Thermal conductivity measurement of liquid materials by a hot-disk method in short-duration microgravity environments

The thermal conductivities of silicone oils with various viscosities and mercury were measured by a hot-disk method in short-duration microgravity environments. The thermal conductivities of silicone oil with low viscosity were affected by the thermal convection on the ground, but the thermal convection was suppressed in microgravity. The thermal conductivities of highly viscous samples were not influenced by thermal convection. The thermal conductivity of mercury measured in microgravity was about 3% lower than that measured on the ground around room temperature. The thermal conductivity measurement conditions on the ground and in microgravity for which there was no influence from thermal convection could be estimated by using the Rayleigh number.