This study develops an analytical model to evaluate the cooling performance of a porous terracotta tubular direct evaporative heat and mass exchanger. By combining energy and mass balance equations with heat and mass ...This study develops an analytical model to evaluate the cooling performance of a porous terracotta tubular direct evaporative heat and mass exchanger. By combining energy and mass balance equations with heat and mass transfer coefficients and air psychrometric correlations, the model provides insights into the impact of design and operational parameters on the exchanger cooling performance. Validated against an established numerical model, it accurately simulates cooling behavior with a Root Mean Square Deviation of 0.43 - 1.18˚C under varying inlet air conditions. The results show that tube geometry, including equivalent diameter, flatness ratio, and length significantly influences cooling outcomes. Smaller diameters enhance wet-bulb effectiveness but reduce cooling capacity, while increased flatness and length improve both. For example, extending the flatness ratio of a 15 mm diameter, 0.6 m long tube from 1 (circular) to 4 raises the exchange surface area from 0.028 to 0.037 m2, increasing wet-bulb effectiveness from 60% to 71%. Recommended diameters range from 5 mm for tubes under 0.5 m to 1 cm for tubes 0.5 to 1 m in length. Optimal air velocities depend on tube length: 1 m/s for tubes under 0.8 m, 1.5 m/s for lengths of 0.8 to 1.2 m, and up to 2 m/s for longer tubes. This model offers a practical alternative to complex numerical and CFD methods, with potential applications in cooling tower optimization for thermal and nuclear power plants and geothermal heat exchangers.展开更多
The Al^＋ ion optical clock is a very promising optical frequency standard candidate due to its extremely small black-body radiation shift. It has been successfully demonstrated with the indirect cooled, quantum-logic...The Al^＋ ion optical clock is a very promising optical frequency standard candidate due to its extremely small black-body radiation shift. It has been successfully demonstrated with the indirect cooled, quantum-logic-based spectroscopy technique. Its accuracy is limited by second-order Doppler shift, and its stability is limited by the number of ions that can be probed in quantum logic processing. We propose a direct laser cooling scheme of AI＋ ion optical clocks where both the stability and accuracy of the clocks are greatly improved. In the proposed scheme, two Al^＋ traps are utilized. The first trap is used to trap a large number of Al^＋ ions to improve the stability of the clock laser, while the second trap is used to trap a single Al^＋ ion to provide the ultimate accuracy. Both traps are cooled with a continuous wave 167nm laser. The expected clock laser stability can reach 9.0 × 10^-17/√τ. For the second trap, in addition to 167nm laser Doppler cooling, a second stage pulsed 234nm two-photon cooling laser is utilized to further improve the accuracy of the clock laser. The total systematic uncertainty can be reduced to about 1 × 10^-18. The proposed Al^＋ ion optical clock has the potential to become the most accurate and stable optical clock.展开更多
The performance of a patented water pumping model with steam-air power was presented, which operates automatically by direct contact cooling method. The main objective was to study feasibility of a pumping model for u...The performance of a patented water pumping model with steam-air power was presented, which operates automatically by direct contact cooling method. The main objective was to study feasibility of a pumping model for underground water. In this model, a heater installed within the heat tank represented sources of waste heat as energy input for finding appropriate conditions of the 10 L pump model. The system operation had five stages： heating, pumping, vapor flow, cooling, and water suction. The overall water heads of 3, 4.5, 6 and 7.5 m were tested. At the same time, it was found that the pump with 50% air volume is sufficient for pumping water to a desired level. In the experiment, the temperatures in the heating and pumping stages were 100-103 ℃and 80-90 ℃, respectively. The pressure in the pumping stage was 12-18 kPa, and the pressure in the suction stage was about-80 kPa, sufficient for the best performance. It could pump 170 L of water at a 2 m suction head, 120 L at a 3.5 m suction head, 100 L at a 5 m suction head, and 65 L at a 6.5 m suction head in 2 h. A mathematical model for larger pumps was also presented, which operates nearly the same as the present system. Economic analysis of the 10 L pump was also included.展开更多
Power Electronic (PE) will play an essential role in future drive concepts. Nowadays, mainly water/glycol-based cooling media are used to cool PE. Due to their high electrical conductivity (EC), water/glycol-based coo...Power Electronic (PE) will play an essential role in future drive concepts. Nowadays, mainly water/glycol-based cooling media are used to cool PE. Due to their high electrical conductivity (EC), water/glycol-based coolants cannot be used for direct cooling of the electrical components. Direct cooling concepts with dedicated transmission fluids show potential usage of fluid in direct contact with electrified parts. This results in special requirements for the fluids and materials. The aimed action as a coolant requires a defined measurement and characterization of fluid properties and heat transfer in order to assess the cooling ability of a fluid. The purpose of the work was to develop a new measurement setup based on the thermal transient method with which the thermal requirements of cooling fluids for a direct cooling concept can be assessed. With this method, relevant transmission fluids have been tested and the thermal performance compared to indirect cooling effect of water/glycol is discussed. The result of the work is that the measurement method is very well suited for the application-related evaluation of the fluids. Direct oil cooling with transmission fluids could increase heat transfer coefficient by a factor of 3 to 8, compared to the indirect cooing with water/glycol as cooling media.展开更多
A review is conducted about the application of the evaporative cooling technology in thermal power plants.Different case studies are considered,namely,evaporative air conditioners,evaporative cooling in direct air-coo...A review is conducted about the application of the evaporative cooling technology in thermal power plants.Different case studies are considered,namely,evaporative air conditioners,evaporative cooling in direct air-cooled systems,gas turbine inlet cooling,wet cooling towers,and hybrid cooling towers with a crosswind effect.Some effort is provided to describe the advantages related to direct evaporative cooling when it is applied in thermal power plants and illustrate the research gaps,which have not been filled yet.In particular,typical case studies are intentionally used to compare the cooling performances when direct evaporative cooling is implemented in different types of cooling towers,including the natural draft wet cooling tower(NDWCT)and the pre-cooled natural draft dry cooling tower(NDDCT).It is shown that the NDWCT provides the best cooling performance in terms of power station cooling,followed by the pre-cooled NDDCT,and the NDDCT;moreover,the evaporative pre-cooling is able to enhance the cooling performance of NDDCT.Besides,on a yearly basis,better NDDCT cooling performances can be obtained by means of a spray-based pre-cooling approach with respect to wet media pre-cooling.Therefore,the use of nozzle spray is suggested for improvement in the performance of indirect/direct air-cooling systems with controlled water consumption.展开更多
The imbalance in heat power generated by various types of chips poses an obstacle to the reliability and performance of heterogeneous integration(HI)packaging technology,leading to excessive cooling that reduces the s...The imbalance in heat power generated by various types of chips poses an obstacle to the reliability and performance of heterogeneous integration(HI)packaging technology,leading to excessive cooling that reduces the system’s energy efficiency.We propose a framework to optimize the impinging nozzle arrangement for energyefficient uniform jet cooling of HI packages.This framework utilizes a convolutional neural network(CNN)-based surrogate model that learns nozzle arrangements and heating scenarios to predict the temperature nonuniformity of the package.The potential optimal designs predicted by the CNN are used for re-training through an experimentally validated numerical analysis model.Combined with this active learning approach,the proposed hierarchical exploration algorithm accelerates optimization by gradually scaling the design options.The optimization results showed an increase in cooling uniformity by up to 39.5%,while the cooling COP improved by up to 200%across the investigated flow rate range(3–8 L/min).The optimized designs were experimentally validated with a maximum error of 4.34%in average thermal resistance.Our framework achieved up to 45.7%data savings compared to the random sampling-based approach.Along with a discussion on applying the CNN model to untrained conditions to further enhance optimization efficiency,our work represents a novel approach to broadly address the rapidly evolving diverse heating scenarios of HI,contributing to improved cooling energy efficiency in data centers and enhanced reliability of high-performance processors.展开更多
Radiative cooling has witnessed substantial progress while its performance is constrained by the thermal reciprocal Kirchhoff’s law.Violating Kirchhoff’s law to pursue nonreciprocal radiative cooling seems promising...Radiative cooling has witnessed substantial progress while its performance is constrained by the thermal reciprocal Kirchhoff’s law.Violating Kirchhoff’s law to pursue nonreciprocal radiative cooling seems promising;however,the energy conservation requirement and radiant flux integrated over the entire hemisphere make the nonreciprocal benefit insignificant.This commentary discusses the practical limits of nonreciprocal radiative cooling and points toward the future direction of directional radiative cooling.展开更多
The back-propagation （BP） neural network is created to predict the performance of a direct evaporative cooling （DEC） air conditioner with GLASdek pads. The experiment data about the performance of the DEC air cond...The back-propagation （BP） neural network is created to predict the performance of a direct evaporative cooling （DEC） air conditioner with GLASdek pads. The experiment data about the performance of the DEC air conditioner are obtained. Some experiment data are used to train the network until these data can approximate a function, then, simulate the network with the remanent data. The predicted result shows satisfying effects.展开更多
文摘This study develops an analytical model to evaluate the cooling performance of a porous terracotta tubular direct evaporative heat and mass exchanger. By combining energy and mass balance equations with heat and mass transfer coefficients and air psychrometric correlations, the model provides insights into the impact of design and operational parameters on the exchanger cooling performance. Validated against an established numerical model, it accurately simulates cooling behavior with a Root Mean Square Deviation of 0.43 - 1.18˚C under varying inlet air conditions. The results show that tube geometry, including equivalent diameter, flatness ratio, and length significantly influences cooling outcomes. Smaller diameters enhance wet-bulb effectiveness but reduce cooling capacity, while increased flatness and length improve both. For example, extending the flatness ratio of a 15 mm diameter, 0.6 m long tube from 1 (circular) to 4 raises the exchange surface area from 0.028 to 0.037 m2, increasing wet-bulb effectiveness from 60% to 71%. Recommended diameters range from 5 mm for tubes under 0.5 m to 1 cm for tubes 0.5 to 1 m in length. Optimal air velocities depend on tube length: 1 m/s for tubes under 0.8 m, 1.5 m/s for lengths of 0.8 to 1.2 m, and up to 2 m/s for longer tubes. This model offers a practical alternative to complex numerical and CFD methods, with potential applications in cooling tower optimization for thermal and nuclear power plants and geothermal heat exchangers.
基金Supported by the National Basic Research Program of China under Grant No 2012CB821300the National Natural Science Foundation of China under Grant Nos 91336213,11304109,91536116 and 11174095the Program for New Century Excellent Talents by the Ministry of Education under Grant No NCET-11-0176
文摘The Al^＋ ion optical clock is a very promising optical frequency standard candidate due to its extremely small black-body radiation shift. It has been successfully demonstrated with the indirect cooled, quantum-logic-based spectroscopy technique. Its accuracy is limited by second-order Doppler shift, and its stability is limited by the number of ions that can be probed in quantum logic processing. We propose a direct laser cooling scheme of AI＋ ion optical clocks where both the stability and accuracy of the clocks are greatly improved. In the proposed scheme, two Al^＋ traps are utilized. The first trap is used to trap a large number of Al^＋ ions to improve the stability of the clock laser, while the second trap is used to trap a single Al^＋ ion to provide the ultimate accuracy. Both traps are cooled with a continuous wave 167nm laser. The expected clock laser stability can reach 9.0 × 10^-17/√τ. For the second trap, in addition to 167nm laser Doppler cooling, a second stage pulsed 234nm two-photon cooling laser is utilized to further improve the accuracy of the clock laser. The total systematic uncertainty can be reduced to about 1 × 10^-18. The proposed Al^＋ ion optical clock has the potential to become the most accurate and stable optical clock.
基金the financial support provided by National Research Council of Thailand and the Energy Technology Division, School of Energy Environment and Materials, King Mongkut’s University of Technology Thonburisupported by the Higher Education Research Promotion and National Research University Project of Thailand, Office of the Higher Education Commission
文摘The performance of a patented water pumping model with steam-air power was presented, which operates automatically by direct contact cooling method. The main objective was to study feasibility of a pumping model for underground water. In this model, a heater installed within the heat tank represented sources of waste heat as energy input for finding appropriate conditions of the 10 L pump model. The system operation had five stages： heating, pumping, vapor flow, cooling, and water suction. The overall water heads of 3, 4.5, 6 and 7.5 m were tested. At the same time, it was found that the pump with 50% air volume is sufficient for pumping water to a desired level. In the experiment, the temperatures in the heating and pumping stages were 100-103 ℃and 80-90 ℃, respectively. The pressure in the pumping stage was 12-18 kPa, and the pressure in the suction stage was about-80 kPa, sufficient for the best performance. It could pump 170 L of water at a 2 m suction head, 120 L at a 3.5 m suction head, 100 L at a 5 m suction head, and 65 L at a 6.5 m suction head in 2 h. A mathematical model for larger pumps was also presented, which operates nearly the same as the present system. Economic analysis of the 10 L pump was also included.
文摘Power Electronic (PE) will play an essential role in future drive concepts. Nowadays, mainly water/glycol-based cooling media are used to cool PE. Due to their high electrical conductivity (EC), water/glycol-based coolants cannot be used for direct cooling of the electrical components. Direct cooling concepts with dedicated transmission fluids show potential usage of fluid in direct contact with electrified parts. This results in special requirements for the fluids and materials. The aimed action as a coolant requires a defined measurement and characterization of fluid properties and heat transfer in order to assess the cooling ability of a fluid. The purpose of the work was to develop a new measurement setup based on the thermal transient method with which the thermal requirements of cooling fluids for a direct cooling concept can be assessed. With this method, relevant transmission fluids have been tested and the thermal performance compared to indirect cooling effect of water/glycol is discussed. The result of the work is that the measurement method is very well suited for the application-related evaluation of the fluids. Direct oil cooling with transmission fluids could increase heat transfer coefficient by a factor of 3 to 8, compared to the indirect cooing with water/glycol as cooling media.
基金supported by the Shandong Natural Science Foundation(Grant No.ZR2022ME008)the Shandong Provincial Science and Technology SMEs Innovation Capacity Improvement Project(2022TSGC2018)+3 种基金the Shenzhen Science and Technology Program(KCXFZ20201221173409026)The financial supports from the“Young Scholars Program of Shandong University”(YSPSDU,No.2018WLJH73)the Open Project of State Key Laboratory of Clean Energy Utilization,Zhejiang University(Program Number ZJUCEU2020011)the Shandong Natural Science Foundation(Grant No.ZR2021ME118)are gratefully acknowledged。
文摘A review is conducted about the application of the evaporative cooling technology in thermal power plants.Different case studies are considered,namely,evaporative air conditioners,evaporative cooling in direct air-cooled systems,gas turbine inlet cooling,wet cooling towers,and hybrid cooling towers with a crosswind effect.Some effort is provided to describe the advantages related to direct evaporative cooling when it is applied in thermal power plants and illustrate the research gaps,which have not been filled yet.In particular,typical case studies are intentionally used to compare the cooling performances when direct evaporative cooling is implemented in different types of cooling towers,including the natural draft wet cooling tower(NDWCT)and the pre-cooled natural draft dry cooling tower(NDDCT).It is shown that the NDWCT provides the best cooling performance in terms of power station cooling,followed by the pre-cooled NDDCT,and the NDDCT;moreover,the evaporative pre-cooling is able to enhance the cooling performance of NDDCT.Besides,on a yearly basis,better NDDCT cooling performances can be obtained by means of a spray-based pre-cooling approach with respect to wet media pre-cooling.Therefore,the use of nozzle spray is suggested for improvement in the performance of indirect/direct air-cooling systems with controlled water consumption.
基金supported by the Basic Science Research Program(Grant No.2022R1A2C3011684)of the National Research Foundation of Korea(NRF)funded by the Ministry of Science and ICT,Koreathe International Cooperative R&D Program(Grant No.RS-2024-00436521)+1 种基金the Korea Institute of Energy Technology Evaluation and Planning(KETEP)funded by the Ministry of Trade,Industry&Energy,Koreasupported by Samsung Electronics Co.,Ltd.Research Program.
文摘The imbalance in heat power generated by various types of chips poses an obstacle to the reliability and performance of heterogeneous integration(HI)packaging technology,leading to excessive cooling that reduces the system’s energy efficiency.We propose a framework to optimize the impinging nozzle arrangement for energyefficient uniform jet cooling of HI packages.This framework utilizes a convolutional neural network(CNN)-based surrogate model that learns nozzle arrangements and heating scenarios to predict the temperature nonuniformity of the package.The potential optimal designs predicted by the CNN are used for re-training through an experimentally validated numerical analysis model.Combined with this active learning approach,the proposed hierarchical exploration algorithm accelerates optimization by gradually scaling the design options.The optimization results showed an increase in cooling uniformity by up to 39.5%,while the cooling COP improved by up to 200%across the investigated flow rate range(3–8 L/min).The optimized designs were experimentally validated with a maximum error of 4.34%in average thermal resistance.Our framework achieved up to 45.7%data savings compared to the random sampling-based approach.Along with a discussion on applying the CNN model to untrained conditions to further enhance optimization efficiency,our work represents a novel approach to broadly address the rapidly evolving diverse heating scenarios of HI,contributing to improved cooling energy efficiency in data centers and enhanced reliability of high-performance processors.
基金funding from the National Natural Science Foundation of China(52422603,52076087,and 52211540005)the Interdisciplinary Research Program of HUST(5003120094)the Natural Science Foundation of Hubei Province(2023AFA072).
文摘Radiative cooling has witnessed substantial progress while its performance is constrained by the thermal reciprocal Kirchhoff’s law.Violating Kirchhoff’s law to pursue nonreciprocal radiative cooling seems promising;however,the energy conservation requirement and radiant flux integrated over the entire hemisphere make the nonreciprocal benefit insignificant.This commentary discusses the practical limits of nonreciprocal radiative cooling and points toward the future direction of directional radiative cooling.
文摘The back-propagation （BP） neural network is created to predict the performance of a direct evaporative cooling （DEC） air conditioner with GLASdek pads. The experiment data about the performance of the DEC air conditioner are obtained. Some experiment data are used to train the network until these data can approximate a function, then, simulate the network with the remanent data. The predicted result shows satisfying effects.
