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Our results are compared with what obtained by other authors using the truncated series approximation technique. The comparative analysis demonstrates considerable accuracy and simplicity of the polynomial interpolation technique. For applications, a series of explicit analytical expressions in the polynomial forms are also presented. | Communications in Physics, Vol. 26, No. 4 (2016), pp. 335-343 DOI:10.15625/0868-3166/26/4/8371 CALCULATION OF EFFECTIVE EMISSIVITY OF THE CONICAL BASE OF ISOTHERMAL DIFFUSE CYLINDRICAL-INNER-CONE CAVITY USING POLYNOMIAL INTERPOLATION TECHNIQUE TA VAN TUAN AND NGUYEN QUANG MINH† Center for Systems Engineering and Integration, National Center for Technological Progress † E-mail: lipro.csei@gmail.com Received 03 June 2016 Accepted for publication 10 April 2017 Abstract. We have used the polynomial interpolation technique to calculate effective emissivity of the conical base of isothermal diffuse cylindrical-inner-cone cavities for various cavity parameters such as axial length, aperture radius in the lid and half-angle of the inner cone. Our results are compared with what obtained by other authors using the truncated series approximation technique. The comparative analysis demonstrates considerable accuracy and simplicity of the polynomial interpolation technique. For applications, a series of explicit analytical expressions in the polynomial forms are also presented. Keywords: angle factor, cylindrical-inner-cone cavity, effective emissivity, polynomial interpolation, integral equations. Classification numbers: 78.20.Ci, 42.79.Gn, 02.60.Ed. I. INTRODUCTION The artificial blackbody cavities are widely used in metrology as standard sources of thermal radiation. In radiation thermometry, the effective emissivity is often used to evaluate the difference in radiation characteristics between artificial blackbody and ideal one. In practice, the value of effective emissivity of an artificial blackbody should be as identified with ideal one as possible with a relative uncertainty of 0.01% or less. Since the direct and accurate measurement of effective emissivity is very difficult, therefore the different calculating methods have been used as a primary mode of investigation of blackbody radiation characteristics [1]. Mathematically, the calculation of effective emissivity
