Performance analysis of liquid desiccant based air-conditioning system under variable fresh air ratios

In conventional air-conditioning system, fresh air volume is always restricted to save energy, which sacrifices indoor air quality (IAQ) to some extent. However, removing the latent load of air by liquid desiccant rather than by cooling is an alternative way of reducing energy consumption. Therefore, IAQ can be improved by increasing the volume of fresh air introduced into an air-conditioning system. In this paper, a liquid desiccant based air-conditioning system is studied, with the system performance under various fresh air ratios analyzed using simulation tests. In addition, the proposed system and a conventional system are compared. In the proposed system, with the increase in fresh air ratio, the heating load for solution regeneration rises, the dehumidification efficiency increases and the regeneration efficiency drops. The coefficient of performance (COP) of the liquid desiccant based system decreases sharply when the fresh air ratio exceeds 60%. The results also show that the proposed system can save power notably. The maximum power saving ratio is 58.9% when the fresh air ratio is 20%; however, the ratio drops when the fresh air ratio increases. These findings will be beneficial in the selection of fresh air ventilation strategies for liquid desiccant based air-conditioning systems.     

热管在空调中的应用

介绍了热管的工作原理和热管技术的特点，回顾了热管在空调中的应用情况，分析了热管技术在空调系统热回收、房间空调除湿、冰蓄冷系统、汽车空调及太阳能吸收式空调中应用的可行性和有效性，对热管式空气换气装置进行了实验研究，结果表明热管技术有很大的节能潜力。     

洁净手术室新风深度除湿与变新风量系统节能设计探讨

医院洁净手术部是医院中能耗较多的单位,净化工程中对节能设计的研究和实践一直是净化设计的重点。文章尝试采用新风深度除湿技术与变新风量空调系统相结合,以求降低净化空调系统能耗,探讨一种手术部可控性强、方便灵活的节能设计方案。     

套管式土壤-空气换热器实验研究

本文介绍了土壤—空气换热系统的工作原理,并进行了相关实验研究。研究结果表明该实验系统具有良好的持续性和稳定性,新风经处理后温度降低、含湿量减小。可以认为在湿热地区,用地能对新风进行降温除湿是夏季改善室内空气品质和节约能耗的有效措施。     

压缩空气溶液除湿系统分析

为了祛除压缩空气中的水蒸气,采用溶液除湿系统对压缩空气进行干燥。建立了压缩空气溶液除湿系统的分析模型,进行了损率和效率计算。并和国内目前普遍使用的压缩空气冷冻除湿方法、冷冻-吸附除湿方法进行分析比较。结果表明,采用溶液除湿系统对压缩空气进行干燥的效率为62.5%,比常规的冷冻除湿系统57.4%和冷冻-吸附除湿系统57%更节能,具有较大的节能潜力。     

新型排风能量回收装置的分析与研究

作者从全铝制板翅式换热器与凝结水间接蒸发冷却联合应用的试验获得的结果出发，对该换热器应用于集中空调系统的能量回收做出了计算，并且进行较为详尽的分析，计算结果表明全新风空调系统使用该能量回收装置后，可以节省机组装机容量50％，节省运行费用一半；这对需要大量新风的厂房，医院的特殊病区等有很好的节能效果；而普通的舒适性空调系统，应用该能量回收装置后也可以节省装机容量20％；这表明在集中空调系统中应用全铝制板翅式换热器既能改善室内空气品质又能回收排风能量，是集中空调系统节能和人性化行之有效的措施：     

Modelling and performance prediction of an integrated central cooling plant for HVAC energy efficiency improvement

The aim of this paper is to explore methods to reduce the energy consumption of a central cooling plant. To achieve this, we have developed a new design for heating, ventilating and air conditioning (HVAC) efficiency improvement. A storage tank together with an immersed heat exchanger is installed in the discharge line between the compressor and condenser. The heat exchanger uses the make-up water of the cooling tower to reduce the refrigerant temperature entering the condenser. To investigate the potential of energy savings, we used a real-world commercial building with a central cooling plant, located in a hot and dry climate, for our case study. The energy consumption and relevant data of the existing central cooling plant were acquired over the course of a typical week in summer. The integrated system has been modeled and analyzed to achieve energy conservation. The performance of the proposed cooling system was simulated using a transient simulation software package. Comparison of the proposed system with existing cooling plant is included in this paper to demonstrate the advantages of our new configuration. Results show that up to 18% power saving can be obtained by using our design.     

转轮除湿与冷却除湿相结合的复合式除湿工艺空调系统

介绍一个转轮除湿与冷却除湿相结合的复合式除湿工艺空调系统，分析比较氯化钙、乙二醇冷冻水载冷剂在同一温度之间及同一载冷剂在不同温度下的换热系数差异，分析该工艺空调系统不能正常运行的原因，并提出改进措施。     

Energy savings potential of a desiccant assisted hybrid air source heat pump system for residential building in hot summer and cold winter zone in China

In hot summer and cold winter zone in China, air conditioning system has four running modes yearly including cooling with dehumidification, cooling, dehumidification and heating in residential buildings. The conventional air source heat pump (ASHP) system is not designed to independently control temperature and humidity, and is not very suitable for the dehumidification mode in the view of building energy consumption. A novel ASHP system combining radiant cooling/heating for residential buildings was presented. The main feature of this hybrid ASHP system is that desiccant wheel and cooling coil accomplish dehumidification process together, and the regenerative heat needed by the desiccant wheel is supplied by the condenser dissipated heat. Based on simulation studies and performance analysis, this paper predicts the primary energy consumption of the hybrid ASHP system in comparison with the conventional ASHP system during the cooling and heating seasons. It was found that primary energy requirement can be reduced by more than 8% in cooling with dehumidification mode, by 50% in dehumidification mode, and by more than 14% in heating mode. The study results prove that the hybrid ASHP system can keep great energy saving and running cost saving yearly, especially in the dehumidification process.     

Comparison of annual energy performances with different ventilation methods for temperature and humidity control

Stratum ventilation has been proposed to accommodate elevated indoor temperatures recommended by governments in East Asia. TRNSYS is used for computation of the space cooling loads, sensible and latent, as well as system energy consumption. Typical configurations of an office, a classroom and a retail shop in Hong Kong are investigated. Desiccant dehumidification with and without solar assistance is utilized for the air treatment under displacement ventilation and stratum ventilation, while simple reheating is adopted under mixed ventilation. Compared with mixing ventilation and displacement ventilation, stratum ventilation derives its energy saving potential largely from the following five factors: the reduction in ventilation, dehumidification and transmission loads, prolonged free cooling period and increased the COP of the chillers. For the office, the year-round energy saving is found to be substantial at 20% and 40% without the need for solar energy provision when compared with displacement ventilation and mixing ventilation respectively. For the classroom and retail shop, the year-round energy saving is at about 25% and at least 37% with the aid of solar energy provision when compared with displacement ventilation and mixing ventilation respectively.     

New type of fresh air processor with liquid desiccant total heat recovery

A liquid desiccant total heat exchanger and small capacity refrigeration cycle combined fresh air processor is proposed here in this paper, in order to improve indoor air quality and decrease the energy consumption of the air-conditioning system. Operating principles of both the total heat recovery device and fresh air processor using liquid desiccant are presented in details. Experimental tests of the fresh air processor installed in a hospital show that energy efficiency ratio (EER) is around 6.3–7.3 in the summer experimental conditions and 4.7–5.0 in the winter experimental conditions. Hour-by-hour simulation, which is based on the climate data in Beijing, shows that the average EER is 5.3 and 4.3 in summer and winter period, respectively. Liquid desiccant has the potential to remove a number of pollutants, avoiding cross contamination. Furthermore, in summer fresh air is dehumidified by contacting liquid desiccant instead of 7 °C chilled water, which avoids wet surfaces in the air-conditioning system and much higher indoor air quality can be achieved.     

Efficiency of energy recovery ventilator with various weathers and its energy saving performance in a residential apartment

The energy recovery ventilator (ERV) is an effective method, which can transfer heat and moisture from the exhaust air into the outdoor fresh air to save energy in buildings. Nowadays, ERV has been widely used in the commercial, industrial and residential buildings in China. Its energy saving performance depends on a lot of factors, such as the outdoor environmental conditions, the enthalpy efficiency of the exchanger, and so on. Based on the relationship among sensible heat, latent heat and enthalpy efficiency, we analyzed the weighted coefficient equations for describing the performance of ERV in different climatic zones in China. According to China weather data, enthalpy efficiency of the exchanger mainly depends on sensible heat efficiency in winter and latent heat efficiency in summer. The energy simulations of a sample apartment in a residential building were made under different operation conditions to study the performance of ERV. The energy saving performances of the ERV were studied with five different outdoor climatic conditions, the enthalpy efficiency, fan power consumption of ERV and fresh air change rate. To improve energy saving performance, better efficient enthalpy exchange material and higher effiencient fans must be explored, while reasonable fresh air change rate as well as proper operation period according to local climate should also be carefully considered.     

新、回风独立空调系统

介绍了上海生物制品研究所有限责任公司生技大楼的全空气空调系统。该系统新风与回风分别单独处理,新风由新风空调箱处理后再送至回风空调箱,然后经过干工况制冷后送至房间。经过测试,这种做法使得回风空调箱没有再热,新风再热量很小,与一次回风空气处理方式相比,再热量及制冷量都大大减少,具有很好的节能示范意义。     

新风换热机组在数据中心空调节能中的利用

IT能耗在所有的电力使用当中所占比重的不断上升,已经成为社会提倡节能降耗主要领域之一。数据中心的高冷负荷、高耗电,已经成为所有的数据中心都无法回避的问题。数据中心空调设计在冬季充分利用室外冷源成为节能设计的首选。笔者通过对新风换气机组的开创性利用,独到的发挥了新风换热机组的节能特性,并通过实验数据测试了其节能功效     

Control strategies for a liquid desiccant air-conditioning system

Liquid desiccants are energy efficient in air dehumidification. A significant amount of research has been conducted on liquid desiccant systems, but little attention has been paid to the control issues surrounding such system. In this study, a novel dedicated outdoor air-conditioning system that adopts liquid desiccant dehumidification is proposed. A simulator of the proposed system is built on the TRNSYS platform. Control methods for the supply air dehumidification and solution regeneration processes are presented, and their effectiveness is evaluated. Two control strategies are developed for the proposed liquid desiccant system based on the evaluation results. The control performances of these two strategies are compared under different operation conditions using simulation tests.     

天津市肿瘤医院肿瘤科研中心工程暖通空调系统方案分析

通过能耗模拟、空气处理过程分析等方式,分析了该工程冷源容量及配置方式、采用冷却除湿加干式风机盘管系统的可行性,以及利用新风消除过渡季及冬季内区余热方案的技术及经济性,并最终确定了合理的系统方案.     

Advancement of solar desiccant cooling system for building use in subtropical Hong Kong

The solar desiccant cooling system (SDCS) had a saving potential of the year-round primary energy consumption as compared to the conventional air-conditioning system for full fresh air application in the subtropical Hong Kong. In order to further enhance its energy efficiency, advancement of the basic SDCS was carried out through a strategy of hybrid design. Six hybrid system alternatives of SDCS were therefore proposed, three for full fresh air design while another three for return air design for the building zone. Year-round performance evaluation of each solar hybrid desiccant cooling system was conducted for typical office application under different climatic and loading conditions. All the six hybrid system alternatives were found technically feasible, with up to 35.2% saving of year-round primary energy consumption against the conventional air-conditioning systems. Among the hybrid alternatives, recommendations were made on the SDCS hybridized with vapour compression refrigeration for full fresh air design; and the SDCS hybridized with vapour absorption refrigeration for return air design, since they had the saving potentials of both primary energy and initial cost. These two hybrid system alternatives used evacuated tubes, a more economical type of solar collectors compared to the PV or PVT panels.     

毛细管辐射空调的湿环境控制与防结露措施

毛细管辐射空调系统具有优良的热舒适性能、无室内噪声影响、高效节能等特点,但受系统庞大复杂、造价较高、夏季易结露等因素影响,限制了辐射空调在夏热冬冷及高湿度地区进一步推广应用。在毛细管辐射空调系统小型化和防止结露的探索实践中,采取温湿度独立控制及新风冷凝除湿方式能使结构简化,加大在别墅及高档住宅中应用的灵活性,采取新风除湿和被动式吸湿材料共同承担室内湿负荷的技术方案,以及减少维护结构水蒸汽渗透量和利用"空气湖"效应,有助于避免维护结构表面结露现象。     

免疫空调系统的构建及其初步分析

基于建筑环境安全性的要求,提出了免疫空调系统的概念。免疫空调系统的构建原则为：热湿分开处理(独立除湿)、空气净化与杀菌消毒的综合集成处理、合理的空调系统形式与布置、新风可调以及紧急免疫。给出了两种可行的免疫空调系统形式：溶液独立除湿与蒸发冷却联合运行的系统、溶液独立除湿与机械制冷联合运行的系统。免疫空调系统具有盐水溶液的净化杀菌、设置紫外线杀菌装置、生物传感器检测有疫情出现时系统转入全新风运行等多重净化免疫机制。对所构建的免疫空调系统在运行费用、适用性等方面进行了初步分析,表明其具有较好的经济性和适用性。     

Membrane heat exchanger in HVAC energy recovery systems, systems energy analysis

The thermal performance of an enthalpy/membrane heat exchanger is experimentally investigated. The heat exchanger utilizes a 60gsm Kraft paper as the heat and moisture transfer surface for HVAC energy recovery. The heat exchanger sensible, latent and total effectiveness have been determined through temperature and moisture content measurements. The annual energy consumption of an air conditioner coupled with an enthalpy/membrane heat exchanger is also studied and compared with a conventional air conditioning cycle using in-house modified HPRate software. The heat exchanger effectiveness are used as thermal performance indicators and incorporated in the modified software. Energy analysis showed that an air conditioning system coupled with a membrane heat exchanger consumes less energy than a conventional air conditioning system in hot and humid climates where the latent load is high. It has been shown that in humid climate a saving of up to 8% in annual energy consumption can be achieved when membrane heat exchanger is used instead of a conventional HVAC system.