The peculiar heat transfer mechanism of supercritical fluids has been studied for a long time, especially the flow and heat transfer in the tubes. Numerous experiments have demonstrated the three heat transfer modes of supercritical fluids: normal heat transfer, improved heat transfer and deteriorated heat transfer. The effects of the pressure, pipe diameter, mass flow rate, heat flux and flow direction also have been well studied in the experiments. From the perspective of theory, the pseudo-boiling theory noticed the similarities between the subcritical boiling and the supercritical fluid heat transfer, and explained the heat transfer mechanism. Another theory focuses the buoyancy and flow acceleration effect caused by the property change also made great success. However, the existing research still yields inconsistent results and more evidences are needed. In this work, the heat transfer characteristics from different horizontal wires immersed in both liquid and supercritical carbon dioxide are studied. For a wide range of bath temperatures (5 ∼ 60 °C) and pressures (5 ∼ 8 MPa), the heat transfer coefficients were measured with a quasi-steady increase and decrease of the heat generation rate. The surface temperature of the wires was derived from the measured resistance. Finally, the boiling curves of both the subcritical cases and supercritical cases were obtained. Meanwhile, the near-wall fluid fields were visualized using the high-speed camera. Different from the prior experiments, this pool-type experiment has avoided the complex turbulence flows, and provides clearer evidences of the different heat transfer modes of the supercritical fluids.
{"title":"Heat Transfer Characteristics of Different Horizontal Wires in Pools of Liquid and Supercritical Carbon Dioxide","authors":"Minyun Liu, Dapeng Xi, Junjie Fei, Yan-ping Huang","doi":"10.1115/icone29-89611","DOIUrl":"https://doi.org/10.1115/icone29-89611","url":null,"abstract":"\u0000 The peculiar heat transfer mechanism of supercritical fluids has been studied for a long time, especially the flow and heat transfer in the tubes. Numerous experiments have demonstrated the three heat transfer modes of supercritical fluids: normal heat transfer, improved heat transfer and deteriorated heat transfer. The effects of the pressure, pipe diameter, mass flow rate, heat flux and flow direction also have been well studied in the experiments. From the perspective of theory, the pseudo-boiling theory noticed the similarities between the subcritical boiling and the supercritical fluid heat transfer, and explained the heat transfer mechanism. Another theory focuses the buoyancy and flow acceleration effect caused by the property change also made great success. However, the existing research still yields inconsistent results and more evidences are needed. In this work, the heat transfer characteristics from different horizontal wires immersed in both liquid and supercritical carbon dioxide are studied. For a wide range of bath temperatures (5 ∼ 60 °C) and pressures (5 ∼ 8 MPa), the heat transfer coefficients were measured with a quasi-steady increase and decrease of the heat generation rate. The surface temperature of the wires was derived from the measured resistance. Finally, the boiling curves of both the subcritical cases and supercritical cases were obtained. Meanwhile, the near-wall fluid fields were visualized using the high-speed camera. Different from the prior experiments, this pool-type experiment has avoided the complex turbulence flows, and provides clearer evidences of the different heat transfer modes of the supercritical fluids.","PeriodicalId":302303,"journal":{"name":"Volume 15: Student Paper Competition","volume":"86 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2022-08-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"114330889","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}
Enpei Wang, Lei Li, M. Wei, Yongsheng Wen, Bowen Zhou
With the extensive application of offshore power plants and attaching importance of nuclear reactor system in marine industry, the narrow rectangular channels used for the compact heat exchanger in marine nuclear plant have drawn growing attention in recent years. Compared to some conventional pipes, the narrow rectangular channels boost the heat removal capacity efficiently and present the characteristics of compact layout, which have extensive application in compact heat exchangers. A significant number of experiments have been conducted on this topic. In this paper, a comprehensive historical review for narrow rectangular thermal-hydraulic characteristics under marine conditions is proposed, including an expansive number of experimental and numerical studies in open literatures for recent decade. The pressure drop and heat transfer characteristics are chiefly clarified in this paper. Additionally, the closely related studies of authors published in the last years are summarized in detailed. The followings are the significant aspects of this paper for dominant contents: (1) on the basis of a compilation of numerous distinguishing criterions, the definitions of narrow rectangular channels and marine motions are presented. (2) the flow characteristics of pressure drop and heat transfer characteristics in narrow rectangular channels under marine conditions are reviewed and summarized, basing on the authors’ published research achievements.
{"title":"Review of Flow Characteristics in Narrow Rectangular Channels Under Marine Conditions","authors":"Enpei Wang, Lei Li, M. Wei, Yongsheng Wen, Bowen Zhou","doi":"10.1115/icone29-93743","DOIUrl":"https://doi.org/10.1115/icone29-93743","url":null,"abstract":"\u0000 With the extensive application of offshore power plants and attaching importance of nuclear reactor system in marine industry, the narrow rectangular channels used for the compact heat exchanger in marine nuclear plant have drawn growing attention in recent years. Compared to some conventional pipes, the narrow rectangular channels boost the heat removal capacity efficiently and present the characteristics of compact layout, which have extensive application in compact heat exchangers. A significant number of experiments have been conducted on this topic. In this paper, a comprehensive historical review for narrow rectangular thermal-hydraulic characteristics under marine conditions is proposed, including an expansive number of experimental and numerical studies in open literatures for recent decade. The pressure drop and heat transfer characteristics are chiefly clarified in this paper. Additionally, the closely related studies of authors published in the last years are summarized in detailed. The followings are the significant aspects of this paper for dominant contents: (1) on the basis of a compilation of numerous distinguishing criterions, the definitions of narrow rectangular channels and marine motions are presented. (2) the flow characteristics of pressure drop and heat transfer characteristics in narrow rectangular channels under marine conditions are reviewed and summarized, basing on the authors’ published research achievements.","PeriodicalId":302303,"journal":{"name":"Volume 15: Student Paper Competition","volume":"21 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2022-08-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"116387622","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}
Due to the particularity of the nuclear-related event, even if it does not have any serious consequences, or even does not occur in China, it may also bring a greater risk of public opinion, that is, the technical risk is low but the public opinion risk is high. In order to provide a scientific basis to identify the impact of Nuclear-related Event occurred in countries Around China (NEAC) on China, we established an integrated classification framework of public opinion risks related to these events, and the indicators of each evaluation dimension have been identified. In another aspect, based on the theory of crisis life cycle and the theory of crisis management 4R, some suggestions on the response strategy of the public opinion risk caused by NEAC were proposed in this paper.
{"title":"Classification Method and Response Strategy of Public Opinion Risk Related to Nuclear-Related Event Occurred in Countries Around China","authors":"H. Zhao, J. Tong","doi":"10.1115/icone29-90446","DOIUrl":"https://doi.org/10.1115/icone29-90446","url":null,"abstract":"\u0000 Due to the particularity of the nuclear-related event, even if it does not have any serious consequences, or even does not occur in China, it may also bring a greater risk of public opinion, that is, the technical risk is low but the public opinion risk is high. In order to provide a scientific basis to identify the impact of Nuclear-related Event occurred in countries Around China (NEAC) on China, we established an integrated classification framework of public opinion risks related to these events, and the indicators of each evaluation dimension have been identified. In another aspect, based on the theory of crisis life cycle and the theory of crisis management 4R, some suggestions on the response strategy of the public opinion risk caused by NEAC were proposed in this paper.","PeriodicalId":302303,"journal":{"name":"Volume 15: Student Paper Competition","volume":"103 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2022-08-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"133601058","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}
Steam condensation in the presence of non-condensable gas is a general phenomenon in various industrial applications. It has been broadly investigated by experimental studies and numerical analyses. Previous experimental studies and numerical analyses have focused on single structure. To evaluate the condensation heat transfer characteristics of steam for various condensation structure, the present work conducted numerical simulations based on various structure at a wide parameter range (pressure from 0.2 to 1.6 MPa and air mass fraction from 0.16 to 0.71). In the assessments, the condensation heat transfer coefficient with various condensation structure (single tube, plate, cylinder, spherical) were investigated. The results indicate that the structure of the condensation surface has a significant effect on the heat transfer characteristics of steam condensation. There is almost no difference in the heat transfer performance of the four condensation structures under the low pressure and high air mass fraction condition. With the increase of pressure and the decrease of air mass fraction, the heat transfer performance of the cylinder is the best, followed by the spherical and plate, and the worst is the single tube. In addition, the condensation heat transfer coefficient (CHTC) of the cylinder can be 40% greater than that of the single tube at a pressure of 1.6MPa and an air mass fraction of 0.16.
{"title":"Numerical Investigations on Structure Effect for Steam Condensation in the Presence of Air Under Vertical Condition","authors":"Shuhang Zhou, Xian-ke Meng, Haozhi Bian, M. Ding","doi":"10.1115/icone29-92081","DOIUrl":"https://doi.org/10.1115/icone29-92081","url":null,"abstract":"Steam condensation in the presence of non-condensable gas is a general phenomenon in various industrial applications. It has been broadly investigated by experimental studies and numerical analyses. Previous experimental studies and numerical analyses have focused on single structure. To evaluate the condensation heat transfer characteristics of steam for various condensation structure, the present work conducted numerical simulations based on various structure at a wide parameter range (pressure from 0.2 to 1.6 MPa and air mass fraction from 0.16 to 0.71). In the assessments, the condensation heat transfer coefficient with various condensation structure (single tube, plate, cylinder, spherical) were investigated. The results indicate that the structure of the condensation surface has a significant effect on the heat transfer characteristics of steam condensation. There is almost no difference in the heat transfer performance of the four condensation structures under the low pressure and high air mass fraction condition. With the increase of pressure and the decrease of air mass fraction, the heat transfer performance of the cylinder is the best, followed by the spherical and plate, and the worst is the single tube. In addition, the condensation heat transfer coefficient (CHTC) of the cylinder can be 40% greater than that of the single tube at a pressure of 1.6MPa and an air mass fraction of 0.16.","PeriodicalId":302303,"journal":{"name":"Volume 15: Student Paper Competition","volume":"1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2022-08-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"122229535","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}
Rod Ejection Accident (REA) is one of the major accidents which may result in the serious consequences during nuclear reactor operation. The study on REA is helpful to understand the physical characteristics and to verify the safety design of the core. The small pressurized water reactor (SPWR) adopts a relatively small amount of control rods. Therefore, when REA occurs, the positive reactivity introduced by the accident may be larger, resulting in more serious consequences. The integral design of SPWR results in different responses to the REA. Thus, it is necessary to investigate the REA of SPWR. In this paper, 3KeyMaster simulation platform, which is coupled with a thermo-hydraulic model and a three-dimensional space-time neutron dynamics model, is used to establish the reactor core model. Four single-beam control rods are selected to carry out REA, respectively. Simulations are performed, and results are collected. The responses of the SPWR are analyzed and accident procedures are obtained. Through analysis, it can be concluded that the serious consequences are caused when the R rod closest to the core, resulting in the maximum nuclear power peak. But the fuel center temperature and cladding temperature do not exceed the limit value, which proves the safety of SPWR and the rationality of core design.
{"title":"Rod Ejection Accident Simulation of a Small Pressurized Water Reactor","authors":"Ziqi Fan, Peiwei Sun, Xinyu Wei","doi":"10.1115/icone29-91878","DOIUrl":"https://doi.org/10.1115/icone29-91878","url":null,"abstract":"\u0000 Rod Ejection Accident (REA) is one of the major accidents which may result in the serious consequences during nuclear reactor operation. The study on REA is helpful to understand the physical characteristics and to verify the safety design of the core. The small pressurized water reactor (SPWR) adopts a relatively small amount of control rods. Therefore, when REA occurs, the positive reactivity introduced by the accident may be larger, resulting in more serious consequences. The integral design of SPWR results in different responses to the REA. Thus, it is necessary to investigate the REA of SPWR.\u0000 In this paper, 3KeyMaster simulation platform, which is coupled with a thermo-hydraulic model and a three-dimensional space-time neutron dynamics model, is used to establish the reactor core model. Four single-beam control rods are selected to carry out REA, respectively. Simulations are performed, and results are collected. The responses of the SPWR are analyzed and accident procedures are obtained.\u0000 Through analysis, it can be concluded that the serious consequences are caused when the R rod closest to the core, resulting in the maximum nuclear power peak. But the fuel center temperature and cladding temperature do not exceed the limit value, which proves the safety of SPWR and the rationality of core design.","PeriodicalId":302303,"journal":{"name":"Volume 15: Student Paper Competition","volume":"1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2022-08-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"125837281","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 magnetic vortex damper, a key unit of the control rod drive mechanism of high-temperature gas-cooled reactor (HTR), is a permanent magnet damper that produces eddy current resistance by rotating the conductor disc in magnetic field, and acts as a speed limit during the rod dropping process. To analyze the influence of neutron irradiation leaking from the core on the damping performance of the permanent magnet damper, the mechanism and the influencing factors of radiation-induced demagnetization of the Nd-Fe-B magnet were summarized through literature investigation and a magnetic vortex damper simulation model was established based on ANSYS Maxwell software and verified by experimental data. Current research shows that the magnet with higher intrinsic coercivity and length diameter ratio results in less demagnetization. The magnet permeance coefficient was simulated by the static magnetic field simulation to calculate its equivalent length diameter ratio. According to the literature experimental results, the equivalent length diameter ratio of the magnet, and its intrinsic coercivity, it was conservatively estimated that the remanence attenuation amplitude of the permanent magnet in this study should not exceed 1%. Based on this simulation model, the damping torque before and after the certain amplitude of magnet remanence attenuation was simulated and the corresponding maximum rod dropping speed was calculated. The simulation results show that the damping torque decrease is within 5%, which can meet the service requirements of high-temperature gas-cooled reactor over its service life.
{"title":"Analysis of Radiation-Induced Demagnetization Influence on the Performance of Permanent Magnet Damper","authors":"H. Wu, He Yan, Xingzhong Diao","doi":"10.1115/icone29-90515","DOIUrl":"https://doi.org/10.1115/icone29-90515","url":null,"abstract":"\u0000 The magnetic vortex damper, a key unit of the control rod drive mechanism of high-temperature gas-cooled reactor (HTR), is a permanent magnet damper that produces eddy current resistance by rotating the conductor disc in magnetic field, and acts as a speed limit during the rod dropping process. To analyze the influence of neutron irradiation leaking from the core on the damping performance of the permanent magnet damper, the mechanism and the influencing factors of radiation-induced demagnetization of the Nd-Fe-B magnet were summarized through literature investigation and a magnetic vortex damper simulation model was established based on ANSYS Maxwell software and verified by experimental data. Current research shows that the magnet with higher intrinsic coercivity and length diameter ratio results in less demagnetization. The magnet permeance coefficient was simulated by the static magnetic field simulation to calculate its equivalent length diameter ratio. According to the literature experimental results, the equivalent length diameter ratio of the magnet, and its intrinsic coercivity, it was conservatively estimated that the remanence attenuation amplitude of the permanent magnet in this study should not exceed 1%. Based on this simulation model, the damping torque before and after the certain amplitude of magnet remanence attenuation was simulated and the corresponding maximum rod dropping speed was calculated. The simulation results show that the damping torque decrease is within 5%, which can meet the service requirements of high-temperature gas-cooled reactor over its service life.","PeriodicalId":302303,"journal":{"name":"Volume 15: Student Paper Competition","volume":"1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2022-08-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"129024545","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 method is developed to find the implicit position of the control rod using the flux value shown by the neutron detectors. When using the 3D core physics analysis code CPACT, the detector response of a set of predicted rod positions can be calculated. On a double duel problem, functions can be built to describe the difference between the prediction and the target. Under the frame of the inverse problem, combinatorial optimization methods are operated to renew the prediction of rod positions by iteration to a result with convergence. By such a method, the results are guaranteed to achieve the self-consistent with the physical and thermal field while reaching stable convergence when the forward calculation software has been fully verified to simulate the real case. In the meanwhile, the appropriate computational cost is needed and can be adjusted with time tolerance. So, we have compared several global search algorithms (Genetic Algorithm, Particle Swarm Optimization, and Characteristic Statistic Algorithm) with their performance. We can also get the conclusion that hidden features and intermediate calculation results are important to improve the search efficiency. However, the responses of the detectors to some remote rods are not obvious, which are not easy to determine. All the methods were tested on the numerical calculation examples of a pressurized water reactor case.
{"title":"Determination of Control Rod Position by Global Optimization Methods","authors":"Zhang Qian, Zhihong Liu, Jing Zhao","doi":"10.1115/icone29-92637","DOIUrl":"https://doi.org/10.1115/icone29-92637","url":null,"abstract":"\u0000 The method is developed to find the implicit position of the control rod using the flux value shown by the neutron detectors. When using the 3D core physics analysis code CPACT, the detector response of a set of predicted rod positions can be calculated. On a double duel problem, functions can be built to describe the difference between the prediction and the target. Under the frame of the inverse problem, combinatorial optimization methods are operated to renew the prediction of rod positions by iteration to a result with convergence. By such a method, the results are guaranteed to achieve the self-consistent with the physical and thermal field while reaching stable convergence when the forward calculation software has been fully verified to simulate the real case. In the meanwhile, the appropriate computational cost is needed and can be adjusted with time tolerance. So, we have compared several global search algorithms (Genetic Algorithm, Particle Swarm Optimization, and Characteristic Statistic Algorithm) with their performance. We can also get the conclusion that hidden features and intermediate calculation results are important to improve the search efficiency. However, the responses of the detectors to some remote rods are not obvious, which are not easy to determine. All the methods were tested on the numerical calculation examples of a pressurized water reactor case.","PeriodicalId":302303,"journal":{"name":"Volume 15: Student Paper Competition","volume":"13 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2022-08-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"124514608","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}
Space nuclear power is the most potential power source for future deep space exploration, interstellar navigation, and planetary surface base station. For medium and high-power space missions, an efficient, compact and reliable energy conversion system that converts nuclear reactor thermal energy into mechanical energy or electrical energy is critical for the entire power system. The Stirling cycle that converts thermal energy into mechanical energy through expansion and compression of working fluids has the advantages of strong load adaptation, high conversion efficiency, modular combination, robust reliability, redundancy, etc. Therefore, it is very suitable for future high-power deep space missions. The technical route of space nuclear power proposed by Nanjing University of Aeronautics and Astronautics is based on the modular Stirling thermoelectric conversion and liquid molten salt core scheme. The present study is the simulation prediction of the thermodynamic performance of the Stirling engine. The working fluid’s composition, physical properties, and leakage properties have great influences on the thermal efficiency, operating lifetime, and reliability of the Stirling cycle. In this regard, a comprehensive study on the properties and effects of H2, He, He-Xe mixture, N2 and air as working fluids was carried out in the present study. The modified Stirling thermodynamic model IPD-MSM was used to simulate the Stirling cycle, and the heat and power losses caused by various irreversible factors were analyzed. Moreover, impacts of operating pressure, heat source temperature, and piston frequency on every heat and power loss were discussed. The results show that the pressure loss and the non-ideal heat transfer loss are the dominant losses. However, different working fluids and operating conditions have different performances of power loss. The effect of operating frequency and working pressure are significant, while the effect of operating temperature is relatively small. The present study provides theoretical support for selecting thermoelectric conversion methods for future medium and high-power space missions.
{"title":"Working Fluids Analysis and Discussions of the Stirling Cycle for Space Nuclear Reactors","authors":"Chenhao Yang, Nailiang Zhuang, Hangbin Zhao, Xiaobin Tang","doi":"10.1115/icone29-91605","DOIUrl":"https://doi.org/10.1115/icone29-91605","url":null,"abstract":"\u0000 Space nuclear power is the most potential power source for future deep space exploration, interstellar navigation, and planetary surface base station. For medium and high-power space missions, an efficient, compact and reliable energy conversion system that converts nuclear reactor thermal energy into mechanical energy or electrical energy is critical for the entire power system. The Stirling cycle that converts thermal energy into mechanical energy through expansion and compression of working fluids has the advantages of strong load adaptation, high conversion efficiency, modular combination, robust reliability, redundancy, etc. Therefore, it is very suitable for future high-power deep space missions. The technical route of space nuclear power proposed by Nanjing University of Aeronautics and Astronautics is based on the modular Stirling thermoelectric conversion and liquid molten salt core scheme. The present study is the simulation prediction of the thermodynamic performance of the Stirling engine. The working fluid’s composition, physical properties, and leakage properties have great influences on the thermal efficiency, operating lifetime, and reliability of the Stirling cycle. In this regard, a comprehensive study on the properties and effects of H2, He, He-Xe mixture, N2 and air as working fluids was carried out in the present study. The modified Stirling thermodynamic model IPD-MSM was used to simulate the Stirling cycle, and the heat and power losses caused by various irreversible factors were analyzed. Moreover, impacts of operating pressure, heat source temperature, and piston frequency on every heat and power loss were discussed. The results show that the pressure loss and the non-ideal heat transfer loss are the dominant losses. However, different working fluids and operating conditions have different performances of power loss. The effect of operating frequency and working pressure are significant, while the effect of operating temperature is relatively small. The present study provides theoretical support for selecting thermoelectric conversion methods for future medium and high-power space missions.","PeriodicalId":302303,"journal":{"name":"Volume 15: Student Paper Competition","volume":"54 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2022-08-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"123395264","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}
Enhancement of pool boiling heat transfer using a honeycomb porous plate (HPP) under atmosphere pressure has been experimentally examined. The previous research found that the critical heat flux (CHF) could be enhanced by up to three times above that of a plain surface. Considering the operating temperature in microelectronic devices, boiling at sub-atmospheric pressures for maintaining the lower surface temperature while removing high heat flux is required. Under circumstances of low pressure, there is a scarcity of research about boiling heat transfer for porous materials. Liquid supply is promoted by capillary action and vapor escape is facilitated by separating liquid flow channels from vapor flow channels in the HPP, and the CHF was expected to be improved even at reduced pressure conditions. Therefore, the CHF in saturated water boiling through an HPP at low pressure was studied in the current research. A more generalized understanding of the system pressure and the enhancement effect was provided, which made it possible to mitigate the enhancement technology bottlenecks through electronic devices and looked upon as further elaboration of the boiling heat transfer mechanism on honey-comb porous surfaces. There were three different pressures (51 kPa, 76 kPa and 100 kPa) investigated on the HPP; the results on the plain surface under the identical operating conditions were the same for each of the three pressures tested on the HPP.
{"title":"The Effect of a Honey-Comb Porous Plate on the Critical Heat Flux Under Reduced Pressure Conditions","authors":"F. Wu, S. Mori","doi":"10.1115/icone29-88834","DOIUrl":"https://doi.org/10.1115/icone29-88834","url":null,"abstract":"\u0000 Enhancement of pool boiling heat transfer using a honeycomb porous plate (HPP) under atmosphere pressure has been experimentally examined. The previous research found that the critical heat flux (CHF) could be enhanced by up to three times above that of a plain surface. Considering the operating temperature in microelectronic devices, boiling at sub-atmospheric pressures for maintaining the lower surface temperature while removing high heat flux is required. Under circumstances of low pressure, there is a scarcity of research about boiling heat transfer for porous materials. Liquid supply is promoted by capillary action and vapor escape is facilitated by separating liquid flow channels from vapor flow channels in the HPP, and the CHF was expected to be improved even at reduced pressure conditions. Therefore, the CHF in saturated water boiling through an HPP at low pressure was studied in the current research. A more generalized understanding of the system pressure and the enhancement effect was provided, which made it possible to mitigate the enhancement technology bottlenecks through electronic devices and looked upon as further elaboration of the boiling heat transfer mechanism on honey-comb porous surfaces. There were three different pressures (51 kPa, 76 kPa and 100 kPa) investigated on the HPP; the results on the plain surface under the identical operating conditions were the same for each of the three pressures tested on the HPP.","PeriodicalId":302303,"journal":{"name":"Volume 15: Student Paper Competition","volume":"44 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2022-08-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"117137079","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 order to reduce the harm to public safety caused by the loss of radioactive sources. A source searching method is proposed to locate orphan gamma source in the environment with obstacles and radiation shielding. The method is divided into two parts: predicting the probability of a radioactive source by Gaussian process regression (GPR) and path planning for the mobile robot using the probabilistic roadmap (PRM) method. The mean function and covariance function of the Gaussian process need to be selected in advance and the hyperparameters are calculated in the training process. Predicted values of GPR are given in the form of Gaussian distribution, which make us able to calculate the probability that there is a radioactive source in the grid and construct a probability map to guide the robot. The path connecting the start grid to the target grid is planned by the PRM method in a very short time, the cost function of A* algorithm in the query phase controls the pattern of the robot. At the beginning of the search, the robot prefers to move to areas with more information, after data above the threshold is detected, the robot switches to the tracking mode, accesses to the radioactive source rapidly. The effectiveness of the proposed method is verified in a simulation experiment in which a 10m × 10m radiation field with five walls is simulated. The searches of gamma point source are all successfully realized in 5 different cases and compared with the total number of discrete grids, the method uses only a small part of the grid data to realize the location. Overall, the results show that the proposed method is efficient for searching and locating orphan radioactive source.
{"title":"A Location Algorithm for Orphan Radioactive Source","authors":"Qian Xiao, Jiejin Cai","doi":"10.1115/icone29-93592","DOIUrl":"https://doi.org/10.1115/icone29-93592","url":null,"abstract":"\u0000 In order to reduce the harm to public safety caused by the loss of radioactive sources. A source searching method is proposed to locate orphan gamma source in the environment with obstacles and radiation shielding. The method is divided into two parts: predicting the probability of a radioactive source by Gaussian process regression (GPR) and path planning for the mobile robot using the probabilistic roadmap (PRM) method. The mean function and covariance function of the Gaussian process need to be selected in advance and the hyperparameters are calculated in the training process. Predicted values of GPR are given in the form of Gaussian distribution, which make us able to calculate the probability that there is a radioactive source in the grid and construct a probability map to guide the robot. The path connecting the start grid to the target grid is planned by the PRM method in a very short time, the cost function of A* algorithm in the query phase controls the pattern of the robot. At the beginning of the search, the robot prefers to move to areas with more information, after data above the threshold is detected, the robot switches to the tracking mode, accesses to the radioactive source rapidly. The effectiveness of the proposed method is verified in a simulation experiment in which a 10m × 10m radiation field with five walls is simulated. The searches of gamma point source are all successfully realized in 5 different cases and compared with the total number of discrete grids, the method uses only a small part of the grid data to realize the location. Overall, the results show that the proposed method is efficient for searching and locating orphan radioactive source.","PeriodicalId":302303,"journal":{"name":"Volume 15: Student Paper Competition","volume":"60 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2022-08-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"115681765","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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