Abstract This study experimentally investigates the small two-phase thermosyphon loop with minichannel evaporator. The influences of heating power, fan power, and inclination angle on the heat transfer performance are presented and the related mechanisms are revealed. Results show that the thermal resistance of the thermosyphon loop tends to decrease as the heating power is increased. It is found that there exists an optimal value of fan power. Interestingly, the invalidity behavior of thermosyphon under the inclination condition prefers to occur at higher heating power. To sum up, the small two-phase thermosyphon loop with minichannel evaporator could produce the excellent heat transfer performance with energy-saving characteristics, indicating its wide potential applications in the field of electronic chip cooling.
{"title":"Experimental Study on the Small Two-phase Thermosyphon Loop with Minichannel Evaporator","authors":"Yang Liu, Zhe Yan, Zhenhua Jiang, Nanxi Li, Baoyu Yang, Yinong Wu","doi":"10.1115/1.4063913","DOIUrl":"https://doi.org/10.1115/1.4063913","url":null,"abstract":"Abstract This study experimentally investigates the small two-phase thermosyphon loop with minichannel evaporator. The influences of heating power, fan power, and inclination angle on the heat transfer performance are presented and the related mechanisms are revealed. Results show that the thermal resistance of the thermosyphon loop tends to decrease as the heating power is increased. It is found that there exists an optimal value of fan power. Interestingly, the invalidity behavior of thermosyphon under the inclination condition prefers to occur at higher heating power. To sum up, the small two-phase thermosyphon loop with minichannel evaporator could produce the excellent heat transfer performance with energy-saving characteristics, indicating its wide potential applications in the field of electronic chip cooling.","PeriodicalId":17404,"journal":{"name":"Journal of Thermal Science and Engineering Applications","volume":"208 3","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-10-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"136318921","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
GURUDATT H. M., G. S. V. L. Narasimham, B. Sadashive Gowda
Abstract The 2016 Kigali amendment suggested phase-out of the HFCs and this process will go on until 2036 in industrialized nations and until 2047 in non-industrial nations to accomplish a condition of 85% decrease of HFCs. The HFC134a refrigerant used in vehicle air conditioning has a Global Warming Potential (GWP) of 1300, which prompted researchers to look for new low-GWP refrigerants. Recent research has revealed that the HydroFluoroOlefin (HFO) refrigerants R1234yf and R1234ze(E) with a GWP of 4 or less, show promise for application in Automobile Air Conditioning (AAC) field. The AAC requires special attention due to frequent leakages of HFC caused by vibration-induced pipe failures. In this research, the low-GWP refrigerants R1234yf and R1234ze(E) are considered to explore the AAC system performance and comparisons are made with the currently used refrigerant HFC134a. The numerical simulations are performed by including and excluding liquid-to-suction heat exchanger/Internal Heat Exchanger (IHX). The results show that use of IHX is advantageous for both R1234yf and R1234ze(E). R1234yf with IHX is a better alternative in the current AAC system working with R134a without IHX, with only a slight compromise in the system's performance and also the performance of R1234yf is better than R1234ze(E). Finally, the numerical simulation results are validated against the experimental results for R134a and R1234yf and found that most of the results agree within 10% deviation for system without IHX and within 15% deviation for system with IHX.
{"title":"EXPERIMENTAL AND NUMERICAL STUDIES ON AN AUTOMOBILE AIR CONDITIONING SYSTEM WITH THE REFRIGERANTS R134a, R1234yf AND R1234ze(E)","authors":"GURUDATT H. M., G. S. V. L. Narasimham, B. Sadashive Gowda","doi":"10.1115/1.4063910","DOIUrl":"https://doi.org/10.1115/1.4063910","url":null,"abstract":"Abstract The 2016 Kigali amendment suggested phase-out of the HFCs and this process will go on until 2036 in industrialized nations and until 2047 in non-industrial nations to accomplish a condition of 85% decrease of HFCs. The HFC134a refrigerant used in vehicle air conditioning has a Global Warming Potential (GWP) of 1300, which prompted researchers to look for new low-GWP refrigerants. Recent research has revealed that the HydroFluoroOlefin (HFO) refrigerants R1234yf and R1234ze(E) with a GWP of 4 or less, show promise for application in Automobile Air Conditioning (AAC) field. The AAC requires special attention due to frequent leakages of HFC caused by vibration-induced pipe failures. In this research, the low-GWP refrigerants R1234yf and R1234ze(E) are considered to explore the AAC system performance and comparisons are made with the currently used refrigerant HFC134a. The numerical simulations are performed by including and excluding liquid-to-suction heat exchanger/Internal Heat Exchanger (IHX). The results show that use of IHX is advantageous for both R1234yf and R1234ze(E). R1234yf with IHX is a better alternative in the current AAC system working with R134a without IHX, with only a slight compromise in the system's performance and also the performance of R1234yf is better than R1234ze(E). Finally, the numerical simulation results are validated against the experimental results for R134a and R1234yf and found that most of the results agree within 10% deviation for system without IHX and within 15% deviation for system with IHX.","PeriodicalId":17404,"journal":{"name":"Journal of Thermal Science and Engineering Applications","volume":"70 9","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-10-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"136261851","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Murat Canpolat, Çagri Sakalar, Serhat Bozkurt, Ahmet Yilmaz Çoban, Deniz Karaçayli, Emre Toker
Abstract The way the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is spread, especially in closed environments, is airborne transmission. The study aims to assess the thermal inactivation of airborne SARS-CoV-2 in a 30 m3 test room as a function of outlet temperature, airflow rate, and operating time of an electric heater, then define a condition to ensure that all air in the room passes through the electric heater. Aerosolized SARS-CoV-2 was delivered to the test room at an ambient temperature of 20 C and 40% humidity. Two electric heaters with different power and airflow rates were operated respectively in the test room to compare their efficiencies in the inactivation of airborne SARS-CoV-2. The first and second electric heaters had power, airflow rates, and outlet temperatures of 1.5 kW, 44 m3/h, 220 °C, and 3 kW, 324 m3/h, and 150 °C, respectively. A fan drew the outside air into the heater. In the first experiment, a 1.5 kW electric heater was operated in the test room for 80 minutes. In the second experiment, a 3 kW electric heater was used in the test room for 75 minutes. Airborne SARS-CoV-2 in the test room was inactivated by 99.00% and 99.96% in the first and second experiments, respectively. A condition is defined to ensure that all the air in the room passes at least once through the electric heater fan.
{"title":"Thermal Inactivation of Airborne SARS-CoV-2 by an Electric Fan Heater in Winter and Defining Conditions to Ensure That All the Air Passes through the Fan","authors":"Murat Canpolat, Çagri Sakalar, Serhat Bozkurt, Ahmet Yilmaz Çoban, Deniz Karaçayli, Emre Toker","doi":"10.1115/1.4063911","DOIUrl":"https://doi.org/10.1115/1.4063911","url":null,"abstract":"Abstract The way the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is spread, especially in closed environments, is airborne transmission. The study aims to assess the thermal inactivation of airborne SARS-CoV-2 in a 30 m3 test room as a function of outlet temperature, airflow rate, and operating time of an electric heater, then define a condition to ensure that all air in the room passes through the electric heater. Aerosolized SARS-CoV-2 was delivered to the test room at an ambient temperature of 20 C and 40% humidity. Two electric heaters with different power and airflow rates were operated respectively in the test room to compare their efficiencies in the inactivation of airborne SARS-CoV-2. The first and second electric heaters had power, airflow rates, and outlet temperatures of 1.5 kW, 44 m3/h, 220 °C, and 3 kW, 324 m3/h, and 150 °C, respectively. A fan drew the outside air into the heater. In the first experiment, a 1.5 kW electric heater was operated in the test room for 80 minutes. In the second experiment, a 3 kW electric heater was used in the test room for 75 minutes. Airborne SARS-CoV-2 in the test room was inactivated by 99.00% and 99.96% in the first and second experiments, respectively. A condition is defined to ensure that all the air in the room passes at least once through the electric heater fan.","PeriodicalId":17404,"journal":{"name":"Journal of Thermal Science and Engineering Applications","volume":"21 4","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-10-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"136262183","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Yun Liu, Wenzhao Wang, Chuanzhi Zhang, Tao Li, Xu Zhao
Abstract The molten salt has been widely used in concentrated solar power generation as an effective high-temperature heat transfer and heat storage working fluid. However, due to the concentrating characteristic of tower receiver, the solar flux distribution of molten salt receiver is extremely non-uniform, and thus the circumferential non-uniform heat flux has a prominent effect on the heat transfer performance and reliability of traditional solar molten salt receiver tube (TRT). In this contribution, in order to solve above problems, we propose some novel folded flow tubes (NFTs), which add a partition in the tube and seal the top with end cap so that the inflow and outflow of the fluid can only proceed from the same cross-section. Then, we apply the binary nitrate (solar salt) as heat transfer fluid, which is a mixture of 60% sodium nitrate and 40% potassium nitrate. Firstly, we analyze some effects such as flow parameters, structure and heat flux loading direction on the convective heat transfer performance of the NFTs. The results show that the circumferential temperature difference of NFTs is about 17 ~ 92k lower than that of TRT, and the molten salt temperature distribution is more uniform accordingly. Moreover, the heat transfer coefficient is increased about 88.37% ∼ 122.85%, which can provide a guidance for the structural optimization of practical solar molten salt receivers to improve the heat transfer performance and reliability.
{"title":"Improving the heat transfer performance of the tower molten salt solar receiver with the novel folded flow tubes","authors":"Yun Liu, Wenzhao Wang, Chuanzhi Zhang, Tao Li, Xu Zhao","doi":"10.1115/1.4063912","DOIUrl":"https://doi.org/10.1115/1.4063912","url":null,"abstract":"Abstract The molten salt has been widely used in concentrated solar power generation as an effective high-temperature heat transfer and heat storage working fluid. However, due to the concentrating characteristic of tower receiver, the solar flux distribution of molten salt receiver is extremely non-uniform, and thus the circumferential non-uniform heat flux has a prominent effect on the heat transfer performance and reliability of traditional solar molten salt receiver tube (TRT). In this contribution, in order to solve above problems, we propose some novel folded flow tubes (NFTs), which add a partition in the tube and seal the top with end cap so that the inflow and outflow of the fluid can only proceed from the same cross-section. Then, we apply the binary nitrate (solar salt) as heat transfer fluid, which is a mixture of 60% sodium nitrate and 40% potassium nitrate. Firstly, we analyze some effects such as flow parameters, structure and heat flux loading direction on the convective heat transfer performance of the NFTs. The results show that the circumferential temperature difference of NFTs is about 17 ~ 92k lower than that of TRT, and the molten salt temperature distribution is more uniform accordingly. Moreover, the heat transfer coefficient is increased about 88.37% ∼ 122.85%, which can provide a guidance for the structural optimization of practical solar molten salt receivers to improve the heat transfer performance and reliability.","PeriodicalId":17404,"journal":{"name":"Journal of Thermal Science and Engineering Applications","volume":"54 2","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-10-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"136262324","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Abstract In this paper, a pressure-swirl atomizing nozzle was proposed to improve the atomization characteristics and enhance the heat transfer characteristics. By modifying the structural parameters of the nozzle, the effect of angles of inclined holes on the swirl plate on the heat transfer characteristics was studied and the structure of nozzle was optimized based on Fluent software. The corresponding relationship between the pressure difference between the inlet and outlet of the nozzle and the flow rate was obtained, which provides a basis for the parameter setting of the DPM. The nozzle was then applied to a spray humidification system of a direct air cooling unit in the power plant. The influences of nozzles arrangement and spray directions on the vacuum degree of the system were studied. The results of numerical study show that the nozzles with inclined holes with an angle of 45° not only have the highest heat transfer efficiency but also have the highest heat transfer uniformity among all the simulated cases. In the air cooling unit of the power plant, when the nozzles are arranged in staggered rows and the angle between the spray direction and the positive direction along the height is kept at 15°, the heat transfer performance of spray humidification is the best; the vacuum degree of the condenser is the highest.
{"title":"Numerical Study on the Application of Pressure-swirl Atomizing Nozzle in a Direct Air Cooling Condenser of the Power Plant","authors":"Tianyun Liu","doi":"10.1115/1.4063921","DOIUrl":"https://doi.org/10.1115/1.4063921","url":null,"abstract":"Abstract In this paper, a pressure-swirl atomizing nozzle was proposed to improve the atomization characteristics and enhance the heat transfer characteristics. By modifying the structural parameters of the nozzle, the effect of angles of inclined holes on the swirl plate on the heat transfer characteristics was studied and the structure of nozzle was optimized based on Fluent software. The corresponding relationship between the pressure difference between the inlet and outlet of the nozzle and the flow rate was obtained, which provides a basis for the parameter setting of the DPM. The nozzle was then applied to a spray humidification system of a direct air cooling unit in the power plant. The influences of nozzles arrangement and spray directions on the vacuum degree of the system were studied. The results of numerical study show that the nozzles with inclined holes with an angle of 45° not only have the highest heat transfer efficiency but also have the highest heat transfer uniformity among all the simulated cases. In the air cooling unit of the power plant, when the nozzles are arranged in staggered rows and the angle between the spray direction and the positive direction along the height is kept at 15°, the heat transfer performance of spray humidification is the best; the vacuum degree of the condenser is the highest.","PeriodicalId":17404,"journal":{"name":"Journal of Thermal Science and Engineering Applications","volume":"1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-10-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"136263899","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Qi Zhang, Yanfang Li, Xuehong Wu, Xueling Zhang, Yanling Wang, Song Jun, Chongyang Liu
Abstract A flexible paraffin/hollow fiber phase change composite was prepared using a simple impregnation method, and the thermal-release performance of a piece of woven paraffin/hollow fiber rectangular blocks was systematically investigated using experimental and numerical methods. The experimental results of the thermal-release performance were highly consistent with the numerical results. Consequently, the thermal-release performance, including the available energy and solidification time, of the paraffin/hollow fiber with different melting temperatures, mass fractions (corresponding to the enthalpy), specific heat, and thermal conductivity were numerically investigated. The available energy of the paraffin/hollow fiber completely depends on the mass fraction of the paraffin. The solidification time mainly depends on the mass fraction of the paraffin and secondarily on the thermal conductivity, while the specific heat has little effect on the solidification time. Therefore, the thermal-release performance of the paraffin/hollow fiber could be optimized through numerical simulation by altering the solidification temperature, mass fraction, thermal conductivity, and specific heat.
{"title":"Experimental and numerical investigations on flexible paraffin/fiber composite phase change material","authors":"Qi Zhang, Yanfang Li, Xuehong Wu, Xueling Zhang, Yanling Wang, Song Jun, Chongyang Liu","doi":"10.1115/1.4063520","DOIUrl":"https://doi.org/10.1115/1.4063520","url":null,"abstract":"Abstract A flexible paraffin/hollow fiber phase change composite was prepared using a simple impregnation method, and the thermal-release performance of a piece of woven paraffin/hollow fiber rectangular blocks was systematically investigated using experimental and numerical methods. The experimental results of the thermal-release performance were highly consistent with the numerical results. Consequently, the thermal-release performance, including the available energy and solidification time, of the paraffin/hollow fiber with different melting temperatures, mass fractions (corresponding to the enthalpy), specific heat, and thermal conductivity were numerically investigated. The available energy of the paraffin/hollow fiber completely depends on the mass fraction of the paraffin. The solidification time mainly depends on the mass fraction of the paraffin and secondarily on the thermal conductivity, while the specific heat has little effect on the solidification time. Therefore, the thermal-release performance of the paraffin/hollow fiber could be optimized through numerical simulation by altering the solidification temperature, mass fraction, thermal conductivity, and specific heat.","PeriodicalId":17404,"journal":{"name":"Journal of Thermal Science and Engineering Applications","volume":"77 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-10-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135514404","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Abstract The application of liquid lithium as a coolant for the forthcoming era of space nuclear reactors exhibits significant potential, and spiral tube heat exchanger components are commonly used in steam generators for reactors. However, the heat transfer characteristics of liquid lithium in spiral tubes are not yet fully understood. This research establishes a non-isothermal heat transfer model incorporating a modified turbulent Prandtl number to analyze the flow of liquid lithium through spiral tubes with varying geometries. Numerical analysis is carried out focusing on the influence of inlet velocity, the distribution of related parameters, and the geometry of spiral tubes. The results demonstrate that in the range of the dimensionless Dean number 8165–13,063, the Nusselt number and the pressure drop present approximately linear relations with the Dean number. For the distribution law of relevant physical quantities, the inner side of the tube displays an eye-anatomy low-flowrate area and a high-temperature area, while a low-pressure area forms on the inner pipe wall. Finally, the pitch and spiral radius are found to be reduced as much as possible to ensure high liquid lithium-based heat transfer performance with a small pressure drop. The optimized design parameters reveal that within the actual design range of non-dimensional pitch of 0.667–10.667 and curvature of 0.0556–0.1667, the non-dimensional pitch and curvature are 0.667–2.667 and 0.1667, respectively. This study offers valuable insights into the heat transfer properties of liquid lithium within heat exchangers of the spiral tube design, promoting its application in space nuclear reactor power supply.
{"title":"Numerical investigation of the heat transfer characteristics of liquid lithium metal in spiral tubes","authors":"Yongfu Liu, Yi He, Peng Tan","doi":"10.1115/1.4063570","DOIUrl":"https://doi.org/10.1115/1.4063570","url":null,"abstract":"Abstract The application of liquid lithium as a coolant for the forthcoming era of space nuclear reactors exhibits significant potential, and spiral tube heat exchanger components are commonly used in steam generators for reactors. However, the heat transfer characteristics of liquid lithium in spiral tubes are not yet fully understood. This research establishes a non-isothermal heat transfer model incorporating a modified turbulent Prandtl number to analyze the flow of liquid lithium through spiral tubes with varying geometries. Numerical analysis is carried out focusing on the influence of inlet velocity, the distribution of related parameters, and the geometry of spiral tubes. The results demonstrate that in the range of the dimensionless Dean number 8165–13,063, the Nusselt number and the pressure drop present approximately linear relations with the Dean number. For the distribution law of relevant physical quantities, the inner side of the tube displays an eye-anatomy low-flowrate area and a high-temperature area, while a low-pressure area forms on the inner pipe wall. Finally, the pitch and spiral radius are found to be reduced as much as possible to ensure high liquid lithium-based heat transfer performance with a small pressure drop. The optimized design parameters reveal that within the actual design range of non-dimensional pitch of 0.667–10.667 and curvature of 0.0556–0.1667, the non-dimensional pitch and curvature are 0.667–2.667 and 0.1667, respectively. This study offers valuable insights into the heat transfer properties of liquid lithium within heat exchangers of the spiral tube design, promoting its application in space nuclear reactor power supply.","PeriodicalId":17404,"journal":{"name":"Journal of Thermal Science and Engineering Applications","volume":"84 2","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-10-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135514415","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Lei Zhang, Jun Zhou, Simeng Zuo, Guangyao An, Jinhua Lang, Wei Yuan
Abstract With the increasing volume of the cooling tower, the influence of environmental factors on the thermal performance of the cooling tower is not clear. Therefore, in order to more comprehensively study the influence mechanism of ambient air parameters on the thermal performance of the natural draft wet cooling tower, the key parameters such as gas-water ratio, circulating water temperature difference and heat transfer in each zone are calculated, and the temperature field and humidity field are also investigated. The results show that the circulating water temperature difference decreases most with the increase of ambient temperature, which is 7.63°C. However, atmospheric pressure makes the circulating water temperature difference decrease the least, which is 0.95°C, resulting in the decrease of heat transfer in the three zones by 14.9%, 10.6% and 26.0% respectively. The increase of relative humidity and atmospheric pressure leads to the increase of contact heat transfer and the decrease of evaporative mass transfer. The increase of ambient temperature makes the contact heat transfer and evaporative mass transfer decrease, and finally the heat and mass transfer capacity of the cooling tower decreases. This study establishes a theoretical basis for further optimization of the thermal performance and energy-saving design of cooling towers.
{"title":"Effect mechanism of ambient air parameters on the thermal performance for cooling towers","authors":"Lei Zhang, Jun Zhou, Simeng Zuo, Guangyao An, Jinhua Lang, Wei Yuan","doi":"10.1115/1.4063875","DOIUrl":"https://doi.org/10.1115/1.4063875","url":null,"abstract":"Abstract With the increasing volume of the cooling tower, the influence of environmental factors on the thermal performance of the cooling tower is not clear. Therefore, in order to more comprehensively study the influence mechanism of ambient air parameters on the thermal performance of the natural draft wet cooling tower, the key parameters such as gas-water ratio, circulating water temperature difference and heat transfer in each zone are calculated, and the temperature field and humidity field are also investigated. The results show that the circulating water temperature difference decreases most with the increase of ambient temperature, which is 7.63°C. However, atmospheric pressure makes the circulating water temperature difference decrease the least, which is 0.95°C, resulting in the decrease of heat transfer in the three zones by 14.9%, 10.6% and 26.0% respectively. The increase of relative humidity and atmospheric pressure leads to the increase of contact heat transfer and the decrease of evaporative mass transfer. The increase of ambient temperature makes the contact heat transfer and evaporative mass transfer decrease, and finally the heat and mass transfer capacity of the cooling tower decreases. This study establishes a theoretical basis for further optimization of the thermal performance and energy-saving design of cooling towers.","PeriodicalId":17404,"journal":{"name":"Journal of Thermal Science and Engineering Applications","volume":"502 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-10-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135570242","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Gustavo A Patiño-Jaramillo, Alejandro Rivera, Julian D. Osorio
Abstract A solar absorption cooling system consisting of a flat plate collector, thermal energy storage tank, and absorption chiller is analyzed in this work. A dimensionless model is developed from the energy balance on each component and the chiller’s characteristic performance curves. The model is used to determine the interaction and influence of different parameters such as tank size, solar collector area, chiller size, cooling load, cooling temperature, heat loss, and mass flow rates on the performance. From the analysis, smaller solar collector areas are required for lower cooling loads and smaller tank volumes. A specific cooling load of 1 × 10−5 will require a specific solar collector area between two and six times larger, depending on the initial tank temperature, than the area required for a baseline system that considers typical commercial design and operation parameters. A similar behavior was observed for the specific tank volume. For the baseline system, the minimum specific area of the collector of 9.57 is achieved for an initial tank temperature of 1.19. For a cooling load of 1 × 10−5, the optimum initial tank temperature will be 1.11 that results in a minimum specific solar collector area of 25.26. A specific tank volume of 4 × 10−4 will also have an optimum initial tank temperature of 1.11 that minimizes the specific solar collector area to a value of 28.18. The approach and analysis in this work can be used to determine design parameters for solar absorption cooling systems based on a proper relation among system’s dimensions to achieve optimum operation.
{"title":"Performance evaluation and optimal design analysis of a continuous-operation solar-driven cooling absorption systems with thermal energy storage","authors":"Gustavo A Patiño-Jaramillo, Alejandro Rivera, Julian D. Osorio","doi":"10.1115/1.4063409","DOIUrl":"https://doi.org/10.1115/1.4063409","url":null,"abstract":"Abstract A solar absorption cooling system consisting of a flat plate collector, thermal energy storage tank, and absorption chiller is analyzed in this work. A dimensionless model is developed from the energy balance on each component and the chiller’s characteristic performance curves. The model is used to determine the interaction and influence of different parameters such as tank size, solar collector area, chiller size, cooling load, cooling temperature, heat loss, and mass flow rates on the performance. From the analysis, smaller solar collector areas are required for lower cooling loads and smaller tank volumes. A specific cooling load of 1 × 10−5 will require a specific solar collector area between two and six times larger, depending on the initial tank temperature, than the area required for a baseline system that considers typical commercial design and operation parameters. A similar behavior was observed for the specific tank volume. For the baseline system, the minimum specific area of the collector of 9.57 is achieved for an initial tank temperature of 1.19. For a cooling load of 1 × 10−5, the optimum initial tank temperature will be 1.11 that results in a minimum specific solar collector area of 25.26. A specific tank volume of 4 × 10−4 will also have an optimum initial tank temperature of 1.11 that minimizes the specific solar collector area to a value of 28.18. The approach and analysis in this work can be used to determine design parameters for solar absorption cooling systems based on a proper relation among system’s dimensions to achieve optimum operation.","PeriodicalId":17404,"journal":{"name":"Journal of Thermal Science and Engineering Applications","volume":"78 6","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-10-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135513644","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Abstract This research aims to create an artificial neural network (ANN) regression model for predicting the performance parameters of the perforated micro-pin fin (MPF) heat sinks for various geometric parameters and inflow conditions. A three-dimensional computational fluid dynamics (CFD) simulation system is developed to generate dataset samples under different operational conditions, which are specified using Latin hypercube sampling (LHS). An ANN model is first obtained by optimizing the model hyper-parameters, which are then deployed to learn from the input feature space that consists of perforation diameter, perforation location, and inflow velocity. For accurate training of the ANN, the model is trained over a range of uniformly distributed data points in the input feature space. The developed multi-layer model predicted Nusselt number and friction factor with the mean absolute percentage error of 4.45% and 1.80%, respectively. Subsequently, the developed surrogate model is used in the optimization study to demonstrate the application of the surrogate model. A multi-objective non-dominated sorting genetic algorithm (NSGA-II) is used to perform the optimization of the perforation location, diameter, and inflow conditions. Negative of the Nusselt number and friction factor are chosen as objectives to minimize. A Pareto front is obtained from the optimization study that shows a set of optimal solutions. Thermal performance of the perforated MPF is increased between 11.5% and 39.77%. The optimizer selected a significantly smaller hole diameter at a higher location and a faster speed to maximize the Nusselt number and minimize the friction factor.
{"title":"Multiobjective optimization of air-cooled perforated micro pin fin heat sink via an artificial neural network surrogate model coupled with NSGA-II","authors":"Deepa Gupta, Probir Saha, Somnath Roy","doi":"10.1115/1.4063682","DOIUrl":"https://doi.org/10.1115/1.4063682","url":null,"abstract":"Abstract This research aims to create an artificial neural network (ANN) regression model for predicting the performance parameters of the perforated micro-pin fin (MPF) heat sinks for various geometric parameters and inflow conditions. A three-dimensional computational fluid dynamics (CFD) simulation system is developed to generate dataset samples under different operational conditions, which are specified using Latin hypercube sampling (LHS). An ANN model is first obtained by optimizing the model hyper-parameters, which are then deployed to learn from the input feature space that consists of perforation diameter, perforation location, and inflow velocity. For accurate training of the ANN, the model is trained over a range of uniformly distributed data points in the input feature space. The developed multi-layer model predicted Nusselt number and friction factor with the mean absolute percentage error of 4.45% and 1.80%, respectively. Subsequently, the developed surrogate model is used in the optimization study to demonstrate the application of the surrogate model. A multi-objective non-dominated sorting genetic algorithm (NSGA-II) is used to perform the optimization of the perforation location, diameter, and inflow conditions. Negative of the Nusselt number and friction factor are chosen as objectives to minimize. A Pareto front is obtained from the optimization study that shows a set of optimal solutions. Thermal performance of the perforated MPF is increased between 11.5% and 39.77%. The optimizer selected a significantly smaller hole diameter at a higher location and a faster speed to maximize the Nusselt number and minimize the friction factor.","PeriodicalId":17404,"journal":{"name":"Journal of Thermal Science and Engineering Applications","volume":"15 2","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-10-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135514305","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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