Vol 111, No 1 (2022)
Original Study Articles
Analysis of losses in fan coil units by using the entropy-statistical method
Abstract
BACKGROUND: Systems with chillers and fan coil units are widely used in air conditioning. Therefore, entropy-statistical analysis of energy losses in a duct-type two-pipe fan coil unit with controlled air flow is relevant.
AIM: This work aimed to review a method for determining losses by using the entropy-statistical method and to calculate losses due to non-ideal heat transfer and hydraulic losses in fan coil units.
MATERIALS AND METHODS: Losses were determined using the entropy-statistical method.
RESULTS: A comparative analysis of the results was performed. Diagrams of the distribution of loss components and recommendations for their reduction are presented.
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Comparison of efficiency losses due to leaks for turbine units of aviation air conditioning systems with petal-type gas-dynamic bearings and ball bearings
Abstract
BACKGROUND: Designers of turbomachines strive to increase the efficiency of expanding compressed gases by reducing all kinds of energy losses, particularly due to clearances between the impeller and the body elements of the turbomachine.
AIM: This article aimed to evaluate a possible increase in efficiency with a decrease in the radial and axial clearance between the blades of a radial-axial impeller and the casing of a centrifugal expander in the designs of turbomachines with ball bearings and petal-type gas-dynamic bearings.
MATERIALS AND METHODS: The radial and axial clearances between the blades of the radial-axial impeller and the centrifugal expander casing in the designs of turbomachines with ball bearings and petal-type gas-dynamic bearings were compared by analyzing the experience of Russian and international experts in developing turbomachines. Models were presented for estimating the efficiency losses of a centrifugal expander depending on the value of the radial and axial clearances. A comparative calculation of the efficiency loss for medium- and high-cooling-capacity refrigeration turbines of aircraft air conditioning systems was performed.
RESULTS: Based on the calculations, a conclusion was derived about the predominance of the influence of the radial clearance. The calculations revealed that with a decrease in the clearances between the impeller and the casing in a design with petal-type bearings, a refrigeration turbine of medium cooling capacity (16 kW, 2 impellers) can be expected to experience an increase in efficiency by an average of 2.3%; this expected increase is 0.75% to 1.4% for a high-capacity refrigeration turbine (55 kW, 3 or 4 impellers). Findings indicate that performing works to reduce radial clearances in the designs of turbomachines with petal-type gas-dynamic bearings is necessary.
13-20
Analysis of the duration of the low-temperature circulation charging of an adsorption methane storage system using the ANSYS Fluent software package
Abstract
Adsorbed natural gas (ANG) systems are a promising alternative to the high-pressure compressed natural gas and low-temperature liquefied natural gas. ANG systems accumulate methane with lower energy consumption and an increased fire and explosion safety due to the gas-bound state in the pores. However, the charging process is complicated due to the thermal effects of adsorption, which reduce the method’s energy efficiency, thus needing an additional thermal control. A study of the duration of low-temperature circulation charging of an elementary adsorption cell of various geometries was conducted under different temperature and pressure modes. The charging completion criterion was achieving 95% limit value of the amount of accumulated methane, which was constant for all considered cases. As a result of modeling, a reduction in the duration of gas accumulation was observed with an increase in the operating pressure. It has been established that the charging time is significantly affected by the gas channel opening diameter, required to reduce the hydraulic resistance of the adsorbent layer as when the channel diameter increased from 4 to 6 mm, the charging time decreased by 138 s or 25% on an average. A twofold smaller effect of ~13% was registered with an increase in the diameter from 2 to 4 mm due to the changing cooling nature.
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Change in the content of phenolic compounds in semi-finished products from endive Cichorium endivia during low-temperature processing
Abstract
BACKGROUND: Research on changes in the content of monomeric and dimeric phenolic compounds and their amount during freezing and storage of semi-finished products is relevant because the varieties of endive Cichorium endivia, which have many useful elements, are applicable for medical and dietary nutrition.
AIM: This article aimed to analyze the kinetics of the oxidation and hydrolysis reactions of phenolic compounds of three varieties of endive during freezing and storage.
MATERIALS AND METHODS: The total content of phenolic compounds and the amount of phenolcarboxylic acids and flavonoids in fresh vegetables and semi-finished products from Russian varieties Kruzhevo and Elvira endive, as well as the Italian variety Kornetto K-56, were determined by spectrophotometry in fresh endive after harvesting, then after homogenization, freezing, and periodically in the process of low-temperature storage.
RESULTS: Kinetic dependencies of changes in the content of phenolic compounds on the duration of storage of semi-finished products from endive varieties Kruzhevo, Elvira, and Kornetto K-56 in a frozen state were revealed. The constants of the reaction rate (pseudo-first order) of the change in the content of the studied substances during storage of endive semi-finished products were calculated. To reduce the loss of cell sap during defrosting to maintain the amount of phenolic compounds during storage of endive semi-finished products, adding pectin in the homogenization stage at an amount of 3.0% by weight of the homogenized endive of the varieties under study is recommended.
CONCLUSIONS: During storage of endive, phenolic compounds are preserved to the maximum, and cell sap losses are reduced within 180 days in the Elvira and Kruzhevo varieties, and within 150 days in the Kornetto K-56 variety. The frozen semi-finished product from homogenized endive of the studied varieties is recommended for use in healthy nutrition technologies, particularly in the production of low-calorie drinks and bakery and confectionery products.
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Development of the technology for creating air conditioning systems in an arid climate (Eritrea)
Abstract
This study aimed to determine the initial data and develop a technology for creating air conditioning systems under the complicated climatic conditions of East Africa. A technique for processing the observational materials is proposed and the corresponding results are stated, which are subsequently used to determine the temperature and humidity of the outdoor and indoor air on the premises of the College of Marine Science and Technology located in the most complicated climatic region of Eritrea. The choice was substantiated, and the calculation and selection of equipment for a special combined environmentally-friendly air conditioning system were performed.
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News
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XXIX Annual General Meeting of the International Academy of Refrigeration: Summary Report
Abstract
The XXIX General Annual Meeting of the International Academy of Refrigeration (IAR) was held on April 21, 2022, at the St. Petersburg National Research University ITMO (ITMO University). The meeting was held in a hybrid mode, in-person and online (Zoom). Professor V.A. Pronin of ITMO University chaired the meeting.
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Low-temperature technology in the context of a new energy transition paradigm (February 1–2, 2022, ITMO National Research University, St. Petersburg)
Abstract
A scientific and technical conference with international participation, “Low-Temperature Engineering under Conditions of a New Energy Transition Paradigm,” was held on February 1–2, 2022, at the National Research University ITMO (ITMO University, St. Petersburg) at the Mega-Faculty “Biotechnologies and Low-Temperature Systems.” It was organized by the International Academy of Refrigeration (IAR), ITMO University, and Working Group “Properties of Refrigerants and Heat Transfer Agents” of the National Committee on Thermophysical Properties of Substances of the Russian Academy of Sciences. Information support was provided by the journals Vestnik Mezhdunarodnoy Akademii Kholoda and Imperiya Kholoda, as well as the web portal Holodinfo.ru. The general sponsors of the conference were TechnoFrost and CryoFrost Engineering.
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Fishery complex of the Murmansk region: renunciation of the use of ozone-depleting substances in perspective
Abstract
The Murmansk State Technical University (MSTU) hosted events on February 2 and 3, 2022, dedicated to the renunciation of the use of ozone-depleting substances and fluorine-containing greenhouse gases of the fishery complex in the Murmansk region, as well as the conference “Legislative restrictions and the transition of fishery enterprises of the Murmansk region to efficient and environmentally friendly refrigerants.”
55-56
BITZER at the 2022 Winter Olympics in Beijing
Abstract
At present, the sport of setting records combines not only the highest skill of the strongest athletes in the world but also the most advanced technology. While the whole world is watching the competition with bated breath, we invited refrigeration industry experts to look behind the scenes of this fantastic event. The BITZER team was active in the technical support of the Olympics, providing compressors to several key facilities. Customers have chosen BITZER because they require exceptional reliability, high energy efficiency, and the use of modern refrigerants. We proudly present the venues for the 2022 Winter Olympics and wish success to the Russian Olympic team!
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After a break in 2021, the Climate World Expo returned to Moscow in a new format
Abstract
After two years of uncertainty and the desire to reunite the industry, the event brought together manufacturers and suppliers of air conditioning, ventilation, and heating systems, as well as industrial and commercial refrigeration equipment, and their consumers, namely engineering, management companies, design and installation organizations.
65-69
Refrigeration industry and agricultural policy in Russia: product safety and quality
Abstract
The annual exhibition “Meat industry. Chicken king. Refrigeration industry for the agro-industrial complex/International Academy of Refrigeration Russia & VIV” and the summit “Agrarian policy of Russia: safety and quality of products” were held at the International Exhibition Center Crocus Expo on March 15–17, 2022. ASTI Group Exhibition Company organized the event.
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Book reviews
The new textbook Automation of Refrigeration Units
Abstract
The new textbook Automation of Refrigeration Units, published by Intermedia (St. Petersburg) in April 2022, presents the program contents of the special subject Automation of Refrigeration Units developed to train students based on the federal state educational standard of higher education. The textbook contains lecture course content from the Department of Refrigeration Machines of the Astrakhan State Technical University and its branch, the Dmitrov Fishing-Industry Technological Institute.
Zhiltsov IB, Novikov IV. Automation of refrigeration units: a textbook. – St. Petersburg: Information Center «Intermedia», 2022. – 258 p. ISBN 978-5-4383-0240-7
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Obituary
Kolosov Mikhail Anatolyevich (29.02.1956 – 17.04.2022)
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