In the past, a compact single-stage centrifugal pump for liquid helium was designed and successfully tested at TU Dresden University. The pump is an integral part of a dual-flow transfer system which reduces the decanting losses of liquid helium from 30% down to 4%. Since the pump transfers the liquid close to saturated conditions, the cavitation characteristics of the pump need to be further...
Heat switches play a crucial role in cryogenic systems, regulating thermodynamic cycles or accelerating cooling processes. Among them, active gas-gap heat switches (AGGHS) are extensively employed, typically utilizing activated carbon and helium as the adsorbent-gas pair. Thermal conductance in AGGHS is controlled by driving gas adsorption or desorption through heating or cooling of the...
Cryogenic control valves are one of the critical components of a cryogenic fluid distribution system. They are used for both control (process and safety) and isolation of the cryogens within the distribution system. In many cases, control of the cryogenic process flow needs to be directly or indirectly accompanied by accurate flow measurement. Fundamentally, cryogenic flow measurement can be...
Hydrogen energy, as a clean and efficient power source, plays a key role in the global energy transition. Hydrogen turbo-expanders, essential in liquid hydrogen production, significantly impact system performance. However, their efficiency is relatively low, primarily due to improper coupling between the nozzle and the impeller. This interaction greatly influences both efficiency and...
At the European Spallation Source (ESS), the high-energy neutrons produced through spallation reaction are moderated to cold and thermal energies using a combination of hydrogen moderators and a light water premoderator, which are optimized to achieve a high cold neutron brightness. The ESS employs two hydrogen moderators positioned above the target wheel, with an estimated nuclear heating of...
At the European Spallation Source (ESS), a cryogenic moderator system (CMS) has been designed to circulate subcooled liquid hydrogen at 17 K with a parahydrogen fraction exceeding 99.5% and a flow rate of 0.25 kg/s for each hydrogen moderator. The nuclear heating for the 5-MW proton beam power is estimated to be 6.7 kW and is projected to increase to 17.2 kW for the four moderators in the...
A high-speed cryogenic helium centrifugal turbine expander with an electric generator brake for experimental helium refrigerator is presented in this paper. This design differs from traditional compressor-braked cryogenic helium turbine expanders. The turbine expander is braked by a permanent magnet generator (PMG), and its shaft is coupled to the PMG to enhance operational stability. The...
As the core equipment of a helium cryogenic system, the safe and stable operation of a helium turbine is critical to the smooth operation of the entire system. During the processing and assembly of the rotor, it is inevitable to produce unbalance. The unbalance force generated by the unbalance measure may affect the stability of the turbine and even cause damage to the equipment. In order to...
Compressor is the key component of pulse tube cryocooler. It introduces the structure of a linear vibration compressors specifically designed for pulse tube cryocoolers. The paper delves deeply into the impact of compressors on four key aspects: support systems, control systems, compressor efficiency, and vibration and noise reduction. Based on the findings, a compressor weighing 160 grams has...
