Investigation of a hybrid system of nocturnal radiative cooling and direct evaporative cooling

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.     

Experimental investigation of two-stage indirect/direct evaporative cooling system in various climatic conditions

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.     

Energy saving potential of an indirect evaporative cooler as a pre-cooling unit for mechanical cooling systems in Iran

The performance of indirect evaporative cooling system (IEC) to pre-cool air for a conventional mechanical cooling system has been investigated for four cities of Iran. For this purpose, a combined experimental setup consisting of an IEC unit followed by a packaged unit air conditioner (PUA) was designed, constructed and tested. Two air simulators were designed and used to simulate indoor heating load and outdoor design conditions. Using of experimental data and an appropriate analytical method, the performance and energy reduction capability of combined system has been evaluated through the cooling season. The results indicate IEC can reduce cooling load up to 75% during cooling seasons. Also, 55% reduction in electrical energy consumption of PUA can be obtained.     

Effectiveness of indirect evaporative cooling and thermal mass in a hot arid climate

In this paper, we compare results of a long-term temperature monitoring in a building with high thermal mass to indoor temperature predictions of a second building that uses an indirect evaporative cooling system as a means of passive cooling (Vivienda Bioclimática Prototipo -VBP-1), for the climatic conditions of Sde Boqer, Negev region of Israel (local latitude 30°52′N, longitude 34°46′E, approximately 480 m above sea level). The high-mass building was monitored from January through September 2006 and belongs to a student dormitory complex located at the Sde Boqer Campus of Ben-Gurion University. VBP-1 was designed and built in Maracaibo, Venezuela (latitude 10°34′N, longitude 71°44′W, elevation 66 m above sea level) and had its indoor air temperatures, below and above a shaded roof pond, as well as the pond temperature monitored from February to September 2006. Formulas were developed for the VBP-1, based on part of the whole monitoring period, which represent the measured daily indoor maximum, average and minimum temperatures. The formulas were then validated against measurements taken independently in different time periods. The developed formulas were here used for estimating the building's thermal and energy performance at the climate of Sde Boqer, allowing a comparison of two different strategies: indirect evaporative cooling and the use of thermal mass.     

交通岗亭间接水蒸发开式空调系统

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。     

Application of radiant cooling as a passive cooling option in hot humid climate

In hot and humid region, air-conditioning is increasingly used to attain thermal comfort. Air-conditioning is highly energy intensive and it is desirable to develop alternative low-energy means to achieve comfort. In a previous experimental investigation using a room equipped with radiant cooling panel, it was found that cooling water kept to 25 °C could be used to attain thermal comfort under some situations, while water at such temperature would not cause condensation of moisture from air on the panel. This paper reports results of a series of whole-year simulations using TRNSYS computer code on applications of radiant cooling to a room model that represents the actual experimental room. Admitting the inability of radiant cooling to accept latent load, chilled water at 10 °C was supplied to cooling coil to precool ventilation air while water cooled by cooling tower was used for radiant cooling in daytime application. For night-time, cooling water from cooling tower supplied for radiant cooling was found to be sufficient to achieve thermal comfort. Such applications are considered to be more amenable to residential houses.     

Performance analysis of a ground-assisted direct evaporative cooling air conditioner

In this paper, the results of performance analysis of a ground-assisted hybrid evaporative cooling system in Tehran have been discussed. A Ground Coupled Circuit (GCC) provides the necessary pre-cooling effects, enabling a Direct Evaporative Cooler (DEC) that cools the air even below its wet-bulb temperature. The GCC includes four vertical ground heat exchangers (GHE) which were arrayed in series configuration. In order to have an accurate prediction of the optimum performance of a GCC, a computational fluid dynamic simulation was performed. Simulation results revealed that the combination of GCC and DEC system could provide comfort condition whereas DEC alone did not. Based on the simulation results the cooling effectiveness of a hybrid system is more than 100%. Thus, this novel hybrid system could decrease the air temperature below the ambient wet-bulb temperature. This environmentally clean and energy efficient system can be considered as an alternative to the mechanical vapor compression systems.     

再循环蒸发冷却中再循环风量的实验研究

介绍了一种再循环蒸发冷却技术,其原理是利用一部分经间接冷却处理的空气作为二次空气直接蒸发制取冷水,用冷水反过来间接冷却室外空气。搭建了相应的实验台,针对夏季实际工况条件,实验研究了再循环风量比例对蒸发冷却效率的影响,给出了合适的再循环风量范围。     

叉流平板式间接蒸发冷却过程数值模拟

建立了数学模型,对叉流平板式间接蒸发冷却过程进行了数值模拟分析,得到了分别沿一、二次空气流动方向一次空气干球温度和二次空气干湿球温度的分布,以及水膜温度的变化情况。     

Innovative low-energy evaporative cooling system for buildings: study of the porous evaporator wall

To face the current increase of building cooling demand and the concerns related to climate changes, an energy-efficient evaporative cooling system using porous material has been developed. This article presents the innovative cooling system and a detailed hygrothermal analysis of its main element: the porous evaporator. A mathematical model and an experimental set-up are presented, which enable to determine the suitable material properties for the evaporator and its impact on the overall cooling system performance, focusing on the optimal use of both energy and water. A good agreement is observed between numerical and experimental results, and the evaporative cooling power is estimated from 12 to 72?W/m² of evaporator wall, depending on the evaporator characteristics. A parametric analysis is conducted to select the best material for the evaporative cooling system. An intrinsic permeability of the material of 4?×?10^?17?m² is recommended for this new cooling system.     

某车间蒸发冷却通风降温系统的设计及运行测试

介绍了蒸发冷却降温技术在某工厂空冷配电室的应用,对其系统运行情况进行了测试分析,结果表明在干燥地区采用直接蒸发冷却通风降温方式消除工业余热可以满足生产需求.     

蒸发冷却半集中式空调系统的控制方案

介绍了蒸发冷却半集中式空调系统的流程。基于该系统不同季节的运行模式,设计了自控方案,以保证该空调系统的安全性和节能性。详细介绍了控制内容和硬件配置。利用组态软件完成PC机与PLC之间的通讯,实现了系统集中控制、数据记录和打印等功能,能为现场设备维护人员提供详细的资料,简化操作、维护工作。工程应用实践表明,该自控系统运行稳定,能达到预期效果。     

间接蒸发冷水机组设计开发及性能分析

基于间接蒸发冷却技术设计了高温冷水机组,其驱动源为室外干空气而非电能,冷水机组的理论出水温度可无限接近进口空气的露点温度。建立了数学模型,并提出了系统的串联冷水流程,以更充分地利用室外干空气的能量。合作开发了第一台间接蒸发冷水机组,通过测试得到了实际机组的性能。最后分析了冷水机组作为湿度独立控制空调系统的高温冷源在中国西部及其他地区的应用。     

多级蒸发冷却空调系统在西北地区的应用

介绍了多级蒸发冷却空调系统的几种形式，对在新疆某工程使用的三级蒸发冷却空调系统运行情况作了测试，比较了三种运行方式的效果，得出该系统的适宜和适用的地域。     

高温高湿环境下湿帘-风机温室降温特性及影响因素研究

通过对上海一栋采用湿帘-风机降温的温室内部温度、湿度的连续实测,验证了高温高湿气候下湿帘-风机在温室中的降温效果。对湿帘风机系统在该环境下的蒸发降温效率及温度梯度进行了测试分析,并应用测试数据对温室热环境模型进行了验证,讨论了空气温度、相对湿度、太阳辐射量等室外环境参数对温室降温能力的影响。     

管式间接-直接组合式蒸发冷却空调系统的工程应用分析

简要介绍对比了几种间接蒸发冷却器的性能特点,并指出管式间接-直接组合式蒸发冷却空调系统的主要形式及分区依据。着重对新疆、甘肃、山西等地的管式间接-直接两级或三级蒸发冷却空调系统的应用情况进行介绍,提出实际工程中机组运行出现的问题,并对具体问题提出改进措施。     

基于蒸发冷却的辐射供冷/热实验台设计探讨

对基于蒸发冷却的辐射供冷/热半集中式空调系统实验台进行了简要介绍,并对实验台的新风系统和水系统设计进行了详细说明.分析了该实验台在中湿度地区不同季节的运行模式,指明了该实验台的特点.     

蒸发冷却空调应用的气候适应性区域划分

采用湿球温度作为区域划分指标,以夏季空调室外计算湿球温度为20,23,28℃作为分区指标的临界值,将基本覆盖全国范围的177个城市划分为通风区、高适应区、适应区及非适应区四个区域。     

国内外蒸发冷却空调技术研究进展(3)

介绍了多级蒸发冷却空调系统、除湿与蒸发冷却相结合的空调系统、半集中式蒸发冷却空调系统、建筑物被动蒸发冷却技术、蒸发冷却自动控制系统及蒸发冷却水的水质处理。