Numerical Evaluation of Ultrasonic Detection of Solid Occlusions in CSP Molten Salt Piping

This work presents a numerical evaluation of the applicability of non-invasive ultrasonic techniques for detecting solid inclusions in concentrated solar power (CSP) systems using molten salts. Under stagnant conditions, molten salts, such as the NaNO3–KNO3 mixture, solidify when the temperature drops below approximately 240 °C at ambient pressure. The study was conducted using finite element method (FEM) simulations in the time domain to model ultrasonic wave propagation and interaction with the solidified inclusions. Numerical analyses revealed that the energy of ultrasonic signals transmitted from the source and captured by the receiver can be used to quantify the energy reflected and scattered by solid inclusions and to statistically determine their spatial distribution within the piping. The study highlights the potential of detecting solid occlusions through statistical analysis of ultrasonic signals. Such an approach would enable decision making for trigger heating strategies to re-melt the solidified inclusions by raising the system’s temperature. This approach contrasts with traditional temperature-based control, which fails to quantify the degree of solidification and may result in frequent, energy-intensive heating whenever the temperature drops below the threshold. The proposed ultrasonic-based detection method thus offers a more energy-efficient and precise solution for managing solidification in CSP molten salt piping.