最新刊期
卷 32 ， 期 6 ， 2011
- 摘要：This paper briefly reviews the developments of hydrogen liquefaction systems. The main hydrogen liquefaction processes worldwide and the production status are summerized. It is found that all the large-scale hydrogen liquefaction systems in use are based on the modified Claude cycle with precooling in which the exergy efficiency is only 20%~30%, but the exergy efficiency of the innovation processes can be reach 40%~50% science 1998. The effects of the hydrogen properties on the efficiency and performance of liquefaction are further discussed. Finally, the development of hydrogen liquefaction system is prospected from the aspects of improved processes and efficient equipments.关键词：pyrology;Hydrogen;Liquefaction cycle;Equipment;efficiency2035|2816|0发布时间：2024-07-18
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Nucleate Pool Boiling Heat Transfer Characteristics of Refrigerant/Oil Mixture with Carbon Nanotubes
摘要：Influence of carbon nanotubes (CNTs) on nucleate pool boiling heat transfer characteristics of refrigerant-oil mixture was investigated experimentally. Four types of CNTs with the outside diameters from 15 nm to 80 nm and the lengths from 1.5 μm to 10 μm were used in the experiments. Test conditions include CNTs mass fractions in the CNTs nanolubricant from 0 to 30 per cent and CNTs nanolubricant mass fractions from 0 to 5 per cent. The experimental results indicate that the presence of CNTs enhances the nucleate pool boiling heat transfer coefficient of R113-oil mixture by a maximum of 61% under the present test conditions. For fixed CNTs physical dimension, the enhancement range changes from 27%~59% to 23%~55% when CNTs nanolubricant mass fraction increases from 1% to 5%; the enhancement range changes from 27%~59% to 33%~61% when CNTs mass fraction in the CNTs nanolubricant increases from 20% to 30%. A correlation for predicting the nucleate pool boiling heat transfer coefficient of refrigerant-oil mixture with CNTs is proposed, and it agrees with 96% of the experimental data within a deviation of ±10%.关键词：engineering thermophysics;carbon nanotubes;correlation;Nucleate boiling;oil;refrigerant1889|2104|0发布时间：2024-07-18 - 摘要：In this paper, recent study on dryout of CO2 during flow boiling heat transfer process is described including the effect of heat flux, mass flow, saturation temperature and diameter of tube, as well as the generation mechanism of dryout phenomenon. Study of critical heat flux, transform of flow type, prediction of dryout vapor quality and measures to suppress dryout occur will become the focus in the future.关键词：engineering thermophysics;flow boiling;Thermophysical properties of CO2;heat transfer characteristics;dryout1940|2166|0发布时间：2024-07-18
- 摘要：In design and calculation of scroll compressor with symmetrical circular arc plus line-shaped top profile, rotating angle of crankshaft at the very moment when centre compression chamber is formed is totally different from that at the beginning of the discharge. There is no complete and distinct elaboration about the two kinds of angles yet, so it may cause large errors in calculating different compression chambers.Through in-depth research on the geometric property of scroll compressor with symmetrical circular arc plus line-shaped top profile, mesh-apart angle and discharge angle are defined and distinction between them is illustrated. According to the feature that reduction of centre compression chamber is due to an increase in wall thickness of top profile, the calculation formula of mesh-apart angle is derived elaborately and the methods to calculate the expanded volume of wall thickness of top profile and discharge angle after modification are presented. The difference between mesh-apart angle and discharge angle is verified through calculation example, it is mentioned that discharge angle of scroll compressor can make an impact on design of discharge port.关键词：pyrology;scroll compressor;Symmetrical circular arc plus line-shaped;Mesh-apart angle;Discharge angle2080|2183|0发布时间：2024-07-18
- 摘要：In order to shed light on how degree of suction gas superheat affects rotary compressor(R22) performances, elaborate experiments were conducted by means of secondary fluid calorimeter test. The results show that, while both of suction and discharge pressures are fixed, mass flowrare can be corrected only by suction gas density when the degree of suction gas superheat is positive, whereas the volume efficiency decline should also be taken into account when the degree of suction gas superheat is negative; and the input power has nothing to do with the degree of suction gas superheat. The above conclusions will help to amend the degree of suction gas superheat in 10-coefficients performance model of rotary compressor.关键词：pyrology;Rotary compressor performance;experimental investigation;Suction gas superheat2078|2637|0发布时间：2024-07-18
- 摘要：In order to clarify the mechanism of secondary nucleation of iceinduced by ultrasound, experiments on ice crystals in degassed sucrose solutions and untreated solutions have been carried out using a novel ultrasonic cold stage device. For each experiment, the ultrasonic waves operated at a power output of 120W. The results show that the ice dendrite crystals growing in a sucrose solution can be broken up into smaller fragments when ultrasound was applied for 2 s, but the pre-existing ice dendrite crystals in a degassed sucrose solution are still unbroken when ultrasound was applied for 6 s. These findings confirm that cavitation induced by ultrasound is a major factor for the fragmentation of ice crystals.关键词：pyrology;Nucleation;ultrasound;Cavitation;ice;Solution2113|2295|0发布时间：2024-07-18
- 摘要：Under the given conditions, the system performances of R744/R600 and R744/R600a to substitute for conventional refrigerant R22 in a subcritical heating cycle were theoretically analyzed respectively with consideration of heat transfer pinch point in heat exchangers. Results show that R744/R600 and R744/R600a have different optimum mass fraction of which the system works with the maximum heating coefficient of performance (COPh). Compared to R22 system, the optimum COPh of R744/R600 and R744/R600a are increased by 11.98% and 8.24%; and increased by 36.43%, 36.24% compared to pure R600 and R600a; increased by 7.07%, 4.71% compared to pure R744 system in a transcritical cycle respectively. With the optimum mass fraction, condensation pressures of R744/R600 and R744/R600 are 0.84MPa and 1.18MPa lower than that of R22. Discharge temperatures are below 90℃ which are also lower than that of R22.关键词：pyrology;Zeotropic mixture;heat pump;R744/R600;R744/R600a;Heat transfer pinch point2818|4880|0发布时间：2024-07-18
- 摘要：A heat pump with economizer was studied under the following experimental conditions: inlet air dry-bulb temperature was -15℃, RH was 60%,while inlet water was 47.5℃. Data was obtained by change opening of electronic expansion valve in the injection pipe line. Result shows that there is an optimum opening for the system. The characteristic of optimum opening was analyzed and concluded as follows: lowest temperature of discharge and suctionand lowest temperature differential between electronic expansion valve’s outlet in injection pipe line and the injection point of compressor.关键词：pyrology;heat pump;economizer;Characteristic study2086|2586|0发布时间：2024-07-18
- 摘要：Combining with a ground source heat pump project in Nanjing, the key issues of Geo-thermal response test are analyzed and the normative test methods and steps are summarized. Vertical double U-tube test wells are taken as testing apparatus, and local soil thermal parameters are collected through field test of two test wells with depth of 100m. Furthermore, the original ground temperature and the inlet and outlet water temperature response curve of the underground heat exchanger are also obtained, which are used to determine the heat exchange quantity of per well depth and other parameters. It is concluded from data analysis: the original ground temperature is 17.95℃; the heat exchange quantity of per well depth is 69.6W/m under summer conditions (35℃) and 51.2W/m under winter conditions (5℃). All of those conclusions prove that comprehensive geological conditions of the project area are suitable for the use of ground source heat pump air conditioning system.关键词：engineering thermophysics;Underground heat exchange system;Geo-thermal response test;Engineering design2063|2702|0发布时间：2024-07-18
- 摘要：Currently displacement ventilation(DV) and cooling ceiling (CC) system has two main disadvantages: condensation when the radiant panel temperature is lower than the dew point temperature of air around it, and the downdraft from the cooling ceiling. Through theoretical analyses, the paper puts forward a method to avoid condensation and downdraft: the radiant panel is covered and airproofed with the film whose long wave transmittance is high, and there is a layer of air or vacuum between the undersurface of panel and the film. The experiment system was designedwith long wave transmittance film, and the capability of the new system was validated through the experiment. It is shown that with the same ambient environment, the indoor temperature in DV/CC system with film is 1.8% higher than that in tradition DV/CC system, and the contaminant concentration is 60% decreased under the breathing zone and 40% decreased above the breathing zone, respectively关键词：municipal engineering;Cooling ceiling;displacement ventilation;Condensation;Downdraft;Film1981|2237|0发布时间：2024-07-18
- 摘要：The new agreement about “accelerate the phase-out of production and consumption of hydro-chlorofluorocarbons (HCFCs)” on the 19th meeting of the Parties to the Montreal Protocol put much more pressure on Chinese refrigeration industry. On the basis of message gotten from the conferences organized by UNIDO in Vienna in 2008 and UNEP in Cairo in 2010, the author summarized the research progress in the HCFCs replacement in recent years in the world. EU have been developing natural refrigerants, such corporations as Dupont are researching and propagating the good performances of HFO-1234yf, DR-2, etc., while the countries in Africa and south-east Asia put more attention to where to get the refrigerant replacement technology and the fund. As for China, besides R32 being considered as a interim refrigerant suitable for China's actual conditions, more works should be done on the development of such natural refrigerants as CO2, R290 as well as the alternative refrigerants with low GWP and thermodynamic properties similar to HCFCs. In addition, special attention should be paid to the standards for the replacement of HCFCs, which is the motivation for the development of refrigeration industry.关键词：engineering thermophysics;Alternative refrigerants;progress;Development trend2021|3539|0发布时间：2024-07-18
- 摘要：A ternary HFC-161 mixture (HFC-161/125/143a with mass ratio 10/45/45) was proposed as an alternative refrigerant to R502. Theoretical results indicated that it is an environmentally friendly refrigerant with zero ODP (ozone depletion potential) and a GWP (global warming potential) value of 3466, which is lower than that of R502, R404A and R507. The thermophysical properties and theoretical cycle performance of HFC-161 mixture under low temperature working conditions and varying working conditions were calculated and compared with R502, R404A and R507 by software Refprop. The calculation results indicated that the operating pressure, pressure ratio, COP and cooling capacity per unit volume of HFC-161 mixture are equivalent to those of R502, and its temperature glide is smaller than that of R404A. Therefore, HFC-161 mixture can be used as a potential alternative refrigerant to R502.2014|2166|0发布时间：2024-07-18
- 摘要：The effects of caboxymethyl chitosan (CMC) coating on the quality of obscure puffer fish (Takifugu obscurus) during storage at 4℃ were studied. Changes in the total viable count of aerobic bacteria, weight loss, total volatile basic nitrogen, trimethylamine, sensory score and the texture indices such as firmness, springiness, resilience and chewiness of the refrigerated puffer fish were investigated. The results showed that compared with the untreated control samples, CMC treatment can suppress bacterial growth, reduce weight loss, and decrease changes in texture indices such as hardness, flexibility, resilience and chewiness, total volatile basic nitrogen, trimethylamine and sensory scores of puffer fish flesh, and extend the shelf life of puffer fish flesh from 4 days to 6 days during cold storage (4℃).关键词：Package and preservation of food;Carboxymethyl chitosan;Puffer fish;quality;Texture1882|2116|0发布时间：2024-07-18
- 摘要：As resources and environment problems which seriously restricts the development of food cold-chain technology have become the main problems of the international community, how to realize the sustainable development of the food cold-chain becomes common concern of cold-chain practitioners. The article discussed the way and highlights several new technology of energy saving and emission reduction in the food cold-chain, e.g. absorption refrigeration technology adapted to engine exhaust system , combined cooling, heating and power, CO2 refrigeration technology, thermoacoustic refrigeration etc.1952|2200|0发布时间：2024-07-18
- 摘要：Effects of treatment with microwave on carbohydrate content and regulation of sugar synthesis enzyme activity of sweet corn were studied. Sweet corn was packaged with polyethylene films after treatment with microwave and stored at 2℃. The results showed that after being processed by microwave the respiration rate of sweet corn was decreased almost 25%, but the moisture content has no significant differences compared with control group. After being stored for 15 days, the soluble sugar content, reducing sugar content and starch content in microwave treatment samples was 29.47% higher, 19.32% higher and 10.97% lower respectively than that in control group. The microwave also promotes the activity of sucrose phosphate synthase and phosphatase in the late storage, and effectively delays the sugar loss during sweet corn storage.关键词：Food package and preservation;Sweet Corn;Microwave;Sugar;Starch1818|2266|0发布时间：2024-07-18
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