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Thermal measurements

Thermal Conductivity

Several energy systems, such as nuclear energy and solar thermal energy, utilize particles as a means for energy transfer and energy storage. High thermal conductivity associated with the particle bed is critical for the safety of a nuclear reactor and to ensure high heat transfers rates to the power cycle in solar energy/energy storage. The porosity of the packed bed affects the overall thermal conductivity. The bed porosity is a function of the particle size, shape, and pressure applied to the bed, but consistently varies from ~0.3 to 0.4 for a random packing of uniformly sized particles (as well as for particles of polydisperse size distribution).  At our FLAIR Lab, we set up a modulated photothermal radiometry system using a continuous wave laser to measure the thermal conductivity of the packed bed sample. MPTR is a non-contact thermal, non-destructive method to measure conductivity and specific heat in situ. In our work we use it to study the thermal conductivity of a packed bed solar particles to investigate efficient energy transfer. This work is supported by DOE SIPS

MPTR set up with 455nm laser
MPTR set up with 455nm laser

Infrared thermography

n a nuclear reactor core, a fuel rod experiences cracking due to rapid changes in the thermal gradient. In a DOE-funded project, we are seeking to develop an instrument that can image the crack in real-time using lock-in thermography for the first time. This is a multidisciplinary project in collaboration with The Ohio State University, Department of Electrical and Computer Engineering, Micron School of Materials Science and Engineering at Boise State, and INL. At the FLAIR lab, we are designing and developing a free-space optical setup to perform lock-in thermography to study the cracking in surrogate fuel materials subjected to large thermal gradients. Ohio State University is modeling the radiation characteristics to determine the optimum experimental conditions. The knowledge gained from the free-space setup will enable us to design an optical fiber bundle-based imaging system that will find practical uses within an actual nuclear reactor. We are currently designing the ideal core size and the number of fibers required to accomplish this task.