最新刊期
卷 36 ， 期 2 ， 2015
- 摘要：Conventional air source heat pump and no-frost air source heat pump can be categorized as general air source heat pump. The physical characteristics and energy consumption of general air source heat pump system in a frost/defrost cycle is analyzed based on the first law of thermodynamics and a generalized performance model is deduced, which can be used for the prediction of performance difference and optimization of existing technologies. This model provides not only a theoretical basic for the development of frost-free air source heat pump, but also a basis for annual performance evaluation of air source heat pump systems.关键词：air source heat pump;frost;defrost;coefficient of performance;performance model1837|2047|3发布时间：2024-07-18
- 摘要：Hydrocarbons as one of the natural refrigerants have drawn much attention for their excellent thermophysical properties and environmental performance(ODP=0,GWP is extremely low). This paper compares the operational performances of HCs with several conventional refrigerants, discusses the research progress of the application of HCs on small commercial freezers from the point of theory and tests, and expounds the progress on compressor, lubricating oil and other relevant aspects. Compared to the traditional refrigerant used in small commercial freezers, hydrocarbons have much higher unit mass refrigerating capacity and COP, lower exhaust temperature. Moreover, in actual operation, their cooling rate is faster and noise level is lower. However, hydrocarbons are flammable. Although the refrigerant charge of small commercial freezers is small, relevant fire or explosion experiments should be done when hydrocarbons leak from a small commercial freezer.关键词：refrigerant substitution;small commercial freezers;HCs;review2136|2203|4发布时间：2024-07-18
- 摘要：The present review summarizes the experimental investigations on the freezing processes of the sessile water droplets and impinged water droplets on cold surfaces. Cold surfaces, environmental conditions, droplets, and additional forces or fields are presented as the dominant factors that influence water droplets freezing. The anti-icing performance of low-energy surface and effects of convection conditions on the water droplets icing processes are highlighted. Finally, the principles of various factors on the water droplets freezing, optimization of super-hydrophobic surface anti-icing performance, and exploration of active control methods on freezing process are recommended to be investigated further, which can be a reference for future researches.关键词：water droplet freezing;cold surface;experiment review;super-hydrophobic/low-energy surface;convection condition;impacting2727|4567|4发布时间：2024-07-18
- 摘要：Shell-side thermodynamic calculation of coil-wound LNG heat exchanger is one of the important problems to be solved. Shell-side heat transfer models on low-temperature conditions are mentioned on very few occasions. It is a necessity to choose the best thermodynamic calculation correlation on cryogenic working conditions. The existing shell-side single phase heat transfer models were evaluated. Using the shell-side measurement data of coil-wound LNG heat exchanger on low-temperature conditions, this paper got the best shell-side heat transfer model for the pre-cooling stage of natural gas liquefaction process, and optimized this model. In conclusion, Abadzic heat transfer model gets the best accuracy and the strongest applicability, so it is properly selected for the pre-cooling stage of natural gas liquefaction process. The accuracy can be improved about 50% by the use of viscosity correction, the factor of which in the pre-cooling stage should be estimated at 1.05.关键词：coefficient of heat transfer;coil-wound heat exchanger;liquefied natural gas;shell-side2145|2223|4发布时间：2024-07-18
- 摘要：In this paper, the temperature uniformity of a self-designed novel multi-temperature thermostat with three chambers was studied. A steady-state three-dimensional numerical model based on one chamber ofthe thermostat was built to simulate its temperature distribution under different heater conditions. The results showed that the most uniform temperature distribution was obtained under the condition that the square-shaped heater was used and installed under the fan. Then with all chambers under such heater condition, the thermostat was tested under mode 1 (the temperatures for the chambers were set to ﹣15 ℃, ﹣10 ℃ and ﹣5 ℃, respectively) and mode 2 (the temperatures for the chambers were set to ﹣20 ℃, ﹣15 ℃ and ﹣10 ℃, respectively). The simulated values were in good agreement with the measured values with the maximum error of 3.1% under mode 1 (the simulated mode) , and the maximum temperature uniformity in the chambers was 0.54 ℃under the two tested modes. The obtained results showed that the temperature distribution within all chambers of this novel multi-temperature thermostat could keep uniform under different tested modes.关键词：multi-temperature;thermostat;temperature field;temperature uniformity;FLUENT simulation1887|2330|1发布时间：2024-07-18
- 摘要：The pool boiling heat transfer of natural refrigerant CO2 outside single horizontal tube is investigated experimentally under different boiling pressure. Smooth tube and enhanced tube(Turbo-EHP) are taken as the single horizontal tube with electrical heating. The relationship of boiling heat transfer coefficient along with the heat flux and the boiling pressure is analyzed, and the heat transfer correlation of smooth tube under heat flux of 10~50 kW/m2 and boiling pressure of 2~4 MPa is obtained. The maximum error is 8.73% when the experimental values are compared with fitting formula. Compared with other existing heat transfer correlations, the new fitting formula of CO2 is matching very well, and the maximum error is 15%. In the range of experimental heat flux and boiling pressure, the overall heat transfer coefficients of the enhanced tube are higher than that of the smooth tube, and its enhancement factors varies from 1.50 to 1.72. This paper makes useful exploration of CO2 pool boiling heat transfer and will benefit the design of evaporator.关键词：CO2;pool boiling;coefficient of heat transfer;heat transfer enhancement1892|2370|1发布时间：2024-07-18
- 摘要：The characteristics of CO2 hydrate formation in nanofluids were investigated experimentally in a small scale reaction system. The effects of type, particle size and mass fraction of nanoparticles on CO2 hydrate formation characteristics were stuided . Compared with pure water, CuO and SiO2 nanoparticles increase gas consumption, but extend induction time of gas hydrate formation. Results show that metal nanoparticle Cu and metal oxide nanoparticle Al2O3 both have a significant impact on the induction time and gas consumption of CO2 hydrate formation. Al2O3 shows a remarkable effcet on characteristics of gas hydrate formation with a particle size of 30 nm. Compared with pure water, the induction time during hydrate formation in 0.1 %-30 nm- Al2O3 nanofluid is reduced by 76.9 %, and gas consumption is increased by 23.2 %. With the increase of Cu nanoparticle mass fraction, CO2 gas consumption is first increased and then decreased. The mechanism of the effect of nanoparticles on characteristics of CO2 hydrate formation was discussed.关键词：cool storage;carbon dioxide hydrate;nanofluids;Induction time;gas consumption1898|2151|9发布时间：2024-07-18
- 摘要：The heat dissipation of super or large computer server CPU has become the bottleneck for the development of high performance computer, therefore the cooling of super or large computer server attracted more and more attention. This paper proposes a type of radiator for cooling of computer server chip, in which heat pipe which is embedded in the radiator base plate is assembled with fin as a whole. A test bench was built, and the performance of the plate type heat pipe radiator and the proposed radiator was compared experimentally. The temperature distribution of the heat pipe body, the fin and the uniform temperature board was simulated numerically. The heat transfer in the condensing section in the proposed radiator is enhanced, so the floor area of the proposed radiator is reduced 50% compared with the plate type heat pipe radiator, and the proposed radiator has a better temperature uniformity. Under the same conditions, the average temperature of the top radiator fin is only increased 17% when the heat flux is increased from 24.3 W/cm2 to 68.6 W/cm2.关键词：chip cooling;heat transfer enhancement;chip radiator;numerical simulation1937|2528|2发布时间：2024-07-18
- 摘要：A new water-cooled auto-cascade refrigeration cycle(WACR) using a binary refrigerant mixture is presented, which adopts a condenser-phase separator instead of a condenser and an evaporative separator in traditional auto-cascade refrigeration cycle. In condenser-phase separator, high boiling point refrigerant can be condensed, and high boiling point and low boiling point refrigerants can be separated. Characteristics of four binary refrigerant mixtures (R22/R23, R290/R170, R134a/R23, and R134a/R170) circulation were analyzed. And the WACR using R22/R23 and R134a/R23 were studied experimentally. In the same condition, the COP of WACR using R22/R23 is higher than that of the WACR system using R134a/R23. Compared with the traditional system, COP of the new water-cooled auto-cascade refrigeration cycle(WACR) is higher from 60% to 100%.关键词：mixed refrigerant;auto-cascade;refrigeration cycle;condenser-phase separator2502|2843|1发布时间：2024-07-18
- 摘要：The energy bus system is a low carbon thermal energy system that can make integration of renewable energy sources or untapped energy sources for district heating and cooling. A small energy bus system was constructed by combining ground soil and surface water as low grade energy. The models of components in the system were developed according to theoretical analyses and test data of manufacturer, and the whole system was constructed by connecting various components on TRNSYS platform. The hourly and annual thermal performance of the system was simulated when it was applied to the Jinmao Chong Ming low-carbon experiment community . The result shows that the annual thermal coefficient of performance of the system is 3.5, while the thermal coefficient of performance for conventional systems is less than 1.5. Both energy saving rate and carbon reduction rate of the system are more than 20%. It can be seen that comprehensive benefits of renewable energy use and energy recovery are achieved in energy bus system.关键词：energy planning;energy bus system;heat pump;system simulation;shallow geothermal energy1874|2350|5发布时间：2024-07-18
- 摘要：In this paper, the single-cylinder rotary compression system with vapor injection is applied in heat pump system to solve the problems of insufficient heating capacity and lower efficiency during lower ambient conditions. The system performances of single-cylinder rotary compression system with vapor injection (called single-cylinder system), dual-cylinder rotary compression system with vapor injection (called dual-cylinder system) and single stage compression system were comparatively tested under the different heating conditions in psychrometric room. The results show that the single-cylinder system has a higher heating capacity compared with single stage compression system when the outdoor temperature is above ﹣15 ℃, and the rates of increase is above 12%. The rate of increase is increased along with the decrease of ambient air temperature. The heating capacity and COP of single-cylinder system are higher than that of the dual-cylinder system, and the increasing ranges are 2.29%, 1.94% respectively. When the outdoor temperature is below ﹣15 ℃, single stage compression system would not operate normally due to the higher discharge temperature. The heating capacity and COP of dual-cylinder system are higher than that of the single-cylinder system, and the increasing ranges are 4.5%, 9.42% respectively. Therefore, the single-cylinder system is suitable for the conditions of outdoor temperature above﹣15 ℃, while the dual-cylinder system is suitable for the conditions of outdoor temperature below ﹣15 ℃.关键词：heat pump system;vapor injection;rotary compressor;heating performance1869|2249|5发布时间：2024-07-18
- 摘要：The cooling process of mixed-refrigerant (MR) cryogenic system is time-consuming, the composition of MR has significant influence on the temperature decreasing rate, and the optimization of the MR charging process is crucial in order to obtain quick temperature decreasing rate and reliable running condition. Based on the fundamental principle of two phase volume node, this article established dynamic simulation method for MR cryogenic system. The simulation results are validated by the experimental data successfully. The main work focuses on the temperature decreasing characteristics of the system with different refrigerant charging process. The results reveal that when the phase change temperature of the charging refrigerant is around the system temperature, the temperature decreasing rate is the quickest. In their own charging temperature field, when the charging CH4 is 12%~16%, and N2 is 9%~ 12% of total MR in system on mole basis, the temperature decreasing rate and working condition of the studied system in this article can be promoted effectively during these two cooling process.关键词：mixed refrigerant;cryogenic system;temperature decreasing characteristics;refrigerant charging rule;dynamic simulation1861|2033|0发布时间：2024-07-18
- 摘要：In a complex simulation of a household refrigerator compressor, the flow coefficient and the corresponding effective flow area of the reed valve are key parameters which should be known previously. In general, the flow coefficient and the corresponding effective flow area can be obtained by experiment. But in fact, it is hard to measure flow coefficient of the reed valve with refrigerant flowing in a closed system. A new method is presented in this paper. A simulation model is built to get the flow coefficient of the reed valve with working medium of air. In addition, we measure the flow coefficients of air by static blow experiment and obtain flow coefficients in varying flux and valve lifts. Changing the medium to R600a, we obtained the flow coefficient of reed valve by numerical simulation. And through the compressor performance test, we validate the correction of flow coefficient indirectly. The results show that the numerical simulation results coincide well with the experiment results as the working medium was air. This model can be used to calculate flow efficient of working medium for R600a.关键词：reed valve;flow coefficient;refrigerator compressor;R600a2077|2176|2发布时间：2024-07-18
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Study of Dehumidification-regeneration Performance of an Internally-heating Regenerated Dehumidifier
摘要：An internally-heating regenerated dehumidifier is proposed, its physical model and mathematical model for heat and mass transfer process are described, and a numerical procedure based on finite difference method is developed to solve the governing equations. By conducting experiment researches, the dehumidifier’s dynamic behavior is measured, and then compared with simulation data. Result shows that the dehumidifier has a high dehumidification efficiency for both indoor air with high moisture content in summer and relatively dry air in microenvironment without inner-cooling device, the time consumed in regeneration and cooling process is much less than that consumed in dehumidification process, and the pressure drop in fix bed is small, which indicates that the dehumidifier can be widely used in dehumidification for small indoor space.关键词：microenvironment;solid dehumidifier;silica gel;numerical simulation;performance experiments2096|2145|1发布时间：2024-07-18 - 摘要：In order to analyze the factors which affect the start-up performance of plate pulsating heat pipe, a plate pulsating heat pipe with parallel trapezoidal channel was experimentally investigated in the forced air convection cooling conditions. Results indicate that heat pipe start-up behavior at low heating power are temperature rise steadily and jump, and the jump case is divided into two categories: the temperature of evaporator and condensation rise steadily and gradually declined; while heat pipe start-up behavior at high heating power is mainly temperature jump. In addition, the full start-up temperature of heat pipe rises with the increased liquid filling ratio and inclination angle, it has nothing to do with the heating power. Specially, heating power influences the start-up speed. The higher heating power leads to the faster heat pipe start-up.关键词：plate pulsating heat pipe;parallel trapezoidal channel;start-up performance;liquid filling ratio;heating power2219|2129|2发布时间：2024-07-18
- 摘要：It is well known that the type and concentration of cryoprotectant (CPAs) exerts a significant influence on the survival rate of cells following cryopreservation. The optimal cryoprotectant for human hepatoma Hep-G2 cell with slow cooling method was determined in the study. The Cells were frozen in Me2SO, glycerol, sucrose and trehalose at different concentration and combination, then stored in a ﹣80 ℃ freezer for one week. The survival rate was assessed by trypan blue dye exclusion test, MTT assay and 24 h attachment assay. The results suggested that 10% (v/v) Me2SO provide effective protection among Me2SO groups; 20% (v/v) glycerol provide effective protection among glycerol groups; when sugars were added, 5%Me2SO(v/v)+0.3mol/L trehalose provide effective protection than the other groups（P<0.05）. In conclusion, 5% Me2SO (v/v)+0.3mol/L trehalose was the presumptive optimal cryoprotectant for human hepatoma Hep-G2 cell during slow freezing.关键词：cryopreservation;cryoprotectants;sugar;viability1966|2102|5发布时间：2024-07-18
- 摘要：A special fixed bed structure is introduced, in which DN20 water pipes pass through the fixed bed. Silica gel is used as solid adsorption materials of fixed bed, and water with different temperatures is supplied in the pipes in the experiment. The regeneration capacity and adsorption effect in the three experiment cases are compared by three evaluation indexes, i.e., dehumidifying capacity, adsorption capacity and energy efficiency ratio. Experiment 1 is best in regeneration capacity and adsorption effect. The analytical capacity of experiment 1 is 36% greater than experiment 2 and 12% than experiment 3. The dehumidification capacity of experiment 1 is 16% greater than experiment 2 and 17% than experiment 3.关键词：fix bed adsorption dehumidification;experimental analysis;adsorption bed structure;adsorption efficiency ratio1976|2182|0发布时间：2024-07-18
- 摘要：Research on the annual performance factor specified in variable speed air-conditioner energy efficiency standard GB21455-2013. A variable speed air-conditioner was studied, two operating modes were established combining with typical meteorological year data. With the experiment and calculation, the air conditioner SEER and HSPF in different cities and different modes were obtained. The running time cumulative rate of temperature range was introduced and relationships between SEER, HSPF and TAS were analyzed, the results show enhancing the air conditioner energy efficiency should focus on improving the different temperature range segment. The APF of each city, each mode and standard GB/T7725-2004 and GB21455-2013 were calculated, the relationships between SEER, HSPF and APF were analyzed. The results show cooling and heating temperature occurrence time specified in the standard do not fully reflect the actually APF of variable speed air-conditioner running at different regions of China and enhancing APF must focus on improving the HSPF.关键词：variable speed air-conditioner;SEER;APF;climatic factors;operating characteristics2307|2285|3发布时间：2024-07-18
- 摘要：The supply air parameter of pressure pre-cooling directly influence the energy consumption of pre-cooling device. In this paper, an experimental platform for pressure pre-cooling is set up, and tomatoes are chosen as experimental objects. The relationship between the tomato center temperature and the time is obtained under the condition of different supply air parameter. By analyzing the principle of tomato pre-cooling time, the tomato pre-cooling results and energy consumption of the pre-cooling device, the optimization scheme of variable supply air speed and temperature is proposed. It is shown that the supply air speed remains 0.9 m/s while the tomato temperature drops from 27 ℃ to 15 ℃, and remains 0.57 m/s while the tomato temperature drops from 15 ℃ to 5 ℃, the energy consumption of the fan can be reduced by 14.5% ~ 17.7%; The supply air temperature remains 4 ℃ while the tomato temperature drops from 27 ℃ to 10 ℃, and remains 2 ℃ while the tomato temperature drops from 10 ℃ to 5 ℃, the energy consumption of the refrigeration system can be reduced by 5.6%~10.5%.关键词：pressure pre-cooling;energy saving;variable supply air parameter;air supply velocity;air supply temperature2344|2364|2发布时间：2024-07-18
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