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Vol 111, No 3 (2022)
Reviews
The Problem of Utilization of Liquefied Natural Gas Vapor at Large-scale LNG Plants
Abstract
The liquefied natural gas (LNG) is stored under low overpressure in a saturated state in large-capacity tanks with multilayer thermal insulation. Owing to the input of heat from the environment through thermal insulation, LNG is continuously evaporated. Since natural gas is a multicomponent mixture, LNG vapors are enriched with its low-boiling components, then the supply of heat from the environment reduces the amount of liquid in the reservoir and changes its chemical composition. Similar phenomena occur during LNG transportation. The present paper deals with the problem of LNG vapor utilization during its storage and transportation. Information is presented on the causes of the LNG vapor formation (boil-off gas) and methods for its disposal during storage and transportation to consumers. A numerical experiment was performed based on the data of LNG storage in large-capacity storage facilities at the Yamal LNG plant. The technique consists of the estimation of material flows toward the system of accumulation and extradition of LNG. The results show that the vapor flow generated from the inflow of new LNG portions into the storage significantly exceeds that generated from the heat supply from the environment.
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Original Study Articles
Selection of a Ship Compressor Using Statistical Data Processing
Abstract
INTRODUCTION: Compressors are essential for supplying compressed air at various pressures and flow rates to the ship’s power systems, and to the ship as a whole. An appropriate choice of the compressor is essential for the proper operation of water transport infrastructure. Hence, it is necessary to consider this issue in detail. If all variables, the compressor selection parameters to be considered, were measured in the same scales and units, it would be possible to suggest adding up all values, but this approach is very crude. The solution is to normalize the values of the variables and then calculate a final criterion based on them.
AIM: Finding a formal criterion by which the selection of a particular compressor will be made.
MATERIAL AND METHODS: The process of selecting a compressor for starting the ship’s engines and for the general operation of the ship is discussed based on exponential and linear rationing methods. Certain parameters of compressors from domestic and foreign manufacturers are offered for statistical processing. Subsequently, data processing was carried out using maximum likelihood estimation and logistic regression.
RESULTS: The result of the study is a single formal criterion, the final rating, instead of several qualitative parameters. A set of characteristics has been determined that describes the optimal compressor based on the above calculations and data processing. A simulation of the probability of assigning a compressor, with a certain set of characteristics, to a positive or negative class has been performed. The training of the model was done using the available training data.
CONCLUSION: Statistical methods of data processing can be applied to an object such as a compressor. Given a set of desired compressor characteristics, it is possible to teach the machine to determine the optimal compressor.
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Local cryotherapy investigation on the biotissue phantom
Abstract
BACKGROUND: Local cryotherapy (LC) is a physiotherapeutic method for the treatment of various diseases, including musculoskeletal disorders. The physician relies on his experience and the data from the LC equipment manufacturer for the given method and exposure modes. This is not sufficient to determine the correct dosing and to understand the effect of the various treatment parameters on the biotissue to have precise control over the effects of the treatment on the biotissues. Hence, it is imperative to conduct a study of different LC methods and modes to perform effective and safe treatments. The surface temperature of the biotissue is a convenient measurable quantity to ensure efficiency and safety. Previous studies show that the target temperature is 10 ± 2 °C, with a lower limit of 0 °C. If the temperature drops below 0 °C, then tissue damage is possible.
AIM: Experimental comparison and identification of the most suitable modes in two methods of contactless local cryotherapy.
MATERIALS AND METHODS: An experimental installation was developed and created. A series of experiments were carried out on a model medium with thermophysical properties close to those of the biotissues. The comparison of liquid nitrogen and air cooling was performed. The temperature was measured with resistance thermometers (Pt100) on a surface and inside of a model medium.
RESULTS: When cooled by liquid nitrogen vapors from a distance of 10 and 15 cm from the surface, the accepted average target temperature of 10 °C was reached in 1.8 and 4.4 min, and at a depth of 8 mm, the temperature was 26.4 and 23.7 °C, respectively. When cooled with air from a distance of 10 cm from the surface with maximum and minimum flow, the target temperature was reached in 2.5 and 13.3 min, at a depth of 8 mm, the temperature was 22.9 and 16.0 °C, respectively. Although air cooling from a distance of 15 cm was not possible to lower the temperature down to the target value, the less intense flow made it possible to lower the internal temperature in the model medium more strongly while having a weaker effect on the surface. This effect can potentially be positive in the treatment of musculoskeletal disorders, mainly joints.
CONCLUSIONS: Among those tested, the most suitable modes of the considered methods that meet the requirements of efficiency, safety, and convenience of practical implementation were identified. For cooling using liquid nitrogen vapors, this is a mode spraying at a distance of 15 cm with a stable technique with a possible exposure time of 4.4 to 15 minutes. For air cooling, this is a mode with a stable technique with a constant flow with the nozzle fixed relative to the surface of the model medium at a distance of 10 cm with a minimum flow rate (350 l/min) with a possible exposure time of 13.3 to 21.5 min.
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Mathematical modeling of the rotor dynamics of a turbomachine on gas foil bearings subjected to vibration
Abstract
BACKGROUND: The use of gas foil bearings is a promising development in the field of turbomachinery due to their economy, autonomous operation capability, and durability. However, gas foil bearings have lower load capacities than other types of bearings. However, turbomachines are complicated, dynamic systems that must meet high standards of safety, sustainability, and durability against external mechanical factors like vibration, shock, etc.
AIM: Development of a mathematical model of rotor dynamics to predict the displacement of the rotor in foil bearings for maintaining separation between the rotor and the housing while being subjected to vibration.
METHODS: A mathematical model of the dynamics of a stiff rotor on gas foil bearings was built and analyzed, taking into account the flexibility of the bearing bushing supports and the housing of the turbomachine. Stationary and transient modes of operation, including the transient modes combined with random vibration, are simulated. The system of ordinary derivatives equations describing the mathematical model was solved by the Rado IIA method. Random vibration was modeled using digital Fourier transformation. The modeling results were analyzed by discrete Fourier transformation and short-time Fourier transformation.
RESULTS AND CONCLUSIONS: Rotor movement trajectories were obtained and the results were compared with author’s previous experimental data. Upper bound of maximal displacements was obtained. The maximum values of rotor displacement can be used to set the optimal values of blade tip gaps.
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Investigation of the physical model of the skim milk drying process in an electric field
Abstract
BACKGROUND: One of the promising approaches for the intensification of technological processes associated with food products is the use of an electric field. An effective solution to this issue requires the development of a physical model of the interaction of an electric field with a raw material of biological origin, taking into account its characteristics and processes occurring at the macro- and the microlevels.
AIM: To develop a physical model of the interaction of an electric field with a raw material of biological origin, taking into account its characteristics and processes occurring at the macro- and microlevels. Evaluation of the efficiency of using the electric field and their influence on the processed product.
MATERIALS AND METHODS: A physical model was developed for the drying of skimmed milk in an electric field using a complex method, including experimental studies and a systematic approach to the processing and substantiation of the results and conclusions.
RESULTS: The electrokinetic phenomenon of microelectroosmosis, which involves the movement of a liquid along the microcapillaries of a porous structure under the action of an electric field was confirmed experimentally. The nature of the kinetics of the process of liquid movement through microcapillaries and its dependence on the parameters of the electric field was experimentally established. The quantitative variation of the height and the rate of rise of the liquid rise along microcapillaries as a function of time was determined for different frequencies of applied electrical impulses.
CONCLUSIONS: The complex model of the convective drying process suggests that the process of drying could be controlled and accelerated by the application of electric pulses due to microelectroosmosis, which activates the transformation of liquid (milk) along the internal (channels) capillaries of the dried particles of skimmed milk powder from the center to its surface.
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Natural refrigerants are favored by the future
Abstract
BACKGROUND: Reducing the harmful impact on the environment is a promising way to the development of low-temperature technology. According to the amendment to the Montreal Agreement, approved by the Russian Federation, the use of hydrofluorocarbons should be reduced by 85% by 2036.
AIMS: To justify the use of hydrocarbons as refrigerants in terms of their effectiveness.
MATERIALS AND METHODS: Here, we have studied the losses of refrigeration plants at different temperature levels (refrigerant boiling points of −25 °С, −18 °С, and −13 °С), while working with the refrigerants R134a, R404A, R1270, and R290 using the entropy-statistical method of thermodynamic analysis.
RESULTS: Experimental results revealed that the natural refrigerants, R1270 and R290 have higher efficiency than the conventional refrigerants R134a and R404A. The values of the cooling coefficient under adiabatic compression are higher by 16.28%, 1.81%, and 1.14% compared to R404A, R1270, and R290, respectively, for installation with a boiling point of −13 °C. Similarly, for installation with a boiling point of −18 °C, these values are higher by 16.84%, 1.13%, and 0.58% compared to R404A, R1270, and R290, respectively. Furthermore, for installation with a boiling point of −25 °C, the values of the cooling coefficient under adiabatic compression are higher by 18.53%, 0.8%, and 0.43% compared to R404A, R1270, and R290, respectively.
In addition, the degree of thermodynamic perfection for R290 is higher by 27.99%, 19.2%, and 14.79% compared to R134a, R404A, and R1270, respectively, for a boiling point of −13 °C. Similarly, for R290 and a boiling point of −18 °C, it is higher by 21.25%, 14.71%, and 9.9% compared to R134a, R404A, and R1270, respectively.Furthermore, for R290 and a boiling point of −25 °C, it is higher by 27.94%, 11.44%, and 3.61% compared to R134a, R404A, and R1270, respectively.
In this study, data on the production of hydrocarbon refrigerants, in particular R1270 and R290, under the Russian Federation are presented. Moreover, quality indicators and the main areas of application for the same are provided here.
CONCLUSIONS: The results of the analysis showed the prospects of using natural refrigerants (R1270 and R290) and allowed us to assess different ways to improve the refrigeration plants.
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Obituary
Garanov Sergey Alexandrovich. 04.09.1955 – 26.11.2022
Abstract
Sergey Alexandrovich Garanov, Associate Professor of Department E-4, has passed away! He was a bright, honest person, a conscientious teacher, and a top-tier specialist in the field of low temperature equipment and air conditioning.
With his work, exactingness, and qualifications, Sergey Alexandrovich made significant contributions to the development and production of air conditioning systems (ACS) in Russia for railway transport. For many years he was the mind and eyes of Russian Railways in the realm of ACS. He was known for his consistent demand and support for the creation and implementation of new technologies. The memory of Sergei Aleksandrovich Garanov would forever be blessed!
The editors of the journal “Refrigeration Technology,” the staff of the Department E-4 of the Power Engineering Faculty of Bauman Moscow State Technical University, A.L. Emelyanov (Doctor of Technical Sciences, Professor, Academician of the International Academy of Refrigeration (IAR), St. Petersburg State University of Low Temperature and Food Technologies), S.E. Buravoy (Doctor of Technical Sciences, Professor, Academician of the IAR, CSC “Petroklima”) offer their sincere condolences to their families and friends.
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Editorials
Erratum in: Goncharova G.Y. et al. “Prospects for Creating a New Generation of Ice banks for Systems with Uneven Heat Loads”
Abstract
We made corrections in the article "Prospects for Creating a New Generation of Ice banks for Systems with Uneven Heat Loads" by G.Y. Goncharova et al. published in 'Refrigeration Technology' 2022;111(2) doi: 10.17816/RF108496. The wrong affiliation info was published on the page 106: "V.M. Gorbatov Federal Research Center for Food Systems of Russian Academy of Science" is the proper title of the organization. The proper title is ""V.M. Gorbatov Federal Research Center for Food Systems" of RAS".
Also we correct the title of the article "Prospects for Creating a New Generation of Ice banks for Systems with Uneven Heat Loads". Current title is "Prospects of a new generation of ice banks development for systems with uneven heat load".
Editorial team and authors belives that these errors did not affect published data interpretation by readers, so the article should not be retracted. The article has been corrected and replaced online.
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Erratum in: "Lyudmila D. Akimova (11.08.1929–12.09.2022)"
Abstract
There was a mistake in the obituary "Lyudmila D. Akimova (11.08.1929–12.09.2022)" published in 'Refrigeration Technology'2022;111(2) doi: 10.17816/RF112047. Previously published text: "The editorial board of the journal “Refrigeration Technology”, the All-Russian Research Institute of the Refrigeration Industry (ARIRI) and the National Committee for the Participation of the Russian Federation in the International Institute of Refrigeration (IIR) are deeply saddened to announce that Akimova Lyudmila Dmitrievna passed away on September 12, 2022 at the age of 94 after a long illness. She was the permanent editor-in-chief (from 1985 to 2020) of the renowned journal “Refrigeration Technology” and academician of the IIR" was replaced .
The new text is: «The editorial board of the journal “Refrigeration Technology” together with All-Russian Scientific Research Institute of Refrigeration Industry – branch of «V.M. Gorbatov Federal Research Center for Food Systems» of RAS and the Russian National Committee for the International Institute of Refrigeration (IIR) announce with deep regret that Liudmila D. Akimova passed away at the age of 93. She was a longstanding editor-in-chief (from 1985 to 2020) of the well-known journal “Kholodilnaya Tekhnika”. Moreover, she was renowned as an academician, which put a lot of effort into the International Academy of Refrigeration (IAR).»
Authors and editors regret readers for these errors. But these errors were not able to significantly affect readers and presented data interpretation by them. So, the article should not be retracted. The article has been corrected and replaced online.
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