| dc.description.abstract | The high temperatures and corrosive environment created by molten salts pose challenges to both traditional and advanced measurement techniques. Experimental measurements of thermal-hydraulic parameters in these environments are paramount to advance the understanding of the molten salts’ behavior, and are necessary for future validation of computational models. An experimental test facility is utilized to characterize the thermal-hydraulic behavior of typical molten salts under steady-state and transient, forced flow conditions, by employing innovative measurement methods. Optical Fiber Distributed Temperature Sensors (OFDTS) have the ability to provide high resolution temperature measurements. These sensors capacity to provide temperature profiles are useful as a monitoring system, and for validation with simulations. Through this experimental study, the application of this technology has been extended to high temperature forced convection environments using FLiNaK as an operating fluid. Axial and radial temperature distributions have been recorded, and two-dimensional temperature fields have been reconstructed from the OFDTS network installed in this facility. Molten salt front velocity has been estimated from this. The effect of OFDTS external coating type, as well as installation configuration was investigated as well. The coatings tested are Polyimide, Aluminum, and a Gold-Carbon hybrid. The different coated OFDTS are specified to have different operating ranges, all below the 600°C temperature of this facility. However, this is a parameter that is based on the coating itself, not the ability of a fiber to make successful measurements. By examining response times and success of these different sensors for their duration under high temperatures, it was concluded that these coatings have little effect on response time or durability. In addition to this, shorter segments as seen in the radial installations see more longevity compared to longer (axial) segments under the same amount of time at temperatures above 500°C. Based on this, it is recommended that polyimide fibers be used even at these high temperatures, due to being the least expensive of the three tested, as well as being the easiest to fabricate into a sensor. Shorter segments exposed too high temperature (< 0.4 m) are also recommended due to the repeated failure of the axial OFDTS. | en |
