Experimental and molecular dynamics study on the thermal conductivity of Octamethyltrisiloxane (MDM)/Decamethyltetrasiloxane (MD2M) mixtures

Octamethyltrisiloxane (MDM)/Decamethyltetrasiloxane (MD₂M) mixtures are considered one of the most suitable working fluids for high temperature Organic Rankine Cycle (ORC) systems and heat pump. As a critical thermophysical property, thermal conductivities of liquid siloxanes are important to understand heat transfer characteristics. In this study, thermal conductivities of MDM/MD₂M mixtures (with MDM mass fraction w_MDM = 0, 0.30, 0.50, 0.70, 1.00) were measured using a transient hot-wire method over a temperature range of 263.15–343.15 K and pressures up to 8 MPa. Then, an empirical model was proposed to reproduce the thermal conductivity regarding temperature and pressure, yielding an average absolute deviation of less than 1 %. In addition, the thermal conductivities of the MDM/MD₂M systems were studied using the non-equilibrium molecular dynamics (NEMD) simulation. The predicted values show good consistency with the experimental results, confirming both the accuracy of the established model and the suitability of the selected force field, while offering a dependable computational method for predicting thermal conductivity. This work provides essential data and theoretical support for evaluating the heat transfer performance and selecting working fluids in MDM/MD₂M-based ORC systems.