Measuring the thermal conductivity of heat transfer fluids via the modified transient plane source (MTPS)

Heat transfer fluids are often a critical performance component in industrial processes and system design. Fluids are used in heat dissipation to maintain stable operating temperatures in a variety of applications, such as diesel engines, chemical production, asphalt storage, and high-power electric transformers. A wide range of fluids specific to various applications are available, thus a reliable and accurate thermal conductivity characterization is extremely important. Thermal conductivity analysis of heat transfer fluids with traditional methods is time-consuming and error-prone due to the impact of convection. Convection often distorts effective thermal conductivity measurement as an additional source of heat transfer. The modified transient plane source method implemented in the C-Therm Technologies TCi Analyzer provides an easy way to accurately measure the thermal conductivity and distinguish this form of heat transfer in negating the impact of convection by (a) employing the shortest test time in commercially available sensors (0.8 s), (b) offering a minimal sample volume requirement (1.25 mL), and (c) employing a low-energy power flux to the specimen under test (approximately 2,600 W m(-2)). This work presents thermal conductivity results generated on three types of heat transfer fluids over a wide temperature range and discusses the significance of the data in relevance to the application.