Heated Meter Bar Techniques

The heated meter bar technique uses temperature sensors along the constant cross-section lengths of a material of known thermal conductivity to quantify the heat flux to an exposed face. Importantly, careful positioning of the temperature sensors allows for extrapolation of the temperature distribution to the exposed face, allowing a non-contact surface temperature measurement. The technique is elegant in its simplicity and, by offering simultaneous and non-contact measurement of surface heat flux and surface temperature, it has been used in a myriad of thermal fluid science studies over the past century, ranging from pool boiling to thermal interface materials. While the heated meter bar technique is simple in principle, some associated pitfalls must be avoided, especially considering the wide range of research areas where the technique can be applied. Particularly, since each application requires a bespoke design, there are countless combinations of design configurations, geometries, heat fluxes, operating temperatures, instrumentation options, accuracy requirements, and other aspects that must be addressed when designing a heated meter bar system. Of particular importance is the accurate quantification of the experimental uncertainty. This chapter addresses the approaches and techniques for the accurate quantification of heat flux and surface temperature using the heated meter bar technique. The foundation of the chapter is a new Monte Carlo technique for accurate and robust characterization of the experimental uncertainties related to the approach. A “design for uncertainty” approach is discussed whereby the uncertainty analysis is implemented at the early-stage design phase. In addition, the overall design process, design guidelines, material selection, fabrication techniques, sensors, and calibration options are discussed. This chapter concludes by discussing two case studies where the technique has been deployed. This chapter is intended to give practitioners the tools required to design, fabricate, calibrate, and use heated meter bars for their unique engineering or research applications. This chapter addresses the approaches and techniques for the accurate quantification of heat flux and surface temperature using the heated meter bar technique. It gives practitioners the tools required to design, fabricate, calibrate, and use heated meter bars for their unique engineering or research applications. One measurement method that has been extensively used by the heat transfer community for characterizing thermal resistance and related properties is the heated meter bar technique. The heated meter bar technique (HMBT) is a function of several measured variables, each with its own level of uncertainty. In order to estimate the uncertainty of the thermal resistance, the error associated with the extrapolated temperature and the heat flux must be determined. The specific thermal resistance of thermal interface materials is measured by the HMBT apparatus. Thus, the precision and accuracy of these measurements depend on a variety of factors, including heat flux, contact area, meter bar length, meter bar thermal conductivity, sensor locations, sensor size, and sensor accuracy and precision.