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A novel dew point evaporative cooling system for sensible cooling of the ventilation air for air conditioning application was constructed and experiments were carried out to investigate the outlet air conditions and the system effectiveness at different inlet air conditions (temperature, humidity and velocity) covering dry, temperate and humid climates. The results showed that wet bulb effectiveness ranged between 92 and 114% and the dew point effectiveness between 58 and 84%. A continuous operation of the system during a typical day of summer season in a hot and humid climate showed that wet bulb and dew point effectiveness were almost constant at about 102 and 76%, respectively. The experiment results were compared with some recent studies in literature. 相似文献
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运用湿能理论探讨了利用自然空气,在无需外界能量输入的情况下实现制冷与制热,包括直接蒸发冷却、间接蒸发冷却、多级间接蒸发冷却、液体除湿蒸发冷却,以及利用自然空气的能量实现液体再生等.该方法突破了传统的蒸发冷却露点温度的限制,同时将自然空气的利用由制冷拓展到制热. 相似文献
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Ghassem Heidarinejad Mojtaba Bozorgmehr Shahram Delfani Jafar Esmaeelian 《Building and Environment》2009
Cooling performance of two-stage indirect/direct evaporative cooling system is experimentally investigated in the various simulated climatic conditions. For this purpose, a two-stage evaporative cooling experimental setup consisting of an indirect evaporative cooling stage (IEC) followed by a direct evaporative cooling stage (DEC) was designed, constructed and tested. Due to the wide variety of climatic conditions in Iran, two air simulators were provided to simulate outdoor design condition of different cities in primary and secondary air streams. Results show that under various outdoor conditions, the effectiveness of IEC stage varies over a range of 55–61% and the effectiveness of IEC/DEC unit varies over a range of 108–111%. Aspects of achieving comfort conditions and power saving have been investigated with related excess water consumption. Considering the evaporative comfort zone, this system can provide comfort condition in a vast region in Iran where direct evaporative alone is not able to provide summer comfort condition. More than 60% power saving could be obtained by this system in comparison with mechanical vapor compression systems with just 55% increase in water consumption with respect to direct evaporative cooling systems. This system can fill the gap between direct evaporative cooling systems and mechanical vapor compression systems as an energy efficient and environmentally clean alternate. 相似文献
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针对西北地区独特的气候特点,分别提出了蒸发冷却+置换通风和蒸发冷却+干式风机盘管2种空调系统形式可在喀什地区实际工程中应用。通过对比发现,第1种系统形式比传统电制冷空调系统节能53%,第2种系统形式比传统电制冷系统的制冷机房内设备节能71%,2种系统节能效果显著。通过对送风状态点露点分析,蒸发冷空调系统无凝结水产生,可避免室内环境污染。蒸发冷却空调系统的独特优势决定了其在西北地区的广泛应用前景。 相似文献
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In this paper, the results of an investigation on a two-stage cooling system have been studied. This system consists of a nocturnal radiative unit, a cooling coil, and an indirect evaporative cooler. During the night in summer, requisite chilled water for a cooling coil unit is provided by nocturnal radiative cooling and is stored in a storage tank. During the next day, the water in the tank provides chilled water for the cooling coil unit and hot outdoor air passes through two-stages: the cooling coil unit and an indirect evaporative cooler. Three sources provide secondary air for the indirect evaporative cooler. The sources are outdoor air, the air leaving from the cooling coil, and the air leaving from the indirect stage (regenerative). The investigation has been conducted in weather conditions in the city Tehran. The results obtained demonstrate that the first stage of the system increases the effectiveness of the indirect evaporative cooler. Also, the regenerative model provides the best comfort conditions. Therefore, this environmentally friendly and energy-efficient system can be considered as an alternative to the mechanical vapor compression systems. 相似文献
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交通岗亭间接水蒸发开式空调系统 总被引:3,自引:0,他引:3
将间接式水蒸发空调系统用于交通岗亭中 ,分析了系统的热力参数 ,建立了系统的数学模型 ,分析一次气流进口相对湿度及换热器效率对系统加湿量的影响 ,并给出计算例子。 相似文献
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In this paper, numerical analyses of the thermal performance of an indirect evaporative air cooler incorporating a M-cycle cross-flow heat exchanger has been carried out. The numerical model was established from solving the coupled governing equations for heat and mass transfer between the product and working air, using the finite-element method. The model was developed using the EES (Engineering Equation Solver) environment and validated by published experimental data. Correlation between the cooling (wet-bulb) effectiveness, system COP and a number of air flow/exchanger parameters was developed. It is found that lower channel air velocity, lower inlet air relative humidity, and higher working-to-product air ratio yielded higher cooling effectiveness. The recommended average air velocities in dry and wet channels should not be greater than 1.77 m/s and 0.7 m/s, respectively. The optimum flow ratio of working-to-product air for this cooler is 50%. The channel geometric sizes, i.e. channel length and height, also impose significant impact to system performance. Longer channel length and smaller channel height contribute to increase of the system cooling effectiveness but lead to reduced system COP. The recommend channel height is 4 mm and the dimensionless channel length, i.e., ratio of the channel length to height, should be in the range 100 to 300. Numerical study results indicated that this new type of M-cycle heat and mass exchanger can achieve 16.7% higher cooling effectiveness compared with the conventional cross-flow heat and mass exchanger for the indirect evaporative cooler. The model of this kind is new and not yet reported in literatures. The results of the study help with design and performance analyses of such a new type of indirect evaporative air cooler, and in further, help increasing market rating of the technology within building air conditioning sector, which is currently dominated by the conventional compression refrigeration technology. 相似文献
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The paper investigated the feasibility of a novel dew point evaporative cooling for air conditioning of buildings in China regions. The issues involved include analyses of China weather conditions, investigation of availability of water for dew point cooling, and assessment of cooling capacity of the system within various regions of China. It is concluded that the dew point system is suitable for most regions of China, particularly northern and west regions of China where the climate is hot and dry during the summer season. It is less suitable for Guangzhou and Shanghai where climates are hot and humid. However, an air pre-treatment process involving a silica-gel dehumidification will enable the technology to be used for these humid areas. Lower humidity results in a higher difference between the dry bulb and dew point of the air, which benefits the system in terms of enhancing its cooling performance. Tap water has adequate temperature to feed the system for cooling and its consumption rate is in the range 2.6–3 litres per kWh cooling output. The cooling output of the system ranges from 1.1 to 4.3 W per m3/h air flow rate in China, depending on the region where the system applies. For a unit with 2 kW of cooling output, the required air volume flow rate varies with its application location and is in the range 570–1800 m3/h. For a 50 m2 building with 60 W/m2 cooling load, if the system operates at working hours, i.e., 09:00 to 17:00 h, its daily water consumption would be in the range of 60–70 litres. Compared with mild or humid climates, the dry and hot climates need less air volume flow rate and less water. 相似文献
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Energy recovery systems can be used in HVAC to reduce energy consumption by recovering wasted energy from the exhausted air to pre-cool inlet fresh air. In this paper, experimental study of utilizing cooling coil (CC) and cooling coil combined with heat exchanger (CCHE) has been developed. Considering the different climate zones in Iran, the experimental study has been done for the areas with high humidity content. In each case, the effects of air-to-air heat exchanger (HE) on the sensible and latent cooling load are investigated. The analysis gives the applicability of HE in Iran for various operational conditions to obtain air with lower moisture content. In CCHE systems more latent load quota is allocated in cooling coils and lower air humidity ratio can be obtained. Also in the cities with higher dew point depression (difference between dry-bulb and dew point temperature) more humidity reduction is achieved and the difference between latent load quotas of CCHE system is higher than CC system. 相似文献
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Existing desiccant cooling systems reduce the temperature of process air either by adopting evaporative coolers or incorporating vapor compression systems. While the former is restricted by inaccurate control, the latter still consumes certain quantity of electric power. To solve this problem, a thermally driven air conditioning system, which combines the technologies of rotary desiccant dehumidification and regenerative evaporative cooling, has been proposed and investigated. In addition to dehumidification, the system is capable of producing chilled water, thereby realizing separate temperature and humidity control without increasing electrical load. To find out the characteristics of produced chilled water and evaluate the feasibility and energy saving potential of this novel system, a mathematical model has been developed. Case studies have been conducted under Air conditioning and Refrigeration Institute (ARI) summer, ARI humid and Shanghai summer conditions. It is found that the system can achieve a thermal COP higher than 1.0 and an electric COP about 8.0. The temperature of chilled water produced by the system is around 14–20 °C. This chilled water can be used with capillary tube mats for radiant cooling. It is suggested that the system can also be designed as a standalone chilled water plant. As a desiccant dehumidification-based chilled water producing technology, this would expand desiccant cooling to a boarder niche application. The effects of chilled water flow rate, air distribution ratio, inlet air conditions and regeneration temperature have been analyzed in detail. Reachable handling regions, which will be helpful to system design and optimization, have been obtained. 相似文献
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本文测试了兰州市内一台金属填料直接蒸发冷却器,获得了干湿球温度、相对湿度、冷却效率、阻力等技术参数。分析了进口处空气干球温度和相对湿度对蒸发冷却效率的影响,发现被测试的机组蒸发冷却效率较低,蒸发冷却段阻力较大,因此,需要改善设计。由于兰州属于干燥地区,因此通过优化设计,蒸发冷却效率有提升的空间。 相似文献
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In this paper, the results of a study on a hybrid system of nocturnal radiative cooling, cooling coil, and direct evaporative cooling in Tehran have been discussed. During a night, the nocturnal radiative cooling provides required chilled water for a cooling coil unit. The cold water is stored in a storage tank. During eight working hours of the next day, hot outdoor air is pre-cooled by means of the cooling coil unit and then it enters a direct evaporative cooling unit. In this period, temperature variation of the conditioned air is investigated. This hybrid system complements direct evaporative cooling as if it consumes low energy to provide cold water and is able to fulfill the comfort condition whereas direct evaporative alone is not able to provide summer comfort condition. The results obtained demonstrate that overall effectiveness of hybrid system is more than 100%. Thus, this environmentally clean and energy efficient system can be considered as an alternative to the mechanical vapor compression systems. 相似文献
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Frank Bruno 《Energy and Buildings》2011,43(12):3475-3483
Technologies which utilise the advantages of evaporative cooling to reduce the temperature of air without the addition of moisture have existed for some time. These systems use a heat exchange media between the evaporation of water process and cooling of air. Research has been conducted on a number of systems utilising these technologies in various configurations and it has been demonstrated that temperatures of the incoming air can approach its dew point temperature. This is considerably lower than the wet bulb temperature which is the limit achieved with conventional direct evaporative cooling systems. Prototypes have been built to demonstrate the principles and temperatures achievable, but the technology has never been developed due to its high cost and complexity. These disadvantages have been addressed in a newly developed indirect evaporative cooler. The paper presents results obtained from testing a prototype cooler installed in both a commercial and residential application in a wide range of ambient conditions. The performance characteristic of the indirect evaporative cooler in regards to its outlet temperatures and electrical energy efficiency is presented. 相似文献
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Steam-injected gas turbine cycle is the modified arrangement of simple gas turbine (GT) cycle, wherein part of steam generated in a heat recovery steam generator is injected into the combustion chamber to increase power output and the efficiency. This paper studies the effect of integration of inlet air cooling, steam injection (SI) and film cooling (FC) on the performance of GT cycle. Two different methods for cooling the inlet air, namely inlet fogging and evaporative cooling, are considered for analysis here. Results show that the inlet fogging is better than evaporative cooling to achieve the lowest temperature at the compressor inlet. Thermodynamic performance of simple GT cycle is also compared with SI in GT cycle. The present study shows that GT cycle with integration of inlet fogging, SI and FC is a better configuration for achieving higher performance. 相似文献
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与蒸发冷却复合的三种除湿空调系统对比分析 总被引:2,自引:0,他引:2
蒸发冷却适用于西北地区等干热气候条件,但对于非干燥地区,单靠蒸发冷却无法得到满意的送风状态,还需与除湿技术相结合.文章分析比较了与蒸发冷却相结合的冷却除湿、转轮除湿及溶液除湿三种不同空调系统,提出了蒸发冷却技术与机械冷却除湿相结合的空调系统方案,并分析了其节能潜力. 相似文献