Total hemispherical emissivity of glass sheets with different thicknesses measured by a transient calorimetric technique

Total emissivity of glass sheets varies with sheet thickness since glass is a semitransparent material. The total hemispherical emissivity, epsilon(h), of fused-silica and soda-lime glass sheets of different thicknesses was measured by a transient calorimetric technique previously proposed. The measured epsilon(h) values are arranged together with those of borosilicate glass sheets reported in our previous work. The epsilon(h) values obtained for various sheets are expressed as functions of sheet thickness and temperature. Further, the Eh values are compared with other published data obtained by experiments and theory, and discussed. An edge effect caused by the temperature distribution on the specimen surface, is clarified and the error involved in the epsilon(h) values measured by the transient calorimetric technique, is estimated. In addition. another edge effect caused by the distribution on the local total hemispherical emissivity on the specimen surface is made clear.