Thermodynamic Analysis Method Research Articles

Field studies of a thermoelectric system for thermal action on the anterior segment of the human eyeball

Objective. The aim of the study is to develop the design of a thermoelectric system (TPS) for thermal action on the anterior segment of the human eyeball, as well as to conduct its field studies.Method. The study is based on the methods of thermodynamic analysis, natural and computational modeling of processes and life support facilities.Result. The design of TPP for thermal impact on the anterior segment of the human eyeball is presented. Its fullscale studies were carried out in accordance with the existing methods of thermophysical measurements. Curves of changes in the temperature of the surface of the gelatin model of the human eyeball over time during cooling and heating were obtained for the supply currents of the thermoelectric module (TEM) included in the TPP, equal to 2.5 A, 3 A, 3.5 A, A and 1 A, 1 .2 A, 1.4 A, as well as changes in the temperature of the object of influence over time when changing the cooling mode to heating and vice versa. To assess the possibilities of heat removal from the hot junctions of TEMs in the system, data were obtained on the change in their temperature over time during the cooling effect for various values of the module supply current.Conclusion. It has been established that standard modules produced by domestic firms can be used as TEMs in the system. The duration of entering the TPP mode is about 230 s. The refore, it seems appropriate to bring the TPP to the operating mode before the actual procedures are carried out. It has been established that the duration of TPP switching from cooling to heating mode and vice versa is 230 s, which requires further optimization of the design and operating modes of the device through the use of more advanced types of TEMs and the use of forced operation of thermal modules in the transient mode.

Modeling of regasification and recirculation processes during the transportation of liquefied natural gas

Objective. The purpose of the research is modeling and analysis of technological processes occurring at the transshipment terminal of liquefied natural gas.Method. The study is based on the methods of thermodynamic analysis, full-scale and computational modeling of processes and objects of refrigeration and cryogenic equipment in order to find optimal solutions in terms of efficiency, reliability and service life of low-temperature installations, machines and apparatus.Result. The article describes the operation algorithm of an LNG transshipment terminal and proposes a mathematical apparatus for modeling the technological processes occurring in it. Information about the causes of the formation of LNG vapors (Boil-off gas (BOG)) during its transportation and reloading is presented, methods for utilizing excess LNG vapors are considered.Conclusion. To maintain the cryogenic temperature of the unloading arms, an LNG recirculation line (recirculation pipelines) is provided.

Non-equilibrium thermodynamics in a single-molecule quantum system

Thermodynamic probes can be used to deduce microscopic internal dynamics of nanoscale quantum systems. Several direct entropy measurement protocols based on charge transport measurements have been proposed and experimentally applied to single-electron devices. To date, these methods have relied on (quasi-)equilibrium conditions between the nanoscale quantum system and its environment, which constitutes only a small subset of the experimental conditions available. In this paper, we establish a thermodynamic analysis method based on stochastic thermodynamics, that is valid far from equilibrium conditions, is applicable to a broad range of single-electron devices and allows us to find the difference in entropy between the charge states of the nanodevice, as well as a characteristic of any selection rules governing electron transfers. We apply this non-equilibrium entropy measurement protocol to a single-molecule device in which the internal dynamics can be described by a two-site Hubbard model.

Natural refrigerants are favored by the future

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.

Fusion calorimetric experiments and QSPR modeling to inversely explore the accuracy of thermodynamic methods: A case study of the apparent activation energies of 18 aromatic nitro compounds

The choice of thermodynamic analysis method will directly affect the accuracy of thermal hazard assessment. In this work, two advanced calorimetric experiments were used to obtain the pyrolysis parameters of 18 aromatic nitro compounds under dynamic and adiabatic conditions, aiming at the inherent thermal risk and explosion characteristics of aromatic nitro compounds in important chemical processes. The multiple linear regression (MLR) and artificial neural network (ANN) models corresponding to six typical thermodynamic analysis methods (FWO, Kissinger, Starink, Friedman, Townsend, and TMRad) were constructed by using the apparent activation energy (Ea) calculated by fitting as the basic sample data and combining with quantitative structure-property relationship (QSPR). Two kinds of parameters in internal and external validation were used as the main indexes to judge the accuracy and reliability of different kinetic analysis methods applied to aromatic nitro compounds. This study is expected to provide theoretical support and technical guidance for the chemical industry in the thermal hazard assessment process of nitro compounds.

Selective recovery of lithium from spent LiFePO4 battery via a self-catalytic air oxidation method

To achieve the long-term healthy development of new energy vehicles and energy storage industries, the recycling of spent lithium-ion batteries is extremely significant. Air oxidation leaching at room temperature can achieve the efficient recovery of lithium from LFP scrap (generated in LiFePO4 material production), but this method is unsuitable for the treatment of cathode materials from spent LFP batteries. In this work, cyclic voltammetry measurements were first innovatively employed to clarify the reasons for the ineffective leaching of lithium from spent LFP materials via air oxidation leaching and provide the theoretical basis for intensified leaching. Subsequently, a novel method of self-catalytic air pressure leaching was proposed to selectively recover lithium from spent LFP batteries, which ingeniously employs green and cost-free air as the oxidant and self-owned Fe in the LiFePO4 as the O2 deliverer and catalyst. 98.9% Li and only 0.41% Fe, and 3.01% P were leached from spent LFP materials under 0.4 MPa of air pressure, n (H2SO4)/n (Li) ratio of 0.5, liquid to solid ratio of 20 mL/g, 90 °C, and 5 h. The leaching kinetic study was performed and it indicated that the leaching kinetics of Li was controlled by chemical reaction. By combining the results of the thermodynamic analysis and various characterization methods, the reaction course of this self-catalytic air pressure leaching was clarified. In particular, AC-TEM and SEM-EDS analysis showed that the dispersed carbon bands covered on the LiFePO4 particles have been destroyed during the oxidation leaching, which significantly promotes the lithium recovery rate. Finally, the economic feasibility and environmental impact evaluations demonstrated that the proposed method has the advantages of high recycling profits, environmental friendliness, and low carbon emissions.

Thermodynamic Evaluation of Asphalt Concrete Properties and its Mixing Energy Consumption by Exergy Structure

Abstract. The relevance of solving the problem of energy saving, today, is enhanced by the requirements of an environmental nature, united by the term “green energy”. Solving the problems of climate conservation is inseparable from solving the problem of energy saving. Green, hydrogen energy, about which there has been a powerful and aggressive debate over the past decade, turned out to be directions far from solving the problems of both energy saving and environmental protection. The solution of both problems of energy saving and environmental protection at the present time and in the foreseeable future is being solved on the basis of the use of traditional primary energy resources, primarily natural gas. In this regard, the need to solve the problem of quantifying the thermodynamic perfection of heat-technological process for producing an asphalt concrete mixture becomes extremely relevant. This assessment is most simply carried out on the basis of the exergy method of thermodynamic analysis with the determination of the exergy structure of the asphalt concrete mixture flow, including thermomechanical, concentration and reaction components. The value of the concentration component of the exergy of the asphalt concrete mixture allows us to assess the energy efficiency of its production at asphalt concrete plants based on the modern exergy method of thermodynamic analysis; gives a quantitative estimate of the energy consumption for the process of mixing the ingredients of the asphalt concrete mixture in the mixing unit of asphalt concrete plants. The paper defines the structure of the exergy of the asphalt concrete mixture, in which the transit reaction component dominates, which determines the specificity of the exergy of the asphalt concrete mixture. The value of the specific mass concentration component of the exergy of the asphalt concrete mixture in comparison with the thermal component is small and the error in determining the concentration component, which cannot be objectively eliminated, does not affect the results of thermodynamic analysis.

Changes in the physical and mechanical properties of aluminum depending on the composition of the alloying elements

Subject of research: the influence of the concentration and composition of alloying elements Mn, Ti, Cr, Y, Mo, W, V on the change in the aluminum recrystallization temperature.
 Purpose of research: to find the optimal concentration of alloying additives, at which the recrystallization temperature reaches its maximum value.
 Methods and objects of research: using the methods of thermodynamic analysis of binary state diagrams of aluminum with alloying additives, it has been established that the nature of the change in the recrystallization temperature depends on what type of eutectic or peritectic reaction the formation of intermetallic compounds belongs to. It is shown that aluminides act as alloy modifiers and impart high mechanical properties to products.
 Main results of research: it was found that for the AlMn system, the optimal content of Mn should be considered 0.2%, for the AlCr system, the maximum increase in the Al recrystallization temperature is observed at 0.6% Cr, for the AlY system, the mechanical properties of Al at elevated temperatures maximum at 1% Y.

Thermodynamic Analysis of an Ethylene Reliquefaction System Using the Entropy-Cycle Method

In this study, a boil-off gas reliquefaction system that is a part of liquid ethylene gas (LEG) carriers is evaluated. The reliquefaction system is formed by two thermally interconnected two-stage refrigeration cycles. The working fluid of the bottoming cycle is ethylene; the working fluid of the topping cycle is propylene. The research is based on determining the irreversibilities in the reliquefaction system cycles using the entropy-cycle method of thermodynamic analysis. The impact of the process performance in the main components on the reliquefaction system energy efficiency has been evaluated by the entropy-cycle method. The greatest thermodynamic irreversibility is observed in the two-stage compression process of the bottoming cycle (9%), total throttling irreversibility in the reliquefaction system (8.5%), and vapor superheating at the suction into the low stage of the two-stage compressor of the bottoming cycle (8%). The results of the study showed that it is necessary to improve the design of expansion devices using the replacement of throttle devices with ejectors when designing cascade ethylene reliquefaction plants. In addition, when operating such systems much attention should be paid to the condition of the insulation of cargo pipelines and the parameters of the cooling system of the cargo compressor.

Thermodynamics second-law analysis in an unsteady conduction and radiation heat transfer system with internal heat source

This paper presents an improved thermodynamic analysis method used to evaluate the irreversibility and efficiency of a coupled conductive-radiative heat transfer process. The exergy analysis of the conductive-radiative process is developed based on the exergy balance equation. In the method, the local entropy generation rates due to the radiative heat transfer and heat conduction processes are calculated. Based on the entropy generation analysis, an exergy analysis is performed, the stored exergy of the system and the exergetic efficiency are determined, and the thermodynamic efficiency of the system is further evaluated. The results are verified by the principle of exergy balance and the exergy generation rate calculated by the method does not deviate from the theoretical value by more than 0.1%. Four heat source distributions are specified in the numerical analysis, which include completely uniform, partially uniform, and non-uniform heat source distributions in the numerical analysis. The effects of heat source distribution, conductive-radiative coefficient and total heat generation rate of medium on entropy generation and stored exergy of system are investigated. The numerical results show that the average temperatures and exergy storage rate of the systems with partially uniform heat source distribution are 5.1–79.7 K and 6.8–49.8% higher than the other distributions, and uniform and centralized heat generation in the internal region of the system is proposed. The total stored exergy of the systems has a tendency to first increase and then decrease, reaching its maximum at N = 1 as the conduction and radiation coefficients increase, and increasing as the total heat generation rate increases.

Insight into kinetic and Thermodynamic Analysis methods for lignocellulosic biomass pyrolysis

Pyrolysis is particularly attractive because it can convert lignocellulosic biomass into bio-oil, gases and solid charcoal in an efficient and environmentally friendly way. Determining the kinetic and thermodynamic parameters is fundamental to elucidate the reaction mechanisms and optimize biomass pyrolysis processes. The applicability and accuracy of kinetic and thermodynamic methods are systematically studied by analyzing theoretically simulated processes which simulate biomass pyrolysis processes and using statistical analyses. In terms of activation energy calculation, the Friedman method is capable of providing accurate activation energies, whereas the KAS and FWO isoconversional methods lead to some systematic errors in the resultant activation energies. The accuracy of the Kissinger method for estimating the frequency factor is dependent on the variation degree of kinetic parameters with conversion. The conventional method for determining thermodynamic parameters is based on the conversion rate peak temperature, which has no theoretical basis. Therefore, the concept of effective thermodynamic parameters is proposed, which are dependent on conversion and heating rate. And the thermodynamic analysis of the simulated processes is comprehensively investigated. Results revealed that the accuracy of the resulting thermodynamic parameters from the conventional method is dependent on the variation degree of kinetic parameters with conversion. It is expected that this study will provide an analysis framework and methodological guideline for the kinetic and thermodynamic analyses of biomass pyrolysis.

REFINEMENT OF THE FOUR-COMPONENT SYSTEM MgO – CaO – Al2O3 – Cr2O3 SUB-SOLIDUS STRUCTURE INCLUDING THE Сa6Al4Cr2O15 COMPOUND

The results of theoretical calculations of the subsolidus structure of the four-component system MgO – CaO – Al2O3 – Cr2O3 are presented, taking into account the three-component compound Сa6Al4Cr2O15. Thermodynamic and geometric topological analysis methods were used to establish stable conodes in the specified system. When dividing the concentration tetrahedron MgO – CaO – Al2O3 – Cr2O3 into elementary ones with the involvement of a geometro-topological analysis, it is possible to make an unambiguous closure to the elementary tetrahedron of faces with incident edges (connodes) through a common vertex. The use of this method allows to minimize the number of necessary thermodynamic calculations. The tetrahedra of the MgO – CaO – Al2O3 – Cr2O3 system, taking into account the stable phases, is caused by the presence of three "internal" conodes passing through the three-dimensional space of the concentration tetrahedron: Сa6Al4Cr2O15 – MgO; MgCa3Al4O10 – CaCr2O4, CaCr2O4 – MgAl2O4, which determine the presence of 14 elementary tetrahedra in the subsolidus region. The lengths of conodes and volumes of elementary tetrahedra were calculated taking into account barycentric coordinates and elements of Euclidean geometry. The phases included in the composition of the tetrahedron with the largest relative volume and the smallest asymmetry CaCr2O4 – СaAl2O4 –MgAl2O4 – MgO (185.6 ‰ and 2.55, respectively) have the highest probability of existence in the system, which will allow the development of a sustainable technology for creating composite materials based on calcium aluminochromite cement, with periclase as an aggregate, without special techniques dosage of initial components. At the same time, in the event of a violation of the technological process, magnesium aluminate spinel will be synthesized in the composition of the unformed material, which will not lead to deterioration of the performance characteristics of the composite used. It should be noted that elementary tetrahedra with a high degree of asymmetry, which require appropriate dosage accuracy when predicting the phase composition of synthesized composite materials, are located in areas of the system that are not technologically advantageous from the point of view of obtaining unformed refractories based on special binder materials, and are interest for materials scientists in the ceramic and refractory industries.

EN Thermodynamic analyses of heat exchangers in cryogenic systems

The problems of thermodynamic analysis associated with the heat exchangers that used in cryogenic technology are discussed. Heat exchangers of high and medium pressure air separation and fluidizing plants operating at different temperature levels were selected for modelling. There are many features according to which the classification of heat exchangers is made. These features include such facts as the number of flows of the working fluid, the relative direction of the flows of working substances, the purpose of the apparatus, and others. These features are also associated with the design of heat exchangers and the software for the design, which contains thermodynamic calculations. The general thermodynamic approach is based on the equation for the values of the thermodynamic efficiency characteristics and the restrictions imposed on them At the exergy method of analysis, the corresponding balance is based on the energy balance equation. On the basis of this balance, the losses from irreversibility of the selected object and its exergy (thermodynamic) efficiency can be directly determined In a heat exchanger, both types of losses exist, but it is not possible to reveal the contribution of each type to total losses using only the exergy balance. This is due to the fact that this balance is drawn up for a closed control surface that reflects a physical object and not logical reasons associated with this object. Meanwhile, the determination of technical losses is an urgent tasks since the change in the thermodynamic parameters that regulate these losses are the basis for increasing the coefficient of the thermodynamic efficiency of the analyzed system A method and an algorithm for calculating the components of losses from irreversibility in these heat exchangers are proposed. The exergy method of thermodynamic analysis was used to calculate the components of these losses for some two-flow heat exchangers. The investigation of the obtained calculation results is presented

Энергосбережение в производстве аммофоса на основе эффективного использования тепловых ВЭР-технологий

Background. The need to increase the production facilities of the key sectors of the Russian economy arises as the consequences of the covid condition and is justified by social, economic and food crises. Guarantees of food security are provided due to stability and development of national facilities of the agro-industrial complex. Thus, on the legislative level a strategy to develop chemical networks has been developed. Also, a plan to develop mineral production in the agricultural sector has been made. The plan is to be carried out based on the best available technologies when redesign and install new facilities that ensure the efficient use of fuel and energy resources. In addition, it is necessary to work out scientific and technical solutions based on energy-saving technologies. All the global problems and the existing tasks in the field of mineral fertilizers production determine the importance of this study, the main purpose of which is to develop energy-saving measures in the production of ammophos. Materials and methods. The subject of the study is an industrial workshop to produce compound fertilizer (ammophos). The production technology is analyzed, the sources of irrational utilization of energy are determined, and the thermal processes of the technology are studied to assess the thermodynamic efficiency. The methods of thermodynamic, economic, and environmental analysis are applied to assess the efficiency of the developed project. Results. Promising trends to improve technological processes are proposed. Also, an energy saving solution based on the utilization of secondary heat of chemical reactions has been developed. An energy-saving cogeneration system has been developed that allows generating heat and electricity. The characteristic of this solution is given. The possibility to use the obtained types of energy in production is considered. The promising outlook to implement the developed solution into production is discussed based on the methods of assessment of performance. Also, the possibility to scale this technological solution to similar industrial facilities is considered. A quantitative assessment of the environmental performance indicator (reduction of the annual volume of CO2) is given when introducing an energy-saving solution into manufacturing. Conclusions. In the future introduction of the developed energy saving measures will make it possible to improve, modernize and build new production facilities that will have different performance indicators both in terms of energy and environmental components. The use of the applied technologies can significantly improve the economic efficiency indicators not only of a specific facility, but of the entire agro-industrial complex.

Concept of PPI energy technology complex upgrading

THE PURPOSE. Development and implementation of a set of theoretical and practical recommendations for creating scientifically founded heat flow diagrams for pulp and paper processes, intensifying heat exchanging processes under the economical use of energy resources. METHODS. The method of thermodynamic analysis on the basis of exergy increments in the process of interaction of heat flows is proposed, it allows evaluating the energy efficiency of both individual PPI units and the entire process flow; mathematical relationship between exergy efficiency of process elements and that of a complex heat flow diagram; schematic diagram of a heat recuperator of PBM drying section with a closed loop for the air delivered to drying. RESULTS. Thermodynamic analysis was made to evaluate energy efficiency of PPI equipment; the relationship between conversion factor of thermal pumping plant and thermodynamic properties of actuating media was obtained. Sulfate pulp production was considered in detail. The low energy efficiency of the existing process flow diagram is shown, with its exergy efficiency being equal to 48%. A main share of the consumed exergy (71% of the incoming one) relates to the recovery boiler processes. The process flow diagram consisting of hydrochemical pulpchips processing is suggested. The recovery boiler and rotary-type lime kiln are removed from that flow diagram. Risks of air and water basins pollution fall. The main ways for increasing energy efficiency of lignosulfonates production at sulfite pulp plants are mentioned. DISCUSSION. Further development of energy efficient pulp technologies can be forecasted on the basis of application of fluid technologies such as supercritical water oxidation (SCWO). The positive results of research in water chemistry under supercritical parameters give promise to predict success in developing the energy efficient pulp technology by exposing pulpchips to water at the subcritical and supercritical parameters. Paper and board production relates to the complex physical–chemical and heat-wet processes. The thermodynamic studies allowed determining low exergy efficiency of a drying section of paper and board machine that is because of inefficient operation of the heat recuperation unit. This circumstance is responsible for the bulk supply of low pressure steam from a heat and power plant. The main ways for improving the heat flow diagram of PBM drying section are shown. Cogeneration issues in the pulp and paper industry are considered. The essential attention is given to environmental safety of energy efficient technologies. CONCLUSION. The paper presents main ways for increasing energy efficiency of basic production processes at pulp and paper enterprises. Based on the analysis of exergy efficiency of individual equipment elements and the entire process flow diagrams bottlenecks were revealed and measures for their removal were suggested.

Analysis of the mechanism of energy consumption for CO2 capture in a power system

The rather high energy penalty of CO2 capture is the critical gap deterring the deployment of Carbon capture and storage technologies. A deeper understanding of the mechanism of CO2 capture will lay a foundation for reducing energy consumption. Accordingly, this paper introduced a thermodynamic analysis method with a new criterion to reveal the mechanism of energy consumption in a power system integrating CO2 capture. The results indicate that although the energy consumption of the separation process in post-combustion capture is generally recognized as the dominant part of the capture penalty, the deterioration of energy utilization in power systems due to the provision of energy for CO2 separation is nonnegligible. For an improvement in separation efficiency, the ceiling of 50% separation efficiency indicates a penalty as low as 6 percent points, and a CO2 capture cost of approximately 24 $/tCO2 can be anticipated. For system integration, improving the energy-supplying method by shifting to an external energy source may be expected to be a preferable way to save energy. With the aid of the new thermodynamic analysis method, a better understanding of the performance of diverse CO2 capture technical routes can be obtained, which may be helpful for reducing energy consumption in CO2 capture technologies.

Modeling and thermodynamic analysis of thermal performance in self-pressurized liquid hydrogen tanks

Liquid hydrogen (LH2) is one of the most economic methods for large-scaled utilization of hydrogen energy. However, safe operation and storage of LH2 relies on accurate prediction of the pressure rise and adequate investigation on thermal behaviors inside LH2 tank. In light of this, a modified thermal multi-zone model (TMZM) considering heat and mass transfer between vapor and liquid is developed in this paper. The model has a maximum relative error of 4.67% in predicting pressure rise against the experimental results from NASA. A thermodynamic analysis method is proposed to clarify the influences of key parameters including the temperature, compressibility factor and density of vapor, and working conditions including heat leakage and initial superheated degree on the pressurization rate. The results indicate that temperature of vapor in the ullage and vapor-liquid interfacial mass transfer rate are two main parameters determining the pressurization rate, and the effects of the two parameters are different between different stages. The distinction of stages depends on heat leakage and initial superheated degree. For the working condition with an initial filling rate of 50% and a heat leakage of 10 W, temperature of vapor is the parameter dominates pressurization rate during 96.8% of the whole self-pressurization process. Heat leakage also has a vital impact on the distinction of stages, when heat leakage increases to 80 W, the temperature of vapor dominating stage will reduce to 46.4%. Furthermore, pressurization rate is sensitive to initial superheated degree in the ullage. An increase of 4 K of the initial superheated degree leads to a 53.3% decrease of the pressurization rate. This study provides a useful method for the reliable design and quick optimization of high performance LH2 tanks.

EN Thermodynamic analysis of a real marine refrigeration system for cruise ship "Scarlet Lady"

This paper presents an energy analysis of the marine refrigeration system as a component of the machi­nery system of the cruise liner “Scalet Lady”. This type of ship is one of the most complex types from an energy point of view, which is associated with a wide variety of energy consumers. The study uses two methods of thermodynamic analysis of real cycles: the method of cycles and entropy-statistical method. For the analysis, the experimental data on the operating modes of the marine refrigeration system has been used. According to the results of processing the experimental data, a thermodynamic cycle has been formed and an energy calculation of the cycle has been performed using classical methods for two-stage refrigeration machines. With the help of the cycle model, the external irreversibility is determined by successively reducing the energy efficiency of the ideal cycle. The Lorentz cycle has been chosen as an ideal model, taking into account the variable temperatures of heat supply and removal during heat exchange “heat source – phase transformations of the refrigerant R407f”. Along with the evaluation of efficiency, the distribution of losses by the components of the refrigeration system has been established, energy weaknesses that require improvement has been identified, and the most effective ways to reduce energy costs have been outlined. Analytical conclusions have a graphical interpretation of the thermodynamic efficiency assessment for the real refrigeration cycle. It has been established that in the considered real cycle of a marine refrige­ration system, the greatest influence on energy efficiency is exerted by external irreversibility in the condenser, in particular, in the overheating zone (25.64% of the total energy consumption of the plant). The effect of irreversibility in the compressor is not fixed

Promising directions for the use of heat from low-potential sources of chemical production

THE PURPOSE. Development of promising directions for improving the technology of an oil refinery (refinery) based on the use of heat from low-temperature sources of the primary oil distillation system.METHODS. The analysis of the technological scheme of the refinery carried out, in order to identify the most energy-intensive system, while using the methods of analytical and thermodynamic analysis. The analysis of energy use in the circuit of an electric desalination plant (EDP) is carried out according on the basis of the data of the technological regulations of the existing EDP-AVT-7. The assessment of the feasibility of the proposed directions and developed solutions was carried out on the basis of the methods of technical, economic and environmental analysis.RESULTS. This article shows the relevance of the problem and substantiates the importance of its consideration for improving energy and environmental efficiency. Based on a common scheme for the primary processing of crude oil, it is noted that this technology has significant energy saving potential. It is proposed to implement promising directions for the rational use of heat, and a modernization solution is presented aimed at improving the technological elements of the EDP-AVT-7 circuit based on the heat recovery of the hydrocarbon vapor-gas mixture.CONCLUSION. The proposed directions and developed measures for the use of heat from low-grade sources in the refinery scheme show their promise due to a significant reduction in technological energy losses, a reduction in fuel consumption and an increase in the efficiency of its use, which, in general, will positively affect the economic and environmental situation in the region.

Thermodynamic analysis of supercritical Brayton cycles using CO2-based binary mixtures for solar power tower system application

Supercritical CO2 Brayton cycle has the advantages of high thermoelectric conversion efficiency and compact structure. However, the high ambient temperature in the desert environment would reduce the cycle thermal efficiency. In this paper, three additive gases were mixed with CO2 to reduce the effect of ambient temperature on cycle efficiency. The thermodynamic analysis method based on the optimal split ratio was applied to evaluate the potential of CO2-based binary mixtures in the SPT systems application for the first time. Meanwhile, the impact of critical cycle parameters on system performance was analyzed and the internal connection of the phenomenon was investigated by discussing the exergy loss of each component under typical operating conditions. The results show that the optimal split ratio decreases with the increase of main compressor inlet temperature and turbine inlet pressure. The change of turbine inlet temperature has little effect on the optimal split ratio. CO2-propane has the potential for practical application because the pressure ratio has little effect on the optimal split ratio. Moreover, it is found that the thermal and exergy efficiencies of CO2-propane are increased by 2.34% and 1.51% compared with CO2 under typical operating conditions based on genetic algorithm optimization.