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 article discusses engineering approaches to solving the problem of oil vapours in generators. Due to the design characteristics of each power plant, it is difficult to find a typical solution. Nevertheless, the ar...The article discusses engineering approaches to solving the problem of oil vapours in generators. Due to the design characteristics of each power plant, it is difficult to find a typical solution. Nevertheless, the article suggests ways to reduce the amount of oil mist. For their implementation, a calculation methodology based on the substitution scheme of the hydraulic path of the bearing support unit is created which takes into account the design features of the bearing and the parameters of the environment around the oil bath. The methodology employed is presented. The numerical method of modelling the aerodynamic fields of the entire hydro generator is used to estimate the air flows and pressures in the oil bath zone of the thrust bearing. Additionally, the method made it possible to track suspected oil particles that could get from the thrust-bearing bath into the surrounding area of the generator. Measures are proposed to reduce the level of oil mist through the competent design of the oil vapour removal system from the bearing bath.展开更多
The so-called indirect evaporative cooling technology is widely used in air conditioning applications.The thermal characterization of tube-type indirect evaporative coolers,however,still presents challenges which need...The so-called indirect evaporative cooling technology is widely used in air conditioning applications.The thermal characterization of tube-type indirect evaporative coolers,however,still presents challenges which need to be addressed to make this technology more reliable and easy to implement.This experimental study deals with the performances of a tube-type indirect evaporative cooler based on an aluminum tube with a 10 mm diameter.In particular,the required tests were carried out considering a range of dry-bulb temperatures between 16℃ and 18℃ and a temperature difference between the wet-bulb and dry-bulb temperature of 2℃∼4℃.The integrated convective heat transfer coefficient inside the tube in the drenching condition has been found to lie in the range between 36.10 and 437.4(W/(m^(2)⋅K)).展开更多
The evaporative cooling,which assists the refrigeration machinery air-conditioning systems test-rig,has been designed.Its structure and working principle were described,and the performance test was conducted and analy...The evaporative cooling,which assists the refrigeration machinery air-conditioning systems test-rig,has been designed.Its structure and working principle were described,and the performance test was conducted and analyzed.The test shows that making full use of the evaporative cooling "free cooling" in Spring and Autumn seasons can fully meet the requirements of air-conditioned comfort through the switch of the function in different seasons.Taking into account the evaporative cooling fan and pump energy consumption,compared with the traditional mechanical refrigeration system,more than 80 percent of energy can be saved,and the energy efficiency ratio of the Unit(EER)is as high as 7.63.Using the two stages of indirect evaporative cooling to pre-cool the new wind in summer,under the conditions of the same air supply temperature requirements,0.83 kg/s chilled water saved can be equivalent to the traditional mechanical refrigeration system,and when the new wind ratio up to 50 percent,more than 10 percent load was reduced in mechanical refrigeration system.The overall EER increased about 35 percent.展开更多
We propose a novel optical-access opened electrostatic trap to study the Stark-potential evaporative cooling of polar molecules by using two charged disk electrodes with a central hole of radius r0 = 1.5 mm, and deriv...We propose a novel optical-access opened electrostatic trap to study the Stark-potential evaporative cooling of polar molecules by using two charged disk electrodes with a central hole of radius r0 = 1.5 mm, and derive a set of new analytical equations to calculate the spatial distributions of the electrostatic field in the above charged-disk layout. Afterwards, we calculate the electric-field distributions of our electrostatic trap and the Stark potential for cold ND3 molecules, and analyze the dependences of both the electric field and the Stark potential on the geometric parameters of our charged-disk scheme, and find an optimal condition to form a desirable trap with the same trap depth in the x, y, and z directions. Also, we propose a desirable scheme to realize an efficient loading of cold polar molecules in the weak-field-seeking states, and investigate the dependences of the loading efficiency on both the initial forward velocity of the incident molecular beam and the loading time by Monte Carlo simulations. Our study shows that the maximal loading efficiency of our trap scheme can reach about 95%, and the corresponding temperature of the trapped cold molecules is about 28.8 inK. Finally, we study the Stark-potential evaporative cooling for cold polar molecules in our trap by the Monte Carlo method, and find that our simulated evaporative cooling results are consistent with our developed analytical model based on trapping-potential evaporative cooling.展开更多
Overtime, reduction in the amount of heat generated in engineering systems in operations have been of great concern and have continuously been under study. It is in line with the above that this research work develope...Overtime, reduction in the amount of heat generated in engineering systems in operations have been of great concern and have continuously been under study. It is in line with the above that this research work developed a mathematical model of an evaporative cooling pad using sintered Nigerian clay. A physical model of the evaporative cooling phenomenon was developed followed by the derivation of the governing equations describing the energy and mass transfer for the clay model from the laws of conservation of continuum mechanics. A set of reasonable and appropriate as-sumptions were imposed upon the physical model. Constitutive relationships were also developed for further analysis of the developed equations. The finite element model of numerical methods was used to analyse the energy transfer governing equations which resulted in the determination of the temperature of the exposed boundary surface at any given time, t2 after the commencement of the evaporative cooling processes. In this paper, it was found out that surface temperature differences could be as much as 6?C in the first cycle of evaporative cooling with the potential of further reduction. Further, an equation for the prediction of the effectiveness of an evaporative cooling system using clay modeled cooling pads was developed. The findings in this research work can be applied in the design, construction and maintenance of evaporative coolers used to dissipate waste heat when a large amount of natural water is not readily available or if for environmental and safety reasons the large water body can no longer absorb waste heat.展开更多
Long range intermolecular interaction potential surface of CaF(~2∑^+) was simulated by employing the MOLPRO program and using the RCCSD(T)/def2-TZVP theory. The predicted data were further fitted to obtain the collis...Long range intermolecular interaction potential surface of CaF(~2∑^+) was simulated by employing the MOLPRO program and using the RCCSD(T)/def2-TZVP theory. The predicted data were further fitted to obtain the collision crosssection. The elastic collision cross-section of CaF at the temperature around 2 mK is as high as 6.5 × 10^(-9) cm^2 and the collision rate is over 4.1 × 10~6 Hz. Additionally, we found that an orientation electric field will simplify the intermolecular interaction potential function from quaternary into ternary and the collision cross-section will be raised by about three orders. All-optical evaporative cooling of cold CaF is discussed in the conclusion.展开更多
The effects of surface-induced evaporative cooling on an atom chip are investigated. The evolutions of temperature, number and phase-space density of the atom cloud are measured when the atom cloud is brought close to...The effects of surface-induced evaporative cooling on an atom chip are investigated. The evolutions of temperature, number and phase-space density of the atom cloud are measured when the atom cloud is brought close to the surface. Rapid decrease of the temperature and number of the atoms is found when the atom-surface distance is 〈 100 ttm. A gain of about a factor of five on the phase-space density is obtained. It is found that the efficiency of the surface-induced evaporative cooling depends on the atom-surface distance and the shape of the evaporative trap. When the atoms are moved very close to the surface, severe heating is observed, which dominates when the holding time is 〉 8 ms. It is important that the surface-induced evaporative cooling offers novel possibilities for the realization of a continuous condensation, where a spatially varying evaporative cooling is required.展开更多
We investigate sympathetic cooling fermions 40K by evaporatively cooling bosonic 87Rb atoms in a magnetic trap with microwave and radio frequency induced evaporations in detail. The mixture of bosonic and fermionic at...We investigate sympathetic cooling fermions 40K by evaporatively cooling bosonic 87Rb atoms in a magnetic trap with microwave and radio frequency induced evaporations in detail. The mixture of bosonic and fermionic atoms is prepared in their polarized spin states IF = 9/2, mF = 9/2) for 40K and IF = 2, mF=2〉 for 87Rb, which is trapped in Quadrupole-Ioffe-Configuration trap. Comparing microwave with radio frequency evaporatively cooling bosonic STRb atoms with sympathetically cooling Fermi gas 40K, we find that the presence of rubidium atoms in the [2, 1} Zeeman states, which are generated in the evaporative process, gives rise to a significant loss of 40K due to inelastic collisions. Thus, the rubidium atoms populated in the [2, 1} Zeeman states should be removed in order to effectively perform sympathetically cooling 40K with the evaporatively cooled STRb atoms.展开更多
This paper presents an experimental demonstration of light-induced evaporative cooling in a magneto-optical trap. An additional laser is used to interact with atoms at the edge of the atomic cloud in the trap. These a...This paper presents an experimental demonstration of light-induced evaporative cooling in a magneto-optical trap. An additional laser is used to interact with atoms at the edge of the atomic cloud in the trap. These atoms get an additional force and evaporated away from the trap by both the magnetic field and laser fields. The remaining atoms have lower kinetic energy and thus are cooled. It reports the measurements on the temperature and atomic number after the evaporative cooling with different parameters including the distance between the laser and the centre of the atomic cloud, the detuning, the intensity. The results show that the light-induced evaporative cooling is a way to generate an ultra-cold atom source.展开更多
Heat stress is identified as a major cause of lower productive and reproductive performance in animal farming. This situation is more common in Saudi Arabia than in other countries because of extremely high ambient te...Heat stress is identified as a major cause of lower productive and reproductive performance in animal farming. This situation is more common in Saudi Arabia than in other countries because of extremely high ambient temperatures experienced during the summers. The evaporative cooling cow group had significantly increased serum E2 concentrations on days 7 and 14 - 19 of their estrous cycles, and significantly decreased serum P4 concentrations on days 7 - 18 of their estrous cycles. Evaporative cooling plus shade lowered ambient temperatures (41.80 ± 0.74 versus 47.40?C ± 0.84?C) have increased the relative humidity (0.33 ± 0.01 versus 0.24 ± 0.01) and decreased the temperature humidity index (80.24 ± 0.60 versus 84.77 ± 0.68) when compared with shade alone. However, cows under shade alone, compared to cows under evaporative cooling with shade, had a larger number of small (10.04 ± 0.54 versus 4.72 ± 0.58), medium (2.80 ± 0.21 versus 1.79 ± 0.17), and large follicles (6.82 ± 0.28 versus 5.66 ± 0.22). These results demonstrated that while evaporative cooling had positive effects on dairy cows in this experiment, changes could have been more profound, if installations of curtains and fans were implemented, which might need further investigation.展开更多
Greenhouses are used for the main purpose of improving the environmental conditions in which plants are grown. There are many parameters can affect the growing of plants inside greenhouse, such as air temperature and ...Greenhouses are used for the main purpose of improving the environmental conditions in which plants are grown. There are many parameters can affect the growing of plants inside greenhouse, such as air temperature and relative humidity. The adjustment of these parameters is achieved by selecting appropriate control actions. This work proposes a controlling technique for greenhouse indoor temperature and relative humidity. The proposed greenhouse cooling system temperature controller is designed to adjust the air volume flow rate in pad-fan cooling system to fix the greenhouse indoor temperature at 20?C and 70% relative humidity. The designed control technique is realized to ensure the required and continuous operation of the greenhouse. Moreover, this work present, a complete mathematical modeling and simulation of cooling system is introduced. In addition, a computer model based on MATLAB SIMULINK software has been used to predict the temperature and relative humidity profiles inside the greenhouse. The results are realized the requirements of the greenhouse cooling system environment.展开更多
The selection of cooling system for hydro-generator in Ertan Hydropower Station is reviewed in this paper. The new viewpoint on air-cooled system of hydraulic generator of recent years is analyzed and described. That ...The selection of cooling system for hydro-generator in Ertan Hydropower Station is reviewed in this paper. The new viewpoint on air-cooled system of hydraulic generator of recent years is analyzed and described. That is, "Full air-cooled system is always preferred to展开更多
We experimentally observe the dynamic evolution of atoms in the evaporative cooling, by in-situ imaging the plugged hole of ultracold atoms. Ultracold rubidium atoms confined in a magnetic trap are plugged using a blu...We experimentally observe the dynamic evolution of atoms in the evaporative cooling, by in-situ imaging the plugged hole of ultracold atoms. Ultracold rubidium atoms confined in a magnetic trap are plugged using a blue-detuned laser beam with a waist of 20 m at a wavelength of 767 nm. We probe the variation of the atomic temperature and width versus the radio frequency in the evaporative cooling. Both the behaviors are in good agreement with the calculation of the trapping potential dressed by the rf signal above the threshold temperature,while deviating from the calculation near the phase transition. To accurately obtain the atomic width, we use the plugged hole as the reference to optimize the optical imaging system by precisely minimizing the artificial structures due to the defocus effect.展开更多
As global energy demand continues to rise and climate change accelerates,the need for sustainable and energy-efficient cooling solutions has reached a critical level.Conventional air conditioning systems heavily rely ...As global energy demand continues to rise and climate change accelerates,the need for sustainable and energy-efficient cooling solutions has reached a critical level.Conventional air conditioning systems heavily rely on energy-intensive mechanical cooling,which significantly contributes to both electricity demand and greenhouse gas emissions.Passive cooling strategies,particularly radiative cooling(RC)and evaporative cooling(EC),present an alternative approach by harnessing natural processes for temperature regulation.While standalone RC can be affected by weather conditions and EC relies on water availability,Radiative-coupled EC(REC)offers a versatile and sustainable cooling solution suitable for various applications.Here we summarize an overview of the theoretical foundations and mathematical models of REC,encompassing REC by bulk water(REC-BW),REC by perspiration(REC-P),and REC by sorbed water(REC-SW).Moreover,we explore a range of applications,spanning from industrial processes to personal thermal management,and examine the advantages and challenges associated with each REC approach.The significance of REC lies in its potential to revolutionize cooling technology,reduce energy consumption,and minimize the environmental impact.REC-BW can conserve water resources in industrial cooling processes,while REC-P offers innovative solutions for wearable electronics and textiles.REC-SW’s adaptability makes it suitable for food preservation and future potable cooling devices.By addressing the challenges posed by REC,including water consumption,textile design,and optimization of bilayer structures,we can unlock the transformative potential of REC and contribute to sustainable cooling technologies in a warming world.展开更多
It’s well known that the performance of a gas turbine (efficiency, heat rate and power generated) is largely dependent on mass flow rate of air, inlet air temperature and turbine inlet temperature (TIT). As turbine i...It’s well known that the performance of a gas turbine (efficiency, heat rate and power generated) is largely dependent on mass flow rate of air, inlet air temperature and turbine inlet temperature (TIT). As turbine inlet temperature is dependent on quantity of burned fuel so that this factor is dropped out from this paper. It’s also known that gas turbines are constant volume machines i.e. at a given shaft speed they always move the same volume of air, but the power out-put of a turbine depends on the flow of mass through it. This is precisely the reason why on hot days, when air is less dense, power output falls off. A rise of one degree Centigrade temperature of inlet air decreases the power output by 1% and at the same time heat rate of the turbine also goes up. This is a matter of great concern to power producers. Many techniques have been developed to cool the inlet air to gas turbine. Some of these techniques to decrease the inlet air temperature are discussed here. The evaporative cooling technique is taken as a case study in this paper. A comparative studying is carried out between a unit using this technique and the same unit when the evaporative cooler is idle. The results advert to an increase in power output by 11.07% and a decrease in heat rate by approximately 4% when inlet air temperature drops from 50°C to 26°C.展开更多
The boiling heat transfer of evaporation cooling in a billet reheating furnace was simulated.The results indicate that the bubbles easily aggregate inside of the elbow and upper side of the horizontal regions in theπ...The boiling heat transfer of evaporation cooling in a billet reheating furnace was simulated.The results indicate that the bubbles easily aggregate inside of the elbow and upper side of the horizontal regions in theπshaped support tubes.The circulation velocity increasing helps to improve the uniformity of vapor distribution and decrease the difference of vapor volume fraction between upper and down at end of the horizontal sections.With the increase of circulation velocity,the resistance loss and the circulation ratio both increase,but the former will decrease with the increase of work pressure.展开更多
Functional textiles that promote daily comfort and productivity must efficiently release body sweats and transmit radiative heat through sweat evaporation and mid-infrared radiation(MIR)(8–13μm).However,most of the ...Functional textiles that promote daily comfort and productivity must efficiently release body sweats and transmit radiative heat through sweat evaporation and mid-infrared radiation(MIR)(8–13μm).However,most of the traditional clothing cannot provide simultaneous sweat evaporation and mid-infrared radiation transmission efficiently,leading to a poor design of personal cooling wearables.Herein,an evaporative/radiative integrated functional fibrous electrospun membrane is meticulously designed and controllably fabricated via facile electrospinning technology for personal cooling management.The developed membrane can be applied as a smart wearable with distinct personal thermal management applications.The promising temperature and humidity responsive vapor transmission of the membrane grants 1.2 times of evaporative cooling than that of traditional cotton.Besides,based on its high mid-infrared radiation transmission(53%)property in the range of 8–13μm,the as-spun membrane provides extra cooling of 1.5°C than that of cotton.Moreover,the building energy saving performances demonstrated that 47.1%annual building cooling can be achieved using the developed electrospun membrane.In general,the evaporative/radiative electrospun membrane creates a passive cooling microclimate for the human body,meeting the growing demand of wearable for personal cooling.展开更多
This paper systematically describes the technical principles,evaluation indicators,system forms and research progress of air-side evaporative cooling air conditioning systems,water-side evaporative cooling air conditi...This paper systematically describes the technical principles,evaluation indicators,system forms and research progress of air-side evaporative cooling air conditioning systems,water-side evaporative cooling air conditioning systems and freon-side evaporative cold coagulation heat air conditioning systems of Data center.In order to reduce the energy consumption of the refrigeration and air-conditioning system in the Data center,the applica-tion conditions and scenarios of the different forms of evaporative cooling air-conditioning systems should be considered comprehensively.Therefore,it is very important that the renewable energy-dry air can be used to the greatest extent.These efforts would contribute to China’s 2030"Carbon Peak"and 2060"Carbon Neutral."展开更多
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.
文摘The article discusses engineering approaches to solving the problem of oil vapours in generators. Due to the design characteristics of each power plant, it is difficult to find a typical solution. Nevertheless, the article suggests ways to reduce the amount of oil mist. For their implementation, a calculation methodology based on the substitution scheme of the hydraulic path of the bearing support unit is created which takes into account the design features of the bearing and the parameters of the environment around the oil bath. The methodology employed is presented. The numerical method of modelling the aerodynamic fields of the entire hydro generator is used to estimate the air flows and pressures in the oil bath zone of the thrust bearing. Additionally, the method made it possible to track suspected oil particles that could get from the thrust-bearing bath into the surrounding area of the generator. Measures are proposed to reduce the level of oil mist through the competent design of the oil vapour removal system from the bearing bath.
基金This work was supported by Natural Science Basic Research Program of Shaanxi(2021JQ-689).
文摘The so-called indirect evaporative cooling technology is widely used in air conditioning applications.The thermal characterization of tube-type indirect evaporative coolers,however,still presents challenges which need to be addressed to make this technology more reliable and easy to implement.This experimental study deals with the performances of a tube-type indirect evaporative cooler based on an aluminum tube with a 10 mm diameter.In particular,the required tests were carried out considering a range of dry-bulb temperatures between 16℃ and 18℃ and a temperature difference between the wet-bulb and dry-bulb temperature of 2℃∼4℃.The integrated convective heat transfer coefficient inside the tube in the drenching condition has been found to lie in the range between 36.10 and 437.4(W/(m^(2)⋅K)).
基金Xi'an Polytechnic University Graduate Innovational Foundation(chx080608)
文摘The evaporative cooling,which assists the refrigeration machinery air-conditioning systems test-rig,has been designed.Its structure and working principle were described,and the performance test was conducted and analyzed.The test shows that making full use of the evaporative cooling "free cooling" in Spring and Autumn seasons can fully meet the requirements of air-conditioned comfort through the switch of the function in different seasons.Taking into account the evaporative cooling fan and pump energy consumption,compared with the traditional mechanical refrigeration system,more than 80 percent of energy can be saved,and the energy efficiency ratio of the Unit(EER)is as high as 7.63.Using the two stages of indirect evaporative cooling to pre-cool the new wind in summer,under the conditions of the same air supply temperature requirements,0.83 kg/s chilled water saved can be equivalent to the traditional mechanical refrigeration system,and when the new wind ratio up to 50 percent,more than 10 percent load was reduced in mechanical refrigeration system.The overall EER increased about 35 percent.
文摘We propose a novel optical-access opened electrostatic trap to study the Stark-potential evaporative cooling of polar molecules by using two charged disk electrodes with a central hole of radius r0 = 1.5 mm, and derive a set of new analytical equations to calculate the spatial distributions of the electrostatic field in the above charged-disk layout. Afterwards, we calculate the electric-field distributions of our electrostatic trap and the Stark potential for cold ND3 molecules, and analyze the dependences of both the electric field and the Stark potential on the geometric parameters of our charged-disk scheme, and find an optimal condition to form a desirable trap with the same trap depth in the x, y, and z directions. Also, we propose a desirable scheme to realize an efficient loading of cold polar molecules in the weak-field-seeking states, and investigate the dependences of the loading efficiency on both the initial forward velocity of the incident molecular beam and the loading time by Monte Carlo simulations. Our study shows that the maximal loading efficiency of our trap scheme can reach about 95%, and the corresponding temperature of the trapped cold molecules is about 28.8 inK. Finally, we study the Stark-potential evaporative cooling for cold polar molecules in our trap by the Monte Carlo method, and find that our simulated evaporative cooling results are consistent with our developed analytical model based on trapping-potential evaporative cooling.
文摘Overtime, reduction in the amount of heat generated in engineering systems in operations have been of great concern and have continuously been under study. It is in line with the above that this research work developed a mathematical model of an evaporative cooling pad using sintered Nigerian clay. A physical model of the evaporative cooling phenomenon was developed followed by the derivation of the governing equations describing the energy and mass transfer for the clay model from the laws of conservation of continuum mechanics. A set of reasonable and appropriate as-sumptions were imposed upon the physical model. Constitutive relationships were also developed for further analysis of the developed equations. The finite element model of numerical methods was used to analyse the energy transfer governing equations which resulted in the determination of the temperature of the exposed boundary surface at any given time, t2 after the commencement of the evaporative cooling processes. In this paper, it was found out that surface temperature differences could be as much as 6?C in the first cycle of evaporative cooling with the potential of further reduction. Further, an equation for the prediction of the effectiveness of an evaporative cooling system using clay modeled cooling pads was developed. The findings in this research work can be applied in the design, construction and maintenance of evaporative coolers used to dissipate waste heat when a large amount of natural water is not readily available or if for environmental and safety reasons the large water body can no longer absorb waste heat.
基金supported by the National Natural Science Foundation of China(Grant Nos.11604164 and U1810129)the Fund for Shanxi "1331 Project" Key Innovation Research Team,China(Grant No.1331KIRT)Excellent Youth Academic Leader in Higher Education of Shanxi Province,China(2018)
文摘Long range intermolecular interaction potential surface of CaF(~2∑^+) was simulated by employing the MOLPRO program and using the RCCSD(T)/def2-TZVP theory. The predicted data were further fitted to obtain the collision crosssection. The elastic collision cross-section of CaF at the temperature around 2 mK is as high as 6.5 × 10^(-9) cm^2 and the collision rate is over 4.1 × 10~6 Hz. Additionally, we found that an orientation electric field will simplify the intermolecular interaction potential function from quaternary into ternary and the collision cross-section will be raised by about three orders. All-optical evaporative cooling of cold CaF is discussed in the conclusion.
基金Project supported by the State Key Basic Research Program (Grant No 2006CB921202)the National Natural Science Foundation of China (Grant No 10334050)
文摘The effects of surface-induced evaporative cooling on an atom chip are investigated. The evolutions of temperature, number and phase-space density of the atom cloud are measured when the atom cloud is brought close to the surface. Rapid decrease of the temperature and number of the atoms is found when the atom-surface distance is 〈 100 ttm. A gain of about a factor of five on the phase-space density is obtained. It is found that the efficiency of the surface-induced evaporative cooling depends on the atom-surface distance and the shape of the evaporative trap. When the atoms are moved very close to the surface, severe heating is observed, which dominates when the holding time is 〉 8 ms. It is important that the surface-induced evaporative cooling offers novel possibilities for the realization of a continuous condensation, where a spatially varying evaporative cooling is required.
基金Project supported by the National Science Foundation for Distinguished Young Scholars of China(Grant No.10725416)the National Basic Research Program of China(Grant No.2006CB921101 and 2011CB921601)the National Science Foundation NSFC Project for Excellent Research Team,China(Grant No.60821004)
文摘We investigate sympathetic cooling fermions 40K by evaporatively cooling bosonic 87Rb atoms in a magnetic trap with microwave and radio frequency induced evaporations in detail. The mixture of bosonic and fermionic atoms is prepared in their polarized spin states IF = 9/2, mF = 9/2) for 40K and IF = 2, mF=2〉 for 87Rb, which is trapped in Quadrupole-Ioffe-Configuration trap. Comparing microwave with radio frequency evaporatively cooling bosonic STRb atoms with sympathetically cooling Fermi gas 40K, we find that the presence of rubidium atoms in the [2, 1} Zeeman states, which are generated in the evaporative process, gives rise to a significant loss of 40K due to inelastic collisions. Thus, the rubidium atoms populated in the [2, 1} Zeeman states should be removed in order to effectively perform sympathetically cooling 40K with the evaporatively cooled STRb atoms.
基金Project supported by the Shanghai Pujiang Programme and the National Basic Research Programme of China (Grant No 2005CB724506)the National Natural Science Foundation of China (Grant No 10604057)
文摘This paper presents an experimental demonstration of light-induced evaporative cooling in a magneto-optical trap. An additional laser is used to interact with atoms at the edge of the atomic cloud in the trap. These atoms get an additional force and evaporated away from the trap by both the magnetic field and laser fields. The remaining atoms have lower kinetic energy and thus are cooled. It reports the measurements on the temperature and atomic number after the evaporative cooling with different parameters including the distance between the laser and the centre of the atomic cloud, the detuning, the intensity. The results show that the light-induced evaporative cooling is a way to generate an ultra-cold atom source.
文摘Heat stress is identified as a major cause of lower productive and reproductive performance in animal farming. This situation is more common in Saudi Arabia than in other countries because of extremely high ambient temperatures experienced during the summers. The evaporative cooling cow group had significantly increased serum E2 concentrations on days 7 and 14 - 19 of their estrous cycles, and significantly decreased serum P4 concentrations on days 7 - 18 of their estrous cycles. Evaporative cooling plus shade lowered ambient temperatures (41.80 ± 0.74 versus 47.40?C ± 0.84?C) have increased the relative humidity (0.33 ± 0.01 versus 0.24 ± 0.01) and decreased the temperature humidity index (80.24 ± 0.60 versus 84.77 ± 0.68) when compared with shade alone. However, cows under shade alone, compared to cows under evaporative cooling with shade, had a larger number of small (10.04 ± 0.54 versus 4.72 ± 0.58), medium (2.80 ± 0.21 versus 1.79 ± 0.17), and large follicles (6.82 ± 0.28 versus 5.66 ± 0.22). These results demonstrated that while evaporative cooling had positive effects on dairy cows in this experiment, changes could have been more profound, if installations of curtains and fans were implemented, which might need further investigation.
文摘Greenhouses are used for the main purpose of improving the environmental conditions in which plants are grown. There are many parameters can affect the growing of plants inside greenhouse, such as air temperature and relative humidity. The adjustment of these parameters is achieved by selecting appropriate control actions. This work proposes a controlling technique for greenhouse indoor temperature and relative humidity. The proposed greenhouse cooling system temperature controller is designed to adjust the air volume flow rate in pad-fan cooling system to fix the greenhouse indoor temperature at 20?C and 70% relative humidity. The designed control technique is realized to ensure the required and continuous operation of the greenhouse. Moreover, this work present, a complete mathematical modeling and simulation of cooling system is introduced. In addition, a computer model based on MATLAB SIMULINK software has been used to predict the temperature and relative humidity profiles inside the greenhouse. The results are realized the requirements of the greenhouse cooling system environment.
文摘The selection of cooling system for hydro-generator in Ertan Hydropower Station is reviewed in this paper. The new viewpoint on air-cooled system of hydraulic generator of recent years is analyzed and described. That is, "Full air-cooled system is always preferred to
基金Supported by the National Key Research and Development Program of China under Grant No 2016YFA0301503the National Natural Science Foundation of China under Grant Nos 11674358 and 11434015the Instrument Project of the Chinese Academy of Sciences under Grant No YJKYYQ20170025
文摘We experimentally observe the dynamic evolution of atoms in the evaporative cooling, by in-situ imaging the plugged hole of ultracold atoms. Ultracold rubidium atoms confined in a magnetic trap are plugged using a blue-detuned laser beam with a waist of 20 m at a wavelength of 767 nm. We probe the variation of the atomic temperature and width versus the radio frequency in the evaporative cooling. Both the behaviors are in good agreement with the calculation of the trapping potential dressed by the rf signal above the threshold temperature,while deviating from the calculation near the phase transition. To accurately obtain the atomic width, we use the plugged hole as the reference to optimize the optical imaging system by precisely minimizing the artificial structures due to the defocus effect.
基金the Natural Science Foundation of Hunan Province(No.2021JJ40732)the Central South University Innovation-Driven Research Program(No.2023CXQD012).
文摘As global energy demand continues to rise and climate change accelerates,the need for sustainable and energy-efficient cooling solutions has reached a critical level.Conventional air conditioning systems heavily rely on energy-intensive mechanical cooling,which significantly contributes to both electricity demand and greenhouse gas emissions.Passive cooling strategies,particularly radiative cooling(RC)and evaporative cooling(EC),present an alternative approach by harnessing natural processes for temperature regulation.While standalone RC can be affected by weather conditions and EC relies on water availability,Radiative-coupled EC(REC)offers a versatile and sustainable cooling solution suitable for various applications.Here we summarize an overview of the theoretical foundations and mathematical models of REC,encompassing REC by bulk water(REC-BW),REC by perspiration(REC-P),and REC by sorbed water(REC-SW).Moreover,we explore a range of applications,spanning from industrial processes to personal thermal management,and examine the advantages and challenges associated with each REC approach.The significance of REC lies in its potential to revolutionize cooling technology,reduce energy consumption,and minimize the environmental impact.REC-BW can conserve water resources in industrial cooling processes,while REC-P offers innovative solutions for wearable electronics and textiles.REC-SW’s adaptability makes it suitable for food preservation and future potable cooling devices.By addressing the challenges posed by REC,including water consumption,textile design,and optimization of bilayer structures,we can unlock the transformative potential of REC and contribute to sustainable cooling technologies in a warming world.
文摘It’s well known that the performance of a gas turbine (efficiency, heat rate and power generated) is largely dependent on mass flow rate of air, inlet air temperature and turbine inlet temperature (TIT). As turbine inlet temperature is dependent on quantity of burned fuel so that this factor is dropped out from this paper. It’s also known that gas turbines are constant volume machines i.e. at a given shaft speed they always move the same volume of air, but the power out-put of a turbine depends on the flow of mass through it. This is precisely the reason why on hot days, when air is less dense, power output falls off. A rise of one degree Centigrade temperature of inlet air decreases the power output by 1% and at the same time heat rate of the turbine also goes up. This is a matter of great concern to power producers. Many techniques have been developed to cool the inlet air to gas turbine. Some of these techniques to decrease the inlet air temperature are discussed here. The evaporative cooling technique is taken as a case study in this paper. A comparative studying is carried out between a unit using this technique and the same unit when the evaporative cooler is idle. The results advert to an increase in power output by 11.07% and a decrease in heat rate by approximately 4% when inlet air temperature drops from 50°C to 26°C.
基金Project(51171041) supported by the National Natural Science Foundation of China
文摘The boiling heat transfer of evaporation cooling in a billet reheating furnace was simulated.The results indicate that the bubbles easily aggregate inside of the elbow and upper side of the horizontal regions in theπshaped support tubes.The circulation velocity increasing helps to improve the uniformity of vapor distribution and decrease the difference of vapor volume fraction between upper and down at end of the horizontal sections.With the increase of circulation velocity,the resistance loss and the circulation ratio both increase,but the former will decrease with the increase of work pressure.
基金the Contract Research(Development of Breathable Fabrics with Nano-Electrospun Membrane,CityU ref.:9231419)the National Natural Science Foundation of China(Study of Multi-Responsive Shape Memory Polyurethane Nanocomposites Inspired by Natural Fibers,Grant No.51673162)Start-up Grant of CityU(Laboratory of Wearable Materials for Healthcare,Grant No.9380116).
文摘Functional textiles that promote daily comfort and productivity must efficiently release body sweats and transmit radiative heat through sweat evaporation and mid-infrared radiation(MIR)(8–13μm).However,most of the traditional clothing cannot provide simultaneous sweat evaporation and mid-infrared radiation transmission efficiently,leading to a poor design of personal cooling wearables.Herein,an evaporative/radiative integrated functional fibrous electrospun membrane is meticulously designed and controllably fabricated via facile electrospinning technology for personal cooling management.The developed membrane can be applied as a smart wearable with distinct personal thermal management applications.The promising temperature and humidity responsive vapor transmission of the membrane grants 1.2 times of evaporative cooling than that of traditional cotton.Besides,based on its high mid-infrared radiation transmission(53%)property in the range of 8–13μm,the as-spun membrane provides extra cooling of 1.5°C than that of cotton.Moreover,the building energy saving performances demonstrated that 47.1%annual building cooling can be achieved using the developed electrospun membrane.In general,the evaporative/radiative electrospun membrane creates a passive cooling microclimate for the human body,meeting the growing demand of wearable for personal cooling.
基金This study was supported by the Shenzhen Sustainable Development Science and Technology Project(2021N033)the National Key Research and Development Program(2016YFC0700404)the National Natural Science Foundation of China(51676145).
文摘This paper systematically describes the technical principles,evaluation indicators,system forms and research progress of air-side evaporative cooling air conditioning systems,water-side evaporative cooling air conditioning systems and freon-side evaporative cold coagulation heat air conditioning systems of Data center.In order to reduce the energy consumption of the refrigeration and air-conditioning system in the Data center,the applica-tion conditions and scenarios of the different forms of evaporative cooling air-conditioning systems should be considered comprehensively.Therefore,it is very important that the renewable energy-dry air can be used to the greatest extent.These efforts would contribute to China’s 2030"Carbon Peak"and 2060"Carbon Neutral."