• Journal of Welding and Joining
• /
• v.21 no.7
• /
• pp.65-70
• /
• 2003

Thermal emissivity is generally affected by surface situation of material such as roughness. In this study, the effect of surface roughness on measuring thermal emissivity is experimented. And emissivity measurement method and equipment using hemisperical mirror is also reviewed. As the result of this research, thermal emissivity increased as long as increasing surface roughness. So, surface roughness is a essential check point when we measure the emissivity.

• Proceedings of the KSRS Conference
• /
• 2007.10a
• /
• pp.337-340
• /
• 2007

Many researches conducted to investigate the relationship between surface emissivity and surface temperature in the past two decades and pointed out that the emissivity play a key role in applying remote sensing data to retrieve surface temperature. The task of surface temperature estimation is so important in many research fields, such as earth energy budgets, evapotranspiration, drought, global change and heat island effect. Therefore, it is indispensable to develop an effective and accurate technique to estimate the emissivity for accurate surface temperature estimations. This study developed an improved emissivity estimation technique for the use of surface temperature retrievals with MODIS data. The result of applying this improved technique using Band 31 of MODIS shows that the accuracy of estimated surface temperatures will be improved. This study also uses MODIS data observed in 2005 to establish the relationship between the surface emissivity correction factor and NDVI. Through the use of these correction factors, the land surface temperature can be retrieved more accurate with MODIS data.

• Proceedings of the KSRS Conference
• /
• 2005.10a
• /
• pp.165-168
• /
• 2005

In this study, emissivity and land surface temperature (LST) were retrieved using the previously developed algorithms and Aqua/MODIS data. And sensitivity of estimated emissivity and LST to the predefined values, such as land cover, normalized difference vegetation index (NOVI) and spectral emissivity were investigated. The methods used for emissivity and LST were vegetation cover method (VCM) and four different split-window algorithms. The spectral emissivity retrieved by VCM was not sensitive to the NOVI error but more sensitive to the land cover error. The comparison of LST showed that the LST was systematically different without regard to the land cover and season. And the LST was very sensitive to the emissivity error excepting the Uliveri et al. This preliminary result indicates that more works are needed for the retrieval of reliable LST from satellite data.

• Nuclear Engineering and Technology
• /
• v.38 no.1
• /
• pp.99-108
• /
• 2006

SNU-RCCS is a water pool type RCCS (Reactor Cavity Cooling System) developed for VHTR (Very High Temperature Reactor) application by SNU (Seoul National University). Since radiation heat transfer is the major process of passive heat removal in a RCCS, it is important to determine the precise emissivity of the reactor vessel. Review studies have used a constant emissivity in the passive heat removal analysis, even though the emissivity depends on many factors such as temperature, surface roughness, oxidation level, wavelength, direction, atmosphere conditions, etc. Therefore, information on the emissivity of a given material in a real RCCS is essential in order to properly analyze the radiation heat transfer in a VHTR. The objectives of this study are to develop a method for compensation of the factors affecting the emissivity measurement using an infrared thermometer and to estimate the true emissivity from the measured emissivity via the developed method, especially in the SNU-RCCS environment. From this viewpoint, we investigated factors such as the attenuation effect of the window, filling gas, and the effect of background radiation on the emissivity measurements. The emissivity of the vessel surface of the SNU-RCCS facility was then measured using a sight tube. The background radiation was subsequently removed from the measured emissivity by solving a simultaneous equation. Finally, the calculated emissivity was compared with the measured emissivity in a separate emissivity measurement device, yielding good agreement with the emissivity increase with vessel temperature in a range of 0.82 to 0.88.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
• /
• v.26 no.6
• /
• pp.493-501
• /
• 2013

LED lighting is sensitive because it made by semiconductor. So it has been researched about radiation of heat technologies for a long time. In addition, measurement and assessment a radiation of heat also conducted. It is necessary to get a date of accuracy temperature on the board after LED driven for measuring Junction temperature of the LED Lighting. For this research, we use 5 chip which is 4 W power on top of LED lighting board made by aluminum. Thermal camera effects to emissivity depending on material and property of the surface in LED board because it determines thermal energy which emitted from material surface. it is not only thermal camera has not a standard about emissivity. It has an error of temperature when emissivity was measured by thermal camera. we confirmed that emissivity and reflected temperature depending on color and quality of the surface throughout experiment.

• Journal of the Korean earth science society
• /
• v.27 no.7
• /
• pp.787-803
• /
• 2006

The drought index has been developed, based on a $8.6{\mu}m$ surface emissivity in the $8-12{\mu}m$ MODIS channels over the African Sahel region (10-20 N, 13 W-35 W) and the Seoul Metropolitan Area (SMA: 37.2-37.7 N, 126.6-127.2 E). The emissivity indicates the $SiO_2$ strength and can vary interannually by vegetation, water vapor, and soil moisture, as a potential indicator of drought conditions. In a well-vegetated region close to 10 N of the Sahel, the Normalized Difference Vegetation Index (NDVI) showed high sensitivity, while the emissivity did not. On the other hand, the NDVI experienced negligible variability in a poorly vegetated region near 20 N, while the emissivity reflected sensitively the effects of atmospheric water vapor and soil moisture conditions. Seasonal variations of the emissivity (0.94-0.97) have been examined over the SMA during the 2003-2004 period compared to NDVI (or Enhanced Vegetation Index; EVI). Here, the dryness was more severe in urban area with less vegetation than in suburban area; the two areas corresponded to the north and south of the Han river, respectively. The emissivity exhibiting a significant spatial correlation of ${\sim}0.8$ with the two indices can supplement their information.

• Journal of the Korean institute of surface engineering
• /
• v.35 no.3
• /
• pp.149-157
• /
• 2002

Spectral emissivity depends on the surface conditions of the materials. The mechanisms that affect the spectral emissivity in anodic oxide films on aluminum were investigated. The aluminum specimens were anodized in a sulfuric acid solution and the thickness of the resulting oxide film formed changed with the anodizing time. FT-IR spectrum analysis identified the anodic oxide film as boehmite ($Al_2$$O_3$.$H_2$O). Both the infrared emisivity and reflectivity of the anodized aluminum were affected by the structure of the anodic oxide film because Al-OH and Al-O-Al have a pronounced absorption band in the infrared region of the spectrum. The presence of an anodic oxide film on aluminum caused a rapid drop in the infrared reflectivity. An aluminum surface in the clean state had an emissivity of approximately 0.2. However, the infrared emissivity rapidly increased to 0.91 as the thickness of the anodic oxide film increased.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
• /
• v.23 no.1
• /
• pp.54-60
• /
• 2011

Procedures for estimation of insulation thickness for a horizontal pipe for condensation control or personnel protection has been investigated, parallel to the previous work of a vertical wall case. Parameters include pipe diameter, emissivity, thermal conductivity, and operating temperatures. The results indicated that the surface emissivity plays a very important role in the design of insulation, specially for the case of high temperature application with low Bi. The effect of surface radiation in such case could be up to 65% of the total. Required insulation thickness for the surface temperature control increases as pipe diameter increases and as surface emissivity decreases. Adequate revision of specifications or standards to include newly invented insulation materials with high emissivity has been also suggested.

• Progress in Superconductivity and Cryogenics
• /
• v.10 no.2
• /
• pp.38-41
• /
• 2008

The relation between surface emissivity and temperature distribution is experimentally and analytically investigated for a conduction-cooled metal plate in vacuum. Experimental set-up consists of a rectangular metal plate placed vertically in a cryostat and thermally anchored to the coldhead of a GM cryocooler at the top. Temperature is measured at a number of locations over the plate with platinum resistors mounted on the plate. A parallel analysis on the balance of heat conduction through the plate and thermal radiation on its surface is performed to numerically calculate the temperature distribution having the same boundary conditions as experiment. By comparing the two results, an average emissivity of the plate is roughly estimated for different metal plates and different surface conditions. The estimated emissivity in present study is less than the listed values for highly polished stainless steel, and meets a fairly good agreement for oxidized copper surface.

• Journal of the Korean Society for Nondestructive Testing
• /
• v.30 no.5
• /
• pp.484-488
• /
• 2010

Infrared emissivity is one of the most important factors for the temperature measurement by infrared thermography. Although the infrared emissivity of an object can be measured from the ratio of blackbody and the object, at room temperature it is practically difficult to measure the value due to the background effects. Hence, quantitative reflectance of bare steel plate and the surface of coating was measured by FT-IR spectroscopy and emissivity was calculated from this. The emissivity of polished bare steel surface was from 0.06 to 0.10 and the value for the unpolished bare steel can not be achieved because optical characteristics changes of surface roughness induces erroneous results. Emissivity of transparent paint coated steel was from 0.50 to 0.84. Depends on the IR absorption regions, which is a characteristic value of the coating, emissivity changes. This study suggests surface condition of material, thickness, roughness et cetra are important factor for IR optical characteristics. Emissivity measurement by reflection method is useful technique to be applied for metal and it with coating applied on the surface. The range of experimental errors of temperature can be narrowed by the application of infrared thermography from the measured thermal emissivity.