On November 30, 2007, the China Association for Standardization (CAS) held a press conference at Beijing Diaoyutai State vip House. Leaders from the China Household Electric Appliance Research Institute, the Chi... On November 30, 2007, the China Association for Standardization (CAS) held a press conference at Beijing Diaoyutai State vip House. Leaders from the China Household Electric Appliance Research Institute, the China Household Electric Appliance Association, and the China Consumers' Association attended and made speeches.……展开更多
Disassembly and recycling of E-waste creates a series of environmental problems. The selection of a technologically reliable, environmentally friendly, economically affordable and socially acceptable recycling technol...Disassembly and recycling of E-waste creates a series of environmental problems. The selection of a technologically reliable, environmentally friendly, economically affordable and socially acceptable recycling technology for E-waste is a significant question. This study establishes a Monte-Carlo mathematical model of cost minimization, given the constraints of environmentally sound handling of the e-waste, in the context of Crystal Ball risk assessment and evaluation software. By following the streams of the different treatment processes, which consist of various technologies including disassembly, recycling and disposal, the econom-ics of various possibilities were identified and the optimal recycling technology proposed. The key factors of the proposed scenarios were determined by using sensitivity analysis. The results of this study show that, for discarded refrigerators, the operating life span plays the key role. The model supports maintenance and resale of the short lived refrigerators. For the longer lived refrigerators material recycling is recommended by the model. Sensitivity analysis shows that purchase cost, plastic sale price, condenser sale price and disassembly costs are the main effects. This study provides a significant technical support for policy making in E-waste management.展开更多
We have successfully developed cryogen-free dilution refrigerators with medium cooling power that can be applied to quantum experiments. Breakthroughs have been made in some key technologies and components of heat swi...We have successfully developed cryogen-free dilution refrigerators with medium cooling power that can be applied to quantum experiments. Breakthroughs have been made in some key technologies and components of heat switches and dilution units. Our prototype has been running continuously and stably for more than 100 hours below 10 m K, with a minimum temperature of 7.6 m K and a cooling power of 450 μW at 100 m K. At the same time, we have also made progress in the application of dilution refrigerators, such as quantum computing, low-temperature detector, and magnet integration. These indicators and test results indicate good prospects for application in physics, astronomy, and quantum information.展开更多
We investigate the finite-time performance of a quantum endoreversible Carnot engine cycle and its inverse operation-Carnot refrigeration cycle,employing a spin-1/2 system as the working substance.The thermal machine ...We investigate the finite-time performance of a quantum endoreversible Carnot engine cycle and its inverse operation-Carnot refrigeration cycle,employing a spin-1/2 system as the working substance.The thermal machine is alternatively driven by a hot boson bath of inverse temperatureβ_(h)and a cold boson bath at inverse temperatureβ_(c)(>βh).While for the engine model the hot bath is constructed to be squeezed,in the refrigeration cycle the cold bath is established to be squeezed,with squeezing parameter r.We obtain the analytical expressions for both efficiency and power in heat engines and for coefficient of performance and cooling rate in refrigerators.We find that,in the high-temperature limit,the efficiency at maximum power is bounded by the analytical valueη_(+)=√sech(2r)(1-η_(C)),and the coefficient of performance at the maximum figure of merit is limited byε_(+)=√sech(2r)(1+ε_(C))/sech(2r)(1+ε_(C))-εC)-1,whereη_(C)=1-β_(h)/β_(c)andε_(C)=β_(h)/(β_(c)-β_(h))are the respective Carnot values of the engines and refrigerators.These analytical results are identical to those obtained from the Carnot engines based on harmonic systems,indicating that the efficiency at maximum power and coefficient at maximum figure of merit are independent of the working substance.展开更多
The dynamic stability analysis of an irreversible refrigerator working at the minimum power input P for given cooling load R was investigated.An irreversible refrigerator model was established based on coupled differe...The dynamic stability analysis of an irreversible refrigerator working at the minimum power input P for given cooling load R was investigated.An irreversible refrigerator model was established based on coupled differential equations.The global asymptotic stability characteristics were proved by constructing Lyapunov function based on Lyapunov stability theory and analyzed by sketching global phase portraits.The influence of parameters such as initial and operating parameters were studied for different values.It was found that an equilibrium point of nonlinear system was the global stability point,and the temperature of the working fluids converged to the stability value as time t approximated to positive infinite.Besides,numerical integrations were carried out to corroborate the global asymptotic stability properties of the system.Finally,the dynamic stability and the thermodynamic properties of the system were analyzed.It was found that the energetic characteristics and the dynamic stability properties were deteriorated as the dimensionless cooling load R~* and the thermal conductance ratio b increased.展开更多
The regenerative refrigeration is an important reverse work-heat conversion cycle with a theoretical coefficient of performance(COP)identical to the Carnot efficiency.Practical regenerative refrigerators are capable o...The regenerative refrigeration is an important reverse work-heat conversion cycle with a theoretical coefficient of performance(COP)identical to the Carnot efficiency.Practical regenerative refrigerators are capable of working down to 4 K and largely fulfill the refrigeration requirement of modern technologies in many fields,especially for space applications.However,the enthalpy flow associated with the pressure dependence,abbreviated as pressure-induced enthalpy flow,brought about by real gas effects degrades the theoretical COP of the refrigerator to below about 30% of the Carnot efficiency at the temperatures of below the critical point.This paper reviews the long history of exploring the real gas effects which dates back to the 1970 s and continues to now.Important explorations of uncovering the loss mechanism and reducing such losses are summarized.The theories that are in accordance with experimental results and simulation results are expounded.We further carry out analyses on the expansion components,including the pulse tube and the clearance gap.Several inferences are made in order to explore the long-lasting puzzles about real gas effects.It is emphasized that the underlying cause of the loss in the regenerator is an indirect effect of the real gas properties.Further study about carrying out a direct verification of the theory is proposed.展开更多
As electronic technology continues to evolve towards miniaturization and integration,the demand for micro-refrigeration technology in microelectronic systems is increasing.Ferroelectric(FE)refrigeration technology bas...As electronic technology continues to evolve towards miniaturization and integration,the demand for micro-refrigeration technology in microelectronic systems is increasing.Ferroelectric(FE)refrigeration technology based on the electrocaloric effect(ECE)has emerged as a highly promising candidate in this field,due to its advantages of high energy efficiency,simple structure,easy miniaturization,low cost,and environmental friendliness.The EC performance of FE materials essentially depends on the phase transition features under the coupled electric and thermal fields,making the E–T phase diagram a core tool for decoding the underlying mechanism of ECE.This paper reviews the development of EC materials,focusing on the comprehensive study of E–T phase diagrams.By correlating the microscopic phase structure of FE materials with the macroscopic physical properties,it clarifies the manipulation mechanism for enhanced ECE performance,providing theoretical support for the targeted design of high-performance EC materials.In the future,the introduction of data-driven methods is expected to enable the high-throughput construction of FE phase diagrams,thereby accelerating the optimization of high-performance EC materials and promoting the practical application of FE refrigeration technology.展开更多
Nanjing’s determination to transform itself from a production base to a research center reflects China’s evolution toward higher-quality development.A refrigerator that thaws frozen meat in 10 minutes and then keeps...Nanjing’s determination to transform itself from a production base to a research center reflects China’s evolution toward higher-quality development.A refrigerator that thaws frozen meat in 10 minutes and then keeps it fresh,a cooker hood that remains clean even after 10 years without disassembling it for cleaning.展开更多
Shock waves in the nozzle during supersonic separation under different conditions can disrupt the flow field’s thermodynamic equilibrium.While it contributes to the recovery of pressure energy,it also leads to the di...Shock waves in the nozzle during supersonic separation under different conditions can disrupt the flow field’s thermodynamic equilibrium.While it contributes to the recovery of pressure energy,it also leads to the dissipation of mechanical energy.This study aimed to investigate the effects of changes in back pressure on the shock wave position and its subsequent impact on the refrigeration performance of nozzles.A mathematical model for the supersonic gas in a nozzle was established and evaluated via experiments.The results show that when the back pressure is less than 0.2 MPa,no shock wave is generated in the nozzle,and high refrigeration and liquefaction efficiency can be ensured while effective pressure recovery is achieved.When the back pressure(pb)is increased from 0.3 to 0.6 MPa,the refrigeration efficiency of the nozzle decreases,and the shock wave position(x shock)is advanced from 157 to 118 mm.The maximum Mach number(Ma)that can be reached by the fluid in the nozzle is reduced from 1.97 to 1.27.When the back pressure is increased from 0.2 to 0.6 MPa,the minimum temperature is increased by 55.18 K.When the back pressure is greater than 0.3 MPa,the Mach number upstream of the shock wave is reduced from 1.97 to 1.27,the shock wave intensity is weakened,and the thickness of the boundary layer separation caused by the shock wave is also decreased accordingly.Therefore,to ensure refrigeration efficiency,measures should be taken to control the back pressure within a reasonable range.展开更多
The environmental wind tunnel of high-speed railway trains serves as a crucial experimental facility for the research and development of high-speed railway technology.The refrigeration system within the wind tunnel is...The environmental wind tunnel of high-speed railway trains serves as a crucial experimental facility for the research and development of high-speed railway technology.The refrigeration system within the wind tunnel is an important subsystem.However,the design of the wind tunnel refrigeration system management program presents significant scientific challenges and limitations.Traditional management approaches in wind tunnel refrigeration systems suffer from prolonged decision-making times and reliance on experiential knowledge,necessitating the need for intelligent transformation.This paper aims to address these issues by exploring existing intelligent management methodologies and defining the concept of a wind tunnel intelligent laboratory along with its primary modules.Furthermore,we propose a water cooler failure prediction model based on the existing equipment model of the wind tunnel's refrigeration system.This model effectively predicts the Remaining Useful Life(RUL) of the water cooler in the case of fouling failure,contributing to enhanced efficiency,cost reduction,and safety improvements in laboratories.展开更多
The electrocaloric(EC)effect refers to the change in the polarization entropy and/or temperature of dielectric materials when an electric field is applied and removed.EC refrigeration has received increasing interest ...The electrocaloric(EC)effect refers to the change in the polarization entropy and/or temperature of dielectric materials when an electric field is applied and removed.EC refrigeration has received increasing interest as an alternative to conventional refrigeration technologies because it provides both high energy efficiency and zero global warming potential.In this review,we first introduce the thermodynamic fundamentals of the EC effect and the mechanism of EC refrigeration cycles.We then present recent advances in EC cooling technologies,from material improvements to device demonstrations,including a critical analysis of existing material and device characterization methodologies and a discussion of how to reliably measure the parameters of materials and devices.Finally,the current challenges and possible future prospects for EC cooling technology are outlined.展开更多
Accessing the milli-Kelvin regime is increasingly important for next-generation quantum technologies and deep-space observations.Among established cryogenic techniques,adiabatic demagnetization refrigeration(ADR)is di...Accessing the milli-Kelvin regime is increasingly important for next-generation quantum technologies and deep-space observations.Among established cryogenic techniques,adiabatic demagnetization refrigeration(ADR)is distinctive for its all-solid-state design,low vibration,and intrinsic gravity independence.Here we present a materials-centered review of ADR refrigerants,connecting classical thermodynamics to modern quantum many-body behavior.Beyond hydrated paramagnetic salts,dense rare-earth oxides and correlated-disorder ceramics,we highlight emerging quantum-engineered refrigerants,including geometrically frustrated magnets,and quantum-critical systems.In these materials,suppressing long-range order and tailoring low-energy excitations redistribute spin entropy into the sub-Kelvin window,enabling large and reversible entropy changes at the lowest accessible temperatures.We discuss the central trade-offs among volumetric entropy density,thermal transport,and magnetic ordering,and outline possible design rules for staged ADR architectures.展开更多
In this paper,an irreversible thermionic refrigerator model based on van der Waals heterostructure with various irreversibilities is established by utilizing combination of non-equilibrium thermodynamics and finite ti...In this paper,an irreversible thermionic refrigerator model based on van der Waals heterostructure with various irreversibilities is established by utilizing combination of non-equilibrium thermodynamics and finite time thermodynamics.The basic performance characteristics of the refrigerator are obtained.The effects of key factors,such as bias voltages,Schottky barrier heights and heat leakages,on the performance are studied.Results show that cooling rates and coefficients of performances(COPs)can attain the double maximum with proper modulation of barrier heights and bias voltages.Increasing cross-plane thermal resistance as well as decreasing electrode-reservoir thermal resistance and reservoir-reservoir thermal resistance can enhance the performance of the device.The optimal performance region is the interval between the maximum cooling rate point and the maximum COP point.By modulating the bias voltage,the working state of the device can fall into the optimal performance region.The optimal performance of the refrigerator when using single layer graphene and a few layers graphene as electrode material is also compared.展开更多
As a novel generation of a rotational gas wave machine,the wave rotor refrigerator(WRR)is an unsteadyflow device used for refrigeration,in whose passages pressured streams directly contact and exchange energy due to th...As a novel generation of a rotational gas wave machine,the wave rotor refrigerator(WRR)is an unsteadyflow device used for refrigeration,in whose passages pressured streams directly contact and exchange energy due to the movement of pressure waves.In this paper,the working mechanism and refrigeration principle are inves-tigated based on the one-dimensional unsteadyflow theory.A basic limitation on main structural parameters and operating parameters is deduced and the wave diagram of WRR to guide designing is sketched.The main influential factors are studied through an experiment.In the DUT Gas Wave Refrigeration Studying and Development Center(GWRSDC)lab,the isentropic efficiency can now reach about 65%.The results show that the WRR is a feasible and promising technology in pressured gas refrigeration cases.展开更多
The pulse tube refrigerator （PTR） is a promising small-scale cryocooler. This paper first briefly introduces the history of the pulse tube refrigerator. It has pointed out that technology improvements and theoretica...The pulse tube refrigerator （PTR） is a promising small-scale cryocooler. This paper first briefly introduces the history of the pulse tube refrigerator. It has pointed out that technology improvements and theoretical developments of the pulse tube refrig- erator closely relate with the internal streaming effects. Then the discovering history and classification of the streaming or DC （direct current） flow effect are summarized. It proposes for the first time that the physical significance of the streaming con- tains the driving mechanisms and the transport mechanisms. It demonstrates that the driving mechanisms are the asymmetry of fluid flow and temperature while the transport mechanisms are a loop or vorticity, which transmits nonlinear dissipations. The important advancements have been made over the past two decades all over the world in research of streaming of the pulse tube refrigerator including Gedeon DC flow, Rayleigb streaming, the third type of DC flow and the regenerator circulation. With regard to Gedeon DC flow, theoretical and experimental analyses have been made and different suppression methods are summarized. In the aspect of Rayleigh streaming, it mainly focuses on the analytical solution of the second-order mass flow and the research of tapered pulse tubes. In particular, limited research on the third type of DC flow and regenerator circulation is presented. The experimental measurement techniques of streaming also are summarized. Finally, this paper briefly discusses the key scientific and technical issues of the current research, and foretells the future development trends of streaming research in PTR.展开更多
In recent years, microchannel heat exchangers have begun to be used in refrigeration and air conditioning systems. This paper introduces a microchannel condenser for domestic refrigerators with a theoretical model to ...In recent years, microchannel heat exchangers have begun to be used in refrigeration and air conditioning systems. This paper introduces a microchannel condenser for domestic refrigerators with a theoretical model to evaluate its performance. The model was used to obtain the optimal design parameters for different numbers of tubes and tube lengths. The results show that the needed tube height of the down- ward section decreases with the number of tubes and the tube diameter. Compared with the original con- denser, the present optimal design parameters can reduce the total metal mass by 48.6% for the two wall two side design and by 26% for the two wall one side design. Thus, the present condenser is much better than the condensers usually used in actual domestic refrigerators.展开更多
Two international standards,ISO 18501:2025,Performance rating of positive displacement refrigerant compressor,and ISO 18483:2025,Performance rating of centrifugal refrigerant compressor,were released at an event held ...Two international standards,ISO 18501:2025,Performance rating of positive displacement refrigerant compressor,and ISO 18483:2025,Performance rating of centrifugal refrigerant compressor,were released at an event held by GREE and Hefei General Machinery Research Institute Co.,Ltd.in Zhuhai,South China’s Guangdong province on June 12.展开更多
Rare-earth based frustrated magnets have attracted great attention as excellent candidates for magnetic refrigeration at sub-Kelvin temperatures,while the experimental identification of systems exhibiting both large v...Rare-earth based frustrated magnets have attracted great attention as excellent candidates for magnetic refrigeration at sub-Kelvin temperatures,while the experimental identification of systems exhibiting both large volumetric cooling capacity and reduced working temperatures far below 1K remains a challenge.Here,through ultra-low temperature magnetism and thermodynamic characterizations,we unveil the large magnetocaloric effect(MCE)realized at sub-Kelvin temperatures in the frustrated Kagome antiferromagnet Gd_(3)BWO_(9) with T_(N)∼1.0 K.The isothermal magnetization curves indicate the existence of field(B)induced anisotropic magnetic phase diagrams,where four distinct magnetic phases for B‖c-axis and five magnetic phases for B‖ab-plane are identified at T<T_(N).The analysis of magnetic entropy S(B,T)data and direct adiabatic demagnetization tests reveal remarkable cooling performance at sub-Kelvin temperatures featured by a large volumetric entropy density of 502.2 mJ/K/cm^(3)and a low attainable minimal temperature T_(min)∼168mK from the initial cooling condition of 2K and 6 T,surpassing most Gd-based refrigerants previously documented in temperature ranges of 0.25–4 K.The realized T_(min)∼168mK far below T_(N)∼1.0K in Gd_(3)BWO_(9) is related to the combined effects of magnetic frustration and criticality-enhanced MCE,which together leave substantial magnetic entropy at reduced temperatures by enhancing spin fluctuations.展开更多
Waste heat generation,upgrading,and refrigeration are the fundamental ways to recover and utilize waste heat.Rationalizing the use of refrigerants also contributes to creating energy savings and minimizing carbon emis...Waste heat generation,upgrading,and refrigeration are the fundamental ways to recover and utilize waste heat.Rationalizing the use of refrigerants also contributes to creating energy savings and minimizing carbon emissions.This study evaluates the thermodynamics,economics,and environment of different refrigerants in three waste heat recovery schemes:generate electricity,heat pump,and refrigeration.Based on this,the entropy weight and technique for order preference by similarity to an ideal solution are combined to assess the overall performance of the refrigerants.A thorough analysis reveals that R1234ze(E)could replace R245fa and R123 in the organic Rankine cycle.The best refrigerant for vapor compression refrigeration and high-temperature heat pump systems is R1243zf.In addition,the multi-objective decision analysis shows that the performance difference among the nine selected refrigerants is the total cost,followed by the environmental impact.The approach successfully recognizes the variations between different refrigerants in the same waste heat recovery scheme and gives a thorough evaluation.It sets instructions for the future use of eco-friendly refrigerants and their application of waste heat recovery schemes.展开更多
[Objectives]This study was conducted to investigate the influence mechanisms of microbial succession in raw milk under cold storage at different temperatures.[Methods]A raw milk sample was collected from a local large...[Objectives]This study was conducted to investigate the influence mechanisms of microbial succession in raw milk under cold storage at different temperatures.[Methods]A raw milk sample was collected from a local large-scale farm in Tangshan and divided into four treatment gradients:a control group(M)rapidly frozen at-80℃,and three experimental groups stored at 4℃(T),6℃(F),and 8℃(Y),respectively.A time series experiment was carried out according to time intervals of 24,48 and 72 h in each experimental group.Traditional microbial culture methods and 16S rRNA high-throughput sequencing were combined to analyze the dynamic changes in microbial abundance and structural variation.[Results]Plate counting revealed significantly lower total bacterial count and psychrotrophic bacteria in the 4℃storage group within 24 h compared with other treatment groups(P<0.01),confirming that maintaining low-temperature cold chain integrity and controlling treatment time(<24 h)can effectively inhibit microbial metabolic activity.16S rRNA sequencing analysis revealed high initial microbial diversity in raw milk,with dominant genera being Lactococcus,Acinetobacter,and Pseudomonas.Low-temperature treatment effectively reduced theαdiversity index of the microbial community.During the later stage of cold storage at 4℃,the relative abundance of Pseudomonas increased to over 90%,making it the dominant bacterial genus.[Conclusions]This study has significant application value for maintaining the quality of milk and dairy products and prolonging their shelf life.展开更多
文摘 On November 30, 2007, the China Association for Standardization (CAS) held a press conference at Beijing Diaoyutai State vip House. Leaders from the China Household Electric Appliance Research Institute, the China Household Electric Appliance Association, and the China Consumers' Association attended and made speeches.……
基金Projects 50574094 supported by the National Natural Science Foundation of ChinaCPEUKF06-11 by the Key Laboratory Open Project of Education Ministry of China200600242 by the Science and Technology Innovation Project of Xuzhou
文摘Disassembly and recycling of E-waste creates a series of environmental problems. The selection of a technologically reliable, environmentally friendly, economically affordable and socially acceptable recycling technology for E-waste is a significant question. This study establishes a Monte-Carlo mathematical model of cost minimization, given the constraints of environmentally sound handling of the e-waste, in the context of Crystal Ball risk assessment and evaluation software. By following the streams of the different treatment processes, which consist of various technologies including disassembly, recycling and disposal, the econom-ics of various possibilities were identified and the optimal recycling technology proposed. The key factors of the proposed scenarios were determined by using sensitivity analysis. The results of this study show that, for discarded refrigerators, the operating life span plays the key role. The model supports maintenance and resale of the short lived refrigerators. For the longer lived refrigerators material recycling is recommended by the model. Sensitivity analysis shows that purchase cost, plastic sale price, condenser sale price and disassembly costs are the main effects. This study provides a significant technical support for policy making in E-waste management.
基金supported by the Beijing Commission of Science and Technology(Grant No.Z211100004021012)Special Research Assistant Program of the Chinese Academy of Sciences(Grant No.E3VP021RX4)。
文摘We have successfully developed cryogen-free dilution refrigerators with medium cooling power that can be applied to quantum experiments. Breakthroughs have been made in some key technologies and components of heat switches and dilution units. Our prototype has been running continuously and stably for more than 100 hours below 10 m K, with a minimum temperature of 7.6 m K and a cooling power of 450 μW at 100 m K. At the same time, we have also made progress in the application of dilution refrigerators, such as quantum computing, low-temperature detector, and magnet integration. These indicators and test results indicate good prospects for application in physics, astronomy, and quantum information.
基金the National Natural Science Foundation of China(Grant No.11875034)the Opening Project of Shanghai Key Laboratory of Special Artificial Microstructure Materials and Technology.
文摘We investigate the finite-time performance of a quantum endoreversible Carnot engine cycle and its inverse operation-Carnot refrigeration cycle,employing a spin-1/2 system as the working substance.The thermal machine is alternatively driven by a hot boson bath of inverse temperatureβ_(h)and a cold boson bath at inverse temperatureβ_(c)(>βh).While for the engine model the hot bath is constructed to be squeezed,in the refrigeration cycle the cold bath is established to be squeezed,with squeezing parameter r.We obtain the analytical expressions for both efficiency and power in heat engines and for coefficient of performance and cooling rate in refrigerators.We find that,in the high-temperature limit,the efficiency at maximum power is bounded by the analytical valueη_(+)=√sech(2r)(1-η_(C)),and the coefficient of performance at the maximum figure of merit is limited byε_(+)=√sech(2r)(1+ε_(C))/sech(2r)(1+ε_(C))-εC)-1,whereη_(C)=1-β_(h)/β_(c)andε_(C)=β_(h)/(β_(c)-β_(h))are the respective Carnot values of the engines and refrigerators.These analytical results are identical to those obtained from the Carnot engines based on harmonic systems,indicating that the efficiency at maximum power and coefficient at maximum figure of merit are independent of the working substance.
基金the Fundamental Research Fund for the Central Universities,China(No.2011011302)National Natural Science Foundation of China(No.51078068)
文摘The dynamic stability analysis of an irreversible refrigerator working at the minimum power input P for given cooling load R was investigated.An irreversible refrigerator model was established based on coupled differential equations.The global asymptotic stability characteristics were proved by constructing Lyapunov function based on Lyapunov stability theory and analyzed by sketching global phase portraits.The influence of parameters such as initial and operating parameters were studied for different values.It was found that an equilibrium point of nonlinear system was the global stability point,and the temperature of the working fluids converged to the stability value as time t approximated to positive infinite.Besides,numerical integrations were carried out to corroborate the global asymptotic stability properties of the system.Finally,the dynamic stability and the thermodynamic properties of the system were analyzed.It was found that the energetic characteristics and the dynamic stability properties were deteriorated as the dimensionless cooling load R~* and the thermal conductance ratio b increased.
基金supported by National Natural Science Foundation of China(No.51506152 and No.51777141)the Fundamental Research Funds for the Central Universities(inter-disciplinary program)under the contract No.kx0080020173427。
文摘The regenerative refrigeration is an important reverse work-heat conversion cycle with a theoretical coefficient of performance(COP)identical to the Carnot efficiency.Practical regenerative refrigerators are capable of working down to 4 K and largely fulfill the refrigeration requirement of modern technologies in many fields,especially for space applications.However,the enthalpy flow associated with the pressure dependence,abbreviated as pressure-induced enthalpy flow,brought about by real gas effects degrades the theoretical COP of the refrigerator to below about 30% of the Carnot efficiency at the temperatures of below the critical point.This paper reviews the long history of exploring the real gas effects which dates back to the 1970 s and continues to now.Important explorations of uncovering the loss mechanism and reducing such losses are summarized.The theories that are in accordance with experimental results and simulation results are expounded.We further carry out analyses on the expansion components,including the pulse tube and the clearance gap.Several inferences are made in order to explore the long-lasting puzzles about real gas effects.It is emphasized that the underlying cause of the loss in the regenerator is an indirect effect of the real gas properties.Further study about carrying out a direct verification of the theory is proposed.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.U25A20232,52325208,52173217,52202128)the Interdisciplinary Research Project for Young Teachers of USTB(Grant No.FRF-IDRY24-002)。
文摘As electronic technology continues to evolve towards miniaturization and integration,the demand for micro-refrigeration technology in microelectronic systems is increasing.Ferroelectric(FE)refrigeration technology based on the electrocaloric effect(ECE)has emerged as a highly promising candidate in this field,due to its advantages of high energy efficiency,simple structure,easy miniaturization,low cost,and environmental friendliness.The EC performance of FE materials essentially depends on the phase transition features under the coupled electric and thermal fields,making the E–T phase diagram a core tool for decoding the underlying mechanism of ECE.This paper reviews the development of EC materials,focusing on the comprehensive study of E–T phase diagrams.By correlating the microscopic phase structure of FE materials with the macroscopic physical properties,it clarifies the manipulation mechanism for enhanced ECE performance,providing theoretical support for the targeted design of high-performance EC materials.In the future,the introduction of data-driven methods is expected to enable the high-throughput construction of FE phase diagrams,thereby accelerating the optimization of high-performance EC materials and promoting the practical application of FE refrigeration technology.
文摘Nanjing’s determination to transform itself from a production base to a research center reflects China’s evolution toward higher-quality development.A refrigerator that thaws frozen meat in 10 minutes and then keeps it fresh,a cooker hood that remains clean even after 10 years without disassembling it for cleaning.
基金supported by the National Science and Technology Major Project of China(2025ZD1406703)the Open Fund of Key Laboratory of Oil&Gas Equipment,Ministry of Education(Southwest Petroleum University)(Grant No.OGE20230206).
文摘Shock waves in the nozzle during supersonic separation under different conditions can disrupt the flow field’s thermodynamic equilibrium.While it contributes to the recovery of pressure energy,it also leads to the dissipation of mechanical energy.This study aimed to investigate the effects of changes in back pressure on the shock wave position and its subsequent impact on the refrigeration performance of nozzles.A mathematical model for the supersonic gas in a nozzle was established and evaluated via experiments.The results show that when the back pressure is less than 0.2 MPa,no shock wave is generated in the nozzle,and high refrigeration and liquefaction efficiency can be ensured while effective pressure recovery is achieved.When the back pressure(pb)is increased from 0.3 to 0.6 MPa,the refrigeration efficiency of the nozzle decreases,and the shock wave position(x shock)is advanced from 157 to 118 mm.The maximum Mach number(Ma)that can be reached by the fluid in the nozzle is reduced from 1.97 to 1.27.When the back pressure is increased from 0.2 to 0.6 MPa,the minimum temperature is increased by 55.18 K.When the back pressure is greater than 0.3 MPa,the Mach number upstream of the shock wave is reduced from 1.97 to 1.27,the shock wave intensity is weakened,and the thickness of the boundary layer separation caused by the shock wave is also decreased accordingly.Therefore,to ensure refrigeration efficiency,measures should be taken to control the back pressure within a reasonable range.
文摘The environmental wind tunnel of high-speed railway trains serves as a crucial experimental facility for the research and development of high-speed railway technology.The refrigeration system within the wind tunnel is an important subsystem.However,the design of the wind tunnel refrigeration system management program presents significant scientific challenges and limitations.Traditional management approaches in wind tunnel refrigeration systems suffer from prolonged decision-making times and reliance on experiential knowledge,necessitating the need for intelligent transformation.This paper aims to address these issues by exploring existing intelligent management methodologies and defining the concept of a wind tunnel intelligent laboratory along with its primary modules.Furthermore,we propose a water cooler failure prediction model based on the existing equipment model of the wind tunnel's refrigeration system.This model effectively predicts the Remaining Useful Life(RUL) of the water cooler in the case of fouling failure,contributing to enhanced efficiency,cost reduction,and safety improvements in laboratories.
基金supported by the National Key R&D Program of China(Grant Nos.2020YFA0711500 and 2020YFA0711503)the National Natural Science Foundation of China(Grant Nos.T2488302,T2342010,52076127)+5 种基金the Natural Science Foundation of Shanghai(Grant Nos.20ZR1471700,22JC1401800,and 24Z511405472)the State Key Laboratory of Mechanical System and Vibration(Grant Nos.MSVZD202211,MSVZD202301,and MSVZD202401)Shanghai Jiao Tong University 2030 InitiativeShanghai Jiao Tong University Si Yuan Scholar Programthe Student Innovation Center and the Instrumental Analysis Center at Shanghai Jiao Tong Universitysupport by Shanghai Jiao Tong University 2030 Initiative。
文摘The electrocaloric(EC)effect refers to the change in the polarization entropy and/or temperature of dielectric materials when an electric field is applied and removed.EC refrigeration has received increasing interest as an alternative to conventional refrigeration technologies because it provides both high energy efficiency and zero global warming potential.In this review,we first introduce the thermodynamic fundamentals of the EC effect and the mechanism of EC refrigeration cycles.We then present recent advances in EC cooling technologies,from material improvements to device demonstrations,including a critical analysis of existing material and device characterization methodologies and a discussion of how to reliably measure the parameters of materials and devices.Finally,the current challenges and possible future prospects for EC cooling technology are outlined.
基金supported by the National Key R&D Program of China(Grant No.2021YFA1400300)the Guangdong Basic and Applied Basic Research Foundation(Grant No.2022A1515111009)the National Natural Science Foundation of China(Grant Nos.12425403,12261131499,52273298)。
文摘Accessing the milli-Kelvin regime is increasingly important for next-generation quantum technologies and deep-space observations.Among established cryogenic techniques,adiabatic demagnetization refrigeration(ADR)is distinctive for its all-solid-state design,low vibration,and intrinsic gravity independence.Here we present a materials-centered review of ADR refrigerants,connecting classical thermodynamics to modern quantum many-body behavior.Beyond hydrated paramagnetic salts,dense rare-earth oxides and correlated-disorder ceramics,we highlight emerging quantum-engineered refrigerants,including geometrically frustrated magnets,and quantum-critical systems.In these materials,suppressing long-range order and tailoring low-energy excitations redistribute spin entropy into the sub-Kelvin window,enabling large and reversible entropy changes at the lowest accessible temperatures.We discuss the central trade-offs among volumetric entropy density,thermal transport,and magnetic ordering,and outline possible design rules for staged ADR architectures.
基金supported by the National Natural Science Foundation of China(Grant Nos.51779262,51576207,51306206)the Hubei Province Natural Science Foundation of China(Grant No.2017CFB498)。
文摘In this paper,an irreversible thermionic refrigerator model based on van der Waals heterostructure with various irreversibilities is established by utilizing combination of non-equilibrium thermodynamics and finite time thermodynamics.The basic performance characteristics of the refrigerator are obtained.The effects of key factors,such as bias voltages,Schottky barrier heights and heat leakages,on the performance are studied.Results show that cooling rates and coefficients of performances(COPs)can attain the double maximum with proper modulation of barrier heights and bias voltages.Increasing cross-plane thermal resistance as well as decreasing electrode-reservoir thermal resistance and reservoir-reservoir thermal resistance can enhance the performance of the device.The optimal performance region is the interval between the maximum cooling rate point and the maximum COP point.By modulating the bias voltage,the working state of the device can fall into the optimal performance region.The optimal performance of the refrigerator when using single layer graphene and a few layers graphene as electrode material is also compared.
基金supported by the National High Technology Research and Development Program of China(2006AA05Z216).
文摘As a novel generation of a rotational gas wave machine,the wave rotor refrigerator(WRR)is an unsteadyflow device used for refrigeration,in whose passages pressured streams directly contact and exchange energy due to the movement of pressure waves.In this paper,the working mechanism and refrigeration principle are inves-tigated based on the one-dimensional unsteadyflow theory.A basic limitation on main structural parameters and operating parameters is deduced and the wave diagram of WRR to guide designing is sketched.The main influential factors are studied through an experiment.In the DUT Gas Wave Refrigeration Studying and Development Center(GWRSDC)lab,the isentropic efficiency can now reach about 65%.The results show that the WRR is a feasible and promising technology in pressured gas refrigeration cases.
基金supported by the National Natural Science Foundation of China(Grant No.51176198)
文摘The pulse tube refrigerator （PTR） is a promising small-scale cryocooler. This paper first briefly introduces the history of the pulse tube refrigerator. It has pointed out that technology improvements and theoretical developments of the pulse tube refrig- erator closely relate with the internal streaming effects. Then the discovering history and classification of the streaming or DC （direct current） flow effect are summarized. It proposes for the first time that the physical significance of the streaming con- tains the driving mechanisms and the transport mechanisms. It demonstrates that the driving mechanisms are the asymmetry of fluid flow and temperature while the transport mechanisms are a loop or vorticity, which transmits nonlinear dissipations. The important advancements have been made over the past two decades all over the world in research of streaming of the pulse tube refrigerator including Gedeon DC flow, Rayleigb streaming, the third type of DC flow and the regenerator circulation. With regard to Gedeon DC flow, theoretical and experimental analyses have been made and different suppression methods are summarized. In the aspect of Rayleigh streaming, it mainly focuses on the analytical solution of the second-order mass flow and the research of tapered pulse tubes. In particular, limited research on the third type of DC flow and regenerator circulation is presented. The experimental measurement techniques of streaming also are summarized. Finally, this paper briefly discusses the key scientific and technical issues of the current research, and foretells the future development trends of streaming research in PTR.
基金Supported by the National Natural Science Foundation of China(No. 50676045)the National High-Tech Research and Devel-opment (863) Program of China (No. 2006AA05Z207)
文摘In recent years, microchannel heat exchangers have begun to be used in refrigeration and air conditioning systems. This paper introduces a microchannel condenser for domestic refrigerators with a theoretical model to evaluate its performance. The model was used to obtain the optimal design parameters for different numbers of tubes and tube lengths. The results show that the needed tube height of the down- ward section decreases with the number of tubes and the tube diameter. Compared with the original con- denser, the present optimal design parameters can reduce the total metal mass by 48.6% for the two wall two side design and by 26% for the two wall one side design. Thus, the present condenser is much better than the condensers usually used in actual domestic refrigerators.
文摘Two international standards,ISO 18501:2025,Performance rating of positive displacement refrigerant compressor,and ISO 18483:2025,Performance rating of centrifugal refrigerant compressor,were released at an event held by GREE and Hefei General Machinery Research Institute Co.,Ltd.in Zhuhai,South China’s Guangdong province on June 12.
基金supported by the National Key Research and Development Program(Grant Nos.2024YFA1611200 and 2023YFA1406500)the National Natural Science Foundation of China(Grant Nos.12141002 and 52088101)the Strategic Priority Research Program of the Chinese Academy of Sciences(Grant No.XDB1270000)。
文摘Rare-earth based frustrated magnets have attracted great attention as excellent candidates for magnetic refrigeration at sub-Kelvin temperatures,while the experimental identification of systems exhibiting both large volumetric cooling capacity and reduced working temperatures far below 1K remains a challenge.Here,through ultra-low temperature magnetism and thermodynamic characterizations,we unveil the large magnetocaloric effect(MCE)realized at sub-Kelvin temperatures in the frustrated Kagome antiferromagnet Gd_(3)BWO_(9) with T_(N)∼1.0 K.The isothermal magnetization curves indicate the existence of field(B)induced anisotropic magnetic phase diagrams,where four distinct magnetic phases for B‖c-axis and five magnetic phases for B‖ab-plane are identified at T<T_(N).The analysis of magnetic entropy S(B,T)data and direct adiabatic demagnetization tests reveal remarkable cooling performance at sub-Kelvin temperatures featured by a large volumetric entropy density of 502.2 mJ/K/cm^(3)and a low attainable minimal temperature T_(min)∼168mK from the initial cooling condition of 2K and 6 T,surpassing most Gd-based refrigerants previously documented in temperature ranges of 0.25–4 K.The realized T_(min)∼168mK far below T_(N)∼1.0K in Gd_(3)BWO_(9) is related to the combined effects of magnetic frustration and criticality-enhanced MCE,which together leave substantial magnetic entropy at reduced temperatures by enhancing spin fluctuations.
基金supported by the National Natural Science Foundation of China(22178190)the National Youth Natural Science Foundation of China(22408195).
文摘Waste heat generation,upgrading,and refrigeration are the fundamental ways to recover and utilize waste heat.Rationalizing the use of refrigerants also contributes to creating energy savings and minimizing carbon emissions.This study evaluates the thermodynamics,economics,and environment of different refrigerants in three waste heat recovery schemes:generate electricity,heat pump,and refrigeration.Based on this,the entropy weight and technique for order preference by similarity to an ideal solution are combined to assess the overall performance of the refrigerants.A thorough analysis reveals that R1234ze(E)could replace R245fa and R123 in the organic Rankine cycle.The best refrigerant for vapor compression refrigeration and high-temperature heat pump systems is R1243zf.In addition,the multi-objective decision analysis shows that the performance difference among the nine selected refrigerants is the total cost,followed by the environmental impact.The approach successfully recognizes the variations between different refrigerants in the same waste heat recovery scheme and gives a thorough evaluation.It sets instructions for the future use of eco-friendly refrigerants and their application of waste heat recovery schemes.
基金Supported by Tangshan Talent Funding Project(A202202005)Dairy Industry Revitalization Major Technological Innovation Project of Hebei Key Research and Development Program(19227516D)High-level Talents Funding Project of Hebei Province(A201803034).
文摘[Objectives]This study was conducted to investigate the influence mechanisms of microbial succession in raw milk under cold storage at different temperatures.[Methods]A raw milk sample was collected from a local large-scale farm in Tangshan and divided into four treatment gradients:a control group(M)rapidly frozen at-80℃,and three experimental groups stored at 4℃(T),6℃(F),and 8℃(Y),respectively.A time series experiment was carried out according to time intervals of 24,48 and 72 h in each experimental group.Traditional microbial culture methods and 16S rRNA high-throughput sequencing were combined to analyze the dynamic changes in microbial abundance and structural variation.[Results]Plate counting revealed significantly lower total bacterial count and psychrotrophic bacteria in the 4℃storage group within 24 h compared with other treatment groups(P<0.01),confirming that maintaining low-temperature cold chain integrity and controlling treatment time(<24 h)can effectively inhibit microbial metabolic activity.16S rRNA sequencing analysis revealed high initial microbial diversity in raw milk,with dominant genera being Lactococcus,Acinetobacter,and Pseudomonas.Low-temperature treatment effectively reduced theαdiversity index of the microbial community.During the later stage of cold storage at 4℃,the relative abundance of Pseudomonas increased to over 90%,making it the dominant bacterial genus.[Conclusions]This study has significant application value for maintaining the quality of milk and dairy products and prolonging their shelf life.
