Isobaric Heat Capacity Measurements of Methanol by Flow Calorimeter at Elevated Temperatures and Pressures

Methanol is the world's recognized renewable, environmentally friendly, efficient low-carbon biofuel and can be widely used in various fields. Based on the new high temperature and pressure flow calorimeter developed in this work, the isobaric heat capacity of fluids can be measured at temperatures T = 298–573 K and pressures up to 15 MPa. The heat loss of the flow calorimeter was calibrated by n-heptane at various temperatures. The isobaric specific heat capacity cp of methanol was measured for temperatures T ranging from 298 to 573 K and pressures p ranging from 0.1 to 15 MPa in both liquid and vapor phases. The experimental data were compared and agreed well with the Helmholtz equation of state (EoS), indicating the average absolute deviation (AAD) of 0.32% and 0.80% for liquid and vapor phases, respectively. A new correlation of heat capacity with temperature and pressure was proposed and used to fit the experimental data of methanol both in liquid and vapor phases, which showed better performance than other models. Based on the new model, our data were able to compare with the available published experimental data, and most data agreed well with our correlation.