Development of a system for adsorption measurements in the 77 – 500 K and 1 – 100 bar range

Abstract

Adsorption is a phenomenon present in various systems important to the field of cryogenics, having a great deal of relevance in the development of vibration-free coolers: these are crucial for the cooling of sensitive detectors, as they offer the possibility of using a sorption compressor, do not have moving parts and do not induce unwanted mechanical vibrations in the system, maintaining its sensibility and greatly minimizing wear due to use. In the context of an ESA-funded project for the development of such a cooler, a study on adequate adsorption materials to use for the non-mechanical cryogenic compressor present in the final system was required. Considering this, a system for measurement of adsorption properties in the range of its operating pressures and temperatures was needed and, independently, also useful in future adsorption studies the laboratory decides to perform. A brief historical and functional review of the adsorption phenomenon, its applications in cryogenics, and available and various methods for its measurement is made. The design and assembly of an adsorption measurement system, through the volumetric (also known as manometric) method, for temperatures in the 77 K to 500 K range and pressures up to 100 bar is detailed. Proof pressure tests were made to validate the design of the vessel, with positive results. Other pre-measurement tests, such as heating and cooling assays, void and dead volume measurements, empty-vessel measurements, were all carried out with an intention to validate and characterize the developed system. A LabVIEWTM interface for the control and automatic acquisition of the system parameters was developed and tested throughout the whole process. Results were taken using a sample of HKUST-1 (also known as Cu3(BTC)2 or BasoliteTM C300) and compared against the results from another group, as well as a partner laboratory, from both their theoretical simulations and their commercial gravimetric system.