最新刊期
卷 37 ， 期 3 ， 2016
- 摘要：In order to reduce the energy consumption of data center cooling system, a hybrid system combining vapor compression and magnetic pump-driven two phase cooling system was proposed. The results show that the energy efficiency ratio (EER) of the pump-driven mode increases firstly then decreases with the increasing of the condenser air face velocity at the outdoor temperature of 15 ℃, and it obtains the maximum value when the condenser air face velocity is 1 m/s. Under the condition of 7.3 kW heat load, the proper switch temperature of two operating modes is obtained by the experiments. Finally, taking Harbin and Shijiazhuang as the example, the best running time ratios of the pump-driven mode are calculated from the simulation.关键词：refrigerating system;energy efficiency ratio;operating mode;compression refrigeration cycle;two phase cooling2060|2076|0发布时间：2024-09-26
- 摘要：Seawater temperatures are the base data for the design and feasibility research of seawater source heat pump system. It’s crucial to the operating efficiency and safety. Getting typical seawater temperature year has significance for system design. This paper puts forward the concept of typical seawater temperature and presents the generation of typical seawater temperature year by analyzing its characteristics. Then this article gets the typical seawater temperature year of Dalian basing on the recent decade seawater temperature data of this area. It shows that the cumulative distribution, mean monthly temperature and data continuity of the results are representative.关键词：sea temperature;water source heat pump;typical temperature year;cumulative distribution function1879|1952|0发布时间：2024-09-26
- 摘要：The composite phase change material (PCM) used in the cold storage transportation system with phase change temperature of 0-5 ℃ are proposed in this paper. The material consists of capric acid and caprylic acid, and the mass ratio of its ingredients is 30:70. The composite was prepared by ultrasonic oscillations. The cooling curve method is used to test the phase change temperature of capric acid-caprylic acid in different mass fraction, the phase diagram is used to find the eutectic melting point and the ideal mass ratio is 30:70. The differential scanning calorimetry (DSC) test showed that the melting temperature of the PCM is 1.5 ℃ and the latent heat is 120.6 J/g. After 30 times and 60 times circulation of freezing and melting experiment, the phase change temperature and the latent heat were stable. The results showed that the composite has large potential in the cold storage system, especially in cold storage transportation system, because of suitable phase change temperature, high latent heat, and good thermal stability.关键词：cold storage system;phase change material;differential scanning calorimety;thermal properties1907|2033|0发布时间：2024-09-26
- 摘要：A defrosting control method based on the optimal average performance of an air source heat pump (ASHP) unit is presented. The deterioration point of an ASHP unit is selected as the defrosting initiation criterion. To verify the feasibility and applicability of the defrosting control method based on the optimal average performance, a test apparatus was established in the psychrometric rooms and the defrosting characteristics of an ASHP unit was investigated experimentally for four different defrosting initiation criteria under different frosting conditions. The frost thickness on the fins, the transient input power and heating capacity were measured. Based on the experimental results, the total heating capacity, total power consumption in the whole frosting/defrosting cycles and average COP of the ASHP unit were analyzed. The experimental results indicated that when the deterioration point of the ASHP unit is selected as the defrosting initiation criterion, the average COP in the whole frosting/defrosting cycles is the maximum, which confirmed that this defrosting initiation criterion is feasible and can be used for the optimal defrosting control of an ASHP unit.关键词：air source heat pump;defrosting experiments;defrosting criterion;optimum defrosting initiation criterion2047|1938|0发布时间：2024-09-26
- 摘要：The selection of ionic liquids (ILs) is crucial to the performance of new absorption working pairs (ILs-CO2) and cycle characteristics of absorption refrigeration. The properties of ILs absorbing CO2 are affected directly by ILs’s species, cation structure, temperature and CO2 partial pressure. In this paper, an experimental system was designed and built to measure CO2 solubility in the ILs. On the principle of low viscosity and better absorption performance, four imidazole bis trifluoromethanesulfonimide ILs ([emim][Tf2N], [bmim][Tf2N], [hmim][Tf2N] and [omim][Tf2N]) were selected and the CO2 solubility in them was measured within 2.0 MPa to 5.0 MPa at 298.15 K, 313.15 K and 328.00 K, respectively. The results show that imidazole bis trifluoromethanesulfonimide ILs have a better performance of absorbing CO2; the longer the alkyl chain of the same family ILs is, the larger the solubility is, and the CO2 solubility increases in the order of [emim][Tf2N]关键词：absorption refrigeration;absorption working pairs;absorption performance;ionic liquid;CO22131|1853|0发布时间：2024-09-26
- 摘要：The thermodynamic property of eutectic liquid in cold plate was analyzed in this paper．A mathematical model has been set up to predict the melting process of cold plate. The melting processes of cold plate with NaCl at ﹣30 ℃ initial temperature were calculated by using numerical method under three environmental temperatures such as ﹣10 ℃, 0 ℃ and 10 ℃. The related experiments were also carried out and the accuracy of the simulation results was verified by the experimental results. The melting process and characteristics of cold plate were obtained under different environmental conditions. The results shows that when environmental temperature is above the eutectic point ﹣21.2 ℃, the environmental temperature will have a great influence on the duration of the melting time as well as the moment for the eutectic to occur phase transition. The computational results are in good agreement with experimental ones. The average deviation of experimental data and computational result is less than 0.5 ℃, which indicates that the mathematical model and the calculating method are reliable.关键词：cold plate;melting;phase change;eutectic ice;eutectic liquid2208|2005|0发布时间：2024-09-26
- 摘要：Nowadays, natural gas hydrates are recognized as an important future energy in 21 Century. Pressure, temperature, the contact area of gas and water, surfactant and other factors affect its formation. The basic properties of the surfactant are introduced in the present paper, and the effects of surfactant on the formation of hydrates are summarized from the changes of surface tension of liquids for gas hydrates formation, micelle formation and the hydrate morphology. The mechanism of surfactant promoting gas hydrates formation is then put forward. In order to form a unified understanding on hydrate formation mechanism, the hydrate form is not only observed, the influence of the surfactant on the formation of the hydrate is also analyzed from the internal structure of the hydrate film for the future research.关键词：surfactant;gas hydrates;review;formation;promotion effect1828|1906|0发布时间：2024-09-26
- 摘要：In order to make ground-coupled heat pump system operate efficiently in long term, soil needs to be maintained heat balance in an annual cycle. Auxiliary cold source or heat source is needed if necessary. An evaluation method of soil heat balance was proposed, heat balance equation was given, and annual heat balance rate of soil was also defined. Soil heat balance point Δg0 and floating range 80%Δg0~120%Δg0 were derived, where the upper and lower limit correspond to the cold critical region and hot critical region, respectively. According to field data of heat storage, heating and cooling experiments based on the demonstration project, heat balance point was 80% and floating range was 65%~95%, which can be used as indices to measure soil heat balance. Based on the indices, it is evaluated that the ground-coupled heat pump with solar seasonal heat storage (GCHPSSHS) system could be applied to severe cold zone and a part of cold zone A of China. The evaluation method of soil heat balance based on annual heat balance rate can be used to analyze soil heat balance problem of ground-coupled heat pump system with auxiliary cold source or heat source, evaluate the regional applicability of the system, and design an efficient system which can keep soil heat balance.关键词：ground-coupled heat pump;soil heat balance;evaluation method;annual heat balance rate;auxiliary cold source or heat source1922|1970|0发布时间：2024-09-26
- 摘要：A series of tests were carried out on a new structure of heat pipe exchanger. It uses acetone as working fluid. The investigation was conducted at different heat loads, the tilt angles of device are 30°、45°、60°、75°、90°and the charging ratio of working fluid is 30%. The angles, length and operation temperature was adjusted in the test to investigate the thermal performance and effectiveness of heat recovery system. It reveals that the maximum heat transport increases with the augment of the operation temperature, evaporation length. Eventually, the experimental data showed that the optimum operating angle is 60°with evaporation length of 270 mm.关键词：thermosyphon;waste heat recovery;heat transfer performance1980|1952|0发布时间：2024-09-26
- 摘要：The performances of single-stage transcritical CO2 cycle with expander, transcritical CO2 two-stage cycle without intermediate heat exchanger, transcritical CO2 two-stage cycle with intermediate heat exchanger, transcritical CO2 two-stage & primary throttling cycle without intermediate heat exchanger and transcritical CO2 two-stage & primary throttling cycle with intermediate heat exchanger are analyzed in refrigeration condition. The results show that the single-stage expander cycle outperforms the other options when the expander efficiency is 60% at the given evaporation temperature (﹣10 ℃~20 ℃). When the evaporation temperature is 5 ℃ and the expander efficiency is greater than 32% , the performance of expander cycle is the best. In the other four two-stage cycles, transcritical CO2 two-stage cycle without intermediate heat exchanger and transcritical CO2 two-stage cycle with intermediate heat exchanger are reasonable options in medium and high evaporation temperature, and the performance of using internal heat exchanger in cycle is much better; transcritical CO2 two-stage & primary throttling cycle without intermediate heat exchanger and transcritical CO2 two-stage & primary throttling cycle with intermediate heat exchanger are more applicable to medium and low evaporation temperature. And the using of internal heat exchanger decreases the cycle performance.关键词：expender;carbon dioxide;transcritical cycle;two-stage;single-stage1939|1944|0发布时间：2024-09-26
- 摘要：Liquefied natural gas is an increasingly widely used clean energy. Establishing cryogenic power generation cycles using LNG cold energy is an important way of cold energy recovery. In the present paper, the key factors affecting the basic LNG power generation cycles are discussed, including LNG-side parameters, working fluids and equipment inlet and outlet parameters. Cycle structural enhancement is also summarized, including Rankine cycle, Brayton cycle, Kalina cycle and the compound cycles. The practical significance of parametric study and diversity of cycle structural enhancement are indicated. It is also pointed out that further research should be based on the selection and the component matching of organic mixed working fluids, and the combination of simulation and experiment, etc.关键词：liquefied natural gas;cold recovery;refrigerant;Rankine cycle1910|1903|0发布时间：2024-09-26
- 摘要：In order to improve the thawing rate and decrease the oxidation deterioration of frozen meat during thawing process, a high voltage electrostatic thawing device was designed, and frozen lamb thawing was studied using the thawing device. The results indicate that with the increasing of electric field intensity, thawing time and juices loss was decreased, the growth of bacteria was inhibited, the color and luster of lamb thawing was improved. Compared with that without high voltage electrostatic field, when the electric field intensity was 12.5 kV/m, the time of thawing frozen lamb was shorten 11.1%, the rate of juices loss was decreased 49.6%, the total microbial counts reduced an order of magnitude and the appearance of lamb was fresh, color and luster difference was obvious. This study provides a new method for improving efficiency and quality of lamb thawing.关键词：meet thawing;high voltage electrostatic field;frozen lamb2209|1926|0发布时间：2024-09-26
- 摘要：The performance of a new ejector is investigated experimentally in this paper. A range of different test points is tested in order to give an overall view of the ejector performance. The motive nozzle inlet temperature is from 19 ℃ to 31 ℃ and the gas cooler outlet pressure is from 6 MPa to 8 MPa. The test facility used in this experimental analysis is a two-phase ejector refrigeration system with R744 as a working fluid. The experiment results show that the ejector works more efficiently when the entrainment ratio changes from 0.4 to 0.8 and the pressure ratio is from 1.09 to 1.20 approximately. Moreover, the best efficiency, which can be achieved when the pressure ratio is 1.132 approximately, is 0.389. The fitted mass flow rate agree well with the experiment results. The experiment results provide a basis for application and design of ejector.关键词：ejector;supercritical;test condition;natural refrigerant;CO22121|1869|0发布时间：2024-09-26
- 摘要：Extremum Seeking Control (ESC) is a class of self-optimizing control strategy that can search for the unknown or slowly varying optimum input with respect to certain performance index, which is effectively a dynamic realization of the gradient search based on a dither-demodulation scheme. For an air-source transcritical CO2 heat-pump water heater, the discharge pressure setpoint is taken as the input to the ESC controller, while the system COP is taken as the performance index, i.e. the feedback signal for the extremum seeking process. A Modelica based dynamic simulation model is developed to perform the simulation study. Simulations are conducted for several scenarios: a fixed operation condition, change of ambient condition and real time varying ambient temperature conditions. Simulation results show that ESC is able to search both fixed and slowly varying optimum. The steady-state error of optimal discharge pressure is less than 1.0%. Compared to the optimum obtained by model based methods, the optimal discharge pressure deviations are less than 5%. The feasibility and accuracy of ESC control strategy are verified.关键词：transcritical CO2 heat pump;optimal discharge pressure;extremum seeking control,;coefficient of performance (COP)2122|1927|0发布时间：2024-09-26
- 摘要：Two different energy efficiency indices EER, COP and APF are both used to evaluate the energy efficiency of room air conditioners, nowadays. In order to compare which air conditioners are more energy-saving, the traditional energy efficiency index EER and COP need to be transformed to APF. This paper presents a method to evaluate APF for room air conditioner by using EER and COP. In the method, APF is transformed to equations referenced to the same intermediate variables including cooling capacity and power consumption under standard condition at first, and then combing the equations of EER and APF to eliminate the intermediate variables. The equation has the capability to calculate APF of room air conditioners with on/off compressor by the energy efficiencies of cooling and heating modes.关键词：room air conditioner;standard of air conditioner;APF;constant-speed2315|2077|0发布时间：2024-09-26
- 摘要：Lotus-type porous copper is a new kind of micro-channel structure with long cylindrical pores aligned in one direction. It can be used as a heat sink for cooling of high-power electronic components. Through experiments and numerical simulations with Flow Simulation, the heat transfer performance of a lotus-type porous copper heat sink with uniform distributed micro-groove was systematically studied. The experimental results showed that this kind of heat sink has an excellent heat transfer coefficient, as high as 10.1 W/(cm2?K), only under a flow rate as low as 110 mL/s. The simulation showed that optimal number and angle of micro-groove existed for the heat sink to reach a maximal equivalent heat transfer coefficient. For water as its coolant, the optimal number and angle of micro-groove were 7-11 and 45°, respectively. And heat transfer performance of the heat sink continuously improved with decreasing of the width of micro-groove. The numerical simulation results were compared with the experimental results, and the reasons for the differences were analyzed.关键词：water cooling;micro-channel;heat transfer enhancement;lotus-type porous copper2121|1893|0发布时间：2024-09-26
- 摘要：In order to get the thermophysical properties of mixed refrigerants R1234yf/R134a, the PVT properties of mixture refrigerant R1234yf/R32 with mass fraction 15%/85%, 25%/75% in the range of 253-313 K were measured by using high-precision PVTx apparatus which is based on the Burnett method. The gas virial equation of these mixed refrigerants was then fitted. The detailed data were provided as the basic thermal physical property of the refrigerant for the further research.关键词：PVTx;mixed refrigerants;R1234yf/R32;virial equation2251|2029|0发布时间：2024-09-26
- 摘要：Heat pump is a machine for renewable energy recovery. Several units of renewable energy can be obtained with the consumption of one unit of electric or mechanical energy. Therefore, heat pump is an important energy saving and environmental protection technology. This paper focuses on the heat pump seasonal performance factor. The transient characteristic of heat pump may change with the variation of ambient temperature or heating capacity. Thus, the research on seasonal performance factor has a significant theoretical and practical value. It is recommended that the renewable energy contribution rate calculation method of heat pump be set as a national standard so that heat pump manufacturing industry will benefit, and the heat pump technology will be applied.关键词：heat pump;primary energy utilization ratio;SEER;SHPF;IPLV;IEER;SCOP;SPF1766|2283|0发布时间：2024-09-26
- 摘要：In order for better selection and energy saving design of data center air conditioning system, energy consumption models for three types of data center air conditioning, air cooling direct expansion unit, dual cooling source chiller and combined refrigeration unit with heat pipe, were established. The annual energy efficiency ratio (AEER) and annual energy consumption of the three types of air-conditions with the same air conditioning load and return air parameters were calculated and analyzed based on the meteorological data of four cities, i.,e., Harbin、Beijing, Shanghai and Guangzhou in DEST,. The results showed that the AEER of these three units increase along with the decrease of the average temperature from south to north. As a result, the AEER of them are 4.07-4.45、4.00-6.84 and 4.27-8.20. Comparing the combined refrigeration unit with heat pipe with air cooling direct expansion unit and dual cooling source chiller, the energy saving rate of the heat pipe is 4.8%-46% and 6.4%-16.6% respectively. In comparison with the air cooling direct expansion unit, the energy saving of dual cooling source unit are obvious, because it can use natural cooling resource to replace or partially replace the compression refrigeration. Compared with dual cooling source chiller, combined refrigeration unit with heat pipe has the advantages of low refrigerant transporting power, high heat exchange efficiency and anti-freezing. Therefore, combined refrigeration unit with heat pipe is the first choice for the data center air conditioning system in low annual temperature area.关键词：air conditioning energy saving;data center;natural cooling;model;analysis2653|2202|0发布时间：2024-09-26
- 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