最新刊期
卷 37 ， 期 5 ， 2016
- 摘要：This paper reviews the study and development of photovoltaic (PV) air conditioning system around the world. The PV air conditioning system is introduced as well as the classification. Both the development of the general air conditioning system and the improvement of photoelectric conversion efficiency indicate that the main technologies for the applications of PV air conditioning system are available. On the other hand, the investments of PV air conditioning system have been decreased significantly due to the price drop of PV modules, the profit from the PV system and the reduction of total necessary PV module areas. Then, four kinds of PV air conditioning systems are described in detail about their structures, the test conditions and the testing results which show the satisfying performances. Finally, this paper discusses five issues for our future work, namely, high-efficiency PV direct-driven air conditioning system, subsidy supports for PV air conditioning system, control strategies, the interactions between human behaviors and energy saving of air conditioning system and developing software for designing PV air conditioning system.关键词：solar;photovoltaic;air conditioning system2068|3300|4发布时间：2024-07-18
- 摘要：A new type of photovoltaic/thermal integrated multiple heat source heat pump water heating system is studied. According to different controlling patterns, three operating modes are proposed which combines air source heat pump and PV/T collector based on multi-port tube. The three operating modes are double heat source operating mode, single solar energy operating mode and single air energy operating mode. The performances of system are evaluated experimentally under different operating modes, including water temperature, heating time and coefficient of performance, etc. When 200 L water is heated from 30 ℃ to 55 ℃ at ambient temperature of 28.5 ℃. Experimental results show that the running time of double heat source operation is shorter than that of single air energy operation and single solar energy operation, decreased by 42% and 54%, respectively. The COP increase 32.78% and 47.64%, respectively. At the same time, the system’s thermodynamic and photovoltaic output characteristics for heating 200 L are investigated experimentally from 9:00 to 17:00. Meanwhile, the effect of solar radiation intensity and PV/T collector’s temperature on the photovoltaic/thermal efficiency is discussed. Comparative experimental results show that the photoelectric efficiency of thermoelectric mode is 25.8% higher than that of single photoelectric mode.关键词：multiple source heat pump water heating system;photovoltaic/thermal (PV/T);multi-port tube;operating mode;photovoltaic/thermal efficiency2289|3077|3发布时间：2024-07-18
- 摘要：In terms of environmental conservation, it is very meaningful to use CO2 as working fluid in the two-phase thermosyphon loop (TPTL) to replace R22. According to the experimental results in some research, the flow boiling or condensation heat transfer coefficient of CO2 is much higher than that of the conventional refrigerants, which means CO2 has the potential in improving the heat transfer performance of the TPTL system. Considering the high heat transfer coefficient of the refrigerant, the convective thermal resistance of the air/water outside is the main restriction of the performance. Thus, the improvement of the heat transfer performance by using CO2 may be limited. The present study compares the heat transfer performance of CO2 and R22 TPTL through experiment. Combined with some heat transfer model, each part of the thermal resistance is analyzed. The result shows that the total thermal resistance of CO2 TPTL is 22%-25% lower than that of R22 TPTL due to the reduction of the boiling and condensation thermal resistance.关键词：two-phase thermosyphon loop;CO2;flow heat transfer;thermal resistance2104|2206|1发布时间：2024-07-18
- 摘要：In theory, using internal heat exchanger in the R134a vehicle air conditioning system can improve the cooling performance significantly，but many experimental studies demonstrates that the internal heat exchanger has a negative effect on the safety of the system. Therefore the advantage and the disadvantage trade off, which makes the merit not conspicuous. Aimed at this situation, the influence of different length of internal heat exchanger on the air conditioning system comprehensive performance is investigated in test bench in this paper. It shows that the adverse effects have certain relationships with the tube length on the basis of the experiments. In addition, this study also obtain a method to avoid adverse effects, by adjusting the expansion valve, condenser air flow and oil, which provides theoretical foundation for the matching of heat regeneration system.关键词：heat regenerative cycle;vehicle air conditioning system;internal heat exchanger;R134a;optimization2195|2694|1发布时间：2024-07-18
- 摘要：This study aims to investigate the phase equilibrium of refrigerant gas hydrates based on thermodynamic theory. A thermodynamic model based on the van der Waals-Platteeuw model is used to predict the hydrate dissociation conditions. Refrigerants modeled in this study include R22, R23, R125 and R143a. The SRK equation of state is employed for modeling the vapor and fluid phases. The deviation values between model predictions and the experimental data are 1.21%, 2.84%, 2.23% and 1.02%, respectively. The phase equilibrium diagram of refrigerant hydrates and quadruple points are obtained. Decomposition heat of refrigerant hydrates is calculated. It is found that the decomposition heat of type Ⅱ refrigerant hydrates is higher than that of type Ⅰ.关键词：gas hydrate;refrigerant;phase equilibrium;thermodynamic model2091|2096|1发布时间：2024-07-18
- 摘要：Due to heating demands, the range of Electric Vehicles (EVs) will significantly decrease when used in cold climate. A study on character of EV heating load is present in this paper, and a new experimental method of heating load evaluation is provided. The heating load of EV was experimentally evaluated and modeled. The ventilation load is responsible for most of the heating load. Under -20 ℃ the ventilation load accounts for 56.2%-84.4% of total load, which is changed with vehicle velocity and blower level. Then the effect of heating load on EV NEDC range was calculated. It can be concluded that the PTC heater will cause a 20.1%-56.4% decrease in NEDC range, while using heat pump to meet the requirement of heating will greatly improve the NEDC range. A 7.4%-13.2% extension can be achieved with a heat pump COP of 1.7.关键词：heat load;heat pump;electric vehicle;range2108|2329|13发布时间：2024-07-18
- 摘要：In view of the defects of traditional working pairs such as ammonia system, water system and Freon system,a new working pair, CO2-[emim][Tf2N], was proposed for the absorption refrigeration cycle. PR equation of state, NRTL model, and WS mixing rule which was obtained from cubic equation and the excess free energy model were utilized to develop GE-EOS thermodynamic model in the paper. The excess Gibbs free energy of binary mixture solution under high pressure and high temperature were obtained with the model. The results showed that the excess Gibbs free energy of the binary mixture solution had maximum when temperature is 453.15 K, pressure is 13.374 MPa and CO2 mole fraction in the liquid phase is 0.392.关键词：CO2-[emim][Tf2N];equation of state;mixing rule;excess Gibbs free energy2540|2221|1发布时间：2024-07-18
- 摘要：The adsorption performance of composite adsorbent is a significant parameter for adsorption refrigeration cycle. An integral adsorbent performance testing device is designed and built to test performance of the adsorbent in this experiment. The feasibility of the device and the performance of composite adsorbent MgCl2-13X are investigated with the testing device. The result shows that the temperature change rate of bottom outside the adsorbent bed is highly near that of the adsorbent at the bottom inside the adsorbent bed. And the deviation of the temperature change rate of the two ranges from 0.01-1.9 ℃/min, and the deviation of average of the temperatures of the two is 3.24% during the processes of adsorption and desorption, which can meet the requirements of the experiment. The experimental results and the SEM images show that the performance of composite adsorbent prepared by immersion method relates to the concentration of MgCl2 solution. MgCl2 can improve the performance of zeolite 13X. And the experimental result shows that the composite adsorbent has the best performance when the concentration of MgCl2 solution is 15%. The maximum adsorption ratio of MX3 is 0.32 g/g. The water uptake rate of MX3 is 0.59 g/min, improving 20% compared to that of pure zeolite 13X.关键词：adsorption refrigeration;composite adsorbents;adsorption rate;immersion method;zeolite 13X1984|2372|5发布时间：2024-07-18
- 摘要：The scroll compression with vapor injection is applied to under-floor heating system to solve the problems of poor heating performance and instability operation under the condition of low ambient temperature in this paper. The compressor discharge temperature，heating performance, power consumption and COP（Coefficient of Performance） are researched and compared with the heating system without vapor injection. The results show that under the ambient temperatures between -20 ℃ and 7 ℃, the under-floor heating system based on vapor-injection compressor has a higher heating capacity and COP compared with the normal heating pump , and the heating capacity is increased by 26.2%, and the COP is increased by 8.7% on average, and power consumption is only increased by 16% on average; and when the ambient temperature is -20 ℃,the discharge temperature is decreased 12 ℃.The experimental results demonstrate that the under-floor heating system based on vapor-injection compressor can better satisfy the demands of low ambient temperature with low energy consumption.关键词：vapor injection;scroll compression;under-floor heating system;heating capacity1819|2362|2发布时间：2024-07-18
- 摘要：The objective is to validate the practical humidifying performance of a solid desiccant coated heat exchanger (DCHE) cooling system in winter. The experimental setup is designed and built to test the humidifyingsystem performance. In this system, the heating water required in regeneration process is coming from the solar collector system. The saturated desiccant is regenerated by the heating water, at the same time the regeneration air is humidified and heated. Under the condition of the temperature of the heating water is 42.0 ℃, the temperature of the air increases from 12.1 ℃ to 31.2 ℃. The average moisture addition D_ave is 3.4 g/kg. The thermal coefficient of performance COP_th is about 2.0.关键词：desiccant;regeneration;desiccant coated heat exchanger;winter conditions2195|2286|3发布时间：2024-07-18
- 摘要：In order to study the effect of ice temperature and ACIT storage on quality of the winter jujube, we put the jujube in the cold precooling room for 24 hours, and divided them into three levels(0 level,1 level,2 level) according to the different maturity. The jujubes of different levels were then placed under the ice temperature (-2.4 ℃) and ACIT storage conditions (-2.4 ℃, 5% O2 concentration and 0.5% CO2 concentration )，and the weight-loss rate ,flesh hardness, peel hardness, brittleness, soluble pectin content and Vc content of the jujube during storage were measured. The results show that ACIT storage condition can effectively delay the decay of the winter jujube, during the whole process of the storage, three grades jujube under air conditioning ice temperature is significantly better than that of ice temperature storage in terms of weight loss rate, brittleness and soluble pectin content and Vc content（P＜0.05）; for peel hardness, 1 grade jujube under ACIT is better than that under ice temperature storage, 0 grade and 2 grade jujube under ice temperature are better than that under ACIT; for flesh hardness, we can get that ice-temperature storage condition has a better effect than ACIT which is better than the common controlled atmosphere storage（P＜0.05）; the quality of the low red index jujube is relatively good.关键词：horticulture;preservation technology;ACIT;winter jujube2066|2494|2发布时间：2024-07-18
- 摘要：In order to enhance the operating performance of air source heat pump, the performance of air source heat pump (ASHP) system with the variable inlet water temperature strategy was experimentally studied. As field test shows, the condition of variable outlet water temperature could satisfy the indoor cooling demmand. Compared with traditional ASHP cooling system adopting fixed 12 ℃ inlet water temperature, this kind of system is proved to be with higher COP and lower power consumption, and therefore is an obvious energy saving system. In addition, the Dymola model was established to verify the experimental results, and the simulation of energy consumption of actual air conditioning system was conducted based on the model. The results indicated that COP would improve 10 percent from 3.99 to 4.39.关键词：air source heat pump;variable inlet water temperature;Dymola simulation;refrigeration performance test;COP1845|2307|3发布时间：2024-07-18
- 摘要：In the vapor compression refrigeration system, the increasing subcooling degree of air conditioner can improve the refrigerating capacity and the coefficient of performance (COP). Based on the principle of thermoelectric refrigeration to increase the subcooling degree, the air conditioner with thermoelectric subcooler was designed in this paper. The performance of air conditioner was tested and compared before and after equipped with the subcooler in the following three operation conditions: the minimum cooling operation condition, the rated cooling operation condition and the maximum cooling operation condition. The results show that, the exit subcooling degrees of condenser at three operation conditions are improved by 2.3 ℃, 1.9 ℃ and 1.5 ℃, respectively. The refrigeration capacities of the air conditioner are increased 3.6%, 3.2% and 4%, respectively. Meanwhile, the COPs of the air conditioner are increased 3.7%, 3.1% and 4%, respectively. In the future, the performance of air conditioner can be improved by the optimization of operation conditions of thermoelectric element.关键词：air conditioner;thermoelectric refrigeration;degree of subcooling;energy efficiency ratio1927|2336|2发布时间：2024-07-18
- 摘要：This paper focused on the impact of outdoor heat exchanger polluted by atmospheric particulates on the system performance with the study object of 1.5 HP residential split-type air conditioner, and the fouling processes of copper tube-aluminum fin and aluminous microchannel heat exchangers were compared. Two sets of units assembled with different outdoor heat exchangers were continuously running in the same atmospheric environment. Capacity, power consumption, discharge temperature ,condensing temperature and plugging ratio were tested to analyze the influence of atmospheric particulate pollution on the long-time performance. The results show that the plugging ratio of outdoor heat exchangers grows exponentially , the refrigerating capacity of the air conditioners assembled with cooper tube-aluminum fin and aluminous microchannel heat exchangers is decreased by 2.1% and 23.2%, power consumption is jumped by 6.2% and 34.6% and COP is decreased by 7.8% and 43.1%. Research problems and direction of long-term performance of aluminous microchannel heat exchangers in air conditioners are pointed out．关键词：heat exchanger;long-term performance;atmospheric particulates;plugging1969|1968|1发布时间：2024-07-18
- 摘要：Testing system is built up to study the heat transfer characteristics of micro-structure and smooth surface under the conditions of different spray height and spray pressure. The experiment is carried out in a closed loop spray cooling system with water as the working fluid with high speed camera. The experimental results indicate that both the spray height and spray pressure play more significant role in the spray cooling performance of the micro-structure surface than smooth surface. When the spray height staying in a high level, decreasing it until the critical height as indicated can obviously improve the heat flux, acquire higher CHF; Continually reducing the spray height can still slightly improve the heat flux, but a large margin reduction of the spray height can result in a decrease of heat flux and even delay the time of transition to two phase region. Thus the influence of spray height has two sides, different from the spray pressure, whose effect is monistic. Increasing the spray pressure can improve the heat flux and enhance the uniformity of the temperature distribution, especially in single phase region, and the heat flux increase obviously until to a stable value with the increasing of spray pressure.关键词：spray cooling;spray height;spray pressure;CHF;temperature uniformity2194|2212|5发布时间：2024-07-18
- 摘要：The pulse tube refrigerator working at liquid nitrogen temperature is widely used in many fields, such as high temperature superconducting. Based on thermoacoustic theory, the phase shift ability of the inertance tube with/ without reservoir is investigated using DeltaEC. A pulse tube refrigerator model is built to investigate the effect of different inertance tube on cooling performance. The simulation results show that the inertance tube without reservoir would has close phase shift ability to the single-segment inertance tube with a reservoir. The pulse tube refrigerator connecting with double-segment inertance tube and reservoir gives a better cooling performance, in which lowest temperature would reach 48.8 K. At last, the test system is built to verify the simulation results.关键词：pulse tube cryogenic cryocooler;inertance tube;thermoacoustic;refrigeration performance test2158|2181|3发布时间：2024-07-18
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Study on Injuries of Porcine MII-stage Oocytes during Cryoprotectants Addition and Removal Processes
摘要：Cryoprotectants addition and removal are essential steps during oocytes cryopreservation, however, high concentration of cryoprotectants may cause osmotic and toxic injuries to oocytes. In order to study the injuries of porcine MII-stage oocytes during cryoprotectants addition and removal processes, cryoprotectant was loaded and unloaded to/from oocytes with traditional methods (one-step method, two-step method), the effects of vitrification solution, thawing solution and dilution solution on the survival rate of oocytes were investigated. The experimental results showed that the osmotic injuries to oocytes happened mainly in two stages: the transfer process from vitrification solution to thawing solution, and the cryoprotectants removal process. The concentration of thawing solution and equilibrium time had a great influence on the survival rate of oocytes. The cryoprotectants removal process was highly correlated with addition process, and the selection of thawing solution concentration and equilibrium time relied on the vitrification solution concentration and equilibrium time. These results could provide a reference for cryopreservation protocols of porcine MII-stage oocytes.关键词：cryopreservation;cryoprotectants;osmotic injury;oocyte1982|2081|2发布时间：2024-07-18 - 摘要：Falling film evaporation, which is one efficient technology of heat and mass transfer, has been used in air separation field. The principles and characteristics of the main downflow condenser/reboiler in air separation are analyzed, the dynamic characteristics of falling film are illustrated from the aspects of the wave characteristics and breakdown characteristics, the influence of inlet flow rate, wall structure, components of working medium and heat flux density on the heat and mass transfer are reviewed in this paper. The occurrence regularity of critical heat flux and the dynamic characteristics of the superheated surface rewetting with liquid film for the progress of falling film of cryogenic liquid nitrogen in the large space plate are emphasized，some available heat transfer correlations for the progress of falling film evaporation in the vertical channels are concluded. Due to the speciality of physical property and channel structure, there is a significant gap applying the existing heat transfer correlations of working medium with normal temperature to the main downflow condenser/reboiler in air separation field. At last, it is pointed out that the further study of falling film evaporation of cryogenic fluid in the complex narrow channel under the small heat transfer temperature difference is needed.关键词：air separation;condenser/reboiler;falling film;evaporation;heat and mass transfer2078|2257|2发布时间：2024-07-18
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