophysical properties, the transitive properties of supercritical methanol flowing in a phi 6 x 1.5 mm round tube, which includes the Reynolds number Re, the Prandtl number Pr, and the film coefficient of heat transfer alpha, are calculated and the change laws of them with temperature, pressure, and velocity are also illustrated. It is shown that all rho, eta, C-P, lambda, Re, Pr, and alpha decrease with the increase of the temperature at constant pressure, but their changing trend is not consistent with the pressure increasing at a constant temperature. rho, eta, and lambda always increase as the pressure increases. C-P, Re, and Pr decrease consistently at 520-540 K and increase first and then decrease at 540-600 K. For alpha, with the increase of pressure, it almost remains stable at 520 K and first increases sharply and then decreases slowly at 530-570 K, but at 580-600 K, it always goes up from the beginning from 100 to 400 bar.