A tale of two cooling curves: Measuring heat capacity using aerodynamic levitation
A tale of two cooling curves: Measuring heat capacity using aerodynamic levitation lead image
Aerodynamic levitation (ADL) creates a contactless environment that can be used to reveal the thermophysical properties of liquid materials by levitating them under gas flow. Unlike other levitation methods, ADL can stably levitate liquid oxides. However, to measure the heat capacity of levitated materials using cooling curves, researchers must first know their emissivity, which is difficult to obtain.
Sun et al. developed a method to measure the heat capacity of materials using ADL without first knowing emissivity. They used two levitation gases, argon and krypton, to generate two independent cooling curves for one sample. The cooling curves allowed them to calculate the emissivity and heat capacity simultaneously, instead of determining emissivity first.
The authors used their multiple-gas cooling method to measure the heat capacity of molten gold, copper, nickel, iron, and palladium. The results agreed well with previous data.
Unlike the heat capacity measurement methods used in other levitation techniques, this method for ADL does not require additional emissivity measurements with a blackbody furnace, which has a limiting maximum temperature. It can be used to study molten materials with high melting points or vapor pressures.
“Since a heat capacity measurement technique didn’t exist for ADL, the method developed in this study is essential for the heat capacity measurement of various molten oxides,” said author Yifan Sun. “Of course, it also allows for heat capacity measurement of molten metals and their alloys.”
Next, the authors hope to improve the assumption they made about the convective heat loss of a levitated sample in a nozzle. They also plan to apply this method to liquid metals and oxides with higher melting points.
Source: “Multiple-gas cooling method for constant-pressure heat capacity measurement of liquid metals using aerodynamic levitator,” by Yifan Sun, Hiroaki Muta, and Yuji Ohishi, Review of Scientific Instruments (2021). The article can be accessed at https://aip.scitation.org/doi/full/10.1063/5.0055555 .
