Magnetocaloric Cooling Near Room Temperature - A Status Quo with Respect to Household Refrigeration

Magnetocaloric cooling is currently a prospering field of scientific investigations. Especially in the last decades a significant increase in research activities took place, mainly with the aim to find a competitive substitution for conventional cooling techniques - primarily with a special focus to vapor compression cycles. At least from a theoretical standpoint magnetocaloric cooling has the potential to exceed efficiencies of conventional cycles. However, there are still a number of challenges that need to be overcome. This paper is intended to give an overview on the status quo of magnetocaloric cooling near room temperature with respect to household refrigeration. Basic data regarding materials and magnet field generation are discussed. The most powerful demonstrators so far published in literature are analyzed and compared to performance requirements for standard household refrigerators. Several hand calculations and further comparisons are used to emphasize the crucial points that will be decisive on whether magnetocaloric is a future option for household refrigeration or not

Cooling Considerations for the Long Length HVDC Cables Cryostat within BEST PATHS Project

HVDC cables have been identified as the preferred solution for future pan-European grids for the transmission over long distances of the large power produced by renewable energy farms which are generally located far for the consumption places. The European project Best Paths has been launched to identify the remaining barriers and propose some innovative solutions to achieve such envisioned grids. As superconductivity offers very attractive and efficient solutions vision studies for long-distance superconducting power transmission lines are conducted. The superconducting technology under study is based on the MgB$_{2}$ conductor cooled with one-phase liquid hydrogen. A flexible cryostat with 15 to 25 K core cooling and with additional shield cooling using liquid nitrogen or hydrogen gas is required. For long length cables the limiting parameters are the cryostat heat load and the pressure drop. The calculation results show the interdependencies of the maximum length between neighboring cooling sections with the heat load on shield and core, mass flows and pressure drop, enthalpy change, viscosity, friction factors and cryostat geometry. The calculations are carried out for different fluid options and diameters, and the corresponding results are presented and discussed

Development of a routinely applicable imaging protocol for fast and precise middle cerebral artery occlusion assessment and perfusion deficit measure in an ovine stroke model : a case study

Temporary middle cerebral artery occlusion (MCAO) in sheep allows modeling of acute large vessel occlusion stroke and subsequent vessel recanalization. However, rapid and precise imaging-based assessment of vessel occlusion and the resulting perfusion deficit during MCAO still represents an experimental challenge. Here, we tested feasibility and suitability of a strategy for MCAO verification and perfusion deficit assessment. We also compared the extent of the initial perfusion deficit and subsequent lesion size for different MCAO durations. The rete mirabile prevents reliable vascular imaging investigation of middle cerebral artery filling status. Hence, computed tomography perfusion imaging was chosen for indirect confirmation of MCAO. Follow-up infarct size evaluation by diffusion-weighted magnetic resonance imaging revealed fluctuating results, with no apparent relationship of lesion size with MCAO at occlusion times below 4 h, potentially related to the variable collateralization of the MCA territory. This underlines the need for intra-ischemic perfusion assessment and future studies focusing on the correlation between perfusion deficit, MCAO duration, and final infarct volume. Temporary MCAO and intra-ischemic perfusion imaging nevertheless has the potential to be applied for the simulation of novel recanalization therapies, particularly those that aim for a fast reperfusion effect in combination with mechanical thrombectomy in a clinically realistic scenario

Machbarkeitstudie für einen industriellen supraleitenden Table Top Elektronenbeschleuniger

At the Forschungszentrum Rossendorf the build-up of the superconducting 1.3 GHz accelerator ELBE is still in progress. Furthermore a new sc photo injector (SRF gun) is under development, which should accelerate electrons up to 10 MeV at 1.3 GHz frequency. The use of electron accelerators is also more and more interesting for applications where the destructive potential of the electrons are used like sterilization of medical waste and medical products, food irradiation or decontamination of sewage. For these processes a high power is required to achieve a high product throughput in a plant. The aim is therefore to use beam powers of around 100 kW or more. Since the applications of electron accelerators in industrial environments are steadily increasing one can speculate about transferring the above named state of the arte technology to industrial electron accelerators. At the FZR a feasibility study of such a table top electron accelerator (TTE) has been performed to investigate its technical limits and marketabilitys

Selective intra-carotid blood cooling in acute ischemic stroke : a safety and feasibility study in an ovine stroke model

Selective therapeutic hypothermia (TH) showed promising preclinical results as a neuroprotective strategy in acute ischemic stroke. We aimed to assess safety and feasibility of an intracarotid cooling catheter conceived for fast and selective brain cooling during endovascular thrombectomy in an ovine stroke model. Transient middle cerebral artery occlusion (MCAO, 3 h) was performed in 20 sheep. In the hypothermia group (n = 10), selective TH was initiated 20 minutes before recanalization, and was maintained for another 3 h. In the normothermia control group (n = 10), a standard 8 French catheter was used instead. Primary endpoints were intranasal cooling performance (feasibility) plus vessel patency assessed by digital subtraction angiography and carotid artery wall integrity (histopathology, both safety). Secondary endpoints were neurological outcome and infarct volumes. Computed tomography perfusion demonstrated MCA territory hypoperfusion during MCAO in both groups. Intranasal temperature decreased by 1.1 °C/3.1 °C after 10/60 minutes in the TH group and 0.3 °C/0.4 °C in the normothermia group (p < 0.001). Carotid artery and branching vessel patency as well as carotid wall integrity was indifferent between groups. Infarct volumes (p = 0.74) and neurological outcome (p = 0.82) were similar in both groups. Selective TH was feasible and safe. However, a larger number of subjects might be required to demonstrate efficacy

Development and Characterization of a Centrifugal Pump for Low-loss Liquid Helium Transfer

At research institutes, liquid helium is supplied in mobile dewars, filled by pressurization of the storage dewar. To reduce the evaporation losses significantly, a pump can be installed. In this article, a prototype of a submersible centrifugal pump is comprehensively investigated by varying process parameters such as shaft speed and sealing gap. The measurements were performed with a single flow transfer line during a standard filling process of dewars, used for the laboratory supply at the TU Dresden. The pump characteristics show wide operating ranges with efficiencies above 50% and peak efficiencies over 80% at high-speed operation. A significant reduction in filling losses and time compared to the traditional process could be demonstrated