Study on a novel thermally driven air conditioning system with desiccant dehumidification and regenerative evaporative cooling

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.     

The effects of operational conditions of the desiccant wheel on the performance of desiccant cooling cycles

A desiccant cooling model is developed and applied to the ventilation, recirculation, makeup, and mix modes of the operating system. The mathematical model is based on the transient coupled heat and mass transfer and is used to predict the performance of the system under various design and operational conditions. The numerical results are validated using experimental measurements. The effects of the regeneration temperature and rotational speed of the desiccant wheel on the COP and output cycle temperature are investigated. The results show the availability of an optimum regeneration temperature and rotational speed in which the output cycle temperature has a minimum value. The optimum regeneration temperature and rotational speed are detected and shown on the Psychrometric charts. Calculating these values has a significant effect on the energy use of these cycles.     

Experimental investigation of a novel desiccant cooling system

Desiccant based air conditioning systems are a suitable way to improve indoor air quality due to its superior humidity control. In this study, a novel desiccant based air conditioning system is designed and tested experimentally to improve the indoor air quality and reduce energy consumption. In the system studied, a heat exchanger, which is not used in this type of systems, for pre-heating the regeneration air with exhaust air is used. This paper reports results of initial operation and operational procedures. The performance of the system and its components is discussed.     

Exergetic modeling and experimental performance assessment of a novel desiccant cooling system

New approaches to space conditioning of buildings are required to resolve economic, environmental, and regulatory issues. One of the alternative systems that is brought to agenda is the desiccant cooling systems, which may provide important advantages in solving air conditioning problems. This study deals with the performance analysis and evaluation of a novel desiccant cooling system using exergy analysis method. The system was designed, constructed and tested in Cukurova University, Adana, Turkey and has been successfully operated since 2008. This system consists of a desiccant wheel, heat exchangers, fans, evaporative cooler, electric heater unit and refrigeration unit. The exergy transports between the components and the destructions in each of the components of the desiccant cooling system are determined for the average measured parameters obtained from the experimental results. Exergy efficiencies of the system components are determined in an attempt to assess their individual performances and the potential for improvements is also presented. The exergetic efficiency values for the whole system on the exergetic product/fuel basis are calculated to range from round 32% to 10% at the varying dead (reference) state temperatures of 0-30 °C.     

大型客车发动机冷却系统与除湿供冷联用的空调系统

介绍了除湿供冷系统的工作原理，探讨了大型客车发动机冷却系统与除湿供冷联用的空调系统的组合形式和工作过程，根据国外资料分析了此项技术的技术经济性能以及在我国的应用前景。     

溶液除湿蒸发冷却空调系统及其若干重要问题

从系统流程的构建、系统性能的研究、系统关键部位的优化等方面介绍了溶液除湿蒸发冷却空调系统的研究情况,探讨了进一步研究中的关键问题.     

浅谈蓄冷式空调系统

简要介绍蓄冷式空调技术的发展过程，阐述了其基本原理和特点，分析比较了与传统空调系统的差异，指出该系统具有良好的节能特性，同时提出了在运行过程中的不足之处。     

空调系统中冷却塔的节能

指出对空调系统中的风机、水泵等的耗能就给予与制冷机组同样的重视,系统节能应整体考虑。分析了冷却塔出水温度对系统性能的影响,举例说明了不同工况的能耗对比。     

Performance analysis on the internally cooled dehumidifier using liquid desiccant

Dehumidifier is one of the most important components in liquid desiccant air-conditioning systems. Previous study shows that the internally cooled dehumidifier may have better mass transfer performance than the adiabatic unit. The effect of flow pattern, especially the flow direction of air to desiccant on the internally cooled dehumidifier performance is numerically analyzed in detail. The result shows that counter-flow configuration of air to desiccant has better dehumidification performance, and parallel-flow configuration performs the poorest with the same conditions, due to more uniform mass transfer driving force expressed in the counter-flow configuration. The decrease of the desiccant concentration is the main factor that influences the internally cooled dehumidifier's performance, while the increase of the desiccant temperature is the main performance restricting factor in adiabatic dehumidifier. Internally cooled dehumidifier has better mass transfer performance compared with adiabatic dehumidifier plus external heat exchanger.     

Experimental investigation and theoretical analysis of solar heating and humidification system with desiccant rotor

In this paper, a solar heating system, which combines the technologies of evacuated tube solar air collector and rotary desiccant humidification together, has been configured, tested and modeled. The system mainly includes 15 m² solar air collectors and a desiccant air-conditioning unit. Two operation modes are designed, namely, direct solar heating mode and solar heating with desiccant humidification mode. Performance model of the system has been created in TRNSYS. The objective of this paper is to check the applicability of solar heating and evaluate the feasibility and potential of desiccant humidification for improving indoor thermal comfort. Experimental results show that the solar heating system can convert about 50% of the received solar radiation for space heating on a sunny day in winter and increases indoor temperature by about 10 °C. Compared with direct solar heating mode, solar heating with desiccant humidification can increase the fraction of the time within comfort region from about 10% to 20% for standalone solar heating and from about 30% to 60% for solar heating with auxiliary heater according to seasonal analysis. It is confirmed that solar heating with desiccant humidification is promising and worthwhile being applied to improving indoor thermal comfort in heating season.     

Condenser heat recovery with a PV/T air heating collector to regenerate desiccant for reducing energy use of an air conditioning room

This paper presents an experimental test along with procedures to investigate the validity of a developed simulation model in predicting the dynamic performance of a condenser heat recovery with a photovoltaic/thermal (PV/T) air heating collector to regenerate desiccant for reducing energy use of an air conditioning room under the prevailing meteorological conditions in tropical climates. The system consists of five main parts; namely, living space, desiccant dehumidification and regeneration unit, air conditioning system, PV/T collector, and air mixing unit. The comparisons between the experimental results and the simulated results using the same meteorological data of the experiment show that the prediction results simulated by the model agree satisfactorily with those observed from the experiments. The thermal energy generated by the system can produce warm dry air as high as 53 °C and 23% relative humidity. Additionally, electricity of about 6% of the daily total solar radiation can be obtained from the PV/T collector in the system. Moreover, the use of a hybrid PV/T air heater, incorporated with the heat recovered from the condenser to regenerate the desiccant for dehumidification, can save the energy use of the air conditioning system by approximately 18%.     

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。     

溶液除湿空调系统在工业厂房应用的能耗分析

通过对深圳某工业厂房分别选用常规冷凝除湿空调系统和溶液除湿空调系统进行系统设计和理论计算分析,比较了两类空调系统的能耗及COP。在夏季室外设计工况下,常规冷凝除湿空调系统的COP为2.94,溶液除湿空调系统的COP为5.42。室外空气含湿量越小,对提高溶液除湿系统的性能越有利。溶液除湿空调系统在节能方面具有较大的优势。     

集中空调冷却塔节能分析与探讨

随着集中空调节能技术的发展,关于冷水系统的节能方案和控制策略已趋于统一,而冷却水侧冷却塔的节能空间仍存在争议。为进一步提高集中空调的节能率,从理论和实际应用两方面分析了冷却塔开机台数和风机运行频率对冷水机组性能乃至整个集中空调系统能耗的影响,得出通过对冷却塔的优化控制可使集中空调节电率提高5%的结论。     

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。     

浅析空调水系统设计及施工中的通病

结合空调工程中存在的一些问题，从水泵扬程、水泵耐压强度等方面，对空调水系统设计及施工中存在的通病进行探讨，以便为今后的设计及施工提供借鉴。     

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。     

Feasibility study of a novel dew point air conditioning system for China building application

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.     

一种集中空调冷量计费方法

以风机盘管空调系统为例,介绍了集中空调系统的控制特点、计费依据和计费原理,在冷量计量的基础上给出了一种可行的计费方法。     

溶液除湿新风机组在手术部净化空调中的应用

传统手术部净化空调系统温湿度耦合控制,为了除湿,需要再热过程,消耗能源较多。净化空调采用温湿度独立控制系统,可以实现室内温湿度参数独立控制,空气处理过程不需要再热。新风处理采用溶液除湿新风机组,溶液再生由热泵承担,综合COP较高。循环空调机组干式运行,不产生冷凝水,减少霉菌的滋生,提高送风的品质。手术部采用该系统,可节约大约30％左右能耗,降低运行费用,减少二氧化碳排放,具有良好的经济及社会效益。