Primary energy that is not transformed into useful work typically takes the form of waste heat. In 2016, rejected thermal energy accounted for over 65 percent of all energy produced in the United States . This presents a need for novel materials to capture this waste heat. When assessing the effectiveness of materials for thermal management the thermal conductivity, or the rate of heat transfer, is a material property that is of utmost importance.
An apparatus to accurately measure thermal conductivity of solids was built for $300 that can allow investigators to simply and cheaply determine this material property. Currently, there are few simple ways to determine the thermal conductivity of a material. Tabulated data is available for values of thermal conductivity for well characterized materials, but this falls short for novel materials. Commercial thermal conductivity meters are specialized equipment and can cost over $10,000.
The apparatus will measure the thermal conductivity of plastic composites (less than about 20 W/mK), by heating one side of the sample at about 25W while allowing the other end of the apparatus to remain at ambient temperature, creating a temperature gradient. The heat flow through the sample and a reference material will be measured at steady state. Thus, the thermal conductivity of the sample can be calculated using the geometry of it and the apparatus. This device makes it possible to screen thermal management materials when it would otherwise be cost prohibitive. Annual United States energy flow chart: https://flowcharts.linl.gov/ (Accessed in April 2018).