Heat loss (2015)
Heat loss is one of the key parameters that cause temperature errors during the calibration of thermometers in metal-freezing-point cells and thus increases the measurement uncertainty. At temperatures above the freezing point of tin, thermal radiation becomes the dominant mode of heat transfer. In addition, radiative heat transfer is especially important in the cells’ glass structures, where total internal reflection (known as “light piping”) can occur. A quantitative measure of the radiative heat loss is difficult to determine with measurements, but a qualitative check can be performed by measuring the vertical temperature profile in a cell during a freezing-point realization. Our custom-built model is capable of modeling both the radiative and conductive heat transfers and can deal with complex radiation phenomena specific to the particular case study. The modeling and experimental results are used to give an estimation of the error due to heat losses.