最新刊期
卷 33 ， 期 6 ， 2012
- 摘要：To set up a platform for evaluating energy efficiency of water chiller and water source heat pump systems with EER or COP, the method of the second thermodynamic perfectibility was introduced. The range of thermodynamic perfectibility of room conditioners, water chillers and water-source heat pumps were calculated. The results show that the thermodynamic perfectibility of most water chillers is in the range of 0.3 to 0.5, the efficient products can reach 0.6, but the thermodynamic perfectibility of air to air products is about 0.2, and the thermodynamic perfectibility of air source heat pump water heaters is between water chillers and air to air products. The thermodynamic perfectibility is a useful index for the performance comparison of same or similar production in difference working conditions. The thermodynamic perfectibility analysis indicated that it characterizes the design and manufacturing level of products at present, and can be important foundation for the decision of minimum allowable performance, energy conservation performance and energy efficiency grade of energy efficiency standards for related products.关键词：pyrology;thermodynamic perfectibility;EER;COP;water chiller;water-source heat pump1878|2332|0发布时间：2024-07-18
- 摘要：Based on industrial Lithium Bromide (LiBr) aqueous solution with concentration 58% in weight, both stability and sintering property of the solution added some nano-particles and relevant dispersant were studied. The results show that an optimum composition could be obtained as concentration of dispersant in the solution varies in 0.3%~0.6%. When heating temperature is at 160℃, the diameter of sintering particles increase greatly during the beginning 24h, and enhance slowly after 48h as the concentration of dispersant varies in 0.1%~1.0%. While the concentration of dispersant is unchanged, the diameter of sintering particles increase dramatically during the beginning 12h, and keep smooth variation after 48h as heating temperature changes from 50℃ to 160℃. After analyzing the microcosmic structure of sintering particles, it is found that the diameter of sintering particles decrease as the concentration of dispersant varies from 0.1% to 1.0%. It shows that the stronger the dispersant, the smaller the diameter of sintering particles, and the thicker the sintering layer. Therefore, it should be compromised between the stability of LiBr aqueous solution added nano-particles with relevant dispersant and sintering phenomenon, and the dispersants that can work under high temperature is better to be chosen.关键词：engineering thermophysics;dispersants;sintering;Nano-LiBr aqueous solution;stability1738|1775|0发布时间：2024-07-18
- 摘要：This paper has had a review of the research progress in the regeneration of dessicants (solid and liquid) assisted by the ultrasonic technology. Particularly, the effect of ultrasonic on the enhancement of desiccant regeneration, the energy consumption of regeneration as well as the model for describing the regeneration process assisted by ultrasonic have been discussed in detail. The current research has proved that the ultrasonic is capable of improving the energy utilization efficiency of low-grade heat for desiccant regeneration, and hence, brings about energy saving potentially. Meanwhile, the possible designs of the ultrasonic regenerator for the regeneration of solid/liquid dessicant are presented as well. Afterwards, some suggestions to the future study on this research field are given.关键词：engineering thermophysics;ultrasound;dessicant;regeneration;enhancement1617|2174|0发布时间：2024-07-18
- 摘要：In order to know the heat transfer enhancement mechanism of liquid-vapor separation condenser, the theoretical design method of tube pass in the condenser was investigated. The Cavallini heat transfer model was chosen to calculate the in-tube mean heat transfer coefficient by the flow pattern estimated according to the refrigerant mass flow rate and average quality in each tube. The two-phase pressure drop model of Cavallini and the single-phase pressure drop model of Darcy-Weisbach were also applied to calculate the pressure drop of condensation zone and sub-cooling zone, respectively. In addition, a case with three schemes was designed here to evaluate the mean heat transfer coefficient and pressure drop, and its thermodynamic performance was evaluated with the Penalty Factor. The result indicated that different schemes of tube pass resulted in the variable refrigerant mass flux rate in tubes, and the more even refrigerant distribution in the condenser, the better its thermodynamic performance. The Penalty Factors of best one of three liquid-vapor separation condensers is about 48.5%~54.1% less than the serpentine condenser with the same heat transfer area at mass velocity of 1200~1500kg/(m2.s). That is to say, the thermal and dynamic characteristics of the liquid-vapor separation condensers with good design scheme are superior to the serpentine condenser at the same conditions.关键词：pyrology;liquid-vapor separation condenser;tube pass scheme;heat transfer coefficient;pressure drop;penalty factor1744|2189|0发布时间：2024-07-18
- 摘要：Radiant panel cooing system has attracted a great concern in engineering design and research due to its advantages of comfort and energy saving. This article studies the variations of indoor air temperature, room wall temperature, human body surface temperature in ceiling cooling room by experiment. The variation roles of convection and radiation heat transfer between human body and the environment at ceiling cooling room are analyzed. The results show that, in the 60 minutes operation of the radiant cooling system, the radiant panel surface temperature, indoor air temperature change significantly, the human garment temperature changes slowly, the convection and radiation heat transfer between human body and the environment increase gradually; after 60 minutes operation of the radiant cooling system, all of the above mentioned tend to be steady.关键词：pyrology;ceiling radiant cooling;surface temperature;convection heat transfer;radiation heat transfer1747|1907|0发布时间：2024-07-18
- 摘要：In present paper, airflow pattern is optimized by using CFD, and it is shown that the airflow pattern with upper supply and bottom return can improve the utilization of the cold air. Telecommunication base station(TBS) with separate heat pipe which can effectively control the temperature of the electrical cabinet under the 40℃ was proposed. Automatic control system can switch air-conditioning system and separate heat pipe system quickly so as to ensure the temperature of the cabinet. COP of the air-conditioning system of the telecommunication base station could reach 6.23 when the average ambient temperature was 27℃. Even in the summer, the compressor operating time in the TBS only takes up 39.1% of the total time, as well as the energy-saving rate reaches 44.7%. All these showed that telecommunication base station with separate heat pipe can save a lot of energy.关键词：pyrology;micro channel;separate heat pipe;energy-saving;telecommunication base station1728|1884|0发布时间：2024-07-18
- 摘要：A detailed review on boiling heat transfer enhancement by surfactant additives are presented in this paper to show the characteristics, bubble behaviors and correlations of boiling heat transfer of surfactant solutions. The results point out that the effects of interfacial adsorption, molecular structures, viscosity and soluble characteristics on boiling heat transfer of surfactant solutions are related to the surfactant ionic natures and concentrations of surfactant solutions in present literature. However, the influences of steam carrying, cloud point, heating method, boiling pressure and parameter coupling on boiling heat transfer of surfactant solutions are not well understood at present. In the aspect of bubble behaviors, the existing literatures show that the bubble behaviors of surfactant solutions are quite different from that of water and more emphasis should be put on the theoretical study. In addition, the boiling heat transfer correlations of surfactant solutions in the open papers exist the deficiency of less experimental data for verification and model parameters difficult to be determined. At last, some aspects that need to be investigated further and some new ideas in these fields are presented.关键词：engineering thermophysics;boiling heat transfer enhancement;surfactants;review;heat transfer correlation1709|2146|0发布时间：2024-07-18
- 摘要：Lewis factor is an important parameter for heat and mass transfer process at dehumidifying conditions. A numerical model for calculating the Lewis factor and a correlation for engineering calculation are established. The Lewis factor is obtained through the numerical model of heat and mass transfer of air-side including the mass transfer between phases and the latent heat transfer using CFD. The effects of fin-and-tube heat exchanger geometries and working conditions as well as the feasibility of existing heat and mass transfer analogies are analyzed. Also the Lewis factor correlation is established through the numerical results. The heat and mass transfer deviations between numerical model and experimental data are 6.93% and 12.1% respectively. The correlation has relative deviation of 5.52% compared with numerical model. The results show that the obtained correlation has sufficient accuracy and applicability instead of numerical model.关键词：pyrology;lewis factor;numerical simulation;heat and mass transfer;analogy relationship;fin-and-tube heat exchangers1791|2221|0发布时间：2024-07-18
- 摘要：A novel plat heat pipe heat sink for multi-chip was designed, and the thermal performance of the heat sink in different air speed, chips numbers and positions, heating power was experimentally investigated. The experimental results showed that the maximum heat transport capacity of the heat sink with one, two and three heat sources were 310W, 390 W and 500 W respectively in the horizontal position, and 275W, 408W, 500W in the vertical application when the chips temperature was less than 80℃ and the ambient temperature was 20℃. For the flat heat pipe heat sink, multiple chips cooling can dissipate more heat than unique source. The results were found to agree well with the experimental data about the thermal spreading effect of the flat heat pipe. It was shown that flat heat pipe accords with the requirements of electronic devices cooling.关键词：pyrology;flat heat pipe;multiple chips cooling;electronic devices;heat sink1902|2233|0发布时间：2024-07-18
- 摘要：A new transcritical CO2 heat pump systems with dual expansion valve and balance CO2 liquid reservoir adjustment device was introduced. The influence of the internal heat exchanger (IHX) on the system performances was analyzed on the basis of relative COP and compressor power. It is concluded that: the compressor power of system with IHX is relatively low when the high side pressure is over 10MPa, and the evaporating temperature is below 0℃. The COP of the system without IHX is about 3% to 5% higher than the system with IHX when the evaporating temperature is over 5℃. The new devices can control high and low side pressure effectively, and decrease the impact of pressure fluctuations on its COP. The experimental results provide important basis for the development of the transcritical CO2 heat pump systems.关键词：pyrology;transcritical CO2;IHX;COP;double throttle valve;experimental study1769|2178|0发布时间：2024-07-18
- 摘要：The single-stage compression heat regenerative cycle of zeotropic refrigerant mixtures was studied. The Linde-Hampson refrigeration cycle characteristics and the main problems were analyzed. The refrigerant mixture R23 and R600a was discussed and selected suitable for -70℃ low temperature refrigerator according to the zeotropic mixture refrigerant properties. The refrigeration system characteristics of different ratio were discussed using refrigerant property analysis software NIST Refprop 8.0. It was compared with the performance of the system through experimental methods under different ratio of refrigerant mixture from different aspects. Finally the reasonable refrigerant mixture R23 / R600a component ratio 3:7 was obtained. The proportion of refrigeration compressor discharge temperature, pressure ratio, and low temperature refrigerator temperature change characteristics was analyzed. And the evaporator and the heat regenerator temperature change characteristics were discussed.关键词：engineering thermophysics;mixed refrigerant;single-stage compression;regenerative cycle;experimental study1823|2182|0发布时间：2024-07-18
- 摘要：Cut roses were selected as the experimental materials and vacuum cooled at three different pressure reduction rates (3.11×104 Pa/min, 1.78×104 Pa/min, 0.62×104 Pa/min). During the vase experiments, the main quality indicators of cut flowers were examined, and comparative analysis were done. The results showed that the different pressure reduction rates had significant influence on the basic qualities of cut roses. The treatment at the medium pressure reduction rate (1.78×104 Pa/min) prevented leakage of the electrolyte, decreased accumulation of the MDA, maintained activity of the SOD, decreased the mass loss, delayed blue changes of the cut roses, prolonged the vase life, achieved the best pre-cooling effect.关键词：pyrology;vacuum cooling;cut flower;pressure reduction rate;quality1704|2194|0发布时间：2024-07-18
- 摘要：The performance of CO2 heat pump water heater was studied experimentally in this paper by comparing a loop heating and a direct heating hot water. In the loop heating mode, with an increase of the water temperature, the compressor inlet and exhaust pressure increased gradually, the power consumption increased and the gas cooler inlet and outlet temperature increased, too. The temperature difference between carbon dioxide and cooling water and heat transfer decreased, the COP of CO2 heat pump system decreased. The operating parameters of the system were stable and the COP remained unchanged in direct heated condition. When the water temperature is 17℃, the COP of the system is about 3.5, much higher than that in loop heating. The results show that the lower inlet temperature can be obtained by modifying the water tank structure and it is a very effective way to improve system performance.关键词：pyrology;CO2 heat pump water heater;loop heating mode;directed heated condition;water tank temperature;COP1874|2033|0发布时间：2024-07-18
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