Advanced Measurement and Visualization Techniques for High-Temperature Heat Pipe Experiments

Abstract

This report conducts a preliminary investigation of the available literature and summarizes some potential advanced measurement and visualization techniques for operating high-temperature heat pipe (HP) that can be implemented to support the United States (U.S.) Department of Energy (DOE) Microreactor Program (MRP). The primary objective for the extensive literature research is to investigate the possibilities and feasibility for the design and construction of an advanced experimental test facility with the aim of producing high-fidelity high-resolution heat pipe data during its operation.Based on the existing HP test facilities at Idaho National Laboratory (INL)including the Single Primary Heat Extraction and Removal Emulator (SPHERE) and the Microreactor Agile Non-Nuclear Experimental Test Bed (MAGNET)further efforts will be made to examine the technical feasibility to HP measurements and support the research, development, and demonstration (RD&D) process for an HP-cooled microreactor. Continuing collaborations with the Nuclear Energy Advanced Modeling and Simulation (NEAMS) program, other research institutes and universities are considered to be extremely important so that the experimental facility and resultant database can satisfy the validation needs of advanced heat pipe modeling codes being developed under DOE NEAMS program. vii

Analyses Supporting Heat Pipe Experiments

“…Experiments which aid the R&D of advanced reactors should also exploit cutting-edge technologies and techniques. Hence, advanced measurement and visualization techniques are currently being developed by multiple institutions [66]. These include fiber optic temperature and strain sensors [16,40,45,67,68], Infrared (IR) thermography, digital image correlation (DIC) [69], high-speed camera flow visualization and pressure measurements of a surrogate fluid [16,45,70,71], radiation based tomography [60], and laser spectroscopy techniques [72].…”

“…These parameters can be utilized in numerous ways: (1) calculation of actual power throughput, (2) compressible flow analysis for vapor, (3) wick and interfacial stress calculations for entrainment, (4) characterization of the transient response of flow rate changes with evaporator power input, condenser cooling power, and limit conditions, (5) better identification of steady state conditions, (6) backcalculation of liquid/vapor flow areas. There are currently no robust method for measuring the liquid and vapor flow rates or velocities within a high-temperature heat pipe, however methods such as laser spectroscopy were proposed [66].…”

Preliminary Design Needs for High-Temperature Heat Pipe Imaging System

“…In addition, the metallic casing of the HPs makes it impossible to visualize the internal part with traditional optic measurement techniques. Based on these measurement needs-as well as the challenges-an extensive literature survey [15] has been conducted by the MRP team and presented with the available and possible advanced manufacturing capabilities.…”

“…To model the HP with computational tools and predict its thermal behavior, the phase change physics with the alkali metal charged in the HP is one of the most essential and crucial pieces, especially during the HP transient scenarios (the starting and cooling phases). Even if there are available computational software and models to deal with the phase change problems, like STAR-CCM+ and MOOSE Sockeye, the verification and validation (V&V) effort is inevitable and indispensable when dealing the hightemperature heat pipe systems [15]. Therefore, it will require the high-fidelity experimental database for the operando heat pipes, such as the void fraction at the HP vapor core region, real-time temperature measurements on the external side of the HP, strain/displacement measurement for the HP structure as well as the containment holding the HP, and sodium vapor pressure inside the HPs at different operating stages.…”