最新刊期
卷 43 ， 期 4 ， 2022
- 摘要：Elastocaloric refrigeration technology is considered one of the most promising new high-efficiency refrigeration technologies for replacing conventional vapor compression technology, owing to its high refrigeration efficiency and specific refrigeration power. This paper analyzes and discusses the thermodynamic basis, dynamic theory, materials, and refrigeration cycle as a reference for investigations of the elastocaloric effect of rubber. According to the literature, natural rubber features the best elastic and thermal properties, with a strain of 600% at 0 °C and a maximum temperature change of 12 K. Twisting natural rubber results in a higher temperature change and can reduce the volume of the refrigeration system. When the strain is 300%, the maximum temperature change is 12.9 K, which is 5.4 times that of the untwisted rubber. Theoretical studies regarding the elastocaloric effect of rubber are relatively mature; however, the development of cooling prototype is limited. Further development is required to promote the practical application of elastocaloric refrigeration technology using natural rubber as the working medium. Thus, it is possible to claim that using natural rubber in elastocaloric refrigeration technology is promising.关键词：solid-state cooling;elastocaloric effect;refrigeration cycle;rubber1038|1173|0发布时间：2024-07-18
- 摘要：Heat-driven thermoacoustic cooling technology utilizes the acoustic power generated by a thermoacoustic engine to drive a thermoacoustic cooler to realize thermal–acoustic–cooling energy conversion. It is a new type of green cooling technology that is environmentally friendly, features near-zero power consumption, and demonstrates adaptability to various heat sources. A heat-driven thermoacoustic cooling system features a wide working temperature range, i.e., from room temperature to liquid helium temperature, and is thus a promising system for a wide range of applications. Based on the development of heat-driven thermoacoustic cooling technology over the past three decades, this paper first introduces its principle and classification. Subsequently, a review of its development based on room-temperature thermoacoustic refrigerators and cryogenic-temperature thermoacoustic cryocoolers is provided. Additionally, the application and relevant studies concerning heat-driven thermoacoustic cooling technology in room-temperature refrigeration, waste heat/cold recovery, natural gas liquefaction, and cryogenic cooling are summarized and analyzed. Synergistic breakthroughs in novel thermal–acoustic–cooling processes, robust resonance mechanisms, efficient thermoacoustic conversions, low-grade energy utilizations, and practical engineering prototypes must be achieved to realize a reliable heat-driven thermoacoustic cooling technology that features high-efficiency, high-power, low onset temperature, and low achievable temperature, and to promote the development and application of new green cooling technologies.关键词：thermoacoustic cooling;thermoacoustic heat engine;thermoacoustic;refrigeration technology1095|884|0发布时间：2024-07-18
- 摘要：Thermoelectric refrigeration is a solid-state refrigeration technology that uses electric energy to achieve refrigeration via the Peltier effect. Compared with vapor compression refrigeration, thermoelectric refrigeration offers the advantages of scalability, vibration-free, high reliability, and high temperature-control accuracy. Based on the development history and basic principles of thermoelectric refrigeration, this study focuses on the research progress of thermoelectric materials, refrigerator structures, functional layer interfaces, and heat sinks. Subsequently, applications of thermoelectric refrigeration are introduced based on their advantages. Finally, investigations regarding thermoelectric refrigeration are summarized and discussed.关键词：thermoelectric refrigeration;Peltier effect;thermoelectric materials1088|989|3发布时间：2024-07-18
- 摘要：Barocaloric materials are a class of materials in which pressure can induce solid-state phase transitions with latent heat release or absorption. An emergent barocaloric refrigeration technology has been established using barocaloric materials as the working substance and pressure as the driving force. Herein, we briefly review the fundamental thermodynamics of the barocaloric effect, barocaloric materials, and barocaloric refrigeration technology. In recent years, many barocaloric materials have been developed, including metals and inorganic, organic, and inorganic–organic hybrid materials. Organic plastic crystals have garnered worldwide attention owing to the discovery of the colossal barocaloric effect in these materials. The combination of greater entropy changes, smaller driving pressures, and lower costs renders these materials promising candidates for barocaloric refrigeration applications. However, barocaloric refrigeration technology has not been investigated extensively. The most critical issue in developing a prototype barocaloric refrigerator is to effectively couple the heat transfer with the pressurization/depressurization. Such coupling can be obtained by selecting a fluid with high thermal conductivity as the heat transfer and pressure conducting medium, adjusting the pressure and flow rate, and optimizing the geometry of the barocaloric materials embedded in the fluid. Additionally, based on a single-stage cooling system, an active barocaloric regenerative prototype refrigerator can be developed for continuous refrigeration applications.关键词：solid-state phase transition;barocaloric refrigeration technology;plastic crystals1037|1196|1发布时间：2024-07-18
- 摘要：Air is an environmentally friendly refrigerant that can be charged into the air cycle refrigeration (ACR) system from the ambient or discharged from the system to the ambient unrestrictedly. The ACR system is widely used in environmental control systems (ECSs) of airplanes, owing to its compact structure, low sealing requirements, high reliability, and easy maintenance. Herein, the configurations and basic characteristics of the ACR system are introduced. Research status concerning the performance analysis, experiments, and key components of the ACR system are summarized. Applications in the fields of air-conditioning, heat pumps, food freezing and refrigeration, airplane ECSs, and energy storage are reviewed. The development and application of key technologies for the ACR system are evaluated. ACR technology has developed rapidly corresponding to the significant progress in the design and manufacturing technology of turbomachinery, efficient heat exchangers, and high-speed motor technology in recent decades. The ACR system is compact and widely used in train air-conditioning and refrigeration systems. The coefficient of performance (COP) of the ACR system is higher than that of the conventional cascade refrigeration system in the refrigeration temperature ranging from -100 °C to -50 °C; therefore, the ACR system is advantageous for food freezing and cold storage. Moreover, the ACR system exhibits significant potential in heat pumps and energy storage applications.关键词：air cycle refrigeration;turbine cooler;plate-fin heat exchanger;key technology1247|1067|0发布时间：2024-07-18
- 摘要：Elastocaloric cooling is based on the phase transition of elastocaloric materials and is driven by uniaxial stress. Elastocaloric cooling technology affords high theoretical refrigeration efficiency and does not result in greenhouse effects; hence, it has been considered an alternative to conventional vapor compression cooling technology. This study focuses on improving the compactness of a prototype elastocaloric refrigerator developed by stretching Ni-Ti wires. Ni-Ti plates are used to substitute Ni-Ti wires as elastocaloric materials to further improve the cooling performance of the elastocaloric refrigerator. In this study, we fabricate a third-generation elastocaloric refrigerator and develop a system-simulation model to predict its performance. The performance of the third-generation prototype is significantly better than those of previous versions; the third-generation elastocaloric refrigerator achieved temperature spans of up to 12 °C and 11.4 °C under adiabatic and cooling conditions, respectively. The refrigerator affords a cooling power density of up to 0.59 W/g under the zero temperature span condition. By increasing the strain and motor speed and using thinner elastocaloric materials with higher latent heat, the third-generation refrigerator is expected to maintain a temperature of 10.7 °C in the refrigerant cabinet at an ambient temperature of 32 °C.关键词：solid-state cooling;elastocaloric cooling;shape-memory alloy;nitinol alloy;refrigerator1186|919|1发布时间：2024-07-18
- 摘要：Clothes dryers are widely used in American and European homes; in particular, specific independent heat-pump dryers are used in European homes. Independent heat-pump dryers feature high efficiency, low power consumption, and clothes protection properties. As a result, they are increasingly being favored by consumers in China. Currently, the mainstream refrigerant used in heat-pump dryers is R134a, belonging to the A1 class and featuring low chronic toxicity and zero flammability; additionally, its maximum Global Warming Potential (GWP) is 1 430. Meanwhile, natural refrigerant R290 belongs to the A3 class featuring low chronic toxicity; it is flammable and can be explosive, and its GWP is lower than 20. This study is performed based on natural refrigerants R290 and R134a; their physical and thermodynamic properties are compared to optimize the system design of a heat pump clothes dryer. Subsequently, the performance of a heat pump clothes dryer using those refrigerants is analyzed. The final system design features an evaporator with φ7 mm diameter copper tubes and hydrophilic plain fins with a fin spacing of 2.2 mm. The condenser features φ5 mm diameter copper tubes and hydrophobic plain fins with a fin spacing of 1.5 mm. An 8.1 mL displacement R290 compressor is used, and the throttling device is a capillary tube with φ1.0 mm diameter and 820 mm length. The results indicate that using R290 in the heat pump system of the clothes dryer satisfies the requirements of international, national, and European standards of the A3 class refrigerant charge limit, implying that if the maximum charge amount of the A3 class refrigerant does not exceed 0.15 kg, the room volume is not restricted. When the R290 charge amount is 0.15 kg, the heat pump dryer energy efficiency index is 23.0, thus achieving the highest level (i.e., A+++) of the current European energy efficiency standard for clothes dryer.关键词：heat pump clothes dryer;global warming potential;refrigerant;R2901091|1208|0发布时间：2024-07-18
- 摘要：Room-temperature magnetic refrigeration has broad application prospects as a high-energy efficient, environmentally friendly, and reliable refrigeration technology. In the past decades, research concerning room-temperature magnetic refrigeration has primarily focused on developing magnetic refrigerants and designing magnetic refrigerators. This paper summarizes several typical room-temperature magnetic refrigerants and magnetic refrigerators that have been investigated and developed. Room-temperature magnetic refrigerants currently being investigated primarily include rare earth metal Gd and its alloys, NaZn-13-type La(Fe,Si)13 series alloys, and Fe2P-type MnFePA series alloys. Their magnetocaloric performances are compared and existing application problems are presented. The existing magnetic refrigerators are primarily classified into reciprocating and rotary magnetic refrigerators based on their operation mode. The operating parameters and refrigeration performance of magnetic refrigerators developed by different research institutions are introduced. In addition, the practical applications of room-temperature magnetic refrigeration technology in different fields are reviewed, and the development trend and perspective of this technology is discussed.关键词：room-temperature magnetic refrigeration;magnetocaloric effect;magnetic refrigerant;magnetic refrigerator1080|904|1发布时间：2024-07-18
- 摘要：Ammonia is an environment-friendly natural refrigerant and has been used in industrial refrigeration for more than a century. This paper discusses the energy-saving and safety technologies of the ammonia refrigeration system and presents an analysis of the factors that primarily affect the energy consumption of the ammonia refrigeration system, including the condensation form, combined cooling and heating, variable frequency technology, and automatic intelligent control. Safety factors are discussed based on low-charge technology, hazard and operability, and the safety of instrumentations. Results show that reasonably applying the above two technologies can effectively improve the safety and energy saving of ammonia refrigeration systems. To promote the safe application and technical development of ammonia refrigeration systems, professional training must be strengthened for personnel responsible for the operation and maintenance of ammonia refrigeration systems.关键词：ammonia;refrigeration system;energy saving;system safety1102|1355|0发布时间：2024-07-18
- 摘要：To investigate the effect of supply air temperature on the comprehensive performance of a vehicle transcritical CO2 refrigeration system, a simulation model of a single-stage transcritical CO2 refrigeration system is established using the GT-Suite simulation software. Based on three designed operating conditions, system performances under different supply air temperatures are compared, the upper limit of the air volumetric flow rate is specified, and the concept of the effective coefficient of performance (COPeff) is proposed and analyzed. Under the same conditions, increasing the supply air temperature can improve the system coefficient of performance (COP), COPeff, and the effective COP with fan power consumption. Under low cooling load conditions, the optimal value of COPb is 3.819, implying that the air supply temperature is optimal. However, when the cooling load increases to a certain level, the optimal air supply temperature is no longer valid. The research presented herein guides the selection of the supply air temperature for vehicle transcritical CO2 refrigeration systems.关键词：transcritical CO2 refrigeration system;supply air temperature;COP;system performance979|800|0发布时间：2024-07-18
- 摘要：In this study, simulation and experimental testing were carried out in a 28 kW variable refrigerant flow system to evaluate the contributions to annual performance factor (APF) from key factors, including heat exchanger area, compressor efficiency, refrigerant charge, system pressure loss, and oil return system. The APF values obtained experimentally and numerically are 4.59 and 4.61, respectively. Meanwhile, the maximum deviation between simulation and experiment is 5.1% at a single test condition, and the deviation of the APF is 0.5%. The results show that for the experimental system, the improvement in a single factor has a limited effect on the APF. For example, if the compressor efficiency increases by 3%, the APF increases by 2.8%. The optimization of the oil return system leads to an approximately 5% increase in the APF. A 10% increase in KA of the heat exchanger results in a 1% improvement of the APF. Therefore, many factors must be considered simultaneously to improve the APF.关键词：VRF;APF;compressor efficiency;system pressure loss;system simulation1007|993|0发布时间：2024-07-18
- 摘要：Fresh air dehumidification systems enable a healthy and comfortable building environment by controlling indoor humidity and replacing indoor air with fresh air. However, the fresh air dehumidification heat pump equipped in the system is limited by the installation space, resulting in low dehumidification efficiency and insufficient capacity. A new air dehumidification system based on a configuration comprising four heat exchangers is proposed herein to fully recover heat from indoor and outdoor air such that the dehumidification capacity and energy efficiency can be improved. Furthermore, it features various operation modes by switching the air and refrigerant flow paths, which satisfies the requirements of fresh air dehumidification in various application scenarios. Simulation and experimental results of the prototype show that the maximum specific moisture extraction rate(SMER) is 3.27 kg/(kW?h) under the rated cooling conditions, which is 35.2% and 59.6% higher than those of systems comprising three and two heat exchanger systems, respectively.关键词：ventilation;dehumidification;heat pump;heat recovery1230|917|0发布时间：2024-07-18
- 摘要：Metal-organic frameworks demonstrate significant application potential in sorption refrigeration driven by low-grade thermal energy owing to their ultrahigh specific surface area, large pore volume, and adjustable structure. Among the most structurally stable MOFs, ZIF-8(Zn) exhibits excellent structural stability and stable sorption properties. Herein, the grand canonical Monte Carlo molecular simulation method is adopted to simulate the sorption reaction between ZIF-8(Zn) and NH3, which is described by the universal force field and transferable potentials for phase equilibria force field parameters, respectively. Using both molecular simulation results and the adsorption refrigeration thermodynamic cycle model, we investigate the adsorption and refrigeration performances of the ZIF-8(Zn)/NH3 working fluid pair. The results show that the isothermal ammonia sorption capacity of ZIF-8(Zn) increases with pressure and that the sorption capacity reaches 0.305 g/g and 0.231 g/g at 298 Kand 398 K, respectively. Moreover, the total heat of sorption at the same temperature increases with pressure owing to the increase in the reaction heat of the NH3 intermolecular interaction. The isothermal sorption heat from the interaction between ZIF-8(Zn) and NH3 is relatively stable at different pressures. Furthermore, the sorption density distribution diagram shows that numerous NH3 molecules are adsorbed at the metal sites. Some NH3 molecules fail to pass through the small channels of ZIF-8(Zn), whereas others accumulated inside the six-membered ring cage of ZIF-8(Zn) after passing through the holes. Finally, the sorption refrigeration system demonstrates stable refrigeration performance and good adaptability to refrigeration temperatures. Ideally, the coefficient of performance (COP) should be 0.43 when the refrigeration temperature is 283 K (ventilation conditions), and it should be able to reach 0.38 when the refrigeration temperature is 243 K (freezing conditions).关键词：adsorption refrigeration cycle;molecular simulation;metal-organic framework;thermodynamics;cooling performance992|843|1发布时间：2024-07-18
- 摘要：A significant amount of unlabeled data are idle when labeled data with known operating statuses are used in the fault diagnosis of conventional refrigeration systems. Therefore, a semi-supervised fault diagnosis method is proposed in this study for refrigeration systems based on the Tri-Training method, which uses the information in unlabeled data to improve fault diagnosis performance. Seven typical faults in a 316 kW centrifugal chiller are used for verification, and the results show the effectiveness of the method. The semi-supervised fault diagnosis model based on Tri-Training can mine unlabeled data information and afford significantly improved performances compared with three typical supervised diagnosis models, i.e., support vector machines, K-nearest neighbor, and random forest. The overall diagnostic accuracy of the proposed system is 99.43%; meanwhile, the diagnosis accuracy of its system-level fault is higher by 1.73%–3.90%, and its false, neglectful, and wrong alarm rates are improved compared with those of the abovementioned three models. Meanwhile, the performance and diversity of the three initial classifiers in the fault diagnosis model are the main factors affecting the use of unlabeled data in refrigeration systems.关键词：refrigeration system;fault diagnosis;semi-supervised learning;Tri-Training;optimization948|869|0发布时间：2024-07-18
- 摘要：A thermodynamic analysis of the variables of a novel absorption generation heat exchange (AGX) on the variable effect lithium-bromide absorption refrigeration cycle (ARC) is performed in this study. The coefficient of performance (COP) of the cycle is 0.75–1.08 when the temperature of the high-pressure generator is 93 °C–140 °C. The abovementioned cycle has more commercial value than the conventional single/double effect ARC. However, the thermodynamic analysis of the parameters in the AGX cycle is limited, and the order of significance of thermodynamic parameters on the COP has not been determined. In this study, a thermodynamic model of the AGX cycle is established using the EES software. The effects of the parameters on the system COP are analyzed. The effects of the operational parameters on the COP are investigated statistically via the analysis of variance to determine the order of significance of the parameters. The results show that when the evaporating temperature (TE) increased by 5 °C, the COP increased by 11.8% (from 1.035 to 1.157); the absorption temperature (TLA) decreased by 5 °C; the COP increased by 9.5% to 1.133; the condensing temperature (TC) decreased by 5 °C; the COP increased by 6.7% to 1.104. TE contributes most significantly to the COP, with a contribution percentage of 45.67%, followed by TLA (29.80%), TC (17.93%), and R1 (0.02%). Therefore, TE should be prioritized in the system design and operation control to maximize the COP of the AGX cycle.关键词：variable effect;absorption refrigeration cycle;parametric evaluation;analysis of variance1140|717|0发布时间：2024-07-18
- 摘要：As a critical component of two-phase cooling systems, the pressure drop characteristics of refrigerants in cold plates with parallel channels significantly affect their heat-transfer performance. In this study, experiments are conducted to investigate the frictional pressure drop of low-pressure refrigerant R1233zd(E) in a cold plate under different mass fluxes (118–1 300 kg/(m2 s)) and inlet subcooling temperatures (2–8 K). The single-phase and two-phase frictional pressure drops of the refrigerant are analyzed simultaneously with the vapor and liquid velocity characteristics. The results show that for the single-phase refrigerant, the frictional pressure drop in the channel first decreases and then increases as the heat flux increases. When the refrigerant enters the two-phase state, the frictional pressure drop increases rapidly with the heat flux. As the mass flux increases, bubble nucleation and an abrupt increase in the frictional pressure drop are delayed. In addition, both the liquid velocity and the slip ratio increase with the heat flux. At the same outlet vapor quality, a higher slip ratio is observed at higher mass fluxes, which results in a more significant increase in the frictional pressure drop.关键词：parallel channel;flow boiling;frictional pressure drop;R1233zd(E)997|1406|0发布时间：2024-07-18
- 摘要：In this study, the air-side heat transfer performance of a mixed flow bubble plate heat exchange is investigated. The control variable method is used to determine factors that affect the heat transfer performance and water flow resistance of the bubble plate. The results show that an appropriate increase in the spray water flow rate can improve the uniformity of the water film distribution on the surface of the bubble plate such that the heat transfer can be improved; the recommended value for the spray water mass flux is no less than 0.347 kg/(s?m). When the plate spacing is increased from 20 to 30 mm, the air-side pressure drop decreases significantly. As the plate spacing further increases, it has a trivial effect on the air-side pressure drop. A 25 mm plate spacing and an average cross-sectional wind speed of 6.66 m/s are optimal parameters in terms of the air-side pressure drop and heat transfer performance. Compared with the anterior position arrangement, the plate dislocation arrangement is more reasonable and affords better heat exchange performance. Results show that the heat exchange effect of the dislocation arrangement is 1.1–1.4 times that of the anterior position arrangement.关键词：evaporative condenser;bubble plate;spray flow channel;heat and mass transfer831|795|0发布时间：2024-07-18
- 摘要：Latent heat thermal energy storage technology is applied to air-source heat pump systems in cold regions to improve their adaptability. Heat is stored during the day and released at night. A simulation is conducted in this study to further investigate the heat storage and discharge characteristics of the system and the effect of applying multistage PCMs (phase-change materials). The results show that the heat storage capacity varies linearly with the charging time, where 18.94 kW?h is achieved at 380 min, and the average COP is 2.51. The heat discharge capacity first increases linearly and then reaches 13.58 kW?h at 180 min. When the inlet water temperature is 35 °C, the system stabilized after six continuous cycles, and its energy storage efficiency is 99.06%. The charging time of the three-stage PCM is reduced by 9.60%; its COP is increased by 3.97%; its total exergy efficiency is increased by 4.84% compared with those of a single-stage PCM. Reducing the melting point of the PCM in the subcooled zone is key to improving the system performance.关键词：air-source heat pump;phase-change thermal energy storage;multi-stage phase-change materials;operating characteristics971|828|0发布时间：2024-07-18
- Address：10/F, Yindu Mansion, 67 Fucheng Road, Haidian Dist, Beijing, China Postal code：100142
- Tel：010-68711412 Email：editor@car.org.cn
- Technical support is provided by Beijing Founder electronics co., LTD 京ICP备09064830号-19
京公网安备11010802024621 - It is recommended to read the content of this site in Chrome&IE9+. Please switch to extreme mode in browser 360.
- Cookies We use cookies to help provide and enhance our service and tailor content. By continuing, you agree to the use of cookies.
0