The aim of this work is to analyze the heat transfer, hydraulic resistance and thermo-hydraulic performance of a new type of heat exchange channels made by additive technology. The main factors affecting the quality of products and determining the heat transfer and hydraulic resistance of the channels are noted. Well-known ratios for calculating hydraulic resistance and heat transfer are not suitable for such high roughness. Data on the AT resistance coefficient of the channels show that even at low Reynolds numbers there is a contribution of roughness. With increasing roughness, the intensification of resistance and heat exchange increases. The transition occurs at 700 < Re < 2000. Comparison of data on heat transfer augmentation and increase of hydraulic losses, as well as their thermo-hydraulic characteristics has been carried out. The hydraulic resistance coefficient of AT channels is significantly higher than the resistance coefficient of smooth channels. Heat transfer augmentation in wave-shaped channels is 2 times higher than augmentation in straight channels. Channels with pin fins allow to achieve a very high heat transfer augmentation (up to 8). Channels with internal grids provide high intensification, but have the highest hydraulic losses. The dependence of the Reynolds analogy factor on the resistance increase factor showed that the straight channels of all geometric forms fit on one dependence closed to the lower boundary line, and have a low hydraulic resistance. Data on channels with pin fins have a large spread. A number of points are above the upper boundary line, which refers to channels with low surface roughness.
本文分析了一种新型增材制造的换热通道的传热特性、水力阻力和热工性能。指出了影响产品质量和决定通道传热和水力阻力的主要因素。众所周知的计算水力阻力和传热的比率不适用于如此高的粗糙度。通道的AT阻力系数数据表明，即使在低雷诺数下，粗糙度也有贡献。随着粗糙度的增加，阻力和热交换的强度增加。转变发生在700 < Re < 2000。比较了换热增大和水力损失增大的数据，以及它们的热液特性。AT通道的水力阻力系数明显高于光滑通道的阻力系数。波浪形通道的换热增益比直线通道的换热增益高2倍。带有销鳍的通道可以实现非常高的传热增强(高达8)。带有内部网格的通道提供高强化，但具有最高的水力损失。雷诺数类比因子对阻力增加因子的依赖关系表明，所有几何形式的直流道在靠近下边线的一项依赖关系上都符合，并且具有较低的水力阻力。带销钉鳍的通道的数据有很大的传播。许多点位于上边界线之上，这是指表面粗糙度较低的通道。
{"title":"THERMO-HYDRAULIC CHARACTERISTICS OF ADDITIVELY MANUFACTURED MINI-CHANNELS","authors":"А.А. Khalatov, І.І. Borisov, S. Kulishov","doi":"10.31472/ttpe.2.2023.3","DOIUrl":"https://doi.org/10.31472/ttpe.2.2023.3","url":null,"abstract":"The aim of this work is to analyze the heat transfer, hydraulic resistance and thermo-hydraulic performance of a new type of heat exchange channels made by additive technology. The main factors affecting the quality of products and determining the heat transfer and hydraulic resistance of the channels are noted. Well-known ratios for calculating hydraulic resistance and heat transfer are not suitable for such high roughness. Data on the AT resistance coefficient of the channels show that even at low Reynolds numbers there is a contribution of roughness. With increasing roughness, the intensification of resistance and heat exchange increases. The transition occurs at 700 < Re < 2000. Comparison of data on heat transfer augmentation and increase of hydraulic losses, as well as their thermo-hydraulic characteristics has been carried out. The hydraulic resistance coefficient of AT channels is significantly higher than the resistance coefficient of smooth channels. Heat transfer augmentation in wave-shaped channels is 2 times higher than augmentation in straight channels. Channels with pin fins allow to achieve a very high heat transfer augmentation (up to 8). Channels with internal grids provide high intensification, but have the highest hydraulic losses. The dependence of the Reynolds analogy factor on the resistance increase factor showed that the straight channels of all geometric forms fit on one dependence closed to the lower boundary line, and have a low hydraulic resistance. Data on channels with pin fins have a large spread. A number of points are above the upper boundary line, which refers to channels with low surface roughness. ","PeriodicalId":23079,"journal":{"name":"Thermophysics and Thermal Power Engineering","volume":"88 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2023-06-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"80714488","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
N. Fialko, R. Dinzhos, Ju.V. Sherenkovskyi, V. Prokopov, N. Meranova
The results of experimental studies of the heat-conducting properties of polymer micro- and nanocomposites based on polyethylene and polycarbonate filled with carbon nanotubes and aluminum particles are presented. The dependences of the heat conductivity of the considered polymer composite materials on the content of the filler are obtained. The possibility of obtaining polymer composites based on polycarbonate with a coefficient of heat conductivity of 50.0 and 25.7 W/(m K) using carbon nanotubes and aluminum particles as fillers, respectively, has been established. The results of studies of the degree of crystallinity of polymer matrices of the considered composites are presented. Data are submitted concerning the correlation between the indicated degree of crystallinity and the heat conductivity coefficient of the studied composite materials. An interpretation of the mechanism of such a dependence is given on the basis of the laws governing the formation of percolation structures from filler particles.
{"title":"THERMOPHYSICAL PROPERTIES OF POLYMER MICRO- AND NANOCOMPOSITES AND THEIR CONNECTION WITH THE STRUCTURAL CHARACTERISTICS OF THE POLYMER MATRIX","authors":"N. Fialko, R. Dinzhos, Ju.V. Sherenkovskyi, V. Prokopov, N. Meranova","doi":"10.31472/ttpe.3.2022.3","DOIUrl":"https://doi.org/10.31472/ttpe.3.2022.3","url":null,"abstract":"The results of experimental studies of the heat-conducting properties of polymer micro- and nanocomposites based on polyethylene and polycarbonate filled with carbon nanotubes and aluminum particles are presented. The dependences of the heat conductivity of the considered polymer composite materials on the content of the filler are obtained. The possibility of obtaining polymer composites based on polycarbonate with a coefficient of heat conductivity of 50.0 and 25.7 W/(m K) using carbon nanotubes and aluminum particles as fillers, respectively, has been established. The results of studies of the degree of crystallinity of polymer matrices of the considered composites are presented. Data are submitted concerning the correlation between the indicated degree of crystallinity and the heat conductivity coefficient of the studied composite materials. An interpretation of the mechanism of such a dependence is given on the basis of the laws governing the formation of percolation structures from filler particles.","PeriodicalId":23079,"journal":{"name":"Thermophysics and Thermal Power Engineering","volume":"46 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2022-08-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"74078140","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The article considers peat as an effective alternative fuel. Its reserves and directions of use in the world and in Ukraine presented and analyzed. The analysis showed that the geological reserves of peat in Ukraine are equivalent to 600 billion cubic meters of natural gas. The main reserves of peat are concentrated in the districts of Polissia. Industrial peat extraction can take place in 12 regions: Volyn, Rivne, Zhytomyr, Kyiv, Cherkasy, Poltava, Sumy, Chernihiv, Khmelnytskyi, Ternopil, Lviv, and Ivano-Frankivsk. It has been shown that, compared to traditional energy carriers, peat fuel has a lower heat of combustion and a fairly high ash content, but during combustion it emits almost no toxic substances and, accordingly, pollutes the environment much less. In home furnaces, peat fuel burned with a higher efficiency than coal, and the ash used as fertilizer. The estimated cost of 1Gj of lower heat of combustion of various types of fuel according to the data of recent years shows a noticeable advantage of peat fuels. The cost of thermal energy obtained from burning 1 ton of peat briquettes is 2 times cheaper than when using coal, 3 times cheaper than gas, and 4 times cheaper than fuel oil. Peat fuel is suitable for use in all types of modern solid fuel combustion devices, which increases the prospect of its implementation on the domestic and foreign fuel markets. The technology for using plant biomass as a filler in peat briquettes and granules developed. Special attention paid to wood, buckwheat husk, sunflower and other grain crops, which have a lower ash content and a higher heat of combustion, the potential of which waste is significant, and the fuel characteristics are able to increase the heat of combustion of composite peat briquettes or peat granules and reduce their ash content. Taking into account that peat used in large quantities as fertilizer for agriculture, a technology developed according to which humic substances first removed from peat for fertilizer, and then biomass added to this peat and a composite peat fuel obtained. This technology involves the integration of technology and extraction of humic substances into the production cycle of a peat briquette plant for the production of composite fuel. The wide implementation of the developed technology of composite peat briquettes at peat briquette factories will allow to increase the production of briquettes by almost 2 times without increasing the consumption of peat raw materials and to produce peat fuel in the range of 0.18-0.2% of geological reserves, which is equivalent to the replacement of more than 1 billion m3 of natural gas. All this allows us to draw a conclusion about the positioning of peat fuel as an effective local type of fuel, which is an alternative to gas and coal.
{"title":"PEAT IS AN EFFECTIVE ALTERNATIVE FUEL","authors":"Yurii Sniezhkin, D. Korinchuk","doi":"10.31472/ttpe.3.2022.1","DOIUrl":"https://doi.org/10.31472/ttpe.3.2022.1","url":null,"abstract":"The article considers peat as an effective alternative fuel. Its reserves and directions of use in the world and in Ukraine presented and analyzed. The analysis showed that the geological reserves of peat in Ukraine are equivalent to 600 billion cubic meters of natural gas. The main reserves of peat are concentrated in the districts of Polissia. Industrial peat extraction can take place in 12 regions: Volyn, Rivne, Zhytomyr, Kyiv, Cherkasy, Poltava, Sumy, Chernihiv, Khmelnytskyi, Ternopil, Lviv, and Ivano-Frankivsk. It has been shown that, compared to traditional energy carriers, peat fuel has a lower heat of combustion and a fairly high ash content, but during combustion it emits almost no toxic substances and, accordingly, pollutes the environment much less. In home furnaces, peat fuel burned with a higher efficiency than coal, and the ash used as fertilizer. The estimated cost of 1Gj of lower heat of combustion of various types of fuel according to the data of recent years shows a noticeable advantage of peat fuels. The cost of thermal energy obtained from burning 1 ton of peat briquettes is 2 times cheaper than when using coal, 3 times cheaper than gas, and 4 times cheaper than fuel oil. Peat fuel is suitable for use in all types of modern solid fuel combustion devices, which increases the prospect of its implementation on the domestic and foreign fuel markets. The technology for using plant biomass as a filler in peat briquettes and granules developed. Special attention paid to wood, buckwheat husk, sunflower and other grain crops, which have a lower ash content and a higher heat of combustion, the potential of which waste is significant, and the fuel characteristics are able to increase the heat of combustion of composite peat briquettes or peat granules and reduce their ash content. Taking into account that peat used in large quantities as fertilizer for agriculture, a technology developed according to which humic substances first removed from peat for fertilizer, and then biomass added to this peat and a composite peat fuel obtained. This technology involves the integration of technology and extraction of humic substances into the production cycle of a peat briquette plant for the production of composite fuel. The wide implementation of the developed technology of composite peat briquettes at peat briquette factories will allow to increase the production of briquettes by almost 2 times without increasing the consumption of peat raw materials and to produce peat fuel in the range of 0.18-0.2% of geological reserves, which is equivalent to the replacement of more than 1 billion m3 of natural gas. All this allows us to draw a conclusion about the positioning of peat fuel as an effective local type of fuel, which is an alternative to gas and coal.","PeriodicalId":23079,"journal":{"name":"Thermophysics and Thermal Power Engineering","volume":"68 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2022-08-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"90650995","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The main purpose of this research is to determine the main dependence’s of the agricultural pellets combustion process and to study the influence of regime parameters on the distribution of temperatures in the combustion chamber, as well as to analyze the biofuels productivity characteristics. Research methods: experimental and theoretical. Results. The research of biofuel combustion process was carried out at the experimental facility of solid fuel boiler with a pellet burner for a passive type house heating. During experimental researches samples of wood pellets, rapeseed pellets and beets pulp were used. On the received graphs the changes in the temperature state of the combustion chamber at the stage of pelletʼs ignition, burning and fading were reflected. It was found that the largest increase in temperature occurs near the wall of the boiler, which is opposite to the burner. As can be seen on the graphs, temperature fluctuations occur as a result of the periodic burning of biofuel in the burner and the arrival of a new portion of pellet from the hopper. As the experiments showed, the temperature level at burning of rapeseed pellets is much lower than in comparison with wood pellets, and to go to the established mode of burning of beet pulp pellets is generally problematic. It is obvious that when setting up the fuel supply system and modes of operation of the fuel it is necessary to take into account heat physical characteristics of fuel, first of all moisture and heat capacity, as well as yield of volatile combustible components. For this purpose, a gas analysis was carried out when burning wood pellets. The selection of combustion products was done in the wild immediately after the boiler. As a result, the NOx and CO concentrations of the appropriate temperature were obtained at the sample site. The nitrogen oxide concentrations should be considered moderate, which cannot be argued about the concentration of carbon monoxide, which requires further research. The obtained results can be used to increase the efficiency of combustion process at burning biofuel in boilers of low power communal and industrial heat power, social-budget sphere and individual-household sector.
{"title":"RESEARCH OF BURNING OF AGRICULTURAL PELLETS IN BOILERS WITH CAPACITY UP TO 25 kW","authors":"O. Lysenko, H. M. Veremiichuk, O. Siryi","doi":"10.31472/ttpe.3.2022.10","DOIUrl":"https://doi.org/10.31472/ttpe.3.2022.10","url":null,"abstract":"The main purpose of this research is to determine the main dependence’s of the agricultural pellets combustion process and to study the influence of regime parameters on the distribution of temperatures in the combustion chamber, as well as to analyze the biofuels productivity characteristics. \u0000Research methods: experimental and theoretical. \u0000Results. The research of biofuel combustion process was carried out at the experimental facility of solid fuel boiler with a pellet burner for a passive type house heating. During experimental researches samples of wood pellets, rapeseed pellets and beets pulp were used. On the received graphs the changes in the temperature state of the combustion chamber at the stage of pelletʼs ignition, burning and fading were reflected. It was found that the largest increase in temperature occurs near the wall of the boiler, which is opposite to the burner. As can be seen on the graphs, temperature fluctuations occur as a result of the periodic burning of biofuel in the burner and the arrival of a new portion of pellet from the hopper. As the experiments showed, the temperature level at burning of rapeseed pellets is much lower than in comparison with wood pellets, and to go to the established mode of burning of beet pulp pellets is generally problematic. It is obvious that when setting up the fuel supply system and modes of operation of the fuel it is necessary to take into account heat physical characteristics of fuel, first of all moisture and heat capacity, as well as yield of volatile combustible components. For this purpose, a gas analysis was carried out when burning wood pellets. The selection of combustion products was done in the wild immediately after the boiler. As a result, the NOx and CO concentrations of the appropriate temperature were obtained at the sample site. The nitrogen oxide concentrations should be considered moderate, which cannot be argued about the concentration of carbon monoxide, which requires further research. The obtained results can be used to increase the efficiency of combustion process at burning biofuel in boilers of low power communal and industrial heat power, social-budget sphere and individual-household sector.","PeriodicalId":23079,"journal":{"name":"Thermophysics and Thermal Power Engineering","volume":"1 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2022-08-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"76783018","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
А.А. Khalatov, І.І. Borisov, G. Kovalenko, M. Muliarchuk
The flow structure and thermo-hydraulic efficiency of cross flow of tube bundles with dimples and helical grooves have been analyzed. The Reynolds number range (103-104) was typical for industrial heat exсhangers. It was found that dimples and grooves decrease scientifically the cylinder wake area and reduces the hydraulic losses. The heat transfer augmentation in five-row tube bundle by dimples is 35-40% while pressure drop increase by 10-15%. The hydraulic resistance of two-row bundle of tube with helical grooves is 20% lower than that of a smooth tube bundle, while heat transfer augmentation is absent. The value of Reynolds analogy factor for tube bundles with dimples and helical grooves exceeds unity. The high thermo-hydraulic efficiency of tube bundles with dimples and helical grooves, allows us to recommend it for practical use in the development of modern heat exchange equipment of the tubular type.
{"title":"APPLICATION OF DIMPLES AND HELICAL GROOVES ON THE OUTTER SURFACE OF TUBES TO INCREASE THERMAL-HYDRAULIC EFFICIENCY OF TUBE BUNDLES AT CROSS FLOW","authors":"А.А. Khalatov, І.І. Borisov, G. Kovalenko, M. Muliarchuk","doi":"10.31472/ttpe.3.2022.11","DOIUrl":"https://doi.org/10.31472/ttpe.3.2022.11","url":null,"abstract":"The flow structure and thermo-hydraulic efficiency of cross flow of tube bundles with dimples and helical grooves have been analyzed. The Reynolds number range (103-104) was typical for industrial heat exсhangers. It was found that dimples and grooves decrease scientifically the cylinder wake area and reduces the hydraulic losses. The heat transfer augmentation in five-row tube bundle by dimples is 35-40% while pressure drop increase by 10-15%. The hydraulic resistance of two-row bundle of tube with helical grooves is 20% lower than that of a smooth tube bundle, while heat transfer augmentation is absent. The value of Reynolds analogy factor for tube bundles with dimples and helical grooves exceeds unity. The high thermo-hydraulic efficiency of tube bundles with dimples and helical grooves, allows us to recommend it for practical use in the development of modern heat exchange equipment of the tubular type.","PeriodicalId":23079,"journal":{"name":"Thermophysics and Thermal Power Engineering","volume":"15 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2022-07-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"79628721","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Methanation, or the generation of synthetic methane through the combination of carbon dioxide and hydrogen, has been attracting more and more attention of researchers and energy scientists in recent years due to the fact that the development of an effective and economically feasible technology for the implementation of this process will allow solving a number of energy and environmental problems. First, it is the accumulation of excess renewable electricity from solar and wind power plants by using it in the creation of another energy-intensive product, namely synthetic natural gas, which removes the problem of coordinating unstable sources of electricity with energy networks. Secondly, methanation becomes another technology for enriching biogas and turning it into biomethane, which will allow it to be used through existing gas networks and contribute to solving the problem of natural gas shortage. The development and improvement of methanation technologies are engaged in many organizations of the world - Germany, Denmark, France, the USA, Japan and others. Research is conducted in two main directions: catalytic methanation and biological methanation. In the first direction, methanation is carried out through the Sabatier reaction using catalysts. The problems of such methanation are: the development of catalysts with high activity, selectivity and resistance to the heat of reaction, the provision of optimal reaction modes, in particular temperature and pressure, through the use of various methods of reactor cooling, control of the reaction mechanism, the use of three-phase reactors, changing their structure, and so on. Biological methanation is carried out using of biological methanogens - so-called archaea, which act as a kind of catalyst. The methanation is carried out either directly in the biomass anaerobic digestion reactor (in-situ methanation) or in a separate reactor into which biogas and hydrogen are fed separately (ex-situ methanation). One of the main problems of in-situ methanation is the simultaneous provision of optimal conditions for both acetoclastic and hydrogenotrophic methanogens. This problem is solved by ex-situ methanation, in which the optimal conditions for anaerobic digestion and methanation processes are provided separately. It is clear that optimal conditions are also provided for biomethanation of pure CO2 and H2, when the «broth» for archaea is created separately. A comparison of catalytic and biological methanation technologies shows that catalytic methanation provides higher energy efficiency and requires much smaller reactor sizes than biological methanation for the same methane yield. However, the latter has a higher resistance to harmful impurities than the catalytic one.
{"title":"METHANATION TECHNOLOGIES FOR PRODUCING SYNTHETIC RENEWABLE METHANE","authors":"V. M. Klimenko, T. Suprun","doi":"10.31472/ttpe.3.2022.6","DOIUrl":"https://doi.org/10.31472/ttpe.3.2022.6","url":null,"abstract":"Methanation, or the generation of synthetic methane through the combination of carbon dioxide and hydrogen, has been attracting more and more attention of researchers and energy scientists in recent years due to the fact that the development of an effective and economically feasible technology for the implementation of this process will allow solving a number of energy and environmental problems. First, it is the accumulation of excess renewable electricity from solar and wind power plants by using it in the creation of another energy-intensive product, namely synthetic natural gas, which removes the problem of coordinating unstable sources of electricity with energy networks. Secondly, methanation becomes another technology for enriching biogas and turning it into biomethane, which will allow it to be used through existing gas networks and contribute to solving the problem of natural gas shortage. \u0000The development and improvement of methanation technologies are engaged in many organizations of the world - Germany, Denmark, France, the USA, Japan and others. Research is conducted in two main directions: catalytic methanation and biological methanation. In the first direction, methanation is carried out through the Sabatier reaction using catalysts. The problems of such methanation are: the development of catalysts with high activity, selectivity and resistance to the heat of reaction, the provision of optimal reaction modes, in particular temperature and pressure, through the use of various methods of reactor cooling, control of the reaction mechanism, the use of three-phase reactors, changing their structure, and so on. Biological methanation is carried out using of biological methanogens - so-called archaea, which act as a kind of catalyst. The methanation is carried out either directly in the biomass anaerobic digestion reactor (in-situ methanation) or in a separate reactor into which biogas and hydrogen are fed separately (ex-situ methanation). One of the main problems of in-situ methanation is the simultaneous provision of optimal conditions for both acetoclastic and hydrogenotrophic methanogens. This problem is solved by ex-situ methanation, in which the optimal conditions for anaerobic digestion and methanation processes are provided separately. It is clear that optimal conditions are also provided for biomethanation of pure CO2 and H2, when the «broth» for archaea is created separately. A comparison of catalytic and biological methanation technologies shows that catalytic methanation provides higher energy efficiency and requires much smaller reactor sizes than biological methanation for the same methane yield. However, the latter has a higher resistance to harmful impurities than the catalytic one.","PeriodicalId":23079,"journal":{"name":"Thermophysics and Thermal Power Engineering","volume":"26 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2022-07-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"88375069","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
In the conditions of military operations taking place on the territory of Ukraine, the reliability of the heat supply system is of particular importance. The destruction of engineering infrastructure, targeted destruction of energy supply sources and fuel blackmail carried out by the Russian Federation leads to the emergence of significant problems of providing heat to urban agglomerations. At the state level, heat supply should be considered as an integral part of national energy security. Ukraine has a unique chance to transform the heat supply system and bring it up to modern European requirements. Therefore, choosing the right strategy for the development of a reliable and stable heat supply system of the country is an urgent scientific and technical problem. The modern and post-war reconstruction of the Ukrainian energy sector is, above all, the implementation of initiatives that are already being implemented in the EU countries. It should be noted that Europe seeks to reduce dependence on Russian fossil fuels by rapidly transitioning to clean energy and joining efforts to achieve a more sustainable energy system. The purpose of this work is to conduct an analysis and substantiation of proposals for ensuring a stable heat supply of infrastructure facilities and urban agglomerations in the conditions of hostilities, emergency situations and further transformation of the heat energy industry of Ukraine in accordance with the standards of the European Union. An assessment of factors affecting energy security and operational reliability of centralized heat supply systems was carried out. Technical solutions are proposed, which allow to ensure the coordinated and stable operation of heat supply systems with the involvement of the latest developments of equipment and technologies of the ITTF of the National Academy of Sciences of Ukraine. Application of these developments can be implemented in heat supply systems in a short period of time. Suggestions and rationale for their use are also provided.
{"title":"DEVELOPMENTS TO INCREASE THE EFFICIENCY OF HEAT SUPPLY IN THE THERMAL POWER INDUSTRY","authors":"V. Demchenko, A. Konyk, N. D. Pogorelova","doi":"10.31472/ttpe.3.2022.7","DOIUrl":"https://doi.org/10.31472/ttpe.3.2022.7","url":null,"abstract":"In the conditions of military operations taking place on the territory of Ukraine, the reliability of the heat supply system is of particular importance. The destruction of engineering infrastructure, targeted destruction of energy supply sources and fuel blackmail carried out by the Russian Federation leads to the emergence of significant problems of providing heat to urban agglomerations. At the state level, heat supply should be considered as an integral part of national energy security. Ukraine has a unique chance to transform the heat supply system and bring it up to modern European requirements. Therefore, choosing the right strategy for the development of a reliable and stable heat supply system of the country is an urgent scientific and technical problem. The modern and post-war reconstruction of the Ukrainian energy sector is, above all, the implementation of initiatives that are already being implemented in the EU countries. It should be noted that Europe seeks to reduce dependence on Russian fossil fuels by rapidly transitioning to clean energy and joining efforts to achieve a more sustainable energy system. \u0000The purpose of this work is to conduct an analysis and substantiation of proposals for ensuring a stable heat supply of infrastructure facilities and urban agglomerations in the conditions of hostilities, emergency situations and further transformation of the heat energy industry of Ukraine in accordance with the standards of the European Union. \u0000An assessment of factors affecting energy security and operational reliability of centralized heat supply systems was carried out. Technical solutions are proposed, which allow to ensure the coordinated and stable operation of heat supply systems with the involvement of the latest developments of equipment and technologies of the ITTF of the National Academy of Sciences of Ukraine. Application of these developments can be implemented in heat supply systems in a short period of time. Suggestions and rationale for their use are also provided.","PeriodicalId":23079,"journal":{"name":"Thermophysics and Thermal Power Engineering","volume":"8 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2022-07-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"84727430","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The combustion process begins with the ignition of the fuel - bringing it to the auto-ignition temperature, which is one of the important components of the kinetic characteristics of the fuel. Fuel ignition does not occur immediately - but after a certain period, during which activation energy is accumulated: heat or active centers, depending on the mechanism of the process - thermal-kinetic or chain-kinetic, sufficient to overcome the potential barrier. At the same time, the period of reaching the self-ignition temperature is the induction period of this reactive system: for self-ignition or the ignition time during ignition. The purpose of the work is to substantiate the kinetic characteristics of the fuel: self-ignition temperature and induction period, methods of their experimental determination for solid fossil fuels and biomass waste. According to the methodology, an installation was created for the experimental determination of the self-ignition temperature and the induction period of solid fuel in the layer. Studies of such fuels as anthracite, hard coal, buckwheat husk, millet, oats, flax husks, birch wood, peat, and paper showed the dependence of the self-ignition temperature on the degree of metamorphosis and volatiles. With an increase in the degree of metamorphism and a decrease in volatiles in solid fuel, the self-ignition temperature increases. However, the self-ignition temperature does not depend on the size of its particles, their number in the layer and the temperature of the oxidizer. The above allows us to conclude that the self-ignition temperature depends only on the conditions of heat exchange (accordingly, on aerodynamics), and the absolute value of the auto-ignition temperature for an infinite space, in the absence of a jet stream, is a constant value, and only then, in the presence of heat exchange (with velocity gradients) , takes one or another value. It was found that the induction period depends only on the initial temperature of the process, the induction period decreases with increasing temperature. This is due to the more intensive transfer of heat to the fuel particles due to the increase in the temperature gradient and the acceleration of the development of the oxidation reaction. The induction period, as shown by the conducted experiments, does not depend on the size of the particles. This can be explained only by the fact that the rate of thermal destruction of the fuel is close to the rate of its heating. The burning time of coal particles, on the contrary, depends on the size of its particles. Expressions for determining the autoignition temperature and the induction period were obtained based on the processing of the results of the conducted experiments. The results of the work can be used in combustion technologies, in which self-ignition of fuel is one of the main components of the process - it ensures combustion in the self-ignition mode of fuel when in contact with an oxidizer.
{"title":"DETERMINATION OF KINETIC CHARACTERISTICS OF SOLID FUEL.","authors":"V. Chmel, I. Novikova","doi":"10.31472/ttpe.3.2022.9","DOIUrl":"https://doi.org/10.31472/ttpe.3.2022.9","url":null,"abstract":"The combustion process begins with the ignition of the fuel - bringing it to the auto-ignition temperature, which is one of the important components of the kinetic characteristics of the fuel. \u0000Fuel ignition does not occur immediately - but after a certain period, during which activation energy is accumulated: heat or active centers, depending on the mechanism of the process - thermal-kinetic or chain-kinetic, sufficient to overcome the potential barrier. At the same time, the period of reaching the self-ignition temperature is the induction period of this reactive system: for self-ignition or the ignition time during ignition. \u0000The purpose of the work is to substantiate the kinetic characteristics of the fuel: self-ignition temperature and induction period, methods of their experimental determination for solid fossil fuels and biomass waste. \u0000According to the methodology, an installation was created for the experimental determination of the self-ignition temperature and the induction period of solid fuel in the layer. \u0000Studies of such fuels as anthracite, hard coal, buckwheat husk, millet, oats, flax husks, birch wood, peat, and paper showed the dependence of the self-ignition temperature on the degree of metamorphosis and volatiles. With an increase in the degree of metamorphism and a decrease in volatiles in solid fuel, the self-ignition temperature increases. However, the self-ignition temperature does not depend on the size of its particles, their number in the layer and the temperature of the oxidizer. \u0000The above allows us to conclude that the self-ignition temperature depends only on the conditions of heat exchange (accordingly, on aerodynamics), and the absolute value of the auto-ignition temperature for an infinite space, in the absence of a jet stream, is a constant value, and only then, in the presence of heat exchange (with velocity gradients) , takes one or another value. \u0000It was found that the induction period depends only on the initial temperature of the process, the induction period decreases with increasing temperature. This is due to the more intensive transfer of heat to the fuel particles due to the increase in the temperature gradient and the acceleration of the development of the oxidation reaction. \u0000The induction period, as shown by the conducted experiments, does not depend on the size of the particles. This can be explained only by the fact that the rate of thermal destruction of the fuel is close to the rate of its heating. The burning time of coal particles, on the contrary, depends on the size of its particles. \u0000Expressions for determining the autoignition temperature and the induction period were obtained based on the processing of the results of the conducted experiments. \u0000The results of the work can be used in combustion technologies, in which self-ignition of fuel is one of the main components of the process - it ensures combustion in the self-ignition mode of fuel when in contact with an oxidizer.","PeriodicalId":23079,"journal":{"name":"Thermophysics and Thermal Power Engineering","volume":"42 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2022-07-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"83209477","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
K. Maletska, L.Yu. Avdieieva, T.Ya. Turchyna, A. Makarenko
Recently, the demand for concentrates and dry powders from natural fruit and berry raw materials has been growing in the food industry. Spray drying is a method that is widely used to increase the shelf life of food products. However, obtaining dry concentrates from clarified, unclarified juices, as well as juices with pulp, by the spraying method has certain difficulties. This is due to the fact that apple juices and purees contain a complex of organic acids (malic, citric, etc.) in combination with a large number of simple carbohydrates. These substances are the main factors of the viscoplastic state of the dried particles in the heated air in the drying chamber. Thermoplastic (adhesive) properties of the material to be dried in the chamber of the spray dryer and hygroscopic in the state of dried powders complicate the conditions for their timely removal from the chamber, separation, unloading, and storage. As a result, the presence of such properties worsens the organoleptic and physicochemical characteristics of dry powders, reduces product yield, and also complicates the operating conditions of drying equipment. The use of structuring additives of various types, which include protein products of various origins, contributes to the improvement of drying conditions. The aim of the work was to study the kinetic characteristics of dehydration of drops of apple juice and compositions with milk proteins in order to determine the feasibility of their use as structuring additives for the preparation of powdered health products based on apple juice by spraying. The research results showed the expediency of using a complex of skim milk proteins and whey protein concentrate as structuring additives. It has been proven that their use improves the structuring and vapor-conducting properties of the material during drying, due to which it is possible to obtain powder products with minimal final moisture while preserving valuable bioactive components.
{"title":"KINETIC CHARACTERISTICS OF DRYING DROPLETS OF APPLE JUICE AND COMPOSITIONS BASED ON THEM WITH MILK PROTEINS","authors":"K. Maletska, L.Yu. Avdieieva, T.Ya. Turchyna, A. Makarenko","doi":"10.31472/ttpe.3.2022.4","DOIUrl":"https://doi.org/10.31472/ttpe.3.2022.4","url":null,"abstract":"Recently, the demand for concentrates and dry powders from natural fruit and berry raw materials has been growing in the food industry. Spray drying is a method that is widely used to increase the shelf life of food products. However, obtaining dry concentrates from clarified, unclarified juices, as well as juices with pulp, by the spraying method has certain difficulties. This is due to the fact that apple juices and purees contain a complex of organic acids (malic, citric, etc.) in combination with a large number of simple carbohydrates. These substances are the main factors of the viscoplastic state of the dried particles in the heated air in the drying chamber. Thermoplastic (adhesive) properties of the material to be dried in the chamber of the spray dryer and hygroscopic in the state of dried powders complicate the conditions for their timely removal from the chamber, separation, unloading, and storage. As a result, the presence of such properties worsens the organoleptic and physicochemical characteristics of dry powders, reduces product yield, and also complicates the operating conditions of drying equipment. The use of structuring additives of various types, which include protein products of various origins, contributes to the improvement of drying conditions. \u0000The aim of the work was to study the kinetic characteristics of dehydration of drops of apple juice and compositions with milk proteins in order to determine the feasibility of their use as structuring additives for the preparation of powdered health products based on apple juice by spraying. \u0000The research results showed the expediency of using a complex of skim milk proteins and whey protein concentrate as structuring additives. It has been proven that their use improves the structuring and vapor-conducting properties of the material during drying, due to which it is possible to obtain powder products with minimal final moisture while preserving valuable bioactive components. \u0000 ","PeriodicalId":23079,"journal":{"name":"Thermophysics and Thermal Power Engineering","volume":"77 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2022-07-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"83905041","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Ways to reduce the carbon capacity of Ukraine's economy through the active use of energy efficiency measures in energy, extensive use of renewable energy sources, in particular hydrogen, with possible problems and risks of transition to low-carbon energy. The aim of the work is to assess the contribution of hydrogen use in the perspective of achieving decarbonized energy of Ukraine, taking into account the advantages, available achievements and obstacles to the movement of the economy on this path. To this end, estimates of energy efficiency of primary energy resources according to the EROEI indicator, in particular, renewable energy sources; indicators of environmental friendliness of basic energy resources according to specific (per unit of energy) greenhouse gas emissions are given; IEA data on the volume of global investments in energy efficiency are presented. The main scientific and technical results of recent times in the field of research on the processes of production, transportation and end use of hydrogen, obtained by teams from a number of institutes of the National Academy of Sciences of Ukraine. The problems of hydrogen energy are in the focus of close attention of scientists in the country. The use of Ukrainian nuclear power plants for hydrogen production is considered. Particular attention is paid to the materials of the draft Hydrogen Strategy of Ukraine until 2050, according to which the volume of hydrogen production in the final period of implementation will be up to 330 billion nm3 annually. The risks of formation and development of energy at RES are assessed, the optimal scenarios of the country's economic development are considered.
{"title":"LOW CARBON ENERGY 2. Hydrogen energy: problems, achievements, possible risks (review)","authors":"B. Basok, Ye.T. Baseyev","doi":"10.31472/ttpe.3.2022.5","DOIUrl":"https://doi.org/10.31472/ttpe.3.2022.5","url":null,"abstract":"Ways to reduce the carbon capacity of Ukraine's economy through the active use of energy efficiency measures in energy, extensive use of renewable energy sources, in particular hydrogen, with possible problems and risks of transition to low-carbon energy. The aim of the work is to assess the contribution of hydrogen use in the perspective of achieving decarbonized energy of Ukraine, taking into account the advantages, available achievements and obstacles to the movement of the economy on this path. To this end, estimates of energy efficiency of primary energy resources according to the EROEI indicator, in particular, renewable energy sources; indicators of environmental friendliness of basic energy resources according to specific (per unit of energy) greenhouse gas emissions are given; IEA data on the volume of global investments in energy efficiency are presented. \u0000The main scientific and technical results of recent times in the field of research on the processes of production, transportation and end use of hydrogen, obtained by teams from a number of institutes of the National Academy of Sciences of Ukraine. The problems of hydrogen energy are in the focus of close attention of scientists in the country. The use of Ukrainian nuclear power plants for hydrogen production is considered. \u0000Particular attention is paid to the materials of the draft Hydrogen Strategy of Ukraine until 2050, according to which the volume of hydrogen production in the final period of implementation will be up to 330 billion nm3 annually. \u0000The risks of formation and development of energy at RES are assessed, the optimal scenarios of the country's economic development are considered.","PeriodicalId":23079,"journal":{"name":"Thermophysics and Thermal Power Engineering","volume":"36 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2022-06-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"91236412","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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