多级蒸发冷却在化工厂变频器室通风降温的应用

介绍传统变频器室的降温方式以及多级蒸发冷却技术的特点,并以贵州福泉某变频器室为例,进行多级蒸发冷却通风降温设计,通过与传统机械全面通风降温及单元式空调柜机降温方案进行比选,可以得出多级蒸发冷却通风降温系统在节能方面和运行投资方面均具有很大的优势,为该系统在贵州地区的应用提供技术参考.     

榆林地区大中型商场蒸发冷却空调系统设计分析

以榆林某大型商场为例,对该商场使用蒸发冷却空调系统的设计方法进行研究,对蒸发冷却空调与传统机械制冷空调的优缺点进行对比,给出了具体的空调送风量数值、空调末端的送回风形式确定以及空调机房的设备布置和配管方式;并将适用于高温空调的层式通风方式与蒸发冷却空调系统结合,希望能够促进蒸发冷却在榆林乃至西北地区的推广应用。     

间接蒸发冷却技术的应用研究与现状

由于我国各地区气候条件不同,蒸发冷却的应用方式也有些不同.通过对直接蒸发冷却和间接蒸发冷却技术原理的分析,提供了分析研究的结果.着重介绍间接蒸发冷却技术在我国的应用研究与现状.     

蒸发冷却空调技术在住宅建筑中的研究进展

介绍蒸发冷却空调技术在住宅领域的研究进展。主要包括:直接蒸发冷却空调技术在住宅建筑的应用、间接蒸发冷却在住宅建筑的应用以及蒸发冷却与其他技术相结合在住宅建筑领域的应用几个部分。参考国内外相关文献及其专利,得出蒸发冷却空调技术在部分地区住宅领域应用效果较好的结论,特别是将蒸发冷却空调技术与其他技术相结合的应用过程中,这项技术能够提高整个机组的运行能效比,使机组运行更加节能、环保。在广阔的农村住宅领域以及"干空气能"丰富的部分地区,蒸发冷却空调技术值得被大力推广。     

蒸发冷却空调地铁站应用的可行性分析

对地铁站的空调通风特点及建筑环境状况进行了分析总结,得出我国现行地铁站空调通风系统耗能大、空气品质不佳等问题,通过对我国现行地铁站空调通风系统的现状与蒸发冷却空调自身特性以及国外此方面实际应用效果的比较得出,若将蒸发冷却这种节能、环保的空调应用于干燥、中湿度地区的地铁站(湿度地区辅助应用),可以较好地解决现行地铁站空调...     

抽水蓄能电站水冷式通风空调系统运行优化与能效评价

围绕抽水蓄能电站地下厂房水冷式通风空调系统经济运行问题,介绍了抽水蓄能电站通风空调的结构及运行方式,归纳阐述了国内部分抽水蓄能电站通风空调系统实际运行中面临的厂房空气湿度大、冷却水温过低与特殊时期常规运行能耗大的问题,提出了通风空调系统运行组合优化方案,设计了地下厂房现场改造实施布置图;最后,通过实例量化评价了所提方案在通风空调减排方面的经济运行效果。结果表明,优化通风空调系统运行方式,不仅可增强通风空调系统可靠性和灵活性,还显著降低了运维成本。     

从南迪普电厂实例谈直接蒸发冷却空调的影响因素及应用

从巴基斯坦南迪普电厂直接蒸发冷却空调实际使用效果同设计结果有较大差异入手,分析了存在差异的原因,进而提出了直接蒸发冷却空调可能的优化措施,并展望了直接蒸发冷却空调的应用前景。     

高效喷雾通风冷却塔在循环水场中的节能分析

高效喷雾通风冷却塔通过通风蒸发、热传导形式带走热量来完成热水的降温过程,其主要特点是喷流雾化和利用循环水的余能来推动空气在冷却塔内的强制流动,从而代替轴流风机达到节电节能的目的。其核心部件是喷雾推进雾化器,其主轴采用高分子非金属耐磨材料制造,克服了用油轴承在水环境中易锈蚀、卡死等故障,减少了设备维修量。2008,中国石化洛阳分公司采用高效喷雾通风塔冷却技术对第三循环水场3号塔进行了改造,投用至今运行稳定,主要运行参数达到了预期的目的,冷却效果与使用轴流风机相当,循环泵电流与改造前相当,没有增加循环水的回水管路阻力。若洛阳石化循环水冷却塔轴流风机全部进行此技术改造,保守计算年可节电1500×10^4kW·h。     

蒸发冷却技术

文章介绍了蒸发冷却技术的原理和分类，详细介绍了直接蒸发冷却和间接蒸发冷却的实际应用情况，指出该技术是节能环保的，是可持续发展的制冷技术，具有应用前景。     

单元式露点蒸发冷却装置的实验研究

本研究设计了一台由干、湿通道相结合的单元式露点蒸发冷却装置,通过实验研究了蒸发冷却装置在空气经过一级冷却的模式1和经过二级冷却的模式2两种运行模式下,不同空气入口参数时的换热效果。实验结果表明,空气的入口温度越高,换热效果越好;低湿度时空气的进出口温差比高湿度时大,但其湿球效率和露点效率反而较低,这说明2种效率并不适用于不同湿度间的冷却效果对比;模式2运行时的换热效果比模式1好。与已有研究成果对比表明,该单元式露点蒸发冷却装置的湿球效率和露点效率分别可以达到120%和88%,为露点蒸发冷却装置的优化设计提供理论依据和优化方向。     

Thermal performance of an evaporatively cooled building: Parametric studies

A single-storey office building in a hot and dry climate is modelled for evaporative cooling. The counterflow cooling tower is modified to precool the tower inlet air by the tower exit air in a heat exchanger. Centralized evaporative air cooling, using the modified cooling tower, and roof evaporative cooling are considered to provide comfortable living conditions in the space. The thermal performance of such a building is analysed for various operating parameters. The study indicates that centralized evaporative air cooling is feasible, to maintain near-perfect comfort conditions in hot and dry climates. Modified cooling tower and roof evaporative cooling further enhance the scope of evaporative cooling for comfort applications.     

Experimental investigation of effect of ventilation strategies on the performance of cold storage

Fresh fruits and vegetables are living organisms that require fresh air to survive while being stored. Respiratory gases can build up and damage produce if there is not enough ventilation during storage. Ventilation is required to prevent an excessive build-up of respiratory gases and to maintain the freshness of produce. In hot and dry areas, air ventilation of refrigerated storage can have a negative impact on food produce quality and affect storage performance. An indoor experimental study was carried out to investigate the air ventilation of the cold room during various modes of air supply. The energy recovery device (ERD) with and without evaporative cooling arrangement is used in the air supply and the performance enhancement is compared. The ERD reduces the air ventilation load by more than 50% compared to direct ventilation of the cold room and consequently, it reduces the total power consumption of air ventilation. Furthermore, the overall cooling performance of the system is improved by up to 45.7% when the ERDs are used compared to the direct supply of fresh air during air change mode and the use of energy-saving equipment has also proven improvements in the desired air conditions for food production.     

Theoretical analysis on heat and mass transfer in a direct evaporative cooler

The heat and mass transfer between air and water film in the direct evaporative cooler is theoretically analyzed in present paper. A simplified cooling efficiency correlation is proposed based on the energy balance analysis of air. The correlation may be applied to the water-drip cross-flow direct evaporative cooler, in which the wet special durable papers with different wave angles form the air channel. The Influences of the air frontal velocity and the thickness of pad module on the cooling efficiency of a direct evaporative cooler are discussed. An optimum frontal velocity of 2.5 m/s is recommended to decide the frontal area of pad module in the given air flow. The simplified correlation of cooling efficiency is validated by the test results of a direct evaporative cooler.     

Improving indoor conditions of a Thai-style mushroom house by means of an evaporative cooler and continuous ventilation

The paper discusses the effect of an evaporative cooling process and continuous ventilation for improving the indoor conditions of a conventional Thai-style mushroom house. A numerical model describing the behaviour of the Thai-style mushroom house model was developed. It was validated by comparing its output with that of the experiment of a small model of a mushroom house. It was found that the combination of evaporative cooling and continuous ventilation reduced the temperature and increased the relative humidity of air inside a mushroom house that is suitable for growing Lentinus.     

Experimental study of a direct evaporative cooling approach for Li-ion battery thermal management

A desirable operating temperature range and small temperature gradient is beneficial to the safety and longevity of lithium-ion (Li-ion) batteries, and battery thermal management systems (BTMSs) play a critical role in achieving the temperature control. Having the advantages of direct access and low viscosity, air is widely used as a cooling medium in BTMSs. In this paper, an air-based BTMS is modified by integrating a direct evaporative cooling (DEC) system, which helps reduce the inlet air temperature for enhanced heat dissipation. Experiments are carried out on 18650-type batteries and a 9-cell battery pack to study how relative humidity and air flow rate affect the DEC system. The maximum temperatures, temperature differences, and capacity fading of batteries are compared between three cooling conditions, which include the proposed DEC, air cooling, and natural convection cooling. In addition, a DEC tunnel that can produce reciprocating air flow is assembled to further reduce the maximum temperature and temperature difference inside the battery pack. It is demonstrated that the proposed DEC system can expand the usage of Li-ion batteries in more adverse and intensive operating conditions.     

A new approach to analysis and optimization of evaporative cooling system II: Applications

After introducing the concepts of moisture entransy, moisture entransy dissipation and thermal resistance based on moisture entransy dissipation (TRMED) in part I of this study, we further analyze several direct/indirect evaporative cooling processes based on the above concepts in this part. The nature of moisture entransy, moisture entransy dissipation and TRMED during evaporative cooling processes was reexamined. The results demonstrate that it is the moisture entransy, not the enthalpy, that represents the endothermic ability of a moist air, and reducing the entransy dissipation by both enlarging the thermal conductance of heat and mass transfer, and decreasing the temperature potential of the moist air, i.e. the difference between the dry-bulb temperature of moist air over its dew-point temperature, will result in a smaller system TRMED, and consequently a better evaporative cooling performance. Then, a minimum thermal resistance law for optimizing evaporative cooling systems is developed. For given mass flow rates of both moist air and water, with prescribed moist air and water conditions, minimizing the TRMED will actually lead to the most efficient evaporative cooling performance. Finally, the thermal conductance allocation for an indirect evaporative cooling system is optimized to illustrate the application of the proposed minimum thermal resistance law.     

Numerical investigation on the heat and mass transfer in a direct evaporative cooler

A simplified mathematical model is developed to describe the heat and moisture transfer between water and air in a direct evaporative cooler. The mass of evaporated water is treated as a mass source of air flow, and the related latent heat of water evaporation is taken as a heat source in the energy equation. The momentum caused by water evaporation is taken into account in the momentum equations. The effective air viscosity and diffusion coefficient are decided experimentally. The models and methods are validated by comparing the numerical results with those of experiment for the same evaporative cooler. The influences of the inlet frontal air velocity, pad thickness, inlet air dry-bulb and wet-bulb temperatures on the cooling efficiency of the evaporative cooler are calculated and analyzed.The cooling effects of the direct evaporative cooler are predicted for use in four different regions in northwest China using the present numerical method and local weather data for air conditioning design. The predicted results show the direct evaporative cooler with high performance pad material may be well applied for air conditioning with reasonable choices for the inlet frontal velocity and pad thickness.     

Performance enhancement of gas turbines by inlet air‐cooling in hot and humid climates

In this paper, a model to study the effect of inlet air‐cooling on gas turbines power and efficiency is developed for two different cooling techniques, direct mechanical refrigeration and an evaporative water spray cooler. Energy analysis is used to present the performance improvement in terms of power gain ratio and thermal efficiency change factors. Relationships are derived for an open gas turbine cycle with irreversible compression and expansion processes coupled to air‐cooling systems. The obtained results show that the power and efficiency improvements are functions of the ambient conditions and the gas turbine pressure ratio. The performance improvement is calculated for, ambient temperatures from 30 to 50°C, the whole range of humidity ratio (10–100%) and pressure ratio from 8 to 12. For direct mechanical refrigeration air‐cooling, the power improvement is associated with appreciable drop in the thermal efficiency. The maximum power gain can be obtained if the air temperature is reduced to its lowest limit that is the refrigerant evaporation temperature plus the evaporator design temperature difference. Water spray cooling process is sensitive to the ambient relative humidity and is suitable for dry air conditions. The power gain and efficiency enhancement are limited by the wet bulb temperature. The performance of spray evaporative cooler is presented in a dimensionless working graph. The daily performance of the cooling methods is examined for an ABB‐11D5 gas turbine operating under the hot humid conditions of Jeddah, Saudi Arabia. The results indicate that the direct mechanical refrigeration increased the daily power output by 6.77% versus 2.57% for the spray air‐cooling. Copyright © 2005 John Wiley & Sons, Ltd.     

Introduction of a simple diagram-based method for analyzing evaporative cooling

Direct evaporative cooling can be profitable in hot arid climates, whereas favourable situations are not frequent in temperate zones. First the climate limits to direct operation are set on the psychrometric diagram. Then an alternative process is considered that can provide free cooling via evaporation for a lot of climatic conditions not particularly dry and very common in temperate climate: indirect evaporative cooling. Air is cooled in an adiabatic humidification process, and then in turn the same air is used to reduce – via a heat exchanger – the temperature of a second stream of air, whose moisture content consequently remains unchanged. The cooling effect is particularly strong when the air to be humidified is the ambient air being discharged.The potential of indirect evaporative cooling in analysed in every climatic condition, dividing the Mollier psychrometric diagram in different zones where the use of this free cooling techniques is advisable or not.