Noble or inert gas recirculation is used for various processes, such as cooling of sensitive equipment in physical experiments, semiconductor production equipment, rapid prototyping or in laser sources. These applications have large differences in the required pressure ratios and mass flows.
The state-of-the-art solution to tackle this challenge is to massively oversize the compressor in pressure and flow. Sometimes the compressor is combined with a pressure vessel, and then valves are used to reduce the output to the required flow and pressure levels. This not only wastes precious energy contained in the pressurised gas, but also demands to oversize the cooling system, which further increases the energy demand, installation footprint and equipment cost. Not infrequently, it is the case that separate buildings are needed to house the standard compressors. This solution is usually justified, as a customised compressor system is even more costly.
However, there is an exciting alternative approach: Using a miniature high-speed turbo compressor in a modular configuration. The main enabler for a modular configuration is the gas-bearing technology, as this allows completely contamination-free operation without the need for a (usually single, central) oil separator. With a modular approach, the required pressure and mass flow is achieved by serializing or paralleling compressor units. This approach leads to a much smaller footprint and energy consumption than using screw or piston compressors.
Celeroton’s CT-NG-2000 compressor is designed such that it can be connected in series and/or in parallel. In serial connection, a higher pressure ratio can be achieved, as reported in an earlier article for a different application. With an increase in pressure, the temperature increases, therefore intercoolers (heat exchangers) are usually used in between the stages, which also increases the thermodynamic efficiency. A typical configuration is depicted as:
Similarly, for an increase in mass flow, the compressors can be paralleled: