To measure total hemispherical emissivities ε
TH(T) of metals at low temperatures, a new transient calorimetric technique is developed to improve its accuracy. The accuracy of this technique mainly depends upon heat loss
Qt through a thermocouple (TC) which suspends a specimen and measures its temperature. To reduce
Qt, an Iron. Constantan TC with diameter of about 20μm is used, and the temperature profile of TC is controlled by a guard heater attached to the other sides of TC. ε
TH(T) of aluminum specimens which shaped wire (99.9994% purity) and plate (99.988%) are measured in the temperature range from 125 to 350K. The specimens are mechanically polished. The roughness of the plate surface is measured.
Qt, evaluated by a combined radiation and conduction heat transfer analysis, is less than 1% of the total power loss of the specimen. ε
TH(T) for wire and annealed plate are in good agreement with each other, and close to the values extrapolated from the date obtained above room temperature. An increase in ε
TH(T) of the plate without annealing may be due to the Beilby/damaged surfaces formed by mechanical polishing.
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