Temperature Measurement Using Multispectral Radiation Thermometry And The Apparent Radiation Characteristics For Semitransparent Medium

Temperature measurement includes contact measuring directly and thenoncontact method. At present, the thermocouple or other types of contactthermometers are very commonly used to measure the surface temperature inengineering applications. It can be convenient and efficient under many simplesituations. However, in some process, contact temperature measurement methods areunsatisfactory, it may be inefficient or even ineffective for time-depend temperaturemeasurement, lead to a large error in results for the contact between thethermocouple and the target to be measured will change the temperature distributionpartly and the contact methods are not sensitive to the variation in temperature. Thenoncontact method can determine the temperature accurately based on analyzing thecorrelativity between the apparent information of the medium and the temperaturedistribution as well as the material property, as the noncontact method does nothingto the physical or chemical affects to the medium.It is always a problem and causes much difficulty determining the temperaturedistribution inner the semitransparent medium, the noncontact temperaturemeasurement can solve the problem efficiently to some extent by simulating thetransfer process in the semitransparent medium and analyzing the apparent emissionwhich can obtain the temperature of the medium.This paper inferred the surface temperature as well as the emissivity j ointly ofthe thermal radiation target utilizing least-square technique applied to MultispectralRadiation Thermometry (MRT), obtained the best spectral model suitable for MRT.We also simulated the radiation transfer process in the two-dimensionalsemitransparent medium, got the apparent emission characters and inferred thetemperature preliminary. In addition, the vector radiation transfer process inone-dimensional semitransparent medium slab was simulated and the apparentemission was analyzed.The main work includes the following three aspects of investigations.(1) Two mathematical methods are developed to meet the need of MRT: theleast-square linear algebraic equations method and the least-square curve-fit methodbased on the basic theory of thermal radiation and noncontact temperaturemeasurement technique. The inferred temperature is obtained by dealing with thenumerical measured radiation intensities. The best spectral model for MRT isdetermined by comparing the relative error between the inferred and true temperature of the target.(2) Based on the physical model of two-dimensional semitransparent mediumradiation transfer process, the Back Monte Carlo Method (BMCM) for apparentspectral emission is established. The apparent spectral emission of thetwo-dimensional semitransparent medium is statistically gained, the temperature isdetermined by the least-square curve-fit method introduced formerly and the errorbetween the inferred temperature and the true one is analyzed.(3) The one-dimensional medium apparent emission is obtained based on thevector radiation transfer physical model, the influence of the temperaturedistribution, optical thickness, scatting albedo and refractive distribution of themedium is examined.