Vol 113, No 3 (2024)

Today, improvement of air separation unit circuitry to reduce either the plant’s cost or the specific energy cost of producing a unit of product is an urgent task. In addition, the issue of the possible use of LNG’s cooling potential for its regasification is becoming increasingly relevant. To study the possible combination of regasification and air separation processes and to determine the estimated dependencies to conclude on the effectiveness of such solution compared to the conventional air separation circuit. Hysys-14 software environment was used to model three air separation circuits with different options for actuating the LNG flow. We specified the relationships between nitrogen sweep efficiency and specific energy costs on the pressure in the cycle. The calculations showed that the energy costs of nitrogen are lower by an average of 46.6%, 27.2%, and 62.4%, respectively, for the first, second, and third circuits compared to the conventional air separation circuit with a pressure reducing valve and the sweep efficiency is higher by an average of 116%, 83%, and 166%, respectively. The study showed that the use of LNG cooling capacity in the air separation unit’s process flow can significantly increase the sweep efficiency, reduce specific energy costs per unit of product, and reduce the cost of the plant. The paper discusses the advantages and disadvantages of each circuit and suggests possible applications of the obtained results.

BACKGROUND: In the Russian Federation, single cryotherapy units (cryosaunas) using liquid nitrogen as a cryogen have been in operation for more than 25 years. Cryosaunas were developed as an alternative to expensive multi-person units. Clinical practice of using cryosaunas has shown their efficacy and safety and the medical indications for cryotherapy has significantly expanded. These achievements are not considered and even challenged by foreign scholars.

AIM: Рromotion of reliable information about the operation principle and advantages of Russian cryosaunas, analysis of modern foreign publications on cryotherapy equipment and technologies, demonstration of the reasons for stagnation of the general cryotherapy method in Western Europe, promotion of a well-founded vision among the Russian professionals about the competitive advantages of various types of cryotherapy equipment.

METHODS: The paper is written “based on” a research published by members of the IIR Working Group on Whole Body Cryotherapy/Cryostimulation, issued as an official IIR document. The authors of this publication claim that despite the rapid spread of the cryotherapy method, the technological foundations of the effectiveness of this method have not yet been identified, and the information of its clinical use is unreliable. This statement contradicts actual facts, since in Russia technological recommendations for effectiveness and safety have been enunciated and proved in relation to single-seat cryosaunas, information and clinical effects when using cryosaunas have been published, including in the IIR-affiliated publications, where members of the cryotherapy development working group published their findings. Inaccurate information on the possibilities of using the whole body cryotherapy method discredits cryogenic therapy in general and hinders speading of highly effective domestic equipment.

RESULTS: The paper provides data on the discrepancy between a description of the operating principle of cryotherapeutic units with nitrogen cooling, description of the history of the development of this class of cryomedical equipment, description of the operating principle of single-seat cryosaunas, technological solutions that ensure therapeutic effectiveness and safety of equipment using liquid nitrogen as a cryogen. The paper provides Information on the reasons for stagnation of the general cryotherapy method in Western European countries, where the main one is the replacement of nitrogen cooling systems with compression refrigerators.

CONCLUSION: Single-seat cryosaunas with nitrogen cooling are a highly effective means of non-drug medical care, the competitive advantages of which are based on the results of many years of research.

BACKGROUND: Agriculture performance is directly related to the proper soil moistening. The moistening nutrient solution should have an optimal temperature (19–24°C), providing a sufficiently high oxygen content in the solution and a generally favorable climate for plants. The temperature of the nutrient solution is of particular importance in countries and regions with dry and hot climate, where the main task is to cool the soil when moistened. A large amount of resources is used to cool the nutrient solution, which significantly increases the production cost.

AIM: To develop an efficient, cost-effective, and sufficiently versatile nutrient solution cooling system for greenhouse crop production.

METHODS: To achieve the aim, we used an advanced adsorption refrigeration system (ARS) powered by secondary and waste heat sources for cooling and some previously developed innovative thermal units.

RESULTS: The use of methyl alcohol (methanol) as a refrigerating agent allowed to reduce the temperature of the heating source to 60–75°C, significantly increase operational flexibility of the ARS, and make it more independent of energy supplies. Hardened activated carbon is used as an adsorbent for the refrigeration system. These improvements allowed to double the system’s performance (with the same adsorber dimensions) and reach a significantly lower boiling point in the evaporator (-5°C...-2°C) compared to the existing commercial alternatives (e.g. adsorption chillers by SorTechAG, Germany).

To intensify the nutrient solution cooling, some cooler designs have been upgraded. We developed a compact, high-performance design of a hydroponic solution cooler, which uses heat pipes (two-phase thermosiphons). Heat pipes in the hydroponic solution cooler allow to increase the amount of transferred heat by several times. The solution cooler design provides for solution recirculation or its mixing using a screw agitator, significantly increasing the heat transfer coefficient when cooling the solution.

CONCLUSION: A high-performance nutrient solution cooler has been developed using hydroponic technologies and an adsorption refrigeration system, where methyl alcohol is used as the refrigerating agent and activated carbon is used as an adsorbent. Significant power savings are achieved through the use of secondary and sufficiently low-potential heat sources.