Contactless, non-intrusive core temperature measurement of a solid body in steady-state

Abstract

Accurate measurement of temperature is critical for understanding thermal behavior and monitoring safety and performance of engineering systems involving heating and cooling. While a number of methods are available for measurement of temperature on the outside surface of solid bodies, there is a lack of contactless, non-invasive methods for determining temperature inside solid bodies. Development of such methods is likely to impact a wide range of engineering systems. This paper describes and validates a method for measurement of internal temperature of a solid body based on measurement of the temperature distribution on its outside surface. A theoretical model is developed for determining the core temperature of a cylinder based on surface temperature measurement. This method is validated by determining the core temperature of a thermal test cell using infrared temperature measurement on the surface, and comparing with measurements from an embedded thermocouple. The two measurements are found to agree well with each other in a variety of heat generation and cooling conditions. While this validation is presented for a cylindrical body, the method lends itself easily to bodies of other shapes. This work contributes towards fundamental thermal metrology, with possible applications in a wide variety of engineering systems.

Non-invasive, transient determination of the core temperature of a heat-generating solid body

“…A number of heat generation rates and external cooling conditions are investigated. Radial thermal conductivity k r is obtained from a past measurement15 on the same thermal test cell using an adiabatic heating method where the thermal response of the cell to external heating is used to determine its thermal properties19. Heat capacity C p is determined from the mass-weighted average of heat capacities of individual material components of the thermal test cell.…”

“…Experimental uncertainty in the core temperature arises primarily from uncertainties in measurement of heat generation Q , radial thermal conductivity k r , and surface temperature field T 0 ( θ , t ) Uncertainty in heat generation rate is expected to be very small since it is measured electrically using precise measurement instruments. Based on error propagation analysis26 in experimental measurement of thermal conductivity k r carried out in the recent past1519, the uncertainty in thermal conductivity measurement has been estimated to be ±5%19. This represents the expected uncertainty in the thermal conductivity measurement due to propagation of errors involved in measurement of quantities needed for determining thermal conductivity.…”

“…Joule heating provides the advantage of close control of heat generation rate through the input electric current, and of varying heat generation as a function of time. Fabrication of the test cell has been described in detail previously15. In brief, a thin metal foil, insulated with Kapton tape is rolled around a thin rod and inserted inside a metal casing.…”

“…The accuracy of infrared based temperature measurement is strongly dependent on the quality of calibration. In this case, the same calibration settings established in past experiments are used15, and experiments are carried out to track the known temperature of a surface as a function of time with the infrared camera. An Instec HCS662V thermal stage is used for this purpose.…”

“…A method for determining the steady-state core temperature of a solid body was recently developed15 based on measurement of the surface temperature distribution of the solid body in steady state. However, this technique was capable of determining only the steady-state core temperature, whereas the transient variation of the core temperature is often much more critical for several reasons.…”