ABSTRACT
Typical contact-type measurements are performed with thermocouples and thermistors. Temperature measurement of powder can be classified as either contact or non-contact types. Contact-type devices, such as thermocouples, measure the temperature in the powder bed, whereas those of non-contact type measure the temperature at the surface of the powder. In the case of a powder bed, the surface temperature may show discrepancies with the internal temperature because the apparent thermal conductivity of the powder bed is lower than that of the bulk material. Thus, radiation thermometers are best suited to a small amount of powder or thinly layered powder bed. In addition to reflection, absorption, and transmission, it should be noted that the effect of scattering is sometimes considerable for objects such as powder beds, porous media, particles, and droplets dispersed in gas or liquid phases. Thus, the effect of scattering on measurements must be determined beforehand.
