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A prize-winning measurement device could aid a wide range of industries

Companies dealing with liquids ranging from wastewater to molten metals could benefit from a prize-winning device developed by researchers at the U.S. Department of Energy’s (DOE) Princeton Plasma Physics Laboratory (PPPL) and Princeton University. The device is an improved rotating Lorentz-force flowmeter (RLFF), which measures the rate at which fluids move through pipes and tubes. The new kind of RLFF does not come into contact with the fluids it measures, meaning that it can be used both with common fluids like saltwater and with high-temperature or corrosive fluids that most flowmeters have difficulty measuring. This capability makes the new RLFFs suitable for many industries.

The novel invention, reported in Measurement Science and Technology, won first place in Princeton University’s 13th Annual Innovation Forum in March. The key innovation is a new type of low-friction bearing that connects the flowmeter to a stationary frame. The near-frictionless operating conditions mean that the flowmeter does not have to be calibrated before installation, a process that consumes time and money.

 “We were able to reduce friction to such trivially small amounts that the flowmeter performance very, very closely matched ideal theoretical performance,” said Michael Hvasta, an associate professional specialist in Princeton University’s Mechanical and Aerospace Engineering (MAE) Department who conducts research at PPPL.

The flowmeter consists of two disks with several evenly spaced magnets located near the rims of the disks. The flowmeter is then connected to the low-friction weighted magnetic bearing that links the device to a frame installed next to a system of pipes or tubes. Within the bearing, a counterweight pulls part of the assembly down and away from a powerful magnet, reducing the contact between moving surfaces and thus minimizing friction. “Now the disk can move nearly friction-free,” Daniel Dudt, a graduate student in the MAE department and coauthor of the paper said. Also, because any friction occurs along the bearing’s central axis, there is little torque on the bearing’s edge that could slow the rotation of the disk.

RLFFs measure the flowing rate of fluids by exploiting the interaction between electricity and magnetism. As an electrically conductive fluid flows past a magnetic field, the field induces a current within the fluid. That current interacts with the magnetic field and causes the disk to rotate. The velocity of the turning disk corresponds to the speed of the fluid.

This type of flowmeter has many advantages.

• First, it can be installed outside a pipe, while fluid is flowing and the system is in operation, so scientists can begin gathering data immediately. Conventional flowmeters, on the other hand, must be placed within a pipe and installed with welds or fittings. To install them, technicians must “drain the system and cut it open, put in the flowmeter, seal everything back up, fill up the system, and then turn it back on,” Hvasta said, describing a procedure that can be both costly and time-consuming.

• Second, an externally installed flowmeter can preserve the integrity of a system of pipes in an environment that must be kept sterile, like those within food or pharmaceutical plants. Since the installation of an RLFF does not involve introducing moving parts or seals within the flow of the liquid, there is no chance of causing a leak.

Hvasta and colleagues plan to do more research showing that the new flowmeter can measure the flow rate of fluids that are only weakly electrically conductive. Such fluids, like molten salt, could be used in the growing field of energy storage. The team is also trying to make the entire assembly more aerodynamic to minimize the amount of wind resistance produced as the bearing spins.

Scientists and coauthors of the paper include Adam Fisher, a graduate student in the MAE Department, and Egemen Kolemen, an assistant professor in the department jointly appointed to PPPL and the University’s Andlinger Center for Energy and the Environment. Research for this paper was conducted under the Laboratory Directed Research and Development Program (LDRD) at PPPL.

PPPL, on Princeton University's Forrestal Campus in Plainsboro, N.J., is devoted to creating new knowledge about the physics of plasmas — ultra-hot, charged gases — and to developing practical solutions for the creation of fusion energy. The Laboratory is managed by the University for the U.S. Department of Energy’s Office of Science, which is the largest single supporter of basic research in the physical sciences in the United States, and is working to address some of the most pressing challenges of our time. For more information, please visit science.energy.gov.

U.S. Department of Energy
Princeton Plasma Physics Laboratory is a U.S. Department of Energy national laboratory managed by Princeton University.

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