Pub Date : 2024-02-01DOI: 10.1134/s004060152402006x
Abstract
The task of energy-efficient heat supply and removal in thermal control, heating and cooling systems is very relevant for many branches of technology. The paper presents the results of the development and study of a 21 m long loop heat pipe (LHP) that is a passive heat-transfer device operating on a closed evaporation-condensation cycle and using capillary pressure to pump a working fluid. These devices can be used in systems where the heat source and the heat sink are removed from each other by a distance measured in meters and even tens of meters, without the use of additional energy sources. The device has a 24 mm diameter evaporator with a 188 mm long heating zone, a vapor line and a liquid line (external/internal diameters of 8/6 mm and 6/4 mm). A 310 mm long pipe-in-pipe heat exchanger equipped with a cooling jacket was used as a condenser. The tests were conducted with the LHP in a horizontal position. Heat was removed from the condenser by forced convection of a water-ethylene glycol mixture with temperatures of 20 and –20°C and a flow rate of 6 dm3/min. The heat load supplied to the evaporator from the electric heater increased from 200 to 1700 W in the first case and to 1300 W in the second. The vapor temperature at the outlet of the evaporator varied from 25 to 62°C and from 24 to 30°C, respectively. Its maximum temperature difference along the length of the vapor line did not exceed 4°C. Such devices can be used in energy-efficient systems for utilizing low-potential heat, heating or cooling remote objects, and for uniformly distributing heat over a large surface area of heat sinks.
{"title":"Development and Study of Operating Characteristics of a Loop Heat Pipe with Increased Heat Transfer Distance","authors":"","doi":"10.1134/s004060152402006x","DOIUrl":"https://doi.org/10.1134/s004060152402006x","url":null,"abstract":"<span> <h3>Abstract</h3> <p>The task of energy-efficient heat supply and removal in thermal control, heating and cooling systems is very relevant for many branches of technology. The paper presents the results of the development and study of a 21 m long loop heat pipe (LHP) that is a passive heat-transfer device operating on a closed evaporation-condensation cycle and using capillary pressure to pump a working fluid. These devices can be used in systems where the heat source and the heat sink are removed from each other by a distance measured in meters and even tens of meters, without the use of additional energy sources. The device has a 24 mm diameter evaporator with a 188 mm long heating zone, a vapor line and a liquid line (external/internal diameters of 8/6 mm and 6/4 mm). A 310 mm long pipe-in-pipe heat exchanger equipped with a cooling jacket was used as a condenser. The tests were conducted with the LHP in a horizontal position. Heat was removed from the condenser by forced convection of a water-ethylene glycol mixture with temperatures of 20 and –20°C and a flow rate of 6 dm<sup>3</sup>/min. The heat load supplied to the evaporator from the electric heater increased from 200 to 1700 W in the first case and to 1300 W in the second. The vapor temperature at the outlet of the evaporator varied from 25 to 62°C and from 24 to 30°C, respectively. Its maximum temperature difference along the length of the vapor line did not exceed 4°C. Such devices can be used in energy-efficient systems for utilizing low-potential heat, heating or cooling remote objects, and for uniformly distributing heat over a large surface area of heat sinks.</p> </span>","PeriodicalId":799,"journal":{"name":"Thermal Engineering","volume":null,"pages":null},"PeriodicalIF":0.5,"publicationDate":"2024-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140152086","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}
Pub Date : 2024-02-01DOI: 10.1134/s0040601524020022
Abstract—
The article addresses the problem of securing reliable and economically efficient operation of cogeneration combined cycle power plants (CCPPs) taking the PGU-450 unit as an example during its operation at partial loads and performing control of the electrical loads in the condensing mode and heat and electrical loads in the cogeneration mode. The main constraints hindering wide-scale involvement of CCPPs to control of electrical and heat loads are noted. The need to switch the gas turbines, which feature limited capacities of bearing variable loads, into a mild operation mode with shifting the main load on the steam turbine is pointed out. A technology of PGU-450 operation at partial loads is suggested: CCPP unloading in accordance with the operation manual to the gas turbine permissible base load, e.g., according to the environmental constraint during its operation in the condensing mode, and further decrease of the power unit electric output at a constant base power output of the gas turbines and heat recovery steam generators through decreasing the steam turbine output by applying bypass steam admission or shifting a part of the high-pressure cylinder (HPC) or the entire HPS, or the steam turbine as a whole to operate in the generator-driven mode. The article presents the results of applying various bypass steam admission configurations during the CCPP operation in the condensing mode, including when shifting part of the HPC or the entire HPC, and the steam turbine as a whole is shifted to operate in the generator-driven mode when the CCPP is shut down in a standby mode in passing off-peak load hours. It has been shown that the use of bypass steam admission during the CCPP operation in the cogeneration mode is more economically efficient than it is in the condensing mode. The article also shows the advantage, in terms of reliability and economic efficiency, of shifting the steam turbine to operate in the generator-driven mode instead of its shutdown during the PGU-450 unit’s operation in the gas turbine unit‒combined heat and power plant (GTU‒CHPP) mode and passing the electric load curve off-peak hours.
{"title":"Improving the PGU-450T Unit’s Maneuverability while Retaining Its Reliability and Economic Efficiency in Variable Load Modes","authors":"","doi":"10.1134/s0040601524020022","DOIUrl":"https://doi.org/10.1134/s0040601524020022","url":null,"abstract":"<span> <h3> <strong>Abstract</strong>—</h3> <p>The article addresses the problem of securing reliable and economically efficient operation of cogeneration combined cycle power plants (CCPPs) taking the PGU-450 unit as an example during its operation at partial loads and performing control of the electrical loads in the condensing mode and heat and electrical loads in the cogeneration mode. The main constraints hindering wide-scale involvement of CCPPs to control of electrical and heat loads are noted. The need to switch the gas turbines, which feature limited capacities of bearing variable loads, into a mild operation mode with shifting the main load on the steam turbine is pointed out. A technology of PGU-450 operation at partial loads is suggested: CCPP unloading in accordance with the operation manual to the gas turbine permissible base load, e.g., according to the environmental constraint during its operation in the condensing mode, and further decrease of the power unit electric output at a constant base power output of the gas turbines and heat recovery steam generators through decreasing the steam turbine output by applying bypass steam admission or shifting a part of the high-pressure cylinder (HPC) or the entire HPS, or the steam turbine as a whole to operate in the generator-driven mode. The article presents the results of applying various bypass steam admission configurations during the CCPP operation in the condensing mode, including when shifting part of the HPC or the entire HPC, and the steam turbine as a whole is shifted to operate in the generator-driven mode when the CCPP is shut down in a standby mode in passing off-peak load hours. It has been shown that the use of bypass steam admission during the CCPP operation in the cogeneration mode is more economically efficient than it is in the condensing mode. The article also shows the advantage, in terms of reliability and economic efficiency, of shifting the steam turbine to operate in the generator-driven mode instead of its shutdown during the PGU-450 unit’s operation in the gas turbine unit‒combined heat and power plant (GTU‒CHPP) mode and passing the electric load curve off-peak hours.</p> </span>","PeriodicalId":799,"journal":{"name":"Thermal Engineering","volume":null,"pages":null},"PeriodicalIF":0.5,"publicationDate":"2024-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140151991","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}
Pub Date : 2024-01-01DOI: 10.1134/s0040601524010026
Abstract—
The article considers a study of the possibility to increase the boiling critical heat flux qcr through the use of surfaces consisting of areas with different heat conductivity. The results of experiments on studying pool boiling heat transfer for saturated dielectric fluid methoxynonafluorobutane (Novec 7100) on bimetallic surfaces are presented. The studies were carried out for bimetallic samples and also for samples made of copper and grade 08Kh18N10T stainless steel in the pressure range 0.1–0.4 MPa. A description of the experimental setup and the procedures used is given. The boiling curves for each sample in the entire presented range of fluid pressures with a step of 0.1 MPa are obtained, and the tables of critical heat-flux values are given. The effect that the liquid pressure has on the relative increase of qcr for bimetallic samples is shown. The values of qcr obtained on all samples are compared with one another, and the increase of qcr on bimetallic surfaces by up to 20% is shown. The previously performed studies are briefly reviewed, and the experimental data obtained by other researchers on boiling heat transfer on surfaces with modulated heat conductivity and for boiling of Novec 7100 fluid are presented, including that on samples with a modified heat-transfer surface. The obtained results are compared with rather few data of other researchers. The temperature field in a bimetallic sample is numerically simulated, and the temperature distribution over the heat-transfer surface is presented. The growth of qcr is due to nonisothermal properties of the heat-transfer surface, which causes the boiling to become regularized.
{"title":"A Simple Method for Increasing the Boiling Critical Heat Flux","authors":"","doi":"10.1134/s0040601524010026","DOIUrl":"https://doi.org/10.1134/s0040601524010026","url":null,"abstract":"<span> <h3>Abstract—</h3> <p>The article considers a study of the possibility to increase the boiling critical heat flux <em>q</em><sub>cr</sub> through the use of surfaces consisting of areas with different heat conductivity. The results of experiments on studying pool boiling heat transfer for saturated dielectric fluid methoxynonafluorobutane (Novec 7100) on bimetallic surfaces are presented. The studies were carried out for bimetallic samples and also for samples made of copper and grade 08Kh18N10T stainless steel in the pressure range 0.1–0.4 MPa. A description of the experimental setup and the procedures used is given. The boiling curves for each sample in the entire presented range of fluid pressures with a step of 0.1 MPa are obtained, and the tables of critical heat-flux values are given. The effect that the liquid pressure has on the relative increase of <em>q</em><sub>cr</sub> for bimetallic samples is shown. The values of <em>q</em><sub>cr</sub> obtained on all samples are compared with one another, and the increase of <em>q</em><sub>cr</sub> on bimetallic surfaces by up to 20% is shown. The previously performed studies are briefly reviewed, and the experimental data obtained by other researchers on boiling heat transfer on surfaces with modulated heat conductivity and for boiling of Novec 7100 fluid are presented, including that on samples with a modified heat-transfer surface. The obtained results are compared with rather few data of other researchers. The temperature field in a bimetallic sample is numerically simulated, and the temperature distribution over the heat-transfer surface is presented. The growth of <em>q</em><sub>cr</sub> is due to nonisothermal properties of the heat-transfer surface, which causes the boiling to become regularized.</p> </span>","PeriodicalId":799,"journal":{"name":"Thermal Engineering","volume":null,"pages":null},"PeriodicalIF":0.5,"publicationDate":"2024-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140047401","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}
Pub Date : 2023-12-18DOI: 10.1134/s0040601523120054
I. A. Klimonov, N. A. Mosunova, V. F. Strizhov, E. V. Usov, V. I. Chukhno
Abstract—
Application of computation tools resting on contemporary physical and mathematical models for substantiating the design solutions adopted for various heat-transfer equipment components helps save time, manpower, and financial resources of design institutions. The variety of both existing reactors and those being designed, which differ from one another both in design and type of coolants calls for the availability of a versatile thermal hydraulic computer code suited for a wide range of applications. The new-generation HYDRA-IBRAE/LM thermal hydraulic module of the EUCLID integrated code, which has been developed as part of the Proryv (Breakthrough) Project, meets these requirements. The operation of this thermal hydraulic module as part of the integrated code opens the possibility to simulate an essentially wider range of reactor plant operation modes and, as a consequence, those of individual heat-transfer equipment components. The developed thermal hydraulic module, which has been certified at the Scientific and Engineering Center for Nuclear and Radiation Safety (SEC NRS), offers the possibility to analyze the thermal hydraulics of sodium, lead, lead–bismuth, gas, and water coolants in various NPP equipment items. Reactor plant steam generators (SGs) belong to the category of equipment components most complex for modeling since they may contain two types of coolants. The article presents study results demonstrating the code’s abilities to analyze in a correct way the processes in the steam generators of only sodium cooled reactor plants, because these plants exist and are actively operated in Russia and around the world. The data presented in the article allow a conclusion to be drawn that the thermal hydraulic module developed at IBRAE RAS is an efficient tool for numerically analyzing complex heat-transfer processes in reactor plants. By using an extended system of closing correlations implemented in the module, it is possible to perform substantiation of design thermal engineering solutions as applied to individual heat-transfer equipment components.
{"title":"Application of the EUCLID Integrated Code’s HYDRA-IBRAE/LM Thermal Hydraulic Module for Analyzing the Steam Generators of Sodium Cooled Reactor Plants","authors":"I. A. Klimonov, N. A. Mosunova, V. F. Strizhov, E. V. Usov, V. I. Chukhno","doi":"10.1134/s0040601523120054","DOIUrl":"https://doi.org/10.1134/s0040601523120054","url":null,"abstract":"<h3 data-test=\"abstract-sub-heading\">Abstract—</h3><p>Application of computation tools resting on contemporary physical and mathematical models for substantiating the design solutions adopted for various heat-transfer equipment components helps save time, manpower, and financial resources of design institutions. The variety of both existing reactors and those being designed, which differ from one another both in design and type of coolants calls for the availability of a versatile thermal hydraulic computer code suited for a wide range of applications. The new-generation HYDRA-IBRAE/LM thermal hydraulic module of the EUCLID integrated code, which has been developed as part of the Proryv (Breakthrough) Project, meets these requirements. The operation of this thermal hydraulic module as part of the integrated code opens the possibility to simulate an essentially wider range of reactor plant operation modes and, as a consequence, those of individual heat-transfer equipment components. The developed thermal hydraulic module, which has been certified at the Scientific and Engineering Center for Nuclear and Radiation Safety (SEC NRS), offers the possibility to analyze the thermal hydraulics of sodium, lead, lead–bismuth, gas, and water coolants in various NPP equipment items. Reactor plant steam generators (SGs) belong to the category of equipment components most complex for modeling since they may contain two types of coolants. The article presents study results demonstrating the code’s abilities to analyze in a correct way the processes in the steam generators of only sodium cooled reactor plants, because these plants exist and are actively operated in Russia and around the world. The data presented in the article allow a conclusion to be drawn that the thermal hydraulic module developed at IBRAE RAS is an efficient tool for numerically analyzing complex heat-transfer processes in reactor plants. By using an extended system of closing correlations implemented in the module, it is possible to perform substantiation of design thermal engineering solutions as applied to individual heat-transfer equipment components.</p>","PeriodicalId":799,"journal":{"name":"Thermal Engineering","volume":null,"pages":null},"PeriodicalIF":0.5,"publicationDate":"2023-12-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"138745522","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}
Pub Date : 2023-12-18DOI: 10.1134/s0040601523120029
A. V. Belyaev, N. E. Sidel’nikov, A. V. Dedov
Abstract
The relevance of studies into hydrodynamics and heat transfer in minichannels is driven by the increased interest in high-pressure power systems and high-tech devices that employ compact and efficient heat exchangers with a high heat flux. The potential for application of small-diameter channels in various industries, including production of heat exchangers, in which various dielectric liquids or freons can be used as a coolant at moderate and high reduced pressures, is being actively investigated today. High heat fluxes should be removed by boiling as the most efficient heat removal mechanism. Proper designing of heat exchangers employing the boiling process requires reliable methods for calculating heat transfer and pressure drop in two-phase flows. The authors have tested the applicability of the known and most reliable methods for calculating pressure drops and heat-transfer coefficient, which have been developed for conventional channels and minichannels, under conditions of increased reduced pressures as high as pr= p/pcr = 0.7. A review of the best-known methods applicable to various diameter (0.16–32 mm) channels is presented, and the predictions by these methods are compared with experimental data. The experiments were performed at a reduced pressure of 0.43, 0.56, and 0.70 in the mass velocity range of G = 200–1000 kg/(m2 s). The experimental setup, the test section, and the experimental procedure are described. The studies were done with R125 refrigerant in a 1.1 mm ID vertical round channel with a heated length of 50 mm. The comparison of the experimental data with predictions by the reviewed procedures demonstrated good performance of calculation methods that had been developed for conventional channels and for particular fluids under conditions close to those under which the experiments were carried out. The pressure losses predicted using the homogeneous model at high reduced pressures are in good agreement with the experimental data.
{"title":"Hydrodynamics and Heat Transfer for a Two-Phase Flow in a Heated Vertical Minichannel at High Reduced Pressures","authors":"A. V. Belyaev, N. E. Sidel’nikov, A. V. Dedov","doi":"10.1134/s0040601523120029","DOIUrl":"https://doi.org/10.1134/s0040601523120029","url":null,"abstract":"<h3 data-test=\"abstract-sub-heading\">Abstract</h3><p>The relevance of studies into hydrodynamics and heat transfer in minichannels is driven by the increased interest in high-pressure power systems and high-tech devices that employ compact and efficient heat exchangers with a high heat flux. The potential for application of small-diameter channels in various industries, including production of heat exchangers, in which various dielectric liquids or freons can be used as a coolant at moderate and high reduced pressures, is being actively investigated today. High heat fluxes should be removed by boiling as the most efficient heat removal mechanism. Proper designing of heat exchangers employing the boiling process requires reliable methods for calculating heat transfer and pressure drop in two-phase flows. The authors have tested the applicability of the known and most reliable methods for calculating pressure drops and heat-transfer coefficient, which have been developed for conventional channels and minichannels, under conditions of increased reduced pressures as high as <i>p</i><sub><i>r</i></sub> <i>= p</i>/<i>p</i><sub><i>cr</i></sub> = 0.7. A review of the best-known methods applicable to various diameter (0.16–32 mm) channels is presented, and the predictions by these methods are compared with experimental data. The experiments were performed at a reduced pressure of 0.43, 0.56, and 0.70 in the mass velocity range of <i>G</i> = 200–1000 kg/(m<sup>2</sup> s). The experimental setup, the test section, and the experimental procedure are described. The studies were done with R125 refrigerant in a 1.1 mm ID vertical round channel with a heated length of 50 mm. The comparison of the experimental data with predictions by the reviewed procedures demonstrated good performance of calculation methods that had been developed for conventional channels and for particular fluids under conditions close to those under which the experiments were carried out. The pressure losses predicted using the homogeneous model at high reduced pressures are in good agreement with the experimental data.</p>","PeriodicalId":799,"journal":{"name":"Thermal Engineering","volume":null,"pages":null},"PeriodicalIF":0.5,"publicationDate":"2023-12-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"138745520","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}
Pub Date : 2023-12-18DOI: 10.1134/s0040601523120108
K. B. Minko, V. I. Artemov, A. A. Klementiev, S. N. Andreev
Abstract
Various literary sources present the results of experiments that were carried out in order to investigate the process of condensation on a horizontal cylinder of a moving steam of freon R-113. These results demonstrate a qualitative disagreement with the trends following from the available theoretical dependencies. The authors of these experimental data indicated some possible reasons for this difference, but a detailed verification of the above assumptions is difficult due to the difficulties in obtaining information about the local characteristics of the condensation process. In this work, the VOF (Volume of Fluid) method is used to simulate the experimental modes of R-113 freon condensation on the surface of a horizontal cylinder from a downward flow moving at a velocity of up to 6 m/s at a pressure close to atmospheric. The Lee model was used to simulate interfacial mass transfer. The selection of its constant was carried out using the algorithm proposed earlier by the authors of this work. Data on changes in the local characteristics of heat transfer during condensation from a moving vapor flow, obtained using the VOF method, are presented. The calculation results are in good agreement with the “unusual” experimental data and confirm the experimentally recorded anomalous (compared to the existing theoretical dependences) increase in the heat-transfer coefficient with an increase in the oncoming flow velocity. It is shown that one of the reasons for the increase in the heat-transfer coefficient is the interaction of the falling condensate film with the vortex structures formed behind the streamlined cylinder. At a certain velocity of the oncoming flow, the falling condensate film is periodically “flooded,” which, in turn, leads to a significant intensification of heat transfer near the lower generatrix of the cylinder. This mechanism is not taken into account in the existing models since, as a rule, it is assumed in them that, after flow separation, the film flows down only due to the action of gravitational forces. A criterion dependence is proposed for determining the boundary of “anomalous” (compared to the theoretical value) heat-transfer intensification.
{"title":"Simulation of Saturated Vapor Condensation from a Downflow on the Surface of a Horizontal Pipe by the VOF Method","authors":"K. B. Minko, V. I. Artemov, A. A. Klementiev, S. N. Andreev","doi":"10.1134/s0040601523120108","DOIUrl":"https://doi.org/10.1134/s0040601523120108","url":null,"abstract":"<h3 data-test=\"abstract-sub-heading\">Abstract</h3><p>Various literary sources present the results of experiments that were carried out in order to investigate the process of condensation on a horizontal cylinder of a moving steam of freon R-113. These results demonstrate a qualitative disagreement with the trends following from the available theoretical dependencies. The authors of these experimental data indicated some possible reasons for this difference, but a detailed verification of the above assumptions is difficult due to the difficulties in obtaining information about the local characteristics of the condensation process. In this work, the VOF (Volume of Fluid) method is used to simulate the experimental modes of R-113 freon condensation on the surface of a horizontal cylinder from a downward flow moving at a velocity of up to 6 m/s at a pressure close to atmospheric. The Lee model was used to simulate interfacial mass transfer. The selection of its constant was carried out using the algorithm proposed earlier by the authors of this work. Data on changes in the local characteristics of heat transfer during condensation from a moving vapor flow, obtained using the VOF method, are presented. The calculation results are in good agreement with the “unusual” experimental data and confirm the experimentally recorded anomalous (compared to the existing theoretical dependences) increase in the heat-transfer coefficient with an increase in the oncoming flow velocity. It is shown that one of the reasons for the increase in the heat-transfer coefficient is the interaction of the falling condensate film with the vortex structures formed behind the streamlined cylinder. At a certain velocity of the oncoming flow, the falling condensate film is periodically “flooded,” which, in turn, leads to a significant intensification of heat transfer near the lower generatrix of the cylinder. This mechanism is not taken into account in the existing models since, as a rule, it is assumed in them that, after flow separation, the film flows down only due to the action of gravitational forces. A criterion dependence is proposed for determining the boundary of “anomalous” (compared to the theoretical value) heat-transfer intensification.</p>","PeriodicalId":799,"journal":{"name":"Thermal Engineering","volume":null,"pages":null},"PeriodicalIF":0.5,"publicationDate":"2023-12-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"138746074","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}
Pub Date : 2023-12-18DOI: 10.1134/s0040601523120030
T. A. Bokova, A. G. Meluzov, N. S. Volkov, A. R. Marov, T. K. Zyryanova, R. V. Sumin, M. D. Pogorelov
Abstract
The results of experimental studies of the applicability of the float-discrete method for measuring the level of a heavy liquid-metal coolant (HLMC) using sealed magnetically controlled contacts as a sensitive element are presented. These contacts register the coolant level in the field of a permanent magnet located on the surface of a heavy liquid-metal coolant. The performance of such a level sensor was studied using a control tank with a lead-bismuth coolant under conditions close to natural ones. This method is simple, but its main problem is maintaining the integrity of sealed magnetically controlled contacts when exposed to high temperatures. The experiments were carried out using a float-discrete level sensor prototype on a high-temperature stand with a lead-bismuth coolant. The data collected during the processing of the results confirm with reliable accuracy the applicability of the float-discrete method for monitoring the level of a heavy liquid-metal coolant. An HLMC level measuring device operating according to this method makes it possible to monitor the level in tanks while maintaining the tightness of the circuit. Due to this, it is possible to abandon the currently common methods for determining the level of HLMC using electric contact level sensors in which the sealing of the circuit is impossible. This device can be used on various experimental stands with liquid-metal coolants as well as in reactor plants and accelerator-controlled systems in the temperature range of 210–230°C, for example MYRRHA. To ensure the operability of the level transmitter at higher temperatures, it is necessary to upgrade the reed switch cooling system.
{"title":"Experimental Studies of the Float-Discrete Method for Measuring the Level of a Heavy Liquid-Metallic Coolant","authors":"T. A. Bokova, A. G. Meluzov, N. S. Volkov, A. R. Marov, T. K. Zyryanova, R. V. Sumin, M. D. Pogorelov","doi":"10.1134/s0040601523120030","DOIUrl":"https://doi.org/10.1134/s0040601523120030","url":null,"abstract":"<h3 data-test=\"abstract-sub-heading\">Abstract</h3><p>The results of experimental studies of the applicability of the float-discrete method for measuring the level of a heavy liquid-metal coolant (HLMC) using sealed magnetically controlled contacts as a sensitive element are presented. These contacts register the coolant level in the field of a permanent magnet located on the surface of a heavy liquid-metal coolant. The performance of such a level sensor was studied using a control tank with a lead-bismuth coolant under conditions close to natural ones. This method is simple, but its main problem is maintaining the integrity of sealed magnetically controlled contacts when exposed to high temperatures. The experiments were carried out using a float-discrete level sensor prototype on a high-temperature stand with a lead-bismuth coolant. The data collected during the processing of the results confirm with reliable accuracy the applicability of the float-discrete method for monitoring the level of a heavy liquid-metal coolant. An HLMC level measuring device operating according to this method makes it possible to monitor the level in tanks while maintaining the tightness of the circuit. Due to this, it is possible to abandon the currently common methods for determining the level of HLMC using electric contact level sensors in which the sealing of the circuit is impossible. This device can be used on various experimental stands with liquid-metal coolants as well as in reactor plants and accelerator-controlled systems in the temperature range of 210–230°C, for example MYRRHA. To ensure the operability of the level transmitter at higher temperatures, it is necessary to upgrade the reed switch cooling system.</p>","PeriodicalId":799,"journal":{"name":"Thermal Engineering","volume":null,"pages":null},"PeriodicalIF":0.5,"publicationDate":"2023-12-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"138745526","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}
Pub Date : 2023-12-18DOI: 10.1134/s0040601523120091
V. G. Lushchik, M. S. Makarova, S. S. Popovich
Abstract
A technique for modeling turbulent flow in a channel with impermeable and permeable walls in the presence of heat supply to the wall is proposed. To close the equations of the boundary layer, a three-parameter differential model of shear turbulence is used, which is supplemented by a transfer equation for a turbulent heat flux. Calculations are carried out for a developed turbulent flow in a round pipe with impermeable and permeable walls for air and binary gas mixtures with a low molecular Prandtl number with parameters corresponding to those in earlier experiments. The results of studies on the effect of the Prandtl number on heat transfer in a pipe with impermeable walls for a coolant with constant physical properties are consistent with the experimental data and empirical dependences of W.M. Kays and B.S. Petukhov for the Nusselt number in the range of Prandtl numbers of 0.2–0.7. It is shown that a positive pressure gradient arising in a pipe under strong gas suction leads to a violation of the similarity of the velocity and temperature profiles and, as a consequence, to a violation of the Reynolds analogy. The use of the transport equation for a turbulent heat flux makes it possible to take into account the complex dependence of the turbulent Prandtl number on the molecular Prandtl number in the viscous sublayer and in the logarithmic boundary layer. The influence of the variability of thermophysical properties and the turbulent Prandtl number on the characteristics of heat transfer in a pipe is estimated. Thus, the difference between the Nu number determined under the assumption of a constant turbulent Prandtl number and the results obtained in calculations using the equation for turbulent heat flux increases with a decrease in the molecular Prandtl number and an increase in the intensity of gas suction.
{"title":"Numerical Investigation of the Influence of the Coolant’s Prandtl Molecular Numbers and the Permeability of the Pipe Wall on Turbulent Heat Transfer","authors":"V. G. Lushchik, M. S. Makarova, S. S. Popovich","doi":"10.1134/s0040601523120091","DOIUrl":"https://doi.org/10.1134/s0040601523120091","url":null,"abstract":"<h3 data-test=\"abstract-sub-heading\">Abstract</h3><p>A technique for modeling turbulent flow in a channel with impermeable and permeable walls in the presence of heat supply to the wall is proposed. To close the equations of the boundary layer, a three-parameter differential model of shear turbulence is used, which is supplemented by a transfer equation for a turbulent heat flux. Calculations are carried out for a developed turbulent flow in a round pipe with impermeable and permeable walls for air and binary gas mixtures with a low molecular Prandtl number with parameters corresponding to those in earlier experiments. The results of studies on the effect of the Prandtl number on heat transfer in a pipe with impermeable walls for a coolant with constant physical properties are consistent with the experimental data and empirical dependences of W.M. Kays and B.S. Petukhov for the Nusselt number in the range of Prandtl numbers of 0.2–0.7. It is shown that a positive pressure gradient arising in a pipe under strong gas suction leads to a violation of the similarity of the velocity and temperature profiles and, as a consequence, to a violation of the Reynolds analogy. The use of the transport equation for a turbulent heat flux makes it possible to take into account the complex dependence of the turbulent Prandtl number on the molecular Prandtl number in the viscous sublayer and in the logarithmic boundary layer. The influence of the variability of thermophysical properties and the turbulent Prandtl number on the characteristics of heat transfer in a pipe is estimated. Thus, the difference between the Nu number determined under the assumption of a constant turbulent Prandtl number and the results obtained in calculations using the equation for turbulent heat flux increases with a decrease in the molecular Prandtl number and an increase in the intensity of gas suction.</p>","PeriodicalId":799,"journal":{"name":"Thermal Engineering","volume":null,"pages":null},"PeriodicalIF":0.5,"publicationDate":"2023-12-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"138745576","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}
Pub Date : 2023-12-18DOI: 10.1134/s0040601523120121
A. B. Tarasenko, O. S. Popel, S. V. Monin
Abstract
On the example of a micro–gas-turbine plant (MGTU) of the C30 Capstone type, an analysis of various options for the use of modern electric energy storage devices as part of a buffer battery was carried out and compared. Gas microturbines with a unit capacity of several tens to hundreds of kilowatts appeared on the market in the 1970s and have become increasingly widely used in autonomous and distributed generation systems. Their competitiveness in comparison with diesel and gas reciprocating power plants is ensured primarily by achieving comparable efficiency values with competitors as a result of the use of a regenerative thermodynamic cycle with highly efficient recuperative heat exchangers and high-speed turbogenerator equipment with air bearings instead of oil bearings. This significantly reduces the operational requirements for the frequency of maintenance of power plants, and also expands the possibilities of using various types of liquid and gaseous fuels (polyfuel) available in the operation area. An important feature of micro–gas-turbine power plants is the DC link and the buffer storage of electrical energy in the power output circuit, which allow one to effectively control the current parameters (regulate them) without changing the engine speed. In traditional versions of such power plants, as a rule, lead-acid batteries are used as a buffer energy storage. The authors considered options for replacing them with supercapacitors and batteries of various types, taking into account such operational factors as the predominance of low ambient temperatures during most of the year (arctic conditions), difficulties in logistics, maintenance conditions for power plants of these batteries, and their considerable cost. The weight and size characteristics of drives are estimated based on different types of elements with an emphasis on products of Russian manufacturers. It is concluded that when operating an MGTU in harsh climatic conditions, it is advisable to use supercapacitor batteries in their buffer storage, despite their low specific energy consumption and high cost.
{"title":"The Selection of Energy Storage for a Micro–Gas-Turbine Plant Operating Autonomously in the Conditions of the North","authors":"A. B. Tarasenko, O. S. Popel, S. V. Monin","doi":"10.1134/s0040601523120121","DOIUrl":"https://doi.org/10.1134/s0040601523120121","url":null,"abstract":"<h3 data-test=\"abstract-sub-heading\">Abstract</h3><p>On the example of a micro–gas-turbine plant (MGTU) of the C30 Capstone type, an analysis of various options for the use of modern electric energy storage devices as part of a buffer battery was carried out and compared. Gas microturbines with a unit capacity of several tens to hundreds of kilowatts appeared on the market in the 1970s and have become increasingly widely used in autonomous and distributed generation systems. Their competitiveness in comparison with diesel and gas reciprocating power plants is ensured primarily by achieving comparable efficiency values with competitors as a result of the use of a regenerative thermodynamic cycle with highly efficient recuperative heat exchangers and high-speed turbogenerator equipment with air bearings instead of oil bearings. This significantly reduces the operational requirements for the frequency of maintenance of power plants, and also expands the possibilities of using various types of liquid and gaseous fuels (polyfuel) available in the operation area. An important feature of micro–gas-turbine power plants is the DC link and the buffer storage of electrical energy in the power output circuit, which allow one to effectively control the current parameters (regulate them) without changing the engine speed. In traditional versions of such power plants, as a rule, lead-acid batteries are used as a buffer energy storage. The authors considered options for replacing them with supercapacitors and batteries of various types, taking into account such operational factors as the predominance of low ambient temperatures during most of the year (arctic conditions), difficulties in logistics, maintenance conditions for power plants of these batteries, and their considerable cost. The weight and size characteristics of drives are estimated based on different types of elements with an emphasis on products of Russian manufacturers. It is concluded that when operating an MGTU in harsh climatic conditions, it is advisable to use supercapacitor batteries in their buffer storage, despite their low specific energy consumption and high cost.</p>","PeriodicalId":799,"journal":{"name":"Thermal Engineering","volume":null,"pages":null},"PeriodicalIF":0.5,"publicationDate":"2023-12-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"138745578","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}
Pub Date : 2023-12-18DOI: 10.1134/s0040601523120042
O. J. Eyenubo, S. O. Otuagoma, K. Owebor, N. U. Enyinnaya, D. O. Ofotoku
Abstract
In this paper, two power plant configurations for distributed energy, simple and cascaded Organic Rankine Cycle (ORC), were proposed, modeled, analyzed and compared from a technical and economic point of view. It is proposed to use rice husks from a typical mill in Nigeria as fuel for the operation of the power plant, while the working fluids for the studied ORC plants are toluene and R245fa refrigerants. Power plants are modeled on the basis of fundamental technical and economic approaches. At the same time, power generation, as well as energy and exergy efficiency were selected as key technical parameters for the study. The desired economic parameter determines the cost of a unit of energy. It has been established that with proper use of rice husks as a renewable energy source, the energy generated by the ORC power plant can help to meet 27–38 MWh daily needs of the rice factory and its surroundings. The results of the analysis of the energy and exergy efficiency of a simple and cascade ORC power plant as presented indicates a better prospect for the latter. The working/thermal capacities of the plant elements and the loss of exergy in them are analyzed. The directions of increasing the efficiency of the rice husk power plant have been identified, primarily by improving high-temperature heat exchangers. The results of an economic analysis of the viability of the simple and cascade ORC power plants are presented. A simple ORC demonstrates the best economic performance with a unit energy cost of $0.115 per kWh compared to $0.124 per kWh of a cascade ORC. However, a holistic study of technical, economic, social and environmental indicators creates prerequisites for the research and development of a cascade ORC installation. The paper also presents the results of an analysis of the sensitivity of plant performance on the volume of annual production of rice husks, the temperature of the exhaust gases at the outlet of the chimney and the coefficient of the import tariff. A feasibility study of the prospects of the proposed technical solution for poorly electrified countries is presented.
{"title":"Techno-Economic Comparison of Simple and Cascade Organic Rankine Cycle for Distributed Energy","authors":"O. J. Eyenubo, S. O. Otuagoma, K. Owebor, N. U. Enyinnaya, D. O. Ofotoku","doi":"10.1134/s0040601523120042","DOIUrl":"https://doi.org/10.1134/s0040601523120042","url":null,"abstract":"<h3 data-test=\"abstract-sub-heading\">Abstract</h3><p>In this paper, two power plant configurations for distributed energy, simple and cascaded Organic Rankine Cycle (ORC), were proposed, modeled, analyzed and compared from a technical and economic point of view. It is proposed to use rice husks from a typical mill in Nigeria as fuel for the operation of the power plant, while the working fluids for the studied ORC plants are toluene and R245fa refrigerants. Power plants are modeled on the basis of fundamental technical and economic approaches. At the same time, power generation, as well as energy and exergy efficiency were selected as key technical parameters for the study. The desired economic parameter determines the cost of a unit of energy. It has been established that with proper use of rice husks as a renewable energy source, the energy generated by the ORC power plant can help to meet 27–38 MWh daily needs of the rice factory and its surroundings. The results of the analysis of the energy and exergy efficiency of a simple and cascade ORC power plant as presented indicates a better prospect for the latter. The working/thermal capacities of the plant elements and the loss of exergy in them are analyzed. The directions of increasing the efficiency of the rice husk power plant have been identified, primarily by improving high-temperature heat exchangers. The results of an economic analysis of the viability of the simple and cascade ORC power plants are presented. A simple ORC demonstrates the best economic performance with a unit energy cost of $0.115 per kWh compared to $0.124 per kWh of a cascade ORC. However, a holistic study of technical, economic, social and environmental indicators creates prerequisites for the research and development of a cascade ORC installation. The paper also presents the results of an analysis of the sensitivity of plant performance on the volume of annual production of rice husks, the temperature of the exhaust gases at the outlet of the chimney and the coefficient of the import tariff. A feasibility study of the prospects of the proposed technical solution for poorly electrified countries is presented.</p>","PeriodicalId":799,"journal":{"name":"Thermal Engineering","volume":null,"pages":null},"PeriodicalIF":0.5,"publicationDate":"2023-12-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"138745518","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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