Directional emittance of dry and moist paper

The directional emittance of dry and moist paper and board samples was measured in two wavelength ranges; the mid-wavelength infrared (MWIR) range and the long-wavelength infrared (LWIR) range. The influence of pulp type, pulp drying, pulp refining, fibre orientation, additives, coating, and observation angle on the emittance of dry paper was examined. The influence of sample moisture and observation angle on the emittance of moist samples was also investigated. The emittance in the LWIR range was higher than the MWIR emittance. The emittance varied with pulp type, especially for TMP, which had a significantly lower emittance compared to the samples made of chemical pulp. The impact of different properties, such as pulp type, refining or coating, was much smaller in the LWIR range than in the MWIR range. Observation angle was found to significantly impact the emittance at angles larger than 60° from the normal direction in the MWIR range, and angles larger than 70° in the LWIR range. The emittance increased with increasing moisture ratio. This increase was most pronounced at low absolute moisture ratios, where an addition of an already small amount of water could impart a large change in emittance. It was found that the emittance and sample moisture could be correlated well using a linear combination of the emittance of dry paper and pure water.

Spectral-Directional Emittance of CuO at High Temperatures

Spectral-directional emittance measurements for cupric oxide (CuO) are presented. The data cover polar angles of 0-84deg from the surface normal, wavelengths between 1.5 and 8μm, and temperatures between 400 and 700°C. The data were generated using a radiometric, direct emission measurement method. The oxide was grown on a very clean, smooth, and mirror-like copper surface, heated in air at 700°C until emission measurements became constant (270h). X-ray diffraction and EDS analyses were performed to characterize the spatial and molecular composition of the copper oxide layer. It is generally found that CuO emittance decreases with increasing polar angle, increases with increasing wavelength, and increases with increasing temperature. Spectral-directional emittance values calculated from the Fresnel relations show good agreement with the measurements up to polar angles of 72deg.