"The Physics of Evolving Matter: Memory, Learning and Evolution" The Geilo School 2022, March 21-31, Geilo, Norway

publishedVersio

Heat exchangers for hydrogen tank filling

The purpose of this report is to give some basic facts about heat exchangers and summarize a series of simulations done on counter-flow concentric tube heat exchangers for hydrogen gas bunkering using the COMSOL Multiphysics software. Part 1 of this report consists of an exploration of how various system parameters (flowrates, pressures, and tube dimensions) influence the properties of a heat exchangers based on pure water as coolant. Part 2 discusses how the heat exchanger performance can be improved using ethylene glycol-water mixtures and compares these results to those using pure water coolant. The Appendix gives tables of heat transfer coefficients for heat exchangers of different sizes using pure water and ethylene glycol-water mixtures.publishedVersio

Aggregation of magnetic holes in a rotating magnetic field

We have experimentally investigated field induced aggregation of nonmagnetic particles confined in a magnetic fluid layer when rotating magnetic fields were applied. After application of a magnetic field rotating in the plane of the fluid layer, the single particles start to form two-dimensional (2D) clusters, like doublets, triangels, and more complex structures. These clusters aggregated again and again to form bigger clusters. During this nonequilibrium process, a broad range of cluster sizes was formed, and the scaling exponents, $z$ and $z'$, of the number of clusters $N(t)\sim t^{z'}$and average cluster size $S(t)\sim t^{z}$ were calculated. The process could be characterized as diffusion limited cluster-cluster aggregation. We have found that all sizes of clusters that occured during an experiment, fall on a single curve as the dynamic scaling theory predicts. Hovewer, the characteristic scaling exponents $z',\: z$ and crossover exponents $\Delta$ were not universal. A particle tracking method was used to find the dependence of the diffusion coefficients $D_{s}$ on cluster size $s$. The cluster motions show features of \textit{\emph{Brownian}} motion. The average diffusion coefficients $$ depend on the cluster sizes $s$ as a power law $\propto s^{\gamma}$ where values of $\gamma$ as different as $\gamma=-0.62\pm0.19$ and $\gamma=-2.08\pm0. were found in two of the experiments

Magnetoresistance of composites based on graphitic discs and cones

We have studied the magnetotransport of conical and disc-shaped nanocarbon particles in magnetic fields |B| ≤ 9 T at temperatures 2 ≤ T ≤ 300 K to characterize electron scattering in a three-dimensional (3D) disordered material of multilayered quasi 2D and 3D carbon nanoparticles. The microstructure of the particles was modified by graphitization at temperatures of 1600 and 2700 °C. We find clear correlations between the microstructure as seen in transmission electron microscopy and the magnetotransport properties of the particles. The magnetoresistance measurements showed a metallic nature of samples and positive magnetoconductance which is a signature of weak localization in disordered systems. We find that the magnetoconductance at low temperatures resembles quantum transport in single-layer graphene despite the fact that the samples are macroscopic and 3D, consisting of stacked and layered particles, which are randomly oriented in the bulk sample. This graphene-like behaviour is attributed to the very weak interlayer coupling between the graphene layers

Utvikling av Mikro-ROV

ROV, systemkonstruksjon, undervannsteknologi, kretskortdesign, filterkonstruksjon, analog signalbehandling, programmering, 3D-design, fysikk og mekanisk arbeidROV, system design, underwater technology, circuit board design, filter design, analog signal processing, programming, 3D design, physics, and mechanical wor

Utvikling av Mikro-ROV

ROV, systemkonstruksjon, undervannsteknologi, kretskortdesign, filterkonstruksjon, analog signalbehandling, programmering, 3D-design, fysikk og mekanisk arbeidROV, system design, underwater technology, circuit board design, filter design, analog signal processing, programming, 3D design, physics, and mechanical wor