Heat capacity of liquid octamethyltrisiloxane (MDM) and hexamethyldisiloxane (MM): Measurement and molecular dynamics study

Abstract

Accurate heat capacity data and models of fluids are necessary to reduce the design margins of engineering equipment. Also, heat capacities are indispensable in the development of high-accuracy equation of state. In this work, liquid heat capacities of Octamethyltrisiloxane (MDM, C8H24O2Si3) and Hexamethyldisiloxane (MM, C6H18OSi2) were obtained with a modified steady-flow calorimeter. Experiments were performed over the temperature range of 313 to 453 K and pressures up to 10 MPa. The expanded relative uncertainty in measurement of heat capacity is less than 0.015. Then, the present experimental heat capacity data were correlated with an empirical model, yielding an average absolute deviation (AAD) of 0.26 % for MDM and 0.38 % for MM. In addition, non-equilibrium molecular dynamics was used to investigate the heat capacity of MDM and MM. The simulation results show not only a reasonable heat capacity’s dependence on temperature but also a high accuracy.