This paper presented an entropy evaluation method for the influences of condense heat recovery system on the environment.Aiming at the damage of the condense heat to the environment,an entropy of resource loss and an ...This paper presented an entropy evaluation method for the influences of condense heat recovery system on the environment.Aiming at the damage of the condense heat to the environment,an entropy of resource loss and an emission entropy from the condense heat recovery system in the air conditioning refrigerating machine were introduced.For the evaluation of the entropies,we developed a new algorithm for the parameter identification,called the composite influence coefficient,based on the Least Squares Support Vector Machine method.By simulation,the numerical experiments shows that the Least Squares Support Vector Machine method is one of the powerful methods for the parameter identification to compute the damage entropy of the condense heat,with the largest training error being-0.025(the relative error being-3.56%),and the biggest test error being 0.015(the relative error being 2.5%).展开更多
The relationship between isothermal magnetic entropy change DELTA S andadiabatic temperature change DELTA T_(ad) was deduced according to the principles of thermodynamics.The MCE and the engineering application were d...The relationship between isothermal magnetic entropy change DELTA S andadiabatic temperature change DELTA T_(ad) was deduced according to the principles of thermodynamics.The MCE and the engineering application were discussed for Gd and several new kinds of magneticrefrigerating materials near room temperature, Gd_5Si_2Ge_2, MnFeP_(0.45)As_(0.55) and LaFe_(11.2)Co_(0.7)Si_(1.1). Isothermal entropy change is proportional to adiabatic temperature change with afactor of T/C (T is temperature, C is heat capacity). When the comparison of magnetacoloric effectis made for two different materials, we should consider isothermal entropy change as well asadiabatic temperature change.展开更多
Our company is a member of China Refrigerating Air Conditioner Industry Association, and Shanghai Refrigerating Air Conditioner Machinery Industry Association as well. In addition, it is also a member of China Washing...Our company is a member of China Refrigerating Air Conditioner Industry Association, and Shanghai Refrigerating Air Conditioner Machinery Industry Association as well. In addition, it is also a member of China Washing Machinery Garment Machinery.展开更多
Idealized cycles of refrigerating machines with adiabatic and isothermal compression of refrigerant vapor were investigated. Energetic characteristics of cycles： specific mass and volume cooling capacity q0 and qv, w...Idealized cycles of refrigerating machines with adiabatic and isothermal compression of refrigerant vapor were investigated. Energetic characteristics of cycles： specific mass and volume cooling capacity q0 and qv, work of compression 1, refrigerating coefficient of performance e and power N for drive of compressor were compared. These characteristics were calculated for eight refrigerants at temperature of their condensation 30 ℃ and temperatures of boiling -15℃ and -30 ℃. The calculations show that the use of isothermal compression of refrigerant vapor ensures economy of energy during refrigerating machine operation.展开更多
This study investigates the heat and mass transfer mechanism of a marine engifie exhaust-powered adsorption refrigerating system by using irreversible thermodynamics. The equations of entropy-production rate and the l...This study investigates the heat and mass transfer mechanism of a marine engifie exhaust-powered adsorption refrigerating system by using irreversible thermodynamics. The equations of entropy-production rate and the linear phenomenological equations of thermodynamic flux and force are established. The conventional experimental facilities of unit tube are developed and the phenomenological coefficients are obtained by fitting the experimental data. It is concluded that the thermodynamic process in the adsorbent bed is determined by the coupling effect of the heat and mass transfer; furthermore, the mass transfer is determined by the heat transfer. Taking some measures to increase heat transfer can improve the performance of the adsorption refrigerating system. The conclusions presented in this paper may be of value to the engineering applications of the system.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
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
To accomplish on-site separation, preconcentration and cold storage of highly volatile organic compounds(VOCs) from water samples as well as their rapid transportation to laboratory, a high-throughput miniaturized pur...To accomplish on-site separation, preconcentration and cold storage of highly volatile organic compounds(VOCs) from water samples as well as their rapid transportation to laboratory, a high-throughput miniaturized purge-and-trap(μP&T) device integrating semiconductor refrigeration storage was developed in this work. Water samples were poured into the purge vessels and purged with purified air generated by an air pump. The VOCs in water samples were then separated and preconcentrated with sorbent tubes. After their complete separation and preconcentration, the tubes were subsequently preserved in the semiconductor refrigeration unit of the μP&T device. Notably, the high integration, small size, light weight, and low power consumption of the device makes it easy to be hand-carried to the field and transport by drone from remote locations, significantly enhancing the flexibility of field sampling. The performances of the device were evaluated by comparing analytical figures of merit for the detection of four cyclic volatile methylsiloxanes(cVMSs) in water. Compared to conventional collection and preservation methods, our proposed device preserved the VOCs more consistently in the sorbent tubes, with less than 5% loss of all analytes, and maintained stability for at least 20 days at 4℃. As a proof-of-concept,10 municipal wastewater samples were pretreated using this device with recoveries ranging from 82.5% to 99.9% for the target VOCs.展开更多
Superelastic martensitic transformation(MT)confers a considerable elastocaloric response to shape memory alloys,but the significant hysteretic loss cripples the energy conversion efficiency.In the present work,large e...Superelastic martensitic transformation(MT)confers a considerable elastocaloric response to shape memory alloys,but the significant hysteretic loss cripples the energy conversion efficiency.In the present work,large elastocaloric effect with high refrigeration efficiency is realized in a polycrystalline Co_(50)V_(35)Ga_(15)Heusler alloy.Experimental results show that the studied alloy undergoes a paramagnetic type MT from L2_(1)cubic austenite to D0_(22)tetragonal martensite with a small thermal hysteresis(ΔT_(hys))of~3 K.By carefully examining the strain rate dependence of superelastic response,it is also found that the stress hysteresis(Δσ_(hys))consists of two components including intrinsic stress hysteresis(Δσ_(hys)^(int.))caused by inherent attribute of MT and extrinsic stress hysteresis(Δσ_(hys)^(ext.))aroused by applied strain rate.Accordingly,we put forward a strain relaxation equation to separate the relative contributions betweenΔσ_(hys)^(int.)andΔσ_(hys)^(ext.)quantitatively,which demonstrates that a smallΔT_(hys)is conducive to substantial decrease inΔσ_(hys)^(int.).Moreover,associated with stress-induced superelastic MT,large reversible adiabatic temperature changes(ΔT_(ad))higher than 11 K are achieved under an applied strain of 6.5%over a temperature range of at least 60 K.With the combination of a large elastocaloric cooling capacity and a low energy dissipation,significant improvements in refrigeration efficiency can be obtained in a wide strain range,being superior to those reported in most of typical elastocaloric materials near room temperature.展开更多
Frustrated lanthanide oxides with dense magnetic lattice and suppressed ordering temperature have potential applications in cryogenic magnetic refrigeration.Herein,the crystal structure,magnetic properties,magnetic ph...Frustrated lanthanide oxides with dense magnetic lattice and suppressed ordering temperature have potential applications in cryogenic magnetic refrigeration.Herein,the crystal structure,magnetic properties,magnetic phase transition(MPT)together with magnetocaloric effect(MCE)of LnOF(Ln=Gd,Dy,Ho,and Er)compounds were investigated.Crystallographic study shows that these compounds crystallize in the centrosymmetric space group R3m with an ideal triangular lattice.No long-range magnetic ordering is observed above 2 K for LnOF(Ln=Gd,Ho,and Er).However,DyOF compound undergoes an MPT from paramagnetic(PM)to antiferromagnetic(AFM)at the Neel temperature(TN≈4 K).Considerable reversible MCE is observed in these triangular-lattice compounds.Under the magnetic field change(μ0ΔH)of 0-2 T,the maximum values of magnetic entropy change(-ΔSMmax)of them are 6.1,9.4,12.7,and 14.1 J/(kg·K),respectively.Interestingly,the value of ErOF with Ising-like spin is 2.3 times that of GdOF,which provides an approach for exploring magnetic refrigerants with excellent low-field cryogenic magnetocaloric effect.展开更多
In the organic Rankine cycle,the refrigerant inevitably interacts with the lubricating oil.This study investigates the interaction mechanism between the fourth-generation refrigerant R1336mzz(Z)and the polyol ester(PO...In the organic Rankine cycle,the refrigerant inevitably interacts with the lubricating oil.This study investigates the interaction mechanism between the fourth-generation refrigerant R1336mzz(Z)and the polyol ester(POE)which is a representative component of the lubricating oil,using molecular dynamics simulations.The research focuses on pentaerythritol ester(PEC)with medium to long chain lengths,specifically PEC9.Relevant parameters such as solubility parameters,diffusion coefficients,binding energies,and radial distribution functions were calculated to elucidate the interaction dynamics.The variation in solubility parameters suggests that the miscibility of PEC9 and R1336mzz(Z)diminishes as the number of PEC9 chains increases.Additionally,the compatibility between these two components deteriorates with rising temperature,which is accompanied by a reduction in their binding energy.The simulation results presented in this study offer theoretical insights into the behavior of refrigerant R1336mzz(Z)upon contact with lubricating oil during actual operation,as well as implications for the operational efficiency of the equipment.展开更多
As one of the core components of a magnetic refrigerator,magnetic refrigeration materials are expected to have not only a considerable magnetocaloric effect but also excellent thermal conductivity.The poor thermal con...As one of the core components of a magnetic refrigerator,magnetic refrigeration materials are expected to have not only a considerable magnetocaloric effect but also excellent thermal conductivity.The poor thermal conductivity of many competitive oxide-based magnetic refrigerants,exemplified by EuTiO3-based compounds,acts as a major limitation to their practical application.Therefore,improving the thermal conductivity of magnetic refrigeration materials has become a research emphasis of magnetic refrigeration in recent years.In this work,a series of EuTiO_(3)(ETO)/Cu composites with different copper additives was prepared using a solid-phase reaction method by introducing appropriate amounts of copper powder.The influence of the introduction of copper on the phase composition,microstructure,thermal conductivity,and magnetocaloric effect of the composites was systematically investigated.Unexpectedly,the thermal conductivity of the composites is enhanced by up to 260%due to copper addition,accompanied by only a 5%decrease in magnetic entropy change and refrigerating capacity.Copper additive forms localized thermal conductive networks and promotes the densification process,resulting in significantly enhanced thermal conductivity of the composites.This work demonstrates the feasibility of improving the thermal conductivity of oxide-base d magnetic refrigeration materials by introducing highly thermally conductive substances.展开更多
The barocaloric effect is considered as one of the most promising refrigeration with the potential to replace traditional gas compression refrigeration.One of the main obstacles to the application of barocaloric mater...The barocaloric effect is considered as one of the most promising refrigeration with the potential to replace traditional gas compression refrigeration.One of the main obstacles to the application of barocaloric materials lies in the requirement for high driving pressures.In this paper,we report on the barocaloric effect of Pb_(3)(VO_(4))_(2),which exhibits a ferroelastic transition from a high-temperature trigonal structure to a low-temperature monoclinic structure at 357 K,accompanied by a substantial volume change.The entropy change induced by hydrostatic pressure can reach up 14 J·kg^(-1)·K^(-1)under a relatively low pressure of 80 MPa.This work is expected to expand the selection range of barocaloric materials.展开更多
Cryogenic magnetic cooling based on the principle of the magnetocaloric effects(MCEs)of magnetic solids has been recognized as an alternative cooling technology due to its significant economic and social benefits.Desi...Cryogenic magnetic cooling based on the principle of the magnetocaloric effects(MCEs)of magnetic solids has been recognized as an alternative cooling technology due to its significant economic and social benefits.Designing novel magnetic materials with good magnetocaloric performance is a prerequisite for practical applications.In this study,three gadolinium-transition metal-based high entropy oxides(HEOs)of Gd(Fe_(1/4)Ni_(1/4)Al_(1/4)Cr_(1/4))O_(3),Gd(Fe_(1/5)Ni_(1/5)Al_(1/5)Cr_(1/5)Co_(1/5))O_(3),and Gd(Fe_(1/6)Ni_(1/6)Al_(1/6)Cr_(1/6)Co_(1/6)Mn_(1/6))O_(3)were designed and systematically characterized regarding their structural and cryogenic magnetic properties.These HEOs were confirmed to crystallize into a single-phase perovskite-type orthorhombic structure with a homogeneous microstructure,reveal a second-order magnetic transition at low temperatures,and exhibit significant cryogenic MCEs.The magnetocaloric performances of the present HEOs,identified by magnetic entropy changes,relative cooling power,and temperature-averaged entropy changes,were com-parable with recently reported candidate materials.The present study indicates potential applications for cryogenic magnetic cooling of the present HEOs and provides meaningful clues for designing and exploring HEOs with good cryogenic magnetocaloric performances.展开更多
Dear Editor,The letter deals with the distributed state and fault estimation of the whole physical layer for cyber-physical systems(CPSs) when the cyber layer suffers from DoS attacks. With the advancement of embedded...Dear Editor,The letter deals with the distributed state and fault estimation of the whole physical layer for cyber-physical systems(CPSs) when the cyber layer suffers from DoS attacks. With the advancement of embedded computing, communication and related hardware technologies, CPSs have attracted extensive attention and have been widely used in power system, traffic network, refrigeration system and other fields.展开更多
Refrigeration systems are essential across various sectors,including food preservation,medical storage,and climate control.However,their high energy consumption and environmental impact necessitate innovative solution...Refrigeration systems are essential across various sectors,including food preservation,medical storage,and climate control.However,their high energy consumption and environmental impact necessitate innovative solutions to enhance efficiency while minimizing energy usage.This paper investigates the integration of Phase Change Materials(PCMs)into a vapor compression refrigeration system to enhance energy efficiency and temperature regulation for food preservation.A multifunctional prototype was tested under two configurations:(1)a standard thermally insulated room,and(2)the same room augmented with eutectic plates filled with either Glaceol(-10℃ melting point)or distilled water(0℃ melting point).Thermocouples were calibrated and deployed to record air and PCM temperatures during freeze–thaw cycles at thermostat setpoints of and Additionally,a-30℃ -35℃ .defrosting resistor and timer were added to mitigate frost buildup,a known cause of efficiency loss.The experimental results show that PCM-enhanced rooms achieved up to 10.98℃ greater temperature stability during defrost cycles and reduced energy consumption by as much as 7.76%(from 0.4584 to 0.4231 kWh/h).Moreover,the effectiveness of PCMs depended strongly on thermostat settings and PCM type,with distilled water demonstrating broader solidification across plates under higher ambient loads.These findings highlight the potential of PCM integration to improve cold-chain performance,offering rapid cooling,moisture retention,and extended product conservation during power interruptions.展开更多
Magnetic refrigeration(MR)technology is regarded as an ideal solution for cryogenic applications,relying on magnetocaloric materials which provide necessary chilling effect.A series of polycrystalline Tm_(1-x)Er_(x)Ni...Magnetic refrigeration(MR)technology is regarded as an ideal solution for cryogenic applications,relying on magnetocaloric materials which provide necessary chilling effect.A series of polycrystalline Tm_(1-x)Er_(x)Ni_(2)Si_(2)(x=0.2,0.4)compounds was synthesized,and their magnetic properties,magnetic phase transition together with magnetocaloric effect(MCE)were studied.The Tm_(1-x)Er_(x)Ni_(2)Si_(2)(x=0.2,0.4)compounds display a field-induced metamagnetic transition from antiferromagnetic(AFM)to ferromagnetism(FM)in excess of 0.2 T,respectively.Meanwhile,the AFM ground state is unstable.Under the field change of 0-2 T,the values of maximal magnetic entropy change(-ΔS_(M)^(max))and refrigerant capacity(RC)for Tm_(0.8)Er_(0.2)Ni_(2)Si_(2)compound are 17.9 J/(kg·K)and 83.5 J/kg,respectively.The large reversible MCE under low magnetic fields(≤2 T)indicates that Tm_(0.8)Er_(0.2)Ni_(2)Si_(2)compound can serve as potential candidate materials for cryogenic magnetic refrigeration.展开更多
Thus far,metal-bonding has presented high efficacy in improving the mechanical,thermal conductive,and anti-corrosion properties of La(Fe,Si)_(13)-based hydrides.However,to ensure high performance,the proportion of met...Thus far,metal-bonding has presented high efficacy in improving the mechanical,thermal conductive,and anti-corrosion properties of La(Fe,Si)_(13)-based hydrides.However,to ensure high performance,the proportion of metal bonders has to be as high as 20 wt%,thereby significantly weakening the magnetocaloric effect(MCE).In this work,small amounts of graphene nanosheets(up to 2 wt%)with high thermal conductivity and specific surface area were incorporated into the La_(0.8)Ce_(0.2)Fe_(11.7)Si_(1.3)Hymatrix through a cold-pressing and sintering process.X-ray diffraction analysis indicates that carbon from graphene can easily diffuse into the lattice of La(Fe,Si)13main phase as an interstitial atom,resulting in a significant increase of the lattice constant accompanied by a significant decrease of the Curie temperature and H content of the composites.While 0.3 wt%graphene doping only has minor improvements in the thermal conductivityλand corrosion resistance of the parent La_(0.8)Ce_(0.2)Fe_(11.7)Si_(1.3)H_(y),further increase of graphene content to 1 wt%causes a significant increase ofλfrom 1.4 W/(m·K)for the parent material to~2 W/(m·K)and a decrease of corrosion current density from 1.43×10^(-5)to 9.63×10^(-6)A/cm^(2).When the graphene content is lower than 0.3 wt%,the large MCE does not significantly deteriorate.In 0-1.5 T,the maximal magnetic-entropy change ASm of 11.5 J/(kg·K)at 336 K for the parent material decreases to 8.2 J/(kg·K)at 306 K for the 2 wt%graphene-dop ed composite.展开更多
基金Supported by Program of Science and Technology of Hunan Province(2007FJ2006)Project the Program of Science and Tech-nology of Hunan Province(2007TP4030)Hunan Provincial Natural Science Foundation of China(08JJ3093)
文摘This paper presented an entropy evaluation method for the influences of condense heat recovery system on the environment.Aiming at the damage of the condense heat to the environment,an entropy of resource loss and an emission entropy from the condense heat recovery system in the air conditioning refrigerating machine were introduced.For the evaluation of the entropies,we developed a new algorithm for the parameter identification,called the composite influence coefficient,based on the Least Squares Support Vector Machine method.By simulation,the numerical experiments shows that the Least Squares Support Vector Machine method is one of the powerful methods for the parameter identification to compute the damage entropy of the condense heat,with the largest training error being-0.025(the relative error being-3.56%),and the biggest test error being 0.015(the relative error being 2.5%).
文摘The relationship between isothermal magnetic entropy change DELTA S andadiabatic temperature change DELTA T_(ad) was deduced according to the principles of thermodynamics.The MCE and the engineering application were discussed for Gd and several new kinds of magneticrefrigerating materials near room temperature, Gd_5Si_2Ge_2, MnFeP_(0.45)As_(0.55) and LaFe_(11.2)Co_(0.7)Si_(1.1). Isothermal entropy change is proportional to adiabatic temperature change with afactor of T/C (T is temperature, C is heat capacity). When the comparison of magnetacoloric effectis made for two different materials, we should consider isothermal entropy change as well asadiabatic temperature change.
文摘Our company is a member of China Refrigerating Air Conditioner Industry Association, and Shanghai Refrigerating Air Conditioner Machinery Industry Association as well. In addition, it is also a member of China Washing Machinery Garment Machinery.
文摘Idealized cycles of refrigerating machines with adiabatic and isothermal compression of refrigerant vapor were investigated. Energetic characteristics of cycles： specific mass and volume cooling capacity q0 and qv, work of compression 1, refrigerating coefficient of performance e and power N for drive of compressor were compared. These characteristics were calculated for eight refrigerants at temperature of their condensation 30 ℃ and temperatures of boiling -15℃ and -30 ℃. The calculations show that the use of isothermal compression of refrigerant vapor ensures economy of energy during refrigerating machine operation.
文摘This study investigates the heat and mass transfer mechanism of a marine engifie exhaust-powered adsorption refrigerating system by using irreversible thermodynamics. The equations of entropy-production rate and the linear phenomenological equations of thermodynamic flux and force are established. The conventional experimental facilities of unit tube are developed and the phenomenological coefficients are obtained by fitting the experimental data. It is concluded that the thermodynamic process in the adsorbent bed is determined by the coupling effect of the heat and mass transfer; furthermore, the mass transfer is determined by the heat transfer. Taking some measures to increase heat transfer can improve the performance of the adsorption refrigerating system. The conclusions presented in this paper may be of value to the engineering applications of the system.
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 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.
基金the National Natural Science Foundation of China (No. 22306146)the PhD Scientific Research Startup Foundation of Xihua University (No. RX2200002003) for their financial support。
文摘To accomplish on-site separation, preconcentration and cold storage of highly volatile organic compounds(VOCs) from water samples as well as their rapid transportation to laboratory, a high-throughput miniaturized purge-and-trap(μP&T) device integrating semiconductor refrigeration storage was developed in this work. Water samples were poured into the purge vessels and purged with purified air generated by an air pump. The VOCs in water samples were then separated and preconcentrated with sorbent tubes. After their complete separation and preconcentration, the tubes were subsequently preserved in the semiconductor refrigeration unit of the μP&T device. Notably, the high integration, small size, light weight, and low power consumption of the device makes it easy to be hand-carried to the field and transport by drone from remote locations, significantly enhancing the flexibility of field sampling. The performances of the device were evaluated by comparing analytical figures of merit for the detection of four cyclic volatile methylsiloxanes(cVMSs) in water. Compared to conventional collection and preservation methods, our proposed device preserved the VOCs more consistently in the sorbent tubes, with less than 5% loss of all analytes, and maintained stability for at least 20 days at 4℃. As a proof-of-concept,10 municipal wastewater samples were pretreated using this device with recoveries ranging from 82.5% to 99.9% for the target VOCs.
基金supported by the National Natural Science Foundation of China(Nos.52261035,52201223,52371006,52371194)Applied Basic Projects of Yunnan province(No.202101BA070001-233).
文摘Superelastic martensitic transformation(MT)confers a considerable elastocaloric response to shape memory alloys,but the significant hysteretic loss cripples the energy conversion efficiency.In the present work,large elastocaloric effect with high refrigeration efficiency is realized in a polycrystalline Co_(50)V_(35)Ga_(15)Heusler alloy.Experimental results show that the studied alloy undergoes a paramagnetic type MT from L2_(1)cubic austenite to D0_(22)tetragonal martensite with a small thermal hysteresis(ΔT_(hys))of~3 K.By carefully examining the strain rate dependence of superelastic response,it is also found that the stress hysteresis(Δσ_(hys))consists of two components including intrinsic stress hysteresis(Δσ_(hys)^(int.))caused by inherent attribute of MT and extrinsic stress hysteresis(Δσ_(hys)^(ext.))aroused by applied strain rate.Accordingly,we put forward a strain relaxation equation to separate the relative contributions betweenΔσ_(hys)^(int.)andΔσ_(hys)^(ext.)quantitatively,which demonstrates that a smallΔT_(hys)is conducive to substantial decrease inΔσ_(hys)^(int.).Moreover,associated with stress-induced superelastic MT,large reversible adiabatic temperature changes(ΔT_(ad))higher than 11 K are achieved under an applied strain of 6.5%over a temperature range of at least 60 K.With the combination of a large elastocaloric cooling capacity and a low energy dissipation,significant improvements in refrigeration efficiency can be obtained in a wide strain range,being superior to those reported in most of typical elastocaloric materials near room temperature.
基金Project supported by the National Key Research and Development Program of China(2022YFB3505101)the National Science Foundation for Excellent Young Scholars(52222107)+2 种基金the National Science Foundation for Distinguished Young Scholars(51925605)the National Natural Science Foundation of China(52171195)the Projects of Ganjiang Innovation Academy,Chinese Academy of Sciences(E055B002)。
文摘Frustrated lanthanide oxides with dense magnetic lattice and suppressed ordering temperature have potential applications in cryogenic magnetic refrigeration.Herein,the crystal structure,magnetic properties,magnetic phase transition(MPT)together with magnetocaloric effect(MCE)of LnOF(Ln=Gd,Dy,Ho,and Er)compounds were investigated.Crystallographic study shows that these compounds crystallize in the centrosymmetric space group R3m with an ideal triangular lattice.No long-range magnetic ordering is observed above 2 K for LnOF(Ln=Gd,Ho,and Er).However,DyOF compound undergoes an MPT from paramagnetic(PM)to antiferromagnetic(AFM)at the Neel temperature(TN≈4 K).Considerable reversible MCE is observed in these triangular-lattice compounds.Under the magnetic field change(μ0ΔH)of 0-2 T,the maximum values of magnetic entropy change(-ΔSMmax)of them are 6.1,9.4,12.7,and 14.1 J/(kg·K),respectively.Interestingly,the value of ErOF with Ising-like spin is 2.3 times that of GdOF,which provides an approach for exploring magnetic refrigerants with excellent low-field cryogenic magnetocaloric effect.
基金supported by Hainan Provincial Natural Science Foundation of China(No.422CXTD509).
文摘In the organic Rankine cycle,the refrigerant inevitably interacts with the lubricating oil.This study investigates the interaction mechanism between the fourth-generation refrigerant R1336mzz(Z)and the polyol ester(POE)which is a representative component of the lubricating oil,using molecular dynamics simulations.The research focuses on pentaerythritol ester(PEC)with medium to long chain lengths,specifically PEC9.Relevant parameters such as solubility parameters,diffusion coefficients,binding energies,and radial distribution functions were calculated to elucidate the interaction dynamics.The variation in solubility parameters suggests that the miscibility of PEC9 and R1336mzz(Z)diminishes as the number of PEC9 chains increases.Additionally,the compatibility between these two components deteriorates with rising temperature,which is accompanied by a reduction in their binding energy.The simulation results presented in this study offer theoretical insights into the behavior of refrigerant R1336mzz(Z)upon contact with lubricating oil during actual operation,as well as implications for the operational efficiency of the equipment.
基金Project supported by the National Key R&D Program of China(2021YFB3501204)the National Science Fund for Distinguished Young Scholars(51925605)+1 种基金the National Science Foundation for Excellent Young Scholars(52222107)the National Natural Science Foundation of China(52171195,52201036)。
文摘As one of the core components of a magnetic refrigerator,magnetic refrigeration materials are expected to have not only a considerable magnetocaloric effect but also excellent thermal conductivity.The poor thermal conductivity of many competitive oxide-based magnetic refrigerants,exemplified by EuTiO3-based compounds,acts as a major limitation to their practical application.Therefore,improving the thermal conductivity of magnetic refrigeration materials has become a research emphasis of magnetic refrigeration in recent years.In this work,a series of EuTiO_(3)(ETO)/Cu composites with different copper additives was prepared using a solid-phase reaction method by introducing appropriate amounts of copper powder.The influence of the introduction of copper on the phase composition,microstructure,thermal conductivity,and magnetocaloric effect of the composites was systematically investigated.Unexpectedly,the thermal conductivity of the composites is enhanced by up to 260%due to copper addition,accompanied by only a 5%decrease in magnetic entropy change and refrigerating capacity.Copper additive forms localized thermal conductive networks and promotes the densification process,resulting in significantly enhanced thermal conductivity of the composites.This work demonstrates the feasibility of improving the thermal conductivity of oxide-base d magnetic refrigeration materials by introducing highly thermally conductive substances.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.52301241 and 52271175)。
文摘The barocaloric effect is considered as one of the most promising refrigeration with the potential to replace traditional gas compression refrigeration.One of the main obstacles to the application of barocaloric materials lies in the requirement for high driving pressures.In this paper,we report on the barocaloric effect of Pb_(3)(VO_(4))_(2),which exhibits a ferroelastic transition from a high-temperature trigonal structure to a low-temperature monoclinic structure at 357 K,accompanied by a substantial volume change.The entropy change induced by hydrostatic pressure can reach up 14 J·kg^(-1)·K^(-1)under a relatively low pressure of 80 MPa.This work is expected to expand the selection range of barocaloric materials.
基金supported by the National Natural Science Foundation of China(No.52171174).The authors acknowledge Dr.Chao Zhang from the Instrumentation Service Center for Physical Sciences at Westlake University for magnetization measurements.
文摘Cryogenic magnetic cooling based on the principle of the magnetocaloric effects(MCEs)of magnetic solids has been recognized as an alternative cooling technology due to its significant economic and social benefits.Designing novel magnetic materials with good magnetocaloric performance is a prerequisite for practical applications.In this study,three gadolinium-transition metal-based high entropy oxides(HEOs)of Gd(Fe_(1/4)Ni_(1/4)Al_(1/4)Cr_(1/4))O_(3),Gd(Fe_(1/5)Ni_(1/5)Al_(1/5)Cr_(1/5)Co_(1/5))O_(3),and Gd(Fe_(1/6)Ni_(1/6)Al_(1/6)Cr_(1/6)Co_(1/6)Mn_(1/6))O_(3)were designed and systematically characterized regarding their structural and cryogenic magnetic properties.These HEOs were confirmed to crystallize into a single-phase perovskite-type orthorhombic structure with a homogeneous microstructure,reveal a second-order magnetic transition at low temperatures,and exhibit significant cryogenic MCEs.The magnetocaloric performances of the present HEOs,identified by magnetic entropy changes,relative cooling power,and temperature-averaged entropy changes,were com-parable with recently reported candidate materials.The present study indicates potential applications for cryogenic magnetic cooling of the present HEOs and provides meaningful clues for designing and exploring HEOs with good cryogenic magnetocaloric performances.
基金supported by the National Natural Science Foundation of China(62303273,62373226)the National Research Foundation,Singapore through the Medium Sized Center for Advanced Robotics Technology Innovation(WP2.7)
文摘Dear Editor,The letter deals with the distributed state and fault estimation of the whole physical layer for cyber-physical systems(CPSs) when the cyber layer suffers from DoS attacks. With the advancement of embedded computing, communication and related hardware technologies, CPSs have attracted extensive attention and have been widely used in power system, traffic network, refrigeration system and other fields.
基金supported in entire part by the Biomaterials and Transport Phenomena Laboratory Agreement No.30303-12-2003,at the University of Medea.
文摘Refrigeration systems are essential across various sectors,including food preservation,medical storage,and climate control.However,their high energy consumption and environmental impact necessitate innovative solutions to enhance efficiency while minimizing energy usage.This paper investigates the integration of Phase Change Materials(PCMs)into a vapor compression refrigeration system to enhance energy efficiency and temperature regulation for food preservation.A multifunctional prototype was tested under two configurations:(1)a standard thermally insulated room,and(2)the same room augmented with eutectic plates filled with either Glaceol(-10℃ melting point)or distilled water(0℃ melting point).Thermocouples were calibrated and deployed to record air and PCM temperatures during freeze–thaw cycles at thermostat setpoints of and Additionally,a-30℃ -35℃ .defrosting resistor and timer were added to mitigate frost buildup,a known cause of efficiency loss.The experimental results show that PCM-enhanced rooms achieved up to 10.98℃ greater temperature stability during defrost cycles and reduced energy consumption by as much as 7.76%(from 0.4584 to 0.4231 kWh/h).Moreover,the effectiveness of PCMs depended strongly on thermostat settings and PCM type,with distilled water demonstrating broader solidification across plates under higher ambient loads.These findings highlight the potential of PCM integration to improve cold-chain performance,offering rapid cooling,moisture retention,and extended product conservation during power interruptions.
基金Project supported by the National Key Research and Development Program of China(2021YFB3501204)the National Natural Science Foundation of China(52171054)+1 种基金the National Science Foundation for Distinguished Young Scholars(51925605)the National Science Foundation for Excellent Young Scholars(52222107)。
文摘Magnetic refrigeration(MR)technology is regarded as an ideal solution for cryogenic applications,relying on magnetocaloric materials which provide necessary chilling effect.A series of polycrystalline Tm_(1-x)Er_(x)Ni_(2)Si_(2)(x=0.2,0.4)compounds was synthesized,and their magnetic properties,magnetic phase transition together with magnetocaloric effect(MCE)were studied.The Tm_(1-x)Er_(x)Ni_(2)Si_(2)(x=0.2,0.4)compounds display a field-induced metamagnetic transition from antiferromagnetic(AFM)to ferromagnetism(FM)in excess of 0.2 T,respectively.Meanwhile,the AFM ground state is unstable.Under the field change of 0-2 T,the values of maximal magnetic entropy change(-ΔS_(M)^(max))and refrigerant capacity(RC)for Tm_(0.8)Er_(0.2)Ni_(2)Si_(2)compound are 17.9 J/(kg·K)and 83.5 J/kg,respectively.The large reversible MCE under low magnetic fields(≤2 T)indicates that Tm_(0.8)Er_(0.2)Ni_(2)Si_(2)compound can serve as potential candidate materials for cryogenic magnetic refrigeration.
基金Project supported by the National Natural Science Foundation of China(52171187,52271192)。
文摘Thus far,metal-bonding has presented high efficacy in improving the mechanical,thermal conductive,and anti-corrosion properties of La(Fe,Si)_(13)-based hydrides.However,to ensure high performance,the proportion of metal bonders has to be as high as 20 wt%,thereby significantly weakening the magnetocaloric effect(MCE).In this work,small amounts of graphene nanosheets(up to 2 wt%)with high thermal conductivity and specific surface area were incorporated into the La_(0.8)Ce_(0.2)Fe_(11.7)Si_(1.3)Hymatrix through a cold-pressing and sintering process.X-ray diffraction analysis indicates that carbon from graphene can easily diffuse into the lattice of La(Fe,Si)13main phase as an interstitial atom,resulting in a significant increase of the lattice constant accompanied by a significant decrease of the Curie temperature and H content of the composites.While 0.3 wt%graphene doping only has minor improvements in the thermal conductivityλand corrosion resistance of the parent La_(0.8)Ce_(0.2)Fe_(11.7)Si_(1.3)H_(y),further increase of graphene content to 1 wt%causes a significant increase ofλfrom 1.4 W/(m·K)for the parent material to~2 W/(m·K)and a decrease of corrosion current density from 1.43×10^(-5)to 9.63×10^(-6)A/cm^(2).When the graphene content is lower than 0.3 wt%,the large MCE does not significantly deteriorate.In 0-1.5 T,the maximal magnetic-entropy change ASm of 11.5 J/(kg·K)at 336 K for the parent material decreases to 8.2 J/(kg·K)at 306 K for the 2 wt%graphene-dop ed composite.
