Session: 11-07-01 Measurements of Thermophysical Properties

Paper Number: 77237

Start Time: Tuesday, 04:20 PM

77237 - Thermal Conductivity Measurement of Stationary and Flowing Molten Salt Using Modulated Photothermal Radiometry 

Molten salts are being used or studied for thermal energy conversion systems, such as concentrating solar power and nuclear power. Thermal conductivity is an important thermophysical property dictating the performance of these systems but its accurate measurement of molten salts has been challenging. The corrosive and conductive nature of these fluids makes it difficult to use traditional contact methods, such as the hot wire method, for accurate measurements. Techniques that require a large volume of the fluids, such as the steady-state method, could also be prone to errors caused by natural convection. On the other hand, commonly used non-contact optical thermoreflectance techniques are difficult to operate at high temperatures. There is a need to develop a novel measurement method that can address the measurement issues mentioned above. Here, we report the thermal conductivity measurement of molten salts using a modulated photothermal radiometry (MPR) technique. MPR is a laser-based, non-contact, frequency domain method that has been used to measure the thermophysical properties of various materials, including bulk materials, thin coatings, and stationary fluids. We develop the technique for the measurement of molten salts at both stationary and flow states. Stationary molten salts, including pure nitrate salt, the solar salt mixture, and chloride-based salts, have been measured using a high-temperature MPR holder under an Argon (Ar) gas environment. The measurement results are compared with those obtained from a laser flash analyzer (LFA) and other reported values. Our results demonstrate the reliability of the MPR method to measure the thermal conductivity of stationary molten salts. We further extend the technique to perform in-operando measurements on flowing fluids. The thermophysical properties of flowing fluids, such as deionized (DI) water, and oil-type heat transfer fluid, XCELTHERM, have been measured under an intermediate temperature range and various flow velocities of the fluids. The experimental results show that the intrinsic thermal conductivity of those flowing fluids can be reliably obtained under certain experimental conditions. Finally, the in-operando technique is applied to a laboratory-scale molten salt loop to demonstrate the capability of measuring flowing molten salts in real-time. Our work shows that the MPR technique is a convenient tool to provide reliable molten salt thermal conductivity data. The reliable thermal conductivity data provided by the MPR technique can help develop the fundamental heat-transport theories of molten salts. The MPR technique could also serve as a diagnostic tool for monitoring the thermophysical properties of flowing molten salts in real-time.

Presenting Author: Ka Man Chung University of California San Diego

Authors:

Ka Man Chung University of California San Diego
Jian Zeng University of California, San Diego
Tianshi Feng University of California, San Diego
Renkun Chen University of California, San Diego