Magnetic resonance signal moment determination using the Earth's magnetic field

Monitoring residual fouling after cleaning of multi-fiber membrane modules fiber-by-fiber using non-invasive MRI monitoring

In this study non-invasive low field magnetic resonance imaging (MRI) technology was used to monitor fouling induced changes in fiber-by-fiber hydrodynamics inside a multi-fiber hollow fiber membrane module containing 401 fibers. Using structural and velocity images the fouling evolution of these membrane modules were shown to exhibit distinct trends in fiber-by-fiber volumetric flow, with increasing fouling causing a decrease in the number of flow active fibers. This study shows that the fouling rate is not evenly distributed over the parallel fibers, which results in a broadening of the fiber to fiber flowrate distribution. During cleaning, this distribution is initially broadened further, as relatively clean fibers are cleaned more rapidly compared to clogged fibers. By tracking the volumetric flow rate of individual fibers inside the modules during the fouling-cleaning cycle it was possible to observe a fouling memory-like effect with residual fouling occurring preferentially at the outer edge of the fiber bundle during repeated fouling-cleaning cycle. These results demonstrate the ability of MRI velocity imaging to quantitatively monitor these effects which are important when testing the effectiveness of cleaning protocols due to the long term effect that residual fouling and memory-like effect may have on the operation of membrane modules.

Noninvasive Magnetic-Marking-Based Flow Metering with Optically Pumped Magnetometers

We present a noninvasive procedure that measures the flow velocity of a fluid by using polarized hydrogen nuclei in the fluid. The measurement procedure is based on a time-of-flight method where magnetic information is applied on the fluid with a permanent magnet and an RF-pulse. In contrast to other methods, this magnetic-marking method works without tracers. The read-out of the magnetic information is performed by optically pumped magnetometers downstream. In order to function, the magnetometers have to be operated in a magnetic shield with magnetic field strengths lower than 100 nT, i.e., in the zero-to-ultra-low-field regime. In this regime, the magnetometers are capable of detecting induced magnetic signals of 10 pT or less with an inline-flow setup. The results presented in this paper demonstrate the viability of optically pumped magnetometers for flow metering. The first metering results yielded an average accuracy of 3% at flow velocities between 13 cm/s and 22.4 cm/s.