最新刊期
卷 35 ， 期 6 ， 2014
- 摘要：A theoretical model of CO2 gas cooler with PAG lubricant was developed. The heat transfer coefficient was predicted based on artificial neural network, and then the model was validated with experimental results. Further calculation shows that the thermal effectiveness increases with the length of the gas cooler tube, but the increase rate decreases gradually. Therefore, the length of the gas cooler tube should be properly designed considering the economical running in the practical applications. For the gas cooler with a smaller diameter (Dh ≤ 2 mm), a small amount of lubricant significantly deteriorates the thermal effectiveness while for that with a larger diameter (Dh ≥ 4 mm), the influence is not so apparent. Consequently, the oil concentration should be decreased as far as possible to keep high heat transfer performance of the small diameter gas cooler. The gas cooler performances better at higher CO2 side pressure. However, the increase rate of the thermal effectiveness decrease gradually as the pressure increases. At pressure approaching to the critical pressure, the degradation of the thermal effectiveness is more significant. Additionally, the deterioration is more apparent as the diameter decreases.关键词：CO2 gas cooler;heat transfer coefficient;lubricant oil;artificial neural network2062|1986|0发布时间：2024-07-18
- 摘要：The theoretical model of the multiple micro-channel parallel flow condenser is established based on the method of distribution parameters, and validity of the model is verified by comparison with the experimental data. Based on this model, the effects of fin height, fin pitch, louver pitch and louver angle on the heat transfer and flow performance of multiple micro-channel parallel flow condenser are investigated. The results show that, as increasing of fin height, the heat transfer rate increases, but the air-side pressure drop decreases; when fin pitch increases, or louver pitch increases, the heat transfer rate and air-side pressure drop all decrease; as increasing of louver angle, the heat transfer rate and air-side pressure drop all increase.关键词：parallel flow condenser;mathematical model;variable structure1929|2292|0发布时间：2024-07-18
- 摘要：In this paper, non-condensable gas (N2) was added to CO2 transcritical refrigeration cycle as additive. And the the effect on refrigerant performance is studied by theoretical analysis and computer simulation. The major thermophysical parameters of CO2 and N2 are analysed. The addition of N2 results in the change of the thermophysical parameters of CO2. The calculated results have shown that additives can increase saturation pressure and liquid specific heat of CO2, but reduce viscosity coefficient, surface tension, the liquid/vapor density ratio and coefficient of thermal conductivity of CO2. N2 can increase gas nucleus in evaporator, and leads to heterogeneous nucleating process in liquid. So the nucleation temperature decreases and heat transfer coefficientis increases. Moreover, the discharge temperature and specific power of compressor are reduced and refrigeration efficiency improves. The more the N2 is added in the system, the more the refrigeration system performance coefficient increases. The paper provides theoretical basis for the research on highly efficient application of CO2 refrigeration system.关键词：refrigeration system;performance analysis;non-condensable gas;nucleate boiling2005|1962|0发布时间：2024-07-18
- 摘要：To enhance the energy efficiency in the liquefied natural gas (LNG) vehicles, thermoelectric generator (TEG) is suggested in recovering the waste heat of the exhaust gas (EG) and the cold energy of the LNG. The TEGs here get higher efficiency than conventional ones, for they work with heat sinks at cryogenic temperatures and there are large temperature differences between EG and LNG. Based on the analyzing of the typical fuel system in the small LNG vehicles, two recovery systems for the LNG vehicles are proposed and the correlative parameters of systems are calculated and analyzed. The generation efficiency of TEGs is calculated and the recovery power of each system is analyzed. It is concluded that the output power of the vaporizer system is larger than that of the self-warming system; TEG with optimized multi-layer material brings larger output power than that with single-layer material for both systems.关键词：thermoelectric;fuel system;liquefied natural gas;vehicle2038|2048|0发布时间：2024-07-18
- 摘要：Ice and compression refrigeration are normally used to preserve caught fish on fishing vessels. At the same time, waste heat dissipated in hot exhaust gas on fishing vessels is rejected to the atmosphere. Utilizing the vast amount of the waste energy for refrigeration is both economical and energy saving. Three kinds of heat driven refrigeration cycles as adsorption, absorption and ejection are introduced in this paper. Advantages and disadvantages of the three cycles are analyzed based on the working condition of ice making on fishing vessels. Emphases have been made on the feasibility of transforming the existing compression refrigeration cycle on fishing vessels by ejection technology. The result shows that 54.5% of fuel for refrigeration system can be saved after combining ejection and compression cycle and the transforming cost can be recovered in 1 year.关键词：refrigeration;cascade refrigeration cycle;eject refrigerating cycle;refrigerated ship1878|2474|0发布时间：2024-07-18
- 摘要：Heat pump intermittent drying(HPID) is an energy-efficient process with high quality products. It is necessary to carry on a further research on its optimal process. A heat pump drying model was built for the cabbage seed with heat pump drying. It included the heat and mass transfer models of the drying air and those of the cabbage seed. The simulation results were used to form the heat pump unit performance index and the dried product performance index. The fuzzy analytical hierarchy process method was used to obtain the optimal HPID process excelling in both the heat pump unit performance index and the dried product performance index. Results show that the HPID with drying period of 3000 s, proportion of 1/6 can obtain the best comprehensive performance for the cabbage seed.关键词：heat pump;intermittent drying;optimization1971|2379|0发布时间：2024-07-18
- 摘要：Seawater source heat pump system (SWHP) is a renewable energy utilization system. But it is lack of practical application study about the system up to now. In this study, a SWHP system in coastal area of the northern Yellow Sea was measured. The winter measurement results showed that the average heating COP of a heat pump unit and the whole system were 2.43 and 1.86 respectively during the measurement period while the corresponding COP were 2.99 and 2.30 respectively during the whole heating season. The summer measurement results showed that the average cooling COP of the system was 3.35 during the measurement period．This paper further analyzed the major cause of the low free cooling system COP, and it is that the fan coil units are not selected by actual seawater temperature, which leads to the low supply and return water temperature difference (only 1 ℃) and high circulating pump energy consumption.关键词：renewable energy;SWHP;district cooling and heating;energy-saving analysis1980|2093|0发布时间：2024-07-18
- 摘要：Cool-storage density is one of the most important parameters for evaluating the performance of refrigerant hydrate. A calorimetric device was set up and a mixing calorimetry method was established to measure the cool-storage density of hydrate slurry according to the law of energy conservation. The cool-storage densities of hydrate slurries formed from R141b/H2O coarse mixture and R141b/H2O microemulsion were measured within 4-12 ℃. The results are 49.6 kJ/kg and 99.1 kJ/kg, which are about 1.5 times and 3 times of that of water, respectively. Volume of storage tank could be reduced significantly by utilizing refrigerant hydrate slurry instead of water.关键词：hydrate slurry;cool-storage density;mixing calorimetry;R141b1914|2186|0发布时间：2024-07-18
- 摘要：Though metro in China today is booming, the typical refrigeration system for metro train air-conditioning is at quite lower energy efficiency level (COP = 2.2-2.3) in comparison with the residential systems under the same operating conditions. A refrigeration system model was developed to predict the metro train air-conditioning system performance. The predictions agreed well with the experimental data. Based on comprehensive modeling and analysis, the refrigerant circuitries of condenser and evaporator were optimized and smaller capacity compressor of higher COP was adopted. Consequently, the optimized system COP increased 21.7% at almost the same cooling capacity and cost. At last, the refrigerant R407C was replaced by R410A and the system were accordingly redesigned, which brought additional 11.3% COP increase and achieved 3. The present method and results could be valuable for designing high performance air-conditioning system of the metro train.关键词：metro train;air-cooled air conditioner;refrigerating system;refrigerant;energy efficiency ratio2011|2099|0发布时间：2024-07-18
- 摘要：The experimental and theoretical researches have been carried out to get the flow boiling heat transfer characteristics of CO2 as a refrigerant in horizontal mini-channel. Based on infrared thermal imaging tests and experimental study on heat transfer coefficients, the heat transfer coefficients of refrigerant are analyzed qualitatively and quantitatively in follow conditions: Heat flux: 2-35 kW/m2,Saturation temperature: ﹣10 ℃-15 ℃, mini-channel inner diameter:1mm or 2 mm. Primary conclusions can be drawn from the results of experiments: The increase of heat flux enhances the nucleate boiling heat transfer of refrigerant inside mini-channel, which leads to the remarkable increase of heat transfer coefficient; the heat transfer coefficient doesn’t always monotonely vary with the saturation temperature: when the saturation temperature is high and even close to the critical temperature of CO2, the heat transfer coefficient rises with the increase of saturation temperature; when the saturation temperature is low, the heat transfer coefficient rises with the decline of saturation temperature. Besides, during the heat transfer process, the dryout quality monotonely falls with the rise of saturation temperature.关键词：mini-channel;heat transfer coefficient;heat flux;saturation temperature;dryout1976|2015|0发布时间：2024-07-18
- 摘要：Lithium bromide absorption refrigeration testing with an electric vibrating system was established. Making use of the testing, performance of major parts of LiBr absorption chiller is analyzed. The main purpose is to analyze the effect of vibration on the performance of heat transfer and cooling during absorption refrigeration. The results indicate that compared with static conditions, the heat transfer property of the absorber and the evaporator has a better performance under vibrating conditions. The vibration contributes to heat transfer enhancement, increases refrigerating capacity and improves the COP.关键词：absorption refrigeration;vibration;heat transfer;enhance2299|2337|0发布时间：2024-07-18
- 摘要：The bubble pump theoretical model was correspondingly established based on drift flow model theory. The analysis was performed on the working characteristics of the bubble pump operating under adiabatic slug flow condition in Einstein refrigeration system. The experiment was conducted on the steady-state process of the bubble pump with saturated water as the working fluid. The bubble pump resistance loss coefficient was fitted with the theoretical calculation data and experimental data of bubble pump by the least square fitting. The theoretical model of bubble pump was corrected to acquire the new empirical correlation, which was verified in terms of credibility .The results show that the experimental result is in reasonable agreement with the theoretical calculation of correction values. The data error of resistance loss coefficient fitted is within 5.3% and the correction results have strong accuracy and feasibility, which perfect the theoretical model of bubble pump. The conclusion provides a theoretical guidance for the optimal design of the bubble pump, which also means a valuable reference for the further research of the bubble pump performance in Einstein refrigeration system.关键词：Einstein refrigeration cycle;bubble pump;parameter fitting;resistance loss12525|15775|0发布时间：2024-07-18
- 摘要：Proposed two new type of solar absorption refrigeration system, analyzed their performance compared with the traditional system under a reasonable set of conditions. The results show：when the sun radiation intensity is high（0.95kW/m2），the cooling capacity of the new system（A type）is 1.6times the traditional system，the other new system（B type）is 3.07times the traditional system，when the sun radiation intensity is low（0.2 kW/m2），the cooling capacity of the new system（A type）is decreased by 70% compared to high radiation intensity conditions，the other（B type）is decreased only by 42.3%，and the traditional system could not provide refrigeration；two new solar refrigeration systems can operate stably by regulate the water flow or compressor speed with solar radiation intensity varies；under the same evaporation and condensing temperature，R600a heat pump system has higher COP and less power consumption than R134a heat pump system under obtaining same cooling capacity；two new type of system was proved viable and economic through economy analysis.关键词：solar energy absorption refrigeration system;performance analysis;refrigerating capacity;coefficient of performance;power consumption2306|2618|0发布时间：2024-07-18
- 摘要：During the electricity defrosting of air cooler, some issues would arise, such as that temperature field would be damaged, energy would be lost , the refrigeration load would be increased, so a set of electric isolation device was designed. At the typical operating condition that cold storage temperature is -18 ℃, electric defrosting of air cooler was studied after using the partition device. Then the questions that how the partition board to influence the cold storage temperature, the temperature field around the air-cooler and the consumption of electric heating defrosting was studied through comparing the experimental data whether the defrosting partition device was used or not. The results indicate that after using the partition device, the variation of cold storage temperature is reduced, the maximum change is decreased by 5 ℃; ambient temperature uniformity around the air cooler is improved, the maximum change is increased by 10 ℃; defrosting energy consumption is reduced by 1/3. So the energy utilization rate for electricity defrosting was improved when partition board was applied.关键词：cold storage;defrosting;partition device;experimental study1959|2058|0发布时间：2024-07-18
- 摘要：With the improvement of electronics performance, the problem of heat dissipation in circuit and chip is becoming more serious, development of high-efficiency electronics cooling systems is urgently needed, and vapor compression refrigeration is believed to be the most promising one. Based on a miniature vapor compression refrigeration system for electronics cooling, when cooling load is fixed as 101.4 W, the impacts of refrigerant charge and capillary length on the refrigeration system, including system pressure, cooling effects of evaporator, power consumed by compressor and coefficient of performance, are studied through experiments. The results show that the increase of refrigerant charge or reduced capillary length will result in higher evaporation pressure, the surface temperature of heat sinks and the power consumption of the compressor will increase, then the coefficient of performance will decrease. When refrigerant charge is 120 g and capillary length is 3m, the overall performance of the experimental system is optimal, temperature of the two heat sinks can be maintained at about 12 ℃, the power consumed by compressor is 41 W, and COP can reach 2.48.关键词：electronics cooling;vapor compression;miniature refrigeration system;refrigerant;capillary length2518|3339|0发布时间：2024-07-18
- 摘要：Based on the model of separated phase flow in two-phase flow, a bubble pump performance test system with water as the working fluid was built to study the performance of guided bubble pump at atmospheric pressure with different lift-tube diameter by theoretical and experimental method. The bubble pump performance is studied under the condition of heating power in 100 ~ 650 W, immersion ratio between 0.2 ~ 0.4, riser diameter at 7 mm, 9 mm ,11 mm, 13 mm and 16 mm, and riser length at 600 mm. The results show that the submergence ratio plays a key role for the lifting capacity of bubble pump; Ascension within a certain range lift-tube diameter can significantly improve the liquid lifting capacity; when the pipe diameter exceeds critical value, not only the liquid lifting capacity is reduced, the bubble pump efficiency is also sharply reduced. It can be seen from the cases that the lifting capacity difference of 11 mm and 16 mm can reach to10.23 g/s, and lifting capacity is decreased by 61.15% while the pipe diameter increases by 5 mm when the heating power is 300W.关键词：guided bubble pump;lift-tube diameter;two-phase flow;separated phase flow model;Einstein refrigeration12828|16862|0发布时间：2024-07-18
- 摘要：An innovative dual-temperature air conditioning system and the corresponding mixed theoretical refrigeration cycle were proposed. The new air-conditioner consists of an air handling unit and a metal radiation panel as its dual-temperature evaporators, a compressor, a condenser, two thermal expansion valves and an ejector. The state properties in the air handling process and the theoretical refrigeration cycle were analyzed and compared with those of the conventional air conditioner with fresh air. Results indicate that the coefficient of performance（COP）of the dual-temperature theoretical refrigeration cycle may be improved by 13.73% to 7.43. But the COP of the dual-temperature refrigeration cycle will drop by somewhat as the amount of fresh air required and indoor moisture increases. However, it is still greater than the COP of the conventional air conditioner by 5.21%.关键词：dual-temperature air conditioner;mixed refrigeration cycle;COP;ejector;metal radiation panel2383|2263|0发布时间：2024-07-18
- 摘要：This paper demonstrated the importance of consistency on nominal working conditions in positive displacement compressor standards. Based on summarizing the status of standards for positive displacement refrigerant compressor in USA, Europe and China, the nominal conditions in these standards are contrasted. Key parameters such as evaporation temperature, condensation temperature of existing standard condition are inconsistency. Research progress of American and Chinese standard is introduced. Summed up the revision of compressor standards that key parameters are in the direction of consistency, and more in line with the actual application of the compressor. Nominal conditions harmonization for positive displacement refrigerant compressor in China is related research ideas are discussed.关键词：positive displacement refrigerant compressors;nominal condition;harmonization;standards1927|2322|0发布时间：2024-07-18
- 摘要：In recent years, Momordica fruit, as a kind of high nutritious fruit, has been developing rapidly in Vietnam. However, the drying studies for Momordica fruit is lacking. In this paper, the heat pump low temperature drying of Momordica fruit were studied and the optimum drying parameters of Momordica fruit were obtained. The nutrient components of momordica fruit were analyzed after drying. The results show that when the wind speed is constant and the air temperature is increased, the drying time is decreased, the sensory evaluation become worse and the loss of carotene is added; when the air temperature is constant, the higher the wind speed is, the shorter the drying time for Momordica fruit, and the worse the sensory evaluation, and the greater the loss of carotene; The optimum drying process parameters for Momordica fruit were air temperature 50 ℃and wind speed 10 m / s.关键词：momordica fruit;heat pump low temperature drying;wind temperature;wind speed1871|2669|0发布时间：2024-07-18
- 关键词：refrigerator;condenser fan;deflecting ring;energy consumption;noise1807|2413|0发布时间：2024-07-18
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