2-Dr. Merete Hallenstvet - Het Aluminium Centrum

Table 2 Comparison of emissivity and chemical stability data for the four different aluminium pigmentsshown in figure 5. A close relation between the silicon oxide coating quality and the chemical resistance ofthe powder coating is foundPigment Emissivitye? L after 8h in10% HClChemicalresistancePigment coatingthickness [nm]A 0.49 - 1.09 very good 10 - 30B 0.48 - 1.02 very good ~ 10C 0.47 - 23 poor No continuous pigmentcoating, dissolved SiO 2 ?D 0.45 - 2.33 OK (?) ~ 20, only partly coatedpigmentU-value calculation and measurementsThe obtained reduction in thermal emissivity from 0.9 to about 0.5 will result inconsiderable energy savings. U-value calculations and measurements have been done usinga Wicline 65 window profile. The results are given in table 3.Table 3 Calculated and measured heat loss in terms of U-values for a Wicline 65 window profile withdifferent emissivity of the powder coatingsEmissivity 0.9 Emissivity 0.5Calculations EN 10077-2 3.01 W/m 2 K 2.43 W/m 2 KMeasurements EN 12412-2 3.07 W/m 2 K 2.40 W/m 2 KThere is an excellent agreement between measured and calculated U-values. It is furthershown that the reduced emissivity of the coating is reducing the heat loss through thewindow frame from 3.07 to 2.40 W/m 2 K, a reduction by more than 20% The part of theheat loss caused by radiation is considerable. The use of this low emissive coating willreduce the energy consumption in buildings correspondingly.CONCLUSIONSA powder coating with heat reflective properties has been developed. The thermalemissivity is slightly below 0.5. This represent a considerable potential for energy savingswhen used for building applications compared to the use of ordinary powder coatings with