最新刊期
卷 33 ， 期 5 ， 2012
- 摘要：Based on sustainable development concept, consideration of natural quality of refrigeration system, a new evaluation methodology has been proposed for the environmental performance of refrigeration and heat pump system with conjunction of the natural quality and the thermodynamic perfectibility. According to the quantitative results of refrigeration nature degree evaluation indexes, there is large room to advance the natural quality of each system. And using the natural quality methodology to evaluate the refrigeration system can show the direction for improving the system.关键词：pyrology;nature degree;thermodynamic perfectibility;refrigeration;heat pump1827|2258|0发布时间：2024-07-18
- 摘要：Data center is a specific building space accommodating and managing data processing equipments which rely on the thermal environment for continuous operation. Based on the review of current research on evaluating thermal environment in data center, this paper defines a dimensionless index to evaluate the effect of air mixing on the equipment and characterize thermal security in local space of data center. This mixing index emphasizes on evaluation of thermal security (or failure potential) of data center environment, which is different from current evaluating system based on average inlet air temperature of data processing equipment. Through the distribution of such a mixing index, not only the distributed characteristics of data center air flow can be understood, places of potential hot spots or overheated space can be located and improved accordingly. Thermal environment of data centers with different building area, equipment layout and air flow pattern can be directly compared using heat weighted mixing index which also helps to guide the thermal design of new data centers and thermal optimization of existing data centers.2208|2533|0发布时间：2024-07-18
- 摘要：According to life circle assessment theory, the environmental effect indicators and corresponding quantification method were introduced in this paper. Then a household air conditioning was taken as an example, and its environmental effect on human health, ecosystem quality and resource consumption were analyzed. Meanwhile, emission of greenhouse gases and polluted gas were carried out. The results show that its total environment indicator score is 690 Pt. Score on ecosystem quality (502.65Pt) is the highest, and score on resource consumption (89.46Pt) is the lowest. Because of electrical power consumed, the operation phase has the most influence indicator score on environment, which reaches to 681Pt. To reduce the environmental impact, more attention should be paid on power saving and new energy utilization. Finally, during life circle of a 1.5p household air conditioning, its CO2 emission is 1.89×104 kg and SO emission is 78.017kg. The evaluation results provide necessary information to air conditioning industry to improve the environment characteristics of air conditioner and supply the valuable information for the environmental decision-making to customers, which makes them consider the cost of the technical characteristics and also consider the environmental impact.关键词：pyrology;environmental assessment and quantification method;life circle assessment;household air conditioning1893|2180|0发布时间：2024-07-18
- 摘要：Experimental studies on the transcritical CO2 two-phase ejector refrigeration cycle were carried out, and the effects of the working conditions and the geometric parameters of the ejector on the performance of the system were analyzed. The experiment results indicate that the COP and cooling capacity of the system increase with the rise of the cooling pressure, while decrease with the increase in the outlet temperature of the gas cooler. For the systems using different throat diameter of the nozzles, the COP of the system using the larger throat diameter of the nozzle is larger than that using the smaller one under the same condition. For systems using different diameter mixing chambers of the ejector, with the increase in the cooling pressure, the COP of the system using the smaller diameter of the mixing chamber varies greatly, and is lower than that of the system using the larger one under the lower cooling pressure condition. While under higher cooling pressure condition, the performance of system using smaller diameter of the mixing chamber is better. The COP of the transcritical CO2 refrigeration cycle with a two-phase ejector is increased by 14% comparing to the traditional cycle at the same condition.关键词：pyrology;ejector refrigeration system;two-phase flow;carbon dioxide1862|2218|0发布时间：2024-07-18
- 摘要：A new thermoacoustic refrigerator which is driven by a double-acting traveling-wave thermoacoustic engine have been researched and designed. Through numerical simulation, we optimize the structure parameters of the refrigerator. Under the design conditions, the new refrigerator reaches a COP of 2.74, a relative Carnot efficiency of 60%, a consumed P-V power of 534W, and a cooling capacity of 1464.9W. In addition, a traditional Stirling refrigerator and the new thermoacoustic refrigerator with double-action operation are calculated and compared for operating pressure ratio, efficiency, cooling capacity and other features, and the simulated results show that the new thermoacoustic refrigerator is very efficient and suitable for coupling with a double-action, traveling-wave thermoacoustic engine. Thermoacoustic refrigerator with double-action operation has good potential as an alternative of ordinary refrigeration technology due to intrinsic high efficiency heat driven mechanism, no moving components and environmental friendliness, etc.关键词：pyrology;refrigeration & cryogenics;thermoacoustic refrigerator;double-action1912|2115|0发布时间：2024-07-18
- 摘要：Liquid-vapor separation condenser (LSC) is a kind of heat exchanger with high in-tube condensation heat transfer coefficient. It adopts some enhancement means, such as the parallel flow condensation with multi tube passes, draining away condensate between two adjacent passes and optimization of the tube number of refrigerant route. In the present paper, the LSC was applied in an HFC410A air conditioning system and measured in the standard air enthalpy difference lab. Compared with the prototype HFC410A system, the cooling capacity and EER of the LSC system were 96.4% and 93.8% respectively. The results present the LSC is a poor substitution for the original condenser. The analysis shows HFC410A reduced the performance of LSC by weakening the liquid-vapor separation effect, which results in the condensation process in HFC410A LSC no longer keeping the quasi-constant wall temperature as that in the HCFC22 LSC. The looping refrigerant mass flux in the HFC410A system was 1.2%~9.2% lower than that of HCFC22 system at the same condensation temperature, and the pressure drop of the LSC in HFC410A system was seen to increase by 39.1%~52.6%.关键词：pyrology;refrigerating performance;enthalpy difference method;liquid-vapor separation condensation1832|2211|0发布时间：2024-07-18
- 摘要：Based on China National Standard-Number Designation and Safety Classification of Refrigerants, refrigerant for the cascade water-to-water heat pump were selected according to principles of environmental-friendly, safety and thermodynamic cycle performances. Different refrigerant combinations for high- and low-temperature cycles in the cascade heat pump were calculated and compared. Results show that combinations of R245fa/R134a, R245fa/R420A, R245fa/R413A, R245ca/R420A are better for the cascade heat pump. It also shows that, considering easy access and economy of refrigerants, R245fa/R134a combination will be a better choice.关键词：engineering thermophysics;cascade heat pump;refrigerant;heat pump1737|2101|0发布时间：2024-07-18
- 摘要：Based on Peng-Robinson general state equation, combined with group contribution principle and a polynomial method, the thermal state model of the new LGWP refrigerant HFO-1234yf was established and validated with required accuracy. By using the computer programming, the state models were solved by a mathematic software and a complete thermal properties of refrigerant were obtained. The thermal properties of HFO-1234yf were compared with R417A and R134a, and the results showed that the saturated vapor pressure and the specific heat capacity under constant pressure of HFO-1234yf has a similar performance with R134a. Both The saturated vapor pressure of both HFO-1234yf and R134a are lower than R417A, and the saturated state enthalpy of HFO-1234yf is lower than R417A, which would lead that the HFO-1234yf system can not have a higher performance coefficient. The models could act as a theoretical basis for the application of HFO-1234yf in automotive air conditioning and fixed refrigeration equipment.关键词：engineering thermophysics;hfo-1234yf;thermal properties simulation;alternative refrigerants;LGWP1876|2436|0发布时间：2024-07-18
- 摘要：Heat exchangers including condenser and evaporator are important equipments in the compression type refrigeration and air conditioning units, and their heat transfer coefficients have a direct effect on the efficiency and cost of the units. The application of the heat transfer enhancement technology is a key route to improve the heat transfer performance of the condenser and evaporator. For the condensation heat transfer enhancement on the tube outside of condenser, the fractured fins of Turbo-C can be separated from the tips to the roots to reduce the effect of the viscous property of condensate on the heat transfer performance at the presence of surface tension. The replacement of the segmental baffles with the helical baffles can improve the flow characteristics and heat transfer performance of the condenser and dry evaporator. Considering the different heat transfer characteristics between the falling film regions and the flooded evaporation regions in the falling film evaporator, different types of enhanced tubes should be used to improve the heat transfer performance of the evaporator.关键词：pyrology;heat transfer enhancement;condenser;evaporator;refrigerant and conditioning units1698|2046|0发布时间：2024-07-18
- 摘要：The three dimensional physical model and mathematical model of turbulent flow and heat transfer in the channel of honeycombed plate heat exchanger were established, and the corresponding flow field and temperature field was numerically simulated. The heat transfer and pressure drop characteristics of the channel were investigated under different Reynolds number. The computed results showed that both the heat transfer coefficient and pressure drop of the channel were obviously increased along with Reynolds number. On the other hand the characteristics of heat transfer and pressure drop of the channel were compared with that of the parallel plate channels. At last, the mechanism of the heat transfer enhancement was analyzed according to fields synergy principle.关键词：engineering thermophysics;honeycombed plate;heat transfer enhancement;numerical simulation;field synergy1858|1836|0发布时间：2024-07-18
- 摘要：This study focuses on the velocity changing characteristics of the horizontal piston wind valves on both sides of the subway station by on-site measurement under winter condition. It has been found that the valve velocity in train-arriving direction presents three typical phases while the valve wind speed in train-leaving direction has two distinct processes. The velocity duration in each phase is investigated and the related ventilation volume is calculated. It has been revealed that the velocity duration of the valve on train-leaving end is longer than that of the valve on train-arriving end. Besides, the maximum and the average velocity values of the valve on train-leaving end are much higher too. It is concluded that, compared with the two single shaft condition, the dual shaft condition has the biggest ventilation volume and the best air-changing effect. The next recommended condition is the single shaft design on train-leaving end.关键词：municipal engineering;field-measurement;train-arriving end;train-leaving end;horizontal piston wind valve;ventilation volume1963|1830|0发布时间：2024-07-18
- 摘要：In order to provide hot water supply for room and full fresh air conditioning for supermarket in a hotel efficiently, combined system between air source heat pump for direct hot water supply and full fresh air conditioning system was designed and implemented, and its matching algorithm was introduced. After using energy storage equipments as hot water storage tanks and cold storage air-conditioner cabinet, and applying PLC system for data acquisition and heat pump heating time control, a solution to the unbalanced load between heating and cooling was proposed. The running state and operating performance in a full year was tested. The results indicated that the system not only satisfied the requirement of hot water supply for room, but also realized the purpose of full fresh air conditioning for supermarket in the hotel. The average synthesis energy efficiency ratio in a year is over 4.7. The practice provided an example of air source heat pump system for combined heating and cooling supply.关键词：municipal engineering;air source heat pump;combined heating and cooling;direct hot water supply;full fresh air conditioning;synthesis energy efficiency ratio1634|2017|0发布时间：2024-07-18
- 摘要：Phase change storage(PCS) system added into the cold storage can stabilize the temperature of the cold storage, extend the preservation time, and achieve a good economical efficiency combined with the peak-valley price. Storage boards were installed as a test system in an incubator, which are filled with water, and the volume ratio between the PCM and the incubator is 1:30. By analyzing the insulation effect, the temperature distribution and the temperature difference between the PCM and air, the experimental data showed that the cold storage with phase change storage system had a temperature fluctuation of 0.6℃ and the maximum temperature difference is 1.1℃, so it can satisfy food fresh-keeping demands and achieve good economical efficiency. This result is important for the phase change storage system to be used in the cold storage.关键词：pyrology;phase-change;storage board;experimental study1593|1949|0发布时间：2024-07-18
- 摘要：The degradation of cellulose membrane, and the application of cellulose membrane in fresh vegetables are mainly investigated through studying its permeability, moisture permeability, and preservation. The results show that: 1 ) Different microbial has different degradation rate to cellulose membranes; 2 ) Cellulose packaging film’s degradation performance is the best that it can be depredated fully after three days by inoculating Penicillium; 3 ) Cellulose packaging film’s permeability is better than plastic film, resulting in the poor effects of green color and anti- browning when preserving fresh vegetables; 4 ) Cellulose membrane has so strong water vapor permeability that it’s water retention is worse than the plastic packaging film.关键词：food packaging and storage;preservation;biodegradable plastic wrap;fresh-cut vegetables1601|2073|0发布时间：2024-07-18
- 摘要：Various experiments were conducted to measure the temperature and flow rate of a Joule-Thomson cryostat corresponding to different precooling temperatures of nitrogen and thermalload. The results demonstrated that the steady-state temperature of cryoprobe changed with precooling temperature, and that the greater the thermal load, the lower the requisite precooling temperature of the nitrogen passing through the Joule-Thomson cryostat. The experiments further indicated that too low precooling temperature of nitrogen is not necessary as it may cause a great waste of nitrogen and lower heat exchanger efficiency; and the nitrogen flow rate increased as the outlet temperature of supply nitrogen decreased. The calculated results of nitrogen flow rate correlated well with the experimental measurement.关键词：pyrology;joule-thomson cryostat;cryoprobe;cryoablation2019|2332|0发布时间：2024-07-18
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