Papers by Keyword: Spectral Emissivity

Abstract: Optical parameters become to the features that are currently taken into account more frequently. There are various reasons of dealing with those parameters. Some of them are due to thermal calculation purposes while the other one are trying to consider low-emissivity functions of various innovative building materials. The paper is focused on spectral emissivity analysis of roof membranes and vapor barriers especially that are applied in sloped roofs and walls with air ventilated cavity. The spectral emissivity in the longwave radiation region was assessed by laboratory method of an infrared spectroscopy. The results present courses of spectral nature as well as its transformation into weighted values. As a result the final comparison demonstrates facts of aiming to point out the possibility of receiving any benefit for thermal aspects purpose.

Abstract: In the spectral emissivity measurement of material, one domain uncertainty source is the measurement of the actual sample surface temperature. This paper presents a novel method on heating the sample—the four channel hot air heating method, with the purpose of making sure that the heat flux is nearly equal to zero inside the sample, which is essential for the low thermal conductive materials. So the temperature difference between the sample surface and inside can be neglected. The FEA (Finite Element Analysis) method, through using FLUENT, was adopted to numerically simulate the temperature profile of the new heating system. The simulation results showed that temperature profile at the direction of X in ±15 mm ranges at the central area of exits of the air-guide duct is almost at ±5°C and at the direction of Y in ±15 mm ranges is nearly ±10°C. The temperature profile was experimentally studied by using thermocouples, the numerical simulation and experimental results were in good coherence.

Abstract: In order to eliminate the temperature difference between center measurement points and surface temperature of the material samples with low thermal conductivity, this paper introduces a new hot airflow double-sided heating method for sample, and describes its principle, application, and the impact of the existing and novel methods on the measurement results of spectral emissivity. Also, we analyze and compare the results of two different samples obtained with these two heating methods. The new method for material samples with low thermal conductivity has outstanding advantages and potential applications.

Abstract: In this article we present the testing, evaluation of infrared radiation properties of polycrystalline materials especially as cordierite-based glass-ceramics. Researches aim to make a comprehensive and systematic exposition of emissivity definition, test principles and test methods. And on the basis of measurement results of the infrared emissivity of cordierite-based glass-ceramics, the Infrared radiation property of this polycrystalline material was discussed. Research has a positive significance on the development of the infrared radiation heating and drying materials.