最新刊期
卷 34 ， 期 5 ， 2013
- 摘要：Air source absorption heat pump (ASAHP) is of great significance for heating in North China. To improve the reliability and efficiency of ASAHP in cold climates, double-stage, double-stage coupling and booster-assisted ASAHP are put forward. Performances of the three proposed systems under different air temperatures are comparatively simulated. For fan coil heating, the double-stage coupling ASAHP performs the best when air temperature below -25℃ is not dominant, otherwise double-stage ASASHP should be considered. Primary energy efficiency (PEE) of ASAHP can be 28% and 19% higher than that of coal boiler when the outdoor air temperature is -15 and -30℃, respectively. As for floor radiant heating, booster-assisted ASAHP performs the best, with a PEE as high as 0.953 and 0.874 when the outdoor air temperature is -15 and -30℃, which is 36% and 25% higher than that of coal boiler. Considering that performance of ASAHP will be better when the air temperature is higher, the energy saving potential over the whole heating season will be much optimistic.关键词：absorption heat pump;comparison;air source;cold regions1675|1900|0发布时间：2024-07-18
- 摘要：An absorber is a key device of absorption refrigeration system, and it directly affects the performance of refrigeration system. As an important absorption type, adiabatic spray absorption process disperses the absorption fluid into fine droplets by nozzles and forms immense surface exposed to the coolant vapor. Therefore, it can improve the absorption performance. In the paper, an improved analytical Newman model is presented which can consider the absorption heat effect on adiabatic spray absorption process. Using the model, the absorption characteristics of the adiabatic spray in aqueous ammonia is studied. The results show that increasing absorption time can increase absorption mass, MA. However, when t/tMax approaches to 0.6, MA has reached to 90% of the maximum absorption mass. In other words, increasing absorption time can hardly improve MA aftert/tMax exceeds 0.6. The maximum absorption time, tMax, is proportional to the square of the droplet radius. Decreasing droplet radius can improve the absorption rate，but this increases the energy consumption of the refrigeration system. The current investigation can result in a better understanding of absorption mechanisms of the adiabatic spray absorption.1678|2004|0发布时间：2024-07-18
- 摘要：This paper designed a solar water tank with dimension of 80cm(height)×40cm(width) ×40cm(length) and the slotting inlet and direct inlet to study discharging performance of tank by presenting some experiments and simulations. The Ri number and the discharging efficiency were introduced to investigate the performance of the different inlet-tanks. The discharging efficiency was introduced to evaluate the thermal performance of the tank with different inlets. The result indicated that slotting inlet improved the efficiency of thermal stratification effectively and promoted discharging performance obviously. The discharging efficiency of slotting inlet was 7% higher than the direct inlet with the flow rate of 5L/min and the gap increased to 25% when the flow rate is 15L/min.关键词：discharging efficiency;CFD simulation;thermal stratification performance1752|2078|0发布时间：2024-07-18
- 摘要：The selection and mixture ratio of the mixed refrigerants are important to a multistage auto-cascade refrigeration system. A simulation method was found for the mixed refrigerants selection and ratio calculation by using the commercial software REFPROP8.0. The saturation pressure and evaporation temperature of the auto-cascade refrigeration system were compared to get the optimal mixture ratio of the mixed refrigerants, that is R600a/R23/R14/R740=45/21/19/16. The temperature of freezer was -150℃ at this mixed refrigerants and the mixture ratio. The results show that the research of multistage auto-cascade refrigeration system can be guided by this simulation method and the expected temperature was got.关键词：auto-cascade refrigeration;mixed refrigerants;simulation;mixture ratio1658|2147|0发布时间：2024-07-18
- 摘要：In order to explore the miscibility of lubricants with the natural refrigerant R290, an experimental device was established. The miscibility of naphthenic oil, paraffinic oil, polyol ester, polyalkylene glycol and alkylbenzene with the natural refrigerant R290 was investigated. The results showed that the dissolution of the highest mass percentages of the refrigerant R290 was in the AB oil, followed by naphthenic oil and paraffinic oil, and finally polyol ester and polyalkylene glycol. The dissolution of the mass percentage of R290 in paraffinic oil, polyol ester and polyalkylene glycol decreased with increasing temperature, and increased with increasing pressure. Moreover, the dissolution of the mass percentage of R290 in a naphthenic oil, polyol ester and polyalkylene glycol decreased with increasing viscosity. Compared with viscosity, temperature and pressure presented greater influence on the dissolution percentage of R290 in lubricants.关键词：refrigerant;R290;refrigerant oil;miscibility1965|1922|0发布时间：2024-07-18
- 摘要：Flow condensation heat transfer is of great significance for the performance of refrigeration system and is an important index of the refrigerant alternatives. In this paper, condensation heat transfer of the new alternative refrigerants is investigated. Recent developments of experiments measurement and relation models of condensation heat transfer of alternative refrigerants inside tubes are reviewed．The applicability and accuracy of correlations of condensation heat transfer for alternative refrigerants are discussed. The change of condensation heat transfer coefficients and pressure drops with influencing factors are summarized．关键词：alternative refrigerant;condensation heat transfer;review1794|2122|0发布时间：2024-07-18
- 摘要：A phase change material (PCM) is prepared for cold storage application of solar air-conditioning systems. On the basis of the self-developed PCM, the mathematical model of a spherical capsule storage ball is built to analyze the variation and influencing factors of the temperature distribution, cold storage capacity and cold storage rate during the charging and discharging process. Experiments on the charging and discharging characteristics of the storage ball are conducted in certain working conditions. The results show that the phase transition of the storage ball completes in 170min. The charging duration can be reduced by decreasing the chilled water temperature, sphere diameter and thickness of the sphere wall, and increasing the thermal conductivity of the sphere wall. In a steady state condition, the charging and discharging capacity are 17.30kJ and 16.46kJ, respectively. In a non-steady state condition, the phase transition completes in 165min with a charging capacity of 16.34kJ.关键词：phase change cold storage;solar air conditioning;influencing factors;non-steady state conditions1754|1985|0发布时间：2024-07-18
- 摘要：A practical indirect expansion solar-air source heat pump water heater (IESASHPWH) is tested for its fundamental performances and analyzed for its annual practical performances. Then three performance optimization schemes are designed, analyzed for their feasibilities and tested for the effects several times under the winter condition. Eventually an operation strategy integrated with all the three optimization schemes is proposed and simulated under annual climate conditions. The result shows that the compound system can reduce annual power consumption by 45.8%.关键词：solar water heater;heat pump water heater;compound system;performance optimization analysis;climatic factors1864|1816|0发布时间：2024-07-18
- 摘要：Air source heat pump, a high efficiency, energy conservation and environmental protection device, is in prospect of wide application and market value. But the unstable performance and lower coefficient of performance (COP) in low ambient temperature restrain the promotion and application of air source heat pump products. This paper analyzed the disadvantages of air source heat pump in low temperature environment through the review of both domestic and international investigations on system improvement in low temperature environment. Besides, the development and trend of air source heat pump is also proposed based on the latest research progresses in the aspects of new alternative refrigerant, the combined air source heat pump with phase change materials as well as the development of new heat pump system, respectively.关键词：air source heat pump;water heater;cold adaptation1860|2119|0发布时间：2024-07-18
- 摘要：The effects of flash tank economizer on performance of air source screw heat pump are studied. The effect of economizer vapor injection pressure on unit performance is theoretically analyzed. The study shows that the lower economizer vapor injection pressure is, the higher heating capacity and compressor power of screw heat pump with flash type economizer are. The COP of heat pump first increased and reduced again with the increase of the economizer vapor injection pressure. There is an optimized point. The experiment was carried out to investigate the effects of flash tank economizer on performance of heat pump at near optimum economizer vapor injection pressure. The simulation results are in good agreement with those of the experiment.关键词：flash tank economizer;air-cooled screw heat pump;economizer vapor injection pressure1785|2078|0发布时间：2024-07-18
- 摘要：Semiconductor refrigeration, known as thermoelectric refrigeration, is applied widely in fields such as industrial production and daily life, due to the advantages of rapid cooling and easy control. The heat dissipation on the hot side is the principle element restricting the coefficient of semiconductor refrigeration. In conventional device, dehumidification is realized by condensing dehumidification method, which lowers the temperature of the cold side of semiconductor and hence restricts the system COP. The semiconductor refrigeration model with heat pipe and solid desiccant is built in this paper, and verified by the experimental results of a 6-stage semiconductor refrigeration equipment with heat pipes. Then the model is used to predict the cooling and dehumidification performances with solid desiccant. The COP of the proposed semiconductor refrigeration system is 1.78, which is much higher than that shown in literature with condensing dehumidification under the same dehumidification amount.关键词：air-conditioning;semiconductor;solid desiccant;heat pipe;dehumidification capacity1850|1860|0发布时间：2024-07-18
- 摘要：Powerless self-driven mine rescue chamber supplies essential survival conditions for the people who are trapped during mine accidents. As the evaporator in the CO2 cooling and dehumidifying system of current rescue chamber has frosting problem, an idea of frostless improvement of the cooling and dehumidifying system is proposed and the equipment structure and working process of the developed system are introduced in this paper. Then, the principle and feasibility of the frostless improvement are analyzed in detail. Furthermore, a control method which uses temperature hierarchical control group valves is stated, and several regulative methods of the system under variable load conditions are analyzed. The results provide reference for further study of mine rescue chamber.关键词：mine accident;rescue chamber;CO2 cooling and dehumidifying system;frostless;hierarchical control2062|2068|0发布时间：2024-07-18
- 摘要：To investigate the effect of CaCO3 concentration and velocity on CaCO3 scaling fouling process on plain and saw-tooth oblique fin tubes, experiments have been done at different CaCO3 concentration and velocity on the two kinds of tubes. The results show that the homogeneous nucleation rate and the growing rate are both increased when CaCO3 concentration increases. This makes the scaling particle concentration and foulantions concentration increase. The former increase gets more scaling on tubes and the later enlarges the heterogeneous nucleation rate and growing rate. Higher velocity decreases the nucleation of scaling, scaling crystal and fouling resistance, but it can prolong the induction period. Higher velocity increases nucleation rate on saw-tooth oblique fin tube first, but the induction period extends and the mass of scaling and fouling resistance decrease. Saw-tooth oblique fin tube has a bigger heat transfer coefficient than plain tube at both clean and fouling conditions and it has smaller fouling resistance and a little more scaling.关键词：oblique fin tube;calcium carbonate;crystallization fouling1870|1856|0发布时间：2024-07-18
- 摘要：The heat transfer and pressure drop characteristics of oscillating heat pipe radiator and corrugated copper radiator for automobile were obtained by experiment. And the results were compared and analyzed. The results showed that the heat transfer and pressure drop performance of oscillating heat pipe radiator for automobile were better than the corrugated copper one. And the heat balance error was analyzed. The experimental results have some guidance to the development of new type automobile radiator.关键词：automobile radiator;oscillating heat pipe;heat transfer performance;pressure drop performance1800|2076|0发布时间：2024-07-18
- 摘要：The recent development of CO2 hydrate slurry formation enhancement in cool storage application was introduced, and the formation enhancement methods of mechanical mixing in combination with additives were presented. A novel CO2 hydrate slurry formation apparatus in cool storage application was recommended. Finally, CO2 hydrate phase equilibrium, CO2 hydrate formation equipment, a variety of CO2 hydrate formation promoting technology, CO2 hydrate cool storage and flow characteristics were suggested to be investigated preferentially to improve the application of CO2 hydrate slurry in cool storage practice.关键词：cool storage;reviews;CO2 hydrate slurry;formation enhancement1743|2037|0发布时间：2024-07-18
- 摘要：To master heat transfer characteristics of locomotive IGBT power module cooler, experimental system on the heat dissipation, substrate temperature range and the effects of air velocity and inlet air temperature on the heat transfer of the heat pipe cooler is built. The experiments are conducted under air velocity at 5-7m/s, inlet air temperature at 30-45℃ and substrate temperature at 70-80℃. Experimental results show that the higher the substrate temperature is, the more heat is dissipated; when the substrate temperature is at 80℃,the heat dissipating capacity is 5400-7400W. The results also show that the optimal working temperature of substrate is at 70-90℃for the cooler. Inlet air temperature has more effects on the heat transfer than air velocity. Considering energy consumption and noise level of, the air velocity flowing through the cooler should not be more than 7m/s. Experimental results provide a scientific basis for the selection and design of the cooler.关键词：IGBT;Traction rectifiers;heat pipe;temperature1805|2098|0发布时间：2024-07-18
- 摘要：Cryotop is one of the best effective methods for oocytes cryopreservation. When Cryotop is inserted into liquid nitrogen, the cooling speed is extremely high, which is difficult to measure by conventional method. In this study, digital oscilloscopes and type T thermocouple of 25 μm diameter were employed to establish a high speed temperature measurement system. The cooling rates of Cryotop device at different carrier material, thickness and cold source temperature were measured. The results showed that when 60μm copper was used as carrier and slush nitrogen was used as cold source, the cooling rate was increased. It could reach 37130 ±1336 K/min, which was twice higher than that of commercially available Cryotop (11982 ± 1936 K/min).关键词：Cryotop;cooling rate;ultra-fast temperature measurement1816|2213|0发布时间：2024-07-18
- 摘要：An experimental scheme is proposed to recover the waste heat of power plant circulating water to dry lignite with heat pump, and the experiment system was developed. Experiments of drying lignite in the temperature of 60℃, 70℃and 80℃ were conducted, and the change of lignite quality with time was measured. The result shows that: the higher the temperature ,the faster drying rate; the longer the effective drying time ,the better the result. Drying 22.5% water at the temperature of 60℃ takes time 25 min; 30.5%-31.5% at 70℃takes 30 min; 42.6% at 80℃ takes 35 min. This paper provides a reference for the practical application of heat pump in the utilization of waste heat of circulating water for drying lignite.关键词：heat pump;lignite;dry;utilization of waste heat;circulating water1842|1970|0发布时间：2024-07-18
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