Vol 112, No 3 (2023)

Krypton is a significant natural resource with great importance for modern industry, medicine, and science. This article considers the issue of preserving the purity of this inert gas of various grades, describes the main processes that can affect the amount of impurities in krypton, and highlights its current applications. Experimental data aimed at elaborating questions about the methodology of surface preparation before contact with high-purity krypton are presented. Moreover, the amount of impurities from the time of container preparation for gas grade 5.8 is evaluated, and dependences of moisture content on the method of preparation and type of surface, which is in contact with high-purity gas, are obtained. Further, statistics on filling containers with argon grade 6.0 and its preliminary preparation are collected. For parameter estimation, cylinders with different types of surfaces are used, both unused and with a service life of more than 10 years. The paper shows various parameters that can affect the purity of krypton. Thanks to the data collected during the experiments, the requirements for future works can be adjusted.

AIMS: This study aimed to analyze the active heat reclaim unit SNAB.065171.001-01 as the main heater of a ventilation system of a real object and to confirm the reliability of the calculation method using obtained experimental data.

MATERIALS AND METHODS: The experimental and computational methods included the technical and economic assessment of active heat reclaim units to determine the characteristics of the device under changing air flow rates and operating temperature conditions. The tests were performed at the laboratory of life support systems of the Faculty of Low-Temperature Energy at the St. Petersburg National Research University of Information Technologies, Mechanics and Optics. The equipment under study was installed in the existing ventilation system of the laboratory. The laboratory ventilation system was equipped with a stepwise air flow control system. The automation system enabled setting five fixed operating modes of the supply and exhaust fans without the possibility of smooth regulation within the flow range. Operational parameters and verified measuring instruments were used in measurements.

RESULTS: This paper describes the results of the determination of the refined nominal characteristics of performance, energy consumption, and conversion coefficient of the active heat reclaim unit. It also presents empirical coefficients necessary for the calculation of these characteristics under arbitrary operating conditions. The calculation methodology was verified through additional experiments. The relative deviation of the calculated conversion coefficient from the experimentally obtained one did not exceed 3% in all experiments.

CONCLUSIONS: The nominal characteristics of the built-in air heat reclaim unit SNAB.065171.001-01 were determined under real operating conditions. The results of the calculation of operational characteristics were compared with the experimental results.

CO₂ refrigeration units are gaining market shares thanks to the ability to provide an energy efficient performance for industrial and commercial refrigeration applications in any climate. As with all the applications, the investment and operation costs should be kept as low as possible, to reduce the payback time and promote the introduction of innovative system solutions.

In this work the flexibility achieved by implementing the pivoting technology in a supermarket refrigeration application is investigated both at design- and partial load conditions. The air conditioning (AC) load is also considered within a wide range of ambient temperatures. The Multi Ejector block utilized will be analyzed in terms of performance and its effect on the compressor combinations at different operating conditions. The objective is to increase the flexibility of the centralized rack through a proper design and sizing of the compressor pack equipped with the pivoting technology, while maintaining the efficiency and reducing the

investment costs. This work shows that a Multi Ejector pivoting-supported system will be beneficial from the flexibility and capital costs point of view, and the benefit will be more consistent if the AC load is part of the integrated system architecture. Furthermore, a thorough investigation has been conducted whenever the ejector capacity is too high compared to the load, proposing two alternative solutions.