最新刊期
卷 38 ， 期 4 ， 2017
- 摘要：As the first artificial refrigeration method developed, absorption refrigeration has been around for more than 200 years. In truth, it has been used in civil and industrial applications for more than 60 years. Absorption refrigeration has developed rapidly in terms of theory and application over the past 20 years, and in the refrigerator market occupies a considerable share, has drawn significant attention from both domestic and foreign manufacturers. With an increase in human energy consumption, in-depth research on new and distributed energy sources and their efficient utilization needs to be carried out. The use of waste heat, renewable solar energy, and geothermal energy make heat-driven refrigeration (heat pumps) an increasingly attractive option.Unlike electric-driven vapor compression refrigeration (heat pump) systems, absorption refrigeration (heat pump) technology can be driven directly using thermal energy from low-grade heat sources, operating at a much lower cost than the electric-driven system. Owing to their environmentally friendly features, including safety, noise-free operation, high reliability, and other significant advantages, absorption systems have adopted a water-lithium bromide solution, an ammonia-ammonia solution, or other natural refrigerant as the working fluid. However, absorption systems have a large footprint, a large initial investment, high cooling load, low energy efficiency (direct combustion form), and other deficiencies. In view of these characteristics, the main research directions at this stage include an optimization of the cycle design, the selection of a working fluid, enhancement of the heat and mass transfer of the system components, and optimization of the system control strategy.The absorption cycle, in a narrow sense, refers to a closed, vapor refrigerant absorbed by the solution refrigeration (heat pumps) cycle. This family of cycle, in accordance with its classification of cycle configuration, includes single absorption cycles, multi-absorption cycles, and combined cycles. Single absorption cycles consist of a basic single-effect absorption cycle, diffusion absorption cycles, membrane absorption cycles, heat booster cycles, gravity-driven valve-operation cycles, and self-cascade cycles. A multiple absorption cycle mainly includes a reabsorption cycle, multi-effect cycles, intermediate-effect cycles, multi-stage cycles, intermediate-stage cycles, and GAX cycles. Combined cycles mainly consist of ejection-absorption cycles, compression-absorption cycles, and expansion-absorption cycles.Existing research into absorption refrigeration technologies includes, but is not limited to, solar energy, medium and low temperature level waste heat utilization, combined heat and power, energy storage (cooling and heat storage), membrane exchange materials, high-temperature corrosion-resistant materials, plastic heat exchangers and so on. The existing absorption cycle was designed to satisfy a certain temperature and concentration range. In the face of new applications, new materials and a new absorption of working fluids, novel absorption cycles can be proposed with greater efficiency, wider ranges of heat-source driven temperature and solution concentration.关键词：refrigeration cycle;absorption refrigeration;lithium bromide;ammonia-water;progress;review2486|2144|13发布时间：2024-07-18
- 摘要：The combination of heat storage technology and air source heat pump (ASHP) can provide heat source for air source heat pump defrosting, solve the problem of variable heat due to the fluctuation of outdoor air parameters, alleviate the contradiction between supply and demand, and perform an important function on the peak load shifting. Through the review of the application of heat storage technology in ASHP, this paper introduces the air source heat pump heat storage defrosting system, the effect of air source heat pump in heating regulation and electric peak-shaving, and its application as a heat pump water heater in hot water supply. It is pointed out that air source heat pump heat storage system will play an important role in defrosting, heating, water heater and electric peak-shaving in the future. The selection and dosage of heat storage materials, the lectotype and volume of heat storage tanks will be the future research directions.关键词：air-source heat pump;heat storage technology;defrosting;water heater;electric peak-shaving2134|2219|4发布时间：2024-07-18
- 摘要：A 3P variable frequency air source heat pump unit was developed and applied in a residential building with floor radiant heating. The system was tested during the winter over a 93d period. The range of the outdoor environment temperatures was ﹣10 ℃ to 16 ℃, with the average value being 3.72 ℃. The heat capacity of the heat pump was 3.82 to 10.06 kW, with the average value at 6.71 kW. The average suction and discharge pressures were 0.55 and 2.28 MPa, respectively, and the compression ratio of the system was small. The energy efficiency ratio (EER) range was 2.32 to 4.71, and the aver?age value of EER was 3.46, indicating a high level of energy efficiency. The temperatures at the height of 0.1, 1, 1.5, and 2 m were measured indoors, and the average values were 20.48, 19.26, 18.75, and 18.01 ℃, respectively; therefore, the temperature field was comfortable because of the negative gradient. The results in the warmest day and coldest day were compared and it is indicated that the average outdoor temperature difference in the two days was 17.21 ℃, and that the heating capacity and EER in the warmest day were 41.9% and 159% of those in the coldest day, respectively. The system showed good environmental adaptability and comfort. Compared with an urban central heating system and a gas-fired boiler heat?ing system, the operating costs were reduced by 39.82% and 56.17%, respectively, and the energy efficiency, safety, and thermal comfort were improved.关键词：air source heat pump;radiant floor heating;application test2636|1916|4发布时间：2024-07-18
- 摘要：A phase change material is a popular functional material, and owing to its high heat storage density, maintains a constant temperature during the process of storing and releasing energy, or is stable within a certain temperature range, which makes the material be able to not only realize energy storage but also achieve temperature control functionality. Composite phase change materials have become a popular research area because of their variety of single material properties, and are widely used in building-energy conservation, the thermal management of electronic devices, and cold chain transport. Its application is quite extensive when the energy supply is not continuous. This paper divides composite phase change materials according to their chemical composition into organic-organic, inorganic-inorganic, and organic-inorganic materials, determines the advantages and disadvantages of different types of composite phase change materials based on the research in recent years, and summarizes their energy storage characteristics. The present applications of composite phase change materials are summarized, and the development of research in this area is further analyzed based on the current energy use and environmental conditions. The research objectives and directions of phase-change thermal storage are illustrated, and it is concluded that future composite phase change materials should be highly efficient, accurate, cheap, environmentally friendly, and biodegradable.2119|1909|18发布时间：2024-07-18
- 摘要：Air pressure inside a refrigerator changes periodically when the temperature of the refrigerator fluctuates around the set value. Mass transfer occurs through the suction surface of refrigerator seals between air inside and outside the refrigerator. Water vapor can permeate through the contact surface, leading to frosting and an increase in thermal load in the refrigerator. To reduce the permeation of water vapor, the calculation method of water vapor permeation through refrigerator seals is developed in this paper. The permeable passage scale of the contact surface is determined to be the magnitude of um with the observation of the seal surface feature, which is much larger than that of the mean free path of the water molecules, determines that a viscous flow occurs when water vapor permeates through the surface. A formula of water vapor permeation is established based on Darcy’s law of viscous flow. The permeation coefficient is fitted with the experiment results of water vapor permeation of the contact surface. The water vapor permeation values calculated through the formula are compared with the experimental data, and the results show that the deviation of water vapor permeation predicted by the established formula is less than 15%, which indicates that the formula can be used to calculate the water vapor permeation through the contact surfaces of refrigerator seals.关键词：refrigerator;seal;water vapor;permeation rate;calculation method2013|1899|1发布时间：2024-07-18
- 摘要：A general district-energy planning method that is suitable for hot summer and cold winter areas is proposed in this paper based on an energy bus system (EBS). In the proposed method, multiple thermal or cooling sources and users (buildings) are connected together using warm and cool lines with distributed variable speed pumps (DVSPs). In the new EBS configuration, thermal devices are used to control the water supply temperature in the side of all sources, chillers and heat pumps installed in all users (buildings) are used to provide space cooling, heating, and domestic hot water. Because of the simultaneously decoupled thermal features of the presented EBS configuration, both energy sources and users are capable of adjusting their thermal devices flexibly according to their own local loads. To demonstrate the new district energy planning method, a hydraulic and thermal model is developed, and a case study is illustrated in detail. The results show that combined with the ground source heat pump, water source heat pump, and steam-driven LiBr units, the given method has good efficiency in utilizing low-grade energy resources, with an integrated COP of 3.85 in the summer and 3.17 in the winter.关键词：energy planning;district heating/cooling;energy bus;distributed heat pump;distributed variable speed pump2079|2047|3发布时间：2024-07-18
- 摘要：A desiccant coated heat exchanger can handle sensible load and latent load simultaneously; however, owing to the influence of adsorption heat, the heat load and moisture load treatment is not synchronous, and the ability to handle sensible load is insufficient. Based on this, another sensible heat exchanger is added in-series for the air secondary treatment. An experiment setup was built to test the dynamic performance of two heat exchangers connected in-series. In addition, the influence of the main operation parameters including the water temperature, air temperature, air humidity, and air velocity on the system performance are analyzed. The results show that a sensible heat exchanger can clearly improve the ability to handle sensible load, particularly during the beginning period, and the cooling capacity of the system is also significantly improved. Moreover, under the experiment conditions, the cooling and heating water temperatures can both improve the cooling capacity and COP, a higher air temperature and relative humidity ratio lead to a better performance, and a lower air velocity is helpful for increasing the average dehumidification capacity and the effective dehumidification time.关键词：dehumidification;desiccant coated heat exchanger;sensible heat exchanger;operating in series;adsorption heat2302|2022|3发布时间：2024-07-18
- 摘要：The discharge of industrial wastewater has been a difficult problem for various enterprises. Aiming to solve this problem, we designed and developed a set of concentrated wastewater treatment devices. These devices are based on low-temperature evaporation technology, in which a heat pump is used as the driving energy source, and air is the circulation medium. We carried out a concentration experiment of a copper-tube waste washing liquid with water content of 95% using this device. The main components of the device are presented in this paper, a heat and mass transfer model of the packing chamber was established using Matlab, and the packing size was determined to be 300 mm×400 mm×500 mm with the model, and an experimental bench was set up. An experimental test and energy efficiency analysis were carried out with the experimental bench. The following conclusions were drawn: the device can run stably; the condensation of water reaches up to 15 L/h; when the pump power is 5.46 kW, the energy efficiency ratio of the device reaches up to 4.54; the air circulating in the device is changed from 31 ℃ to 43 ℃, and the relative humidity is 94.6%. After operating for a certain period of time to reach the maximum concentration, the volume reached about 3/4 of the original, and the water was clear, which will greatly reduce the cost of industrial wastewater treatment.关键词：low temperature evaporation;heat pump;concentrate;performance study1895|1947|0发布时间：2024-07-18
-
Study of Gas Distribution Characteristics on VM-PT Cryocooler Operating at Liquid Helium Temperature
摘要：Vuilleumier gas-coupling pulse tube cryocooler (VM-PT) is a novel kind of cryocooler capable of attaining liquid helium temperature. For investigating on the complex mechanism of gas distribution between two stages, a numerical model of VM-PT cryocooler was built by using Sage software. The influence of the operating frequency, the average pressure, the length of capillary tube and the filling length of Er3Ni on the distribution characteristics of mass flow were studied respectively. The results showed that those four parameters would change the gas distribution between two stages and then influence the coldest temperature of VM-PT cryocooler. By weighing the cooling capacity of working gas and the losses of regenerator, those parameters had its optimal value for the performance of cryocooler. Then, an experimental bench was built to verify the results of simulation. By optimizing the parameters of capillary tube and the filling method of a cold regenerator, a no-load temperature of 3.86 K was obtained in the experiment and the cooling capacity at 4.2 K was demonstrated to be about 10 mW.关键词：cryogenic refrigerating machine;liquid helium temperature range;pulse tube cryocooler;VM cryocooler;gas distribution1944|1798|0发布时间：2024-07-18 - 摘要：The development of a high-quality wine cabinet requires a method to make the temperature distribution in the cabinet as uniform as possible. In this study, basic ideas for achieving a uniform temperature in a wine cabinet are presented, including a uniform transport of cold air, avoiding the sinking of cold air, reducing door heat leakage, and enhancing the air turbulence. In addition, preliminary schemes are illustrated accordingly, including the arrangement of the air outlet, the division of space, the air curtain on top of the cabinet, and the transverse direction of the air outlet. An optimized scheme was obtained through a comparison and analysis of the simulation performance of each scheme. The results show that the combination of four preliminary schemes can achieve the best temperature uniformity in a wine cabinet. A performance test of a 389 L wine cabinet under a set temperature of 8 ℃ shows that the maximum temperature difference can be reduced from 12.6 ℃ to 2.0 ℃ through the optimized scheme at an ambient temperature of 32 ℃. It was verified that the optimized scheme is able to improve the temperature uniformity in a wine cabinet effectively.关键词：indirect-type refrigeration;wine cabinet;temperature field;temperature uniformity;performance test1991|2010|0发布时间：2024-07-18
- 摘要：In automotive air conditioning applications, parallel flow microchannel evaporators have become increasingly attractive owing to their compactness and high thermal performance per unit weight. However, a misdistribution of the refrigerant among the parallel microchannel tubes deteriorates the heat transfer performance of a microchannel evaporator and limites extensive promotion. Therefore, it is important to study the heat transfer characteristics of microchannel evaporator and how to improve the uniformity of refrigerant distribution. In this paper, an automotive air-conditioning test bench with R134a as refrigerant was set up. First, the heat transfer and exergy loss of the double-row and four-pass microchannel evaporator were analyzed. Then the surface of the evaporator is photographed by infrared camera Distribution image. As the evaporator inlet temperature increased from 21 ℃ to 42 ℃, the cooling capacity increased from 2.37 kW to 4.19 kW, while the evaporator exergy loss increased first and then decreased. And the exergy loss of the evaporator first increases and reaches a peak of 0.21 kW as the inlet air reaches 27 ℃, then decreases to a minimum value of 0.16 kW as the inlet air reaches 42 ℃. The σ value which represents the surface temperature distribution uniformity of the evaporator increases from 2.5 to 19.5 as the inlet air increases from 21 ℃ to 27 ℃. When the inlet air is 42 ℃, the value of σ decreases to 1.8. The surface temperature of the evaporator is the most uneven when the inlet air temperature is 27 ℃, and is most uniform when the inlet air temperature is 42 ℃. Therefore, the performance of the evaporator can be improved effectively at a relatively high air inlet temperature, and the rate of exergy loss and the value of σ decrease by 26.1% and 91.0%, respectively. Moreover, properly increase the compressor speed can effectively improve the surface temperature distribution uniformity of the evaporator.关键词：automotive air-conditioning;microchannel evaporator;temperature field;heat transfer characteristics2123|2018|7发布时间：2024-07-18
- 摘要：To obtain its average particle size and size distribution, ice slurry treated with ethylene glycol was produced through a vacuum method, and images of ice particles in the ice slurry were obtained using a microscopic observation system. The effects of the stirring speed, initial ethylene glycol concentration, and ice packing fraction (IPF) on the average particle size were investigated experimentally. Meanwhile, the experimental particle size distributions were also compared with normal, log-normal, Gamma, and Weibull distributions. The results indicate that the size distributions of the ice particles under different experiment conditions were in accordance with the Gamma distribution. The average particle size of the ice crystals measured at five stirring speeds of 100, 200, 300, 400, and 500 r/min were 46.5, 46.0, 44.0, 44.2, and 45.2 μm, respectively, which indicates that the stirring speed has little influence on the average particle size. The higher the concentration of ethylene glycol, the smaller the average particle size, which was decreased to 74.8 μm from 34.3 μm when the concentration of ethylene glycol was varied from 1% to 7%. Moreover, the average particle size of the ice crystals increased with an increase in the ice packing fraction. However, the amplitude was not clear until the ice packing fraction reached a certain threshold of about 18%.关键词：particle size distribution;experimental study;ice slurry;vacuum ice2081|1933|2发布时间：2024-07-18
- 摘要：Based on a study on the effects of a biological preservative on the quality of pomfret, ice formulation through a compound of biological preservatives was optimized using an orthogonal experimental design method involving two factors and three levels by assessing the quality indicators (sensory evaluation), microbial index (total viable counts (TVC) and aerobic plate counts (APC)), and physiochemical index (total volatile basic nitrogen (TVB-N), thiobarbituric acid value (TBA), and K value). According to the results, pomfret treated with ice containing 0.5% (w/v) tea polyphenols and 0.15% (v/v) phytic acid showed better indicators than the control group, and its shelf life can be extended from 11 ~ 12 days to 21 ~23 days under a temperature of 1 ℃.关键词：tea polyphenols;phytic acid;biological preservative ice;preservation;pomfret2034|1985|2发布时间：2024-07-18
- 摘要：Preservation is an important part of modern agriculture, and is an important way to improving the "time and space" value of fruits and vegetables. With the development of physical technologies, many types of physical preservation methods have been developed. Based on existing research, the effects of temperature, light, electricity, and magnetism on the preservation of fruits and vegetables are summarized. Firstly, controlling the temperature field uniformity and volatility slows down the metabolism and water loss. Second, the appropriate light intensity, electric field intensity, and magnetic field strength can also improve the storage time of fruits and vegetables, thereby reducing a loss of nutrients.关键词：fruits and vegetables;fresh;field theory;temperature field2004|2065|3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