Experimental investigation is performed to investigate the cooling characteristics in the front zone of effusion configuration. Effects of blowing ratio,multi-hole arrangement mode,hole-to-hole pitch and jet orientati...Experimental investigation is performed to investigate the cooling characteristics in the front zone of effusion configuration. Effects of blowing ratio,multi-hole arrangement mode,hole-to-hole pitch and jet orientation angle on the adiabatic film cooling effectiveness are concentrated on. The results show that the film layer displays an obvious"developing"feature in the front zone of effusion cooling scheme,for either the staggered or inline multi-hole arrangement. The varying gradient of the laterally-averaged adiabatic cooling effectiveness along the streamwise direction is greater for the staggered arrangement than that for the inline arrangement. The holes array arranged in staggered mode with small hole-tohole pitches is in favor of obtaining developed film coverage layer rapidly.展开更多
Regarding the complexity and inconsistency of results in existing evaluation methods of mine cooling system, this paper clarifies the advantages, disadvantages and application of various mine cooling sys- tems through...Regarding the complexity and inconsistency of results in existing evaluation methods of mine cooling system, this paper clarifies the advantages, disadvantages and application of various mine cooling sys- tems through principle analysis, and divides all the cooling systems into air-cooling, ice-cooling and water-cooling according to the transportation of cold energy. On this basis, the paper proposes a simple and efficient evaluation method for mine cooling system. The first index of this method is the air temper- ature at point C which is 15 m away from the return wind corner at working face. A cooling system will be judged ineligible if the air temperature at point C is above 30 ℃ during operation, because in this case, the combustible gases in coal will sharply overflow, inducing gas incidents. Based on the preliminary judg- ment of the first index, another two evaluation indexes are proposed based on the cooling ability and dehumidification of an airflow volume of 1000 m3/min at point C to evaluate the investment and opera- tion cost of mine cooling system. This evaluation method has already been successfully applied in the cooling system design of Zhangshuanglou coal mine.展开更多
Disturbance effect is one of the important factors for wind damage to large cooling towers.Existing studies on the wind-induced interference of cooling tower groups are aimed at the same size and the lack of wind-indu...Disturbance effect is one of the important factors for wind damage to large cooling towers.Existing studies on the wind-induced interference of cooling tower groups are aimed at the same size and the lack of wind-induced interference effects between cooling towers of different sizes.With the background of the additional cooling tower project at Shandong Luxi Power Plant in China,the rigid body pressure wind tunnel test is carried out to obtain 194 conditions for the three combinations of the existing four-tower combination(small size),the new two-tower combination(large size)and the six-tower combination surface wind pressure distribution.Numerical simulation of the surrounding flow field of the cooling tower group with the most unfavorable interference condition of the six-tower combination is conducted using the computational fluid dynamics(CFD)method.Based on this,the characteristics of the average and pulsating wind pressure distribution of the cooling tower surface under the six-tower combination are mainly studied,and the load interference coefficients of the large-sized cooling tower and the small-sized cooling tower under the three tower group combinations are compared.The velocity flow field and vorticity changes around the cooling tower group at unfavorable wind angles are analyzed,and the wind-induced interference mechanism between cooling tower groups of different sizes is mainly refined.Research shows that the interference effect between such cooling tower groups of different sizes is much larger than that of cooling tower groups of the same size,which is specifically manifested as the enhancement effect of small-sized cooling towers and the shielding effect of large-sized cooling towers.The interference coefficient of large-sized cooling tower groups increases by 28%,and the interference coefficient of small-sized cooling tower groups decreases by 6.4%.The airflow acceleration caused by the pinch effect between small-sized cooling tower groups has an adverse effect on large-sized cooling towers and can significantly increase the magnitude of local wind load.The shielding effect of large-sized cooling towers can reduce the overall wind load of small-sized cooling towers.The research conclusions can provide the basis of wind load value design for wind resistance design of such large cooling tower addition projects.展开更多
In the present work, computational simulations was made using ANSYS CFX to predict the improvements in film cooling performance with dual trench. Dual-trench confguradon consists of two trenches together, one wider tr...In the present work, computational simulations was made using ANSYS CFX to predict the improvements in film cooling performance with dual trench. Dual-trench confguradon consists of two trenches together, one wider trench and the other is narrow trench that extruded from the wider one. Several blowing ratios in the range （0.5：5） were investigated. The pitch-to-diameter ratio of 2.775 is used. By using the dual trench configuration, the coolant jet impacted the trench wall two times allowing increasing the spreading of coolant laterally in the trench, reducing jet velocity and jet completely covered on the surface. The results indicate that this configuration increased adiabatic effectiveness as blowing ratio increased. The spatially averaged adiabatic effectiveness reached 57.6% for at M= 2. No observed film blow-off at all blowing ratios. The adiabatic film effectiveness of dual trench case outperformed the narrow trench case, laidback fan-shaped hole, fan-shaped hole and cylinder hole at different blowing ratios.展开更多
The experimental study focuses on the heat flux on a double cone blunt body in the presence of tangential-slot super- sonic injection into hypersonic flow. The tests are conducted in a contoured axisymmetric nozzle wi...The experimental study focuses on the heat flux on a double cone blunt body in the presence of tangential-slot super- sonic injection into hypersonic flow. The tests are conducted in a contoured axisymmetric nozzle with Mach numbers of 7.3 and 8.1, and the total temperature is about 900 K. The injection Mach number is 3.2, and total temperature is 300 K. A constant voltage circuit is developed to supply the temperature detectors instead of the normally used constant current circuit. The schlieren photographs are presented additionally to visualize the flow and help analyze the pressure relationship between the cooling flow and the main flow. The dependence of the film-cooling effectiveness on flow parameters, i.e. the blow ratio, the convective Mach number, and the attack angle, is determined. A semi-empirical formula is tested by the present data, and is improved for a better correlation.展开更多
In this paper,we introduce a method of quantitatively evaluating and controlling the space charge effect of a lasercooled three-dimensional（3 D） ion system in a linear Paul trap.The relationship among cooling effici...In this paper,we introduce a method of quantitatively evaluating and controlling the space charge effect of a lasercooled three-dimensional（3 D） ion system in a linear Paul trap.The relationship among cooling efficiency,ion quantity,and trapping strength is analyzed quantitatively,and the dynamic space distribution and temporal evolution of the 3 D ion system on a secular motion period time scale in the cooling process are obtained.The ion number influences the eigen-micromotion feature of the ion system.When trapping parameter q is ～ 0.3,relatively ideal cooling efficiency and equilibrium temperature can be obtained.The decrease of axial electrostatic potential is helpful in reducing the micromotion heating effect and the degradation in the total energy.Within a single secular motion period under different cooling conditions,ions transform from the cloud state（each ion disperses throughout the envelope of the ion system） to the liquid state（each ion is concentrated at a specific location in the ion system） and then to the crystal state（each ion is subjected to a fixed motion track）.These results are conducive to long-term storage and precise control,motion effect suppression,high-efficiency cooling,and increasing the precision of spectroscopy for a 3 D ion system.展开更多
This article reviews the research progress of measurement techniques and materials on the mechanocaloric effect over the past few decades.Mechanocaloric materials can be divided into elastocaloric and barocaloric mate...This article reviews the research progress of measurement techniques and materials on the mechanocaloric effect over the past few decades.Mechanocaloric materials can be divided into elastocaloric and barocaloric materials depending on the applied uniaxial stress or hydrostatic pressure.Elastocaloric materials include non-magnetic shape memory alloys,polymers,and rare-earth compounds.Barocaloric materials include magnetic shape memory alloys,ferroelectric ceramics,superionic conductors,and oxyfluorides.The mechanocaloric effects of these classes of materials are systematically compared in terms of the isothermal entropy change and adiabatic temperature change.In addition to the thermal effects,other characteristics closely related to the application of mechanocaloric materials are also summarized.Finally,perspectives for further development of mechanocaloric materials in the solid-state cooling area are discussed.展开更多
We present a cooling scheme with a tripod configuration atomic ensemble trapped in an optomechanical cavity.With the employment of two different quantum interference processes,our scheme illustrates that it is possibl...We present a cooling scheme with a tripod configuration atomic ensemble trapped in an optomechanical cavity.With the employment of two different quantum interference processes,our scheme illustrates that it is possible to cool a resonator to its ground state in the strong cavity-atom coupling regime.Moreover,with the assistance of one additional energy level,our scheme takes a larger cooling rate to realize the ground state cooling.In addition,this scheme is a feasible candidate for experimental applications.展开更多
An orthogoual experimental scheme was designed for optimizing a water-cooled structure of the divertor plate. There were three influencing factors： the radius R of the water- cooled pipe, and the pipe spacing L1 and ...An orthogoual experimental scheme was designed for optimizing a water-cooled structure of the divertor plate. There were three influencing factors： the radius R of the water- cooled pipe, and the pipe spacing L1 and L3. The influence rule of different factors on the cooling effect and thermal stress of the plate were studied, for which the influence rank was respectively R 〉 L1 〉 L3 and L3 〉 R 〉 L1. The highest temperature value decreased when R and L1 increased~ and the maximum thermal stress value dropped when R, L1 and L3 increased. The final optimized results can be summarized as： R equals 6 mm or 7 mm, L1 equals 19 mm, and L3 equals 20 mm. Compared with the initial design, the highest temperature value had a small decline~ and the maximum thermal stress value dropped by 19~ to 24~. So it was not ideal to improve the cooling effect by optimizing the geometry sizes of the water-cooled structure, even worse than increasing the flow speed, but it was very effective for dropping the maximum thermal stress value. The orthogoaal experimental method reduces the number of experiments by 80%, and thus it is feasible and effective to optimize the water-cooled structure of the divertor plate with the orthogonal theory.展开更多
The mixed-field effect at the hyperfine level of the rovibronic ground state of the^(127)I^(79)Br(X^(1)Σ,v=0,J=0)molecule is computed on the J-I uncoupled basis of|JM_(J)I_(1)M_(1)I_(2)M_(2)>,where J is the molecu...The mixed-field effect at the hyperfine level of the rovibronic ground state of the^(127)I^(79)Br(X^(1)Σ,v=0,J=0)molecule is computed on the J-I uncoupled basis of|JM_(J)I_(1)M_(1)I_(2)M_(2)>,where J is the molecular total angular momentum excluding nuclear spin,M_J is the projection number of J,I_(1) and I_(2) are the nuclear spins of the iodine and bromine atoms,and M_(1) and M_(2) are the projection numbers of I_(1) and I_(2),respectively.When the two applied electric and magnetic fields are parallel,the perturbations are rare and only one perturbation is observed in a relatively large field regime in our computation range.However,when the two fields are off-parallel,the perturbations increase significantly and some sublevels show the Feshbach-like resonance phenomenon.Therefore,such sublevels transit between weak-field seeking and strong-field seeking repeatedly,which can be utilized to enhance or suppress cold molecular collision and chemical reaction rates.Such behavior of the molecular hyperfine structure in the mixed off-parallel fields may also be utilized to construct an electric-field-assisted anti-Helmholtz magnetic trap for cold molecules and to realize evaporative cooling of cold molecules(sub-mK)into the ultracold regime(μK).展开更多
基金Supported by the National Natural Science Foundation of China(51276090)
文摘Experimental investigation is performed to investigate the cooling characteristics in the front zone of effusion configuration. Effects of blowing ratio,multi-hole arrangement mode,hole-to-hole pitch and jet orientation angle on the adiabatic film cooling effectiveness are concentrated on. The results show that the film layer displays an obvious"developing"feature in the front zone of effusion cooling scheme,for either the staggered or inline multi-hole arrangement. The varying gradient of the laterally-averaged adiabatic cooling effectiveness along the streamwise direction is greater for the staggered arrangement than that for the inline arrangement. The holes array arranged in staggered mode with small hole-tohole pitches is in favor of obtaining developed film coverage layer rapidly.
基金supported by the key project of National Natural Science Foundation ‘‘Deep Heat Governance and Utilization’’ (Nos.51134005 and 41402273)the Doctoral Fund of Ministry of Education (No. 20130023110021)
文摘Regarding the complexity and inconsistency of results in existing evaluation methods of mine cooling system, this paper clarifies the advantages, disadvantages and application of various mine cooling sys- tems through principle analysis, and divides all the cooling systems into air-cooling, ice-cooling and water-cooling according to the transportation of cold energy. On this basis, the paper proposes a simple and efficient evaluation method for mine cooling system. The first index of this method is the air temper- ature at point C which is 15 m away from the return wind corner at working face. A cooling system will be judged ineligible if the air temperature at point C is above 30 ℃ during operation, because in this case, the combustible gases in coal will sharply overflow, inducing gas incidents. Based on the preliminary judg- ment of the first index, another two evaluation indexes are proposed based on the cooling ability and dehumidification of an airflow volume of 1000 m3/min at point C to evaluate the investment and opera- tion cost of mine cooling system. This evaluation method has already been successfully applied in the cooling system design of Zhangshuanglou coal mine.
基金supported in part by the National Natural Science Foundations(Nos. 51878351, U1733129,51761165022)the Outstanding Youth Fund of Jiangsu Natural Science Foundation(No. BK20160083).
文摘Disturbance effect is one of the important factors for wind damage to large cooling towers.Existing studies on the wind-induced interference of cooling tower groups are aimed at the same size and the lack of wind-induced interference effects between cooling towers of different sizes.With the background of the additional cooling tower project at Shandong Luxi Power Plant in China,the rigid body pressure wind tunnel test is carried out to obtain 194 conditions for the three combinations of the existing four-tower combination(small size),the new two-tower combination(large size)and the six-tower combination surface wind pressure distribution.Numerical simulation of the surrounding flow field of the cooling tower group with the most unfavorable interference condition of the six-tower combination is conducted using the computational fluid dynamics(CFD)method.Based on this,the characteristics of the average and pulsating wind pressure distribution of the cooling tower surface under the six-tower combination are mainly studied,and the load interference coefficients of the large-sized cooling tower and the small-sized cooling tower under the three tower group combinations are compared.The velocity flow field and vorticity changes around the cooling tower group at unfavorable wind angles are analyzed,and the wind-induced interference mechanism between cooling tower groups of different sizes is mainly refined.Research shows that the interference effect between such cooling tower groups of different sizes is much larger than that of cooling tower groups of the same size,which is specifically manifested as the enhancement effect of small-sized cooling towers and the shielding effect of large-sized cooling towers.The interference coefficient of large-sized cooling tower groups increases by 28%,and the interference coefficient of small-sized cooling tower groups decreases by 6.4%.The airflow acceleration caused by the pinch effect between small-sized cooling tower groups has an adverse effect on large-sized cooling towers and can significantly increase the magnitude of local wind load.The shielding effect of large-sized cooling towers can reduce the overall wind load of small-sized cooling towers.The research conclusions can provide the basis of wind load value design for wind resistance design of such large cooling tower addition projects.
基金Supprted by Harbin Engineering University Scholarship under Grant No. 20100903D01
文摘In the present work, computational simulations was made using ANSYS CFX to predict the improvements in film cooling performance with dual trench. Dual-trench confguradon consists of two trenches together, one wider trench and the other is narrow trench that extruded from the wider one. Several blowing ratios in the range （0.5：5） were investigated. The pitch-to-diameter ratio of 2.775 is used. By using the dual trench configuration, the coolant jet impacted the trench wall two times allowing increasing the spreading of coolant laterally in the trench, reducing jet velocity and jet completely covered on the surface. The results indicate that this configuration increased adiabatic effectiveness as blowing ratio increased. The spatially averaged adiabatic effectiveness reached 57.6% for at M= 2. No observed film blow-off at all blowing ratios. The adiabatic film effectiveness of dual trench case outperformed the narrow trench case, laidback fan-shaped hole, fan-shaped hole and cylinder hole at different blowing ratios.
基金Project supported by the National Natural Science Foundation of China(Grant No.11172326)the Scientific Research Program of National University of Defense Technology,China(Grant No.0100010112001)
文摘The experimental study focuses on the heat flux on a double cone blunt body in the presence of tangential-slot super- sonic injection into hypersonic flow. The tests are conducted in a contoured axisymmetric nozzle with Mach numbers of 7.3 and 8.1, and the total temperature is about 900 K. The injection Mach number is 3.2, and total temperature is 300 K. A constant voltage circuit is developed to supply the temperature detectors instead of the normally used constant current circuit. The schlieren photographs are presented additionally to visualize the flow and help analyze the pressure relationship between the cooling flow and the main flow. The dependence of the film-cooling effectiveness on flow parameters, i.e. the blow ratio, the convective Mach number, and the attack angle, is determined. A semi-empirical formula is tested by the present data, and is improved for a better correlation.
基金Project supported by the National Key Research and Development Program of China(Grant No.2017YFA0304401)the National Natural Science Foundation of China(Grant Nos.11622434,11474318,91336211,and 11634013)+2 种基金the Strategic Priority Research Program of the Chinese Academy of Sciences(Grant No.XDB21030100)Hubei Province Science Fund for Distinguished Young Scholars(Grant No.2017CFA040)the Youth Innovation Promotion Association of the Chinese Academy of Sciences(Grant No.2015274)
文摘In this paper,we introduce a method of quantitatively evaluating and controlling the space charge effect of a lasercooled three-dimensional（3 D） ion system in a linear Paul trap.The relationship among cooling efficiency,ion quantity,and trapping strength is analyzed quantitatively,and the dynamic space distribution and temporal evolution of the 3 D ion system on a secular motion period time scale in the cooling process are obtained.The ion number influences the eigen-micromotion feature of the ion system.When trapping parameter q is ～ 0.3,relatively ideal cooling efficiency and equilibrium temperature can be obtained.The decrease of axial electrostatic potential is helpful in reducing the micromotion heating effect and the degradation in the total energy.Within a single secular motion period under different cooling conditions,ions transform from the cloud state（each ion disperses throughout the envelope of the ion system） to the liquid state（each ion is concentrated at a specific location in the ion system） and then to the crystal state（each ion is subjected to a fixed motion track）.These results are conducive to long-term storage and precise control,motion effect suppression,high-efficiency cooling,and increasing the precision of spectroscopy for a 3 D ion system.
基金Project supported by the National Natural Science Foundation of China(Grant No.11474280).
文摘This article reviews the research progress of measurement techniques and materials on the mechanocaloric effect over the past few decades.Mechanocaloric materials can be divided into elastocaloric and barocaloric materials depending on the applied uniaxial stress or hydrostatic pressure.Elastocaloric materials include non-magnetic shape memory alloys,polymers,and rare-earth compounds.Barocaloric materials include magnetic shape memory alloys,ferroelectric ceramics,superionic conductors,and oxyfluorides.The mechanocaloric effects of these classes of materials are systematically compared in terms of the isothermal entropy change and adiabatic temperature change.In addition to the thermal effects,other characteristics closely related to the application of mechanocaloric materials are also summarized.Finally,perspectives for further development of mechanocaloric materials in the solid-state cooling area are discussed.
基金Project supported by the National Key Research and Development Program of China(Grant No.2017YFA0304503)Key Research and Development Project of Guangdong Province,China(Grant No.2020B030300001)the National Natural Science Foundation of China(Grant Nos.828330256,11636220,11805279,1173401,and 11504430)。
文摘We present a cooling scheme with a tripod configuration atomic ensemble trapped in an optomechanical cavity.With the employment of two different quantum interference processes,our scheme illustrates that it is possible to cool a resonator to its ground state in the strong cavity-atom coupling regime.Moreover,with the assistance of one additional energy level,our scheme takes a larger cooling rate to realize the ground state cooling.In addition,this scheme is a feasible candidate for experimental applications.
基金supported by National Basic Research Program of China(973 Program)(No.2013GB102000)
文摘An orthogoual experimental scheme was designed for optimizing a water-cooled structure of the divertor plate. There were three influencing factors： the radius R of the water- cooled pipe, and the pipe spacing L1 and L3. The influence rule of different factors on the cooling effect and thermal stress of the plate were studied, for which the influence rank was respectively R 〉 L1 〉 L3 and L3 〉 R 〉 L1. The highest temperature value decreased when R and L1 increased~ and the maximum thermal stress value dropped when R, L1 and L3 increased. The final optimized results can be summarized as： R equals 6 mm or 7 mm, L1 equals 19 mm, and L3 equals 20 mm. Compared with the initial design, the highest temperature value had a small decline~ and the maximum thermal stress value dropped by 19~ to 24~. So it was not ideal to improve the cooling effect by optimizing the geometry sizes of the water-cooled structure, even worse than increasing the flow speed, but it was very effective for dropping the maximum thermal stress value. The orthogoaal experimental method reduces the number of experiments by 80%, and thus it is feasible and effective to optimize the water-cooled structure of the divertor plate with the orthogonal theory.
基金Project supported by the National Natural Science Foundation of China (Grant No.12004199)。
文摘The mixed-field effect at the hyperfine level of the rovibronic ground state of the^(127)I^(79)Br(X^(1)Σ,v=0,J=0)molecule is computed on the J-I uncoupled basis of|JM_(J)I_(1)M_(1)I_(2)M_(2)>,where J is the molecular total angular momentum excluding nuclear spin,M_J is the projection number of J,I_(1) and I_(2) are the nuclear spins of the iodine and bromine atoms,and M_(1) and M_(2) are the projection numbers of I_(1) and I_(2),respectively.When the two applied electric and magnetic fields are parallel,the perturbations are rare and only one perturbation is observed in a relatively large field regime in our computation range.However,when the two fields are off-parallel,the perturbations increase significantly and some sublevels show the Feshbach-like resonance phenomenon.Therefore,such sublevels transit between weak-field seeking and strong-field seeking repeatedly,which can be utilized to enhance or suppress cold molecular collision and chemical reaction rates.Such behavior of the molecular hyperfine structure in the mixed off-parallel fields may also be utilized to construct an electric-field-assisted anti-Helmholtz magnetic trap for cold molecules and to realize evaporative cooling of cold molecules(sub-mK)into the ultracold regime(μK).
