最新刊期
卷 32 ， 期 5 ， 2011
- 摘要：Both domestic and international investigations on high-temperature heat pump technology are reviewed in this paper. It is shown that most studies focused on the development of the environment-friendly refrigerant and the system efficiency. The recent development on high-temperature heat pump system and centrifugal heat pump units are introduced. Based on the application in industry, it can be concluded that: the high-temperature heat pump technology can be widely used in oil heating, chemical engineering, sewage heat recovery, sea water desalination and drying , and has good effect in energy saving. Besides, the development direction and trend of the high-temperature heat pump is also discussed in this paper.关键词：pyrology;high-temperature heat pump;Outlet temperature;coefficient of performance1947|2316|0发布时间：2024-08-02
- 摘要：The absence of evaluation standard seriously constraints the development of multi-function heat pump (MHP) in China. First, the basic principle of MHP is introduced briefly, and the current testing standards are discussed in detail based on different working modes of MHP, respectively. In order to make performance evaluation of MHP more accurate, MHP are then suggested to be divided into 11 categories in accordance with different forms, such as heat sources. Moreover, according to the characteristics of five different climatic regions in China, cumulative time distribution of MHP under various work modes and ambient temperature zones is analyzed. Finally, the annual performance factor (APF) to evaluate the comprehensive performance of MHP is determined.关键词：pyrology;Multi-functional heat pump;Hot water supply;Performance evaluation;Testing method2001|1935|0发布时间：2024-08-02
- 摘要：In order to investigate the heating performance of quasi two-stage compression heat pump system using R32, an experimental setup was established. The results showed that the discharge temperature of the quasi two-stage compression heat pump system was 10℃~20℃ lower than that of the single stage compression system, not exceeding the limit of 130℃, and the heat pump can steadily run for long time under the condensing temperature of 40℃ and the evaporating temperature varying from -10 to -5℃. The heating capacity of the quasi two-stage compression system with R32 is 12% higher than that of the single stage compression system, and the heating COPh depending on the intermediate vapor pressure is higher or lower than that of single stage compression system, and the suitable comparative value of intermediate vapor pressure is 0.9~1.1.关键词：pyrology;heat pump;R32;quasi two-stage compression;heating performance1786|1930|0发布时间：2024-08-02
- 摘要：Mechanism of RBM effects in liquid desiccant process was analyzed. Experiments were conducted to test RBM effect in the process of dehumidification and regeneration, as well as RBM effects on performance of heat and mass transfer. The results show that: RBM effect is triggered by the surface tension gradient and density gradient in radial and flow direction, which are caused by heat and mass transfer between air and solution. RBM effect has significant effect on the efficiency of heat and mass transfer rate and wetting rate，and the effect varies greatly due to different heat and mass exchange conditions .关键词：engineering thermophysics;Liquid desiccant;RBM effect;heat and mass transfer;Gas-liquid interface1920|1933|0发布时间：2024-08-02
- 摘要：An experimental investigation is carried out on a vapor chamber which is designed with some wick pillar as bracing structure. Meanwhile, CFD software Fluent is used as the the numerical simulation tool. Comparison between the numerical results and experimental results at different heat flux ranging from 5 to 23W/cm2 is studied. When the heat flux is 23W/cm2，the center temperature of vapor chamber at the evaporation side is nearly 319K，and the temperature at both evaporation and cooling sides is uniform. The comparison between the vapor chamber and copper plate with the same size at the same thermal condition shows that vapor chamber have a better thermal performance than the copper plate. The center temperature of the copper plate at the evaporation side is nearly 367K. Vapor chamber make heat-dissipation more effective at a large heat flux. The results also show gravity has little effect on vapor chamber, and the difference between numerical and experimental results decrease as the heat flux increases.关键词：engineering thermophysics;heat pipe;vapor chamber;Cooling;numerical simulation1860|1914|0发布时间：2024-08-02
- 摘要：It is one of the most important concerns for the researcher in the building energy saving field in what kind of air conditioning should be used to save energy. Due to the high efficiency of variable refrigerant flow (VRF) systems, the power simulation program of VRF systems is increasingly developing. In this paper, the power simulation program of a VRF system is developed with the evaporation temperature control module built in EnergyPlus based on BESP. The power consumption of a VRF system in actual office rooms in common summer days is calculated, which is compared with the experimental results. The comparison result is finally used for the analysis and modification of the module.关键词：pyrology;VRF system;EnergyPlus;validation;Energy simulation1951|2130|0发布时间：2024-08-02
- 摘要：With the rapid growth of underground projects, the temperature control dehumidifier with parallel condensers has been widely used for its energy saving and high efficiency. The influence of the 3-way modulating control valve in temperature control dehumidifier with parallel condensers on unit cooling, dehumidifying and supply air temperature was studied, The result shows that: (1) the continuous temperature adjustment could be achieved by adjusting the opening degree of the three-way valve. The effective region of the three-way valve was between 30% and 80%; (2) the opening degree of the three-way valve has influence on the dehumidification of the unit; when the open degree is between 50% and 65%, the unit has the lowest value in input power and highest value in dehumidification; (3) the refrigerant’s flow rate could be modulated by modulating the opening degree of the 3-way valve, and the highest flow appeared when the opening degree is between 50% and 70%. The ways of adjustment are very useful for improving the efficiency of temperature control dehumidifier with parallel condensers.关键词：pyrology;Temperature control dehumidifier;The flow rate of refrigerant;Three-way modulating control valve2010|1996|0发布时间：2024-08-02
- 摘要：Ice accretion on power lines is a random natural phenomenon and may seriously harm to the safety of power network. However, the mechanism of the freezing process of super-cooled water droplet impacting on wires is still not fully understood at present. In this paper, an experimental investigation on the freezing mechanism of the super-cooled water droplet impacting on a cold wire surface is performed. The morphological characters and the impact dynamics of a single super-cooled droplet collide on the cylindrical metal surfaces have been revealed with high-speed photographing. An instantaneous freezing phenomenon of the super-cooled impacting droplet was identified and the condition boundary for this kind of freezing was obtained statistically from the experimental data for the surfaces of stainless steel, copper and aluminum, on which the super-cooled droplets impinging with speeds of 2.2 m/s and 4.3 m/s. Meanwhile, the dynamic images of the ice accretion on a real aluminum wire with the droplet impinging rate from 0.6 to 2.2 drops/s in ambient temperature from -2℃ to -8℃ were obtained and the morphological behaviors of these accretion processes were analyzed.关键词：engineering thermophysics;Super-cooled water droplet;Freezing mechanism;Impact;Instantaneous freezing;Ice growth2045|1817|0发布时间：2024-08-02
- 摘要：Based on the analysis of all the forces and moments acting on the orbiting scroll and the Oldham ring, the dynamic model of the CO2 scroll compressor prototype was established. At the condition of three different speeds, the forces acting on the Oldham ring and the orbiting scroll were calculated respectively. The simulation results propose that the maximum values of the forces acting on the Oldham ring are 21.07N, 25.71N and 30.81N respectively, the maximum values of the forces acting on the crank pin are 899.89N, 1045.34N and 1133.51N respectively, and the mechanical friction losses on the main bearing are increased. At the above given operating conditions, the friction loss between the orbiting scroll and fixed scroll is the largest one and covers about 45 percent of the overall mechanical friction losses, the second is the friction loss on the main bearing and covers about 33 percent, and the friction loss on the Oldham ring is very small and only covers about 0.23 percent.关键词：Power machinery and engineering;CO2;Scroll;Globally convergent Newton method;Mechanical friction loss1974|1923|0发布时间：2024-08-02
- 摘要：The response surface method is applied to design the heat exchanger with decreasing tube diameter, for the traditional design methods are not suitable for the optimization of the performance and cost of heat exchanger simultaneously. The method fits the relationship among the tube length, fin pitch, performance and cost of heat exchanger into a quadratic continuous function that can be solved directly. The accuracy of the method is verified by applying it to the optimization of 7mm tube heat exchanger, the deviation from the experimental data is 0.3%. Using the method for the optimization of 9.52mm tube heat exchanger into 5mm tube heat exchanger, the cost and refrigeration charge of designed heat exchanger decrease by 28% and 39.8%, respectively, while the performance is unchanged.关键词：pyrology;Refrigeration and cryogenics;room air conditioner;Response surface method;Tube diameter;design1969|1891|0发布时间：2024-08-02
- 摘要：Based on Monte Carlo method, the air-side heat transfer and flow of parallel flow condenser are optimized under the working state of household air-conditioning, and effects upon heat transfer coefficient and pressure drop caused by various fin geometric parameter combinations are analyzed . According to the results of optimization, the height of fin and the length of shutter are the main factors which affect heat transfer. If the two factors are both increased, the heat transfer coefficient will be increased and in the meantime the pressure drop reduced. Besides, it can be concluded that the width of fin will greatly affect pressure loss, as any slight decrease of the former will cause great reduction of the latter. But the width of fin has little effect on heat transfer coefficient. Meanwhile, the fin pitch and shutter angle are secondary factors which influence heat transfer coefficient and pressure drop. The decrease of fin pitch or any increase of the shutter angle can lead to increase of heat transfer coefficient and pressure drop. The fin geometric parameter combination gotten through this method can greatly improve Parallel Flow Condenser’s heat transfer ability on the premise of satisfying pressure drop.关键词：engineering thermophysics;Household air-conditioning;parallel flow condenser;parameter optimization;Monte Carlo1846|1848|0发布时间：2024-08-02
- 摘要：Sound velocity of fluid is important thermodynamic parameter. But viewing from the existing literature, there is a lack of sound velocity data. This paper presents the calculation of sound velocity for the adiabatic two-phase flow of refrigerant through capillary tube based on homogenous equilibrium model. According to the definition of sound velocity and Martin-Hou equation of state the sound velocity is obtained using the finite difference method. The sound velocities of three refrigerants, R22, R134a, R744, have been calculated in this paper. The calculation results have been validated by published experimental data and showed fair agreement with the experimental data with an error band of 4%. According to the calculated two-phase sound velocity data, the sonic curves were drawn in the pressure-enthalpy diagram. The data and curves show that the sound velocity increases with the entropy at the same pressure. From the triple point pressure sound velocity on the isentropic curve increases firstly and then decreases. Sound velocity on the isenthalpic curve decreases monotonically for R134a and R744. But the sound velocity of R22 increases firstly then decreases.关键词：engineering thermophysics;Sound velocity;Sonic line;Homogenous equilibrium;Two-phase;Refrigerant properties2087|2072|0发布时间：2024-08-02
- 摘要：After suspending TiO2 nanoparticles ( particle size 20 nm) in low temperature BaCl2 solution, TiO2- BaCl2- H2O nanofluid with volume fraction of 1.13 % could be obtained through supersonic oscillator by adding hydrophilic dispersant. The discharging performance of BaCl2 solution and nanofluids were tested. The experimental results show that nanofluids have remarkably larger rate of cool discharging than BaCl2 solution, and the cool discharge capacity of nanofluids are more than BaCl2 solution during the same time; the heat transfer coefficient of heat exchanger is improved remarkably, and the total heat transfer coefficient of nanofluid in the heat exchanger is higher than that of BaCl2 solution, which verified the nanoparticles contribute to strengthen the heat performance of PCM.关键词：engineering thermophysics;nanofluids;Phase change cool storage;Cool discharge;heat transfer;TiO21946|1848|0发布时间：2024-08-02
- 摘要：This experiment studied the effect of cardboard boxes and plastic boxes on cold-room precooling and pressure precooling, as well as the effect of different specifications sweet corns on precooling. The quality of sweet corns between cartons and cartons + PE film after cold-room precooling during 0 degrees Celsius storage is compared. The result showed that sweet corns which packaged by cartons and plastic box using pressure precooling speed 60min and 10min less than the cold-room precooling;useing the same precooling,plastic box showed lower weight loss than the carton box; so it is better using plastic box and pressure precooling.The precooling rate of the small、middle and big sweet corns is respectively 130min、140min、150min, different specifications cucumbers differ greatly, so different pecifications sweet corn should be precooled separately;and sensory evaluation of sweet corns packaged by carton boxes and carton boxes+PE film after 8 and 12 days storage drops to 3 as well as the sugar content drops of 10%, the Vc content drops of 5% and the TSS content drops of 2%,so sweet corns must be saled before then.Comprehensive considerate the quality changes during storage carton and carton + PE film packaging showed big differences, therefore, sweet corn storage period using cartons + PE film packaging effect is better.关键词：Package and preservation of food;Sweet Corn;Package;Cold-room precooling;Press precooling;storage1882|2161|0发布时间：2024-08-02
- 摘要：Since vacuum ice-temperature preservation technology combines ice-temperature preservation and vacuum preservation, it is called the third generation preservation technology of agricultural product. The key to achieving this technology is to measure the ice-temperature of fruits and vegetables under vacuum pressure. In this paper a large number of experiments about the ice-temperature of tomatoes and peppers under different vacuum pressures were conducted, and the ice-temperature of the two fruits and vegetables under atmospheric pressure、0.08MPa、0.06MPa、0.04MPa were measured, based on which the ice-temperature formulas were fitted. The experimental results show that different storage pressures have different impact on the ice-temperature trends of fruits and vegetables.关键词：Package and preservation of food;Ice-temperature preservation;Vacuum preservation;Vacuum ice-temperature preservation;Ice-temperature;experimental study1896|1888|0发布时间：2024-08-02
- 摘要：In pressure precooling, cooling uniformity directly affects the fresh quality of fruits and vegetables besides cooling rate. An index to evaluate cooling uniformity based on standard deviation, uniformity σ, is put forward in this paper. Pressure precooling device has been established and experimental investigations on golden-pear precooling process were conducted with different conditions such as airflow rates, vent hole shape and size of carton and array style of fruits and vegetables in carton. The relevant parameters affecting cooling uniformity of golden-pears were analyzed. The results imply that the fluid field was good with straight array style of fruits and vegetables in carton. The uniformity σ is about 0.15 under the conditions of cooling airflow rate 1.5~2m/s, circular vent hole and the vent hole size about 45mm.关键词：Package and preservation of food;Postharvest handling;Pressure precooling;Cooling uniformity;Airflow rate;Vent hole shape;Vent hole size;Array style1851|1822|0发布时间：2024-08-02
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