置换通风与冷却顶板

介绍了冷却顶板和置换通风的基本原理，以及两者在提高人体热舒适性和室内空气品质方面的优越性，并指出两者的结合使用可带来明显的节能效果。     

A combined system of chilled ceiling,displacement ventilation and desiccant dehumidification

Different types of heating, ventilation, and air-conditioning (HVAC) systems consume different amounts of energy yet they deliver similar levels of acceptable indoor air quality (IAQ) and thermal comfort. It is desirable to provide buildings with an optimal HVAC system to create the best IAQ and thermal comfort with minimum energy consumption. In this paper, a combined system of chilled ceiling, displacement ventilation and desiccant dehumidification is designed and applied for space conditioning in a hot and humid climate. IAQ, thermal comfort, and energy saving potential of the combined system are estimated using a mathematical model of the system described in this paper. To confirm the feasibility of the combined system in a hot and humid climate, like China, and to evaluate the system performance, the mathematical model simulates an office building in Beijing and estimates IAQ, thermal comfort and energy consumption. We conclude that in comparison with a conventional all-air system the combined system saves 8.2% of total primary energy consumption in addition to achieving better IAQ and thermal comfort. Chilled ceiling, displacement ventilation and desiccant dehumidification respond consistently to cooling source demand and complement each other on indoor comfort and air quality. It is feasible to combine the three technologies for space conditioning of office building in a hot and humid climate.     

夏季湿热地区置换通风和冷却顶板复合系统节能潜力研究

根据上海一办公楼置换通风和冷却顶板复合系统的设计及运行特点,应用EnergyPlus软件模拟了采用转轮除湿方式的复合系统的供冷季能耗,并分别模拟了采用冷却除湿方式的复合系统、带热回收装置的混合通风系统和置换通风系统的供冷季能耗以进行对比。结果表明,在湿热地区采用转轮除湿方式可比冷却除湿方式节约制冷机冷量,空调季总能源费用比混合通风系统节约30%左右。     

Model-based optimal supervisory control of chilled ceiling displacement ventilation system

The aim of this paper is to develop an optimized online supervisory control predictive tool for the chilled ceiling displacement ventilation (CC/DV) system to minimize energy consumption while creating the best indoor air quality (IAQ) and thermal comfort. The online controller is designed to operate under an optimized control strategy with five control set points. A dynamic multi-variable objective cost function is formulated for the supervisory control of the CC/DV system performance indices and constraints, and is solved using genetic algorithm. The design of the optimized controller takes into consideration the response time of three-way valves, reheat, and supply fan to employ signaled changes in set points.The developed online controller response to load changes and its ability to change system set points to optimally meet unknown load and constrains are tested and evaluated under the simulated ‘real life’ environment for a case study. It is shown that the implemented online optimized controller is robust, and its development contributes to improved CC/DV system energy efficiency.     

Chilled ceiling displacement ventilation design charts correlations to employ in optimized system operation for feasible load ranges

This paper expands Ghaddar et al. [N. Ghaddar, K. Ghali, R. Saadeh, A. Keblawi, Design charts for combined chilled ceiling displacement ventilation system (1438-RP), ASHRAE Transactions, 143 (2) (2008) 574-587] design charts of combined chilled ceiling (CC) displacement ventilation (DV) system to operating sensible load ranges from 40 W/m² to 100 W/m². It develops a global correlation of system load and operational parameters, with comfort measured by vertical temperature gradient and indoor air quality measured by the stratification height. The correlations are used for a known transient load profile in generating optimal settings of the CC/DV system operational parameters and associated energy consumption.An example is illustrated to show how the correlation could be used to size the system and to provide optimized control of the CC/DV system operation at low computational cost. Results of the current model are compared to the published case study of an optimized operation based on transient simulations of the space thermal model to achieve minimum operation cost [M. Mossolly, N. Ghaddar, K. Ghali, L. Jensen, Optimized operation of combined chilled ceiling displacement ventilation system using genetic algorithm, ASHRAE Transactions, 143 (2) (2008) 541-554]. The design correlations resulted in good agreement with published data (within 3% error in energy consumption and average 6% error in predictions of comfort and stratification height) at 1/4 of the computational time. The presented methodology provides an alternative for using the correlation for supervisory online controllers for the CC/DV system based on physically derived correlations.     

冷却顶板对置换通风系统的影响:CFD研究

以计算流体力(CFD)的模型为基础,采用有限容积法对带有冷却顶板的置换通风系统和不带冷却顶板的普通置换通风系统的温度场、气流分布及人体的热舒适性进行了模拟分析,模拟结果表明,冷却顶板-置换通风系统可以减小室内温度梯度,提高人体热舒适性。     

Air quality in rooms conditioned by chilled ceiling and mixed displacement ventilation for energy saving

A transient-contaminant-transport model is developed for assessing IAQ in the breathing zone when introducing return air into rooms conditioned by CC/DV system to save energy. The steady state transport model of [1] is extended to transient conditions while accounting for significant wall plumes associated with external loads.Experiments are performed to validate the extended model predictions of IAQ expressed in the level of CO₂ concentration. Experiments are conducted in a chamber with two external walls in Kuwait Climate. Measurements are recorded in time of the air temperature and CO₂ concentration at selected locations in the room and compared with values predicted by the model. Experimental results agreed well with model predictions. The maximum errors in predicted CO₂ concentrations are less than ±25 ppm in presence of external load. 60% fresh air fraction resulted in 37% less energy consumption compared with 100% fresh air CC/DV system.The validated model is applied to a case study in Kuwait to evaluate energy saving over the cooling season for a typical office space while using mixed DV air. Energy savings of up to 20.6% can be realized using mixed supply air while maintaining IAQ compared with energy used for the 100% fresh air.     

置换通风在办公建筑中的应用与分析

利用计算流体力学(CFD)方法，对使用置换通风的办公建筑进行计算机数值模拟对室内空气的速度场、温度场进行分析，认为置换通风在提高空内空气品质和节能方面具有一定的效果。     

置换通风加冷却顶板系统避免结露和下降气流的方法

提出了一种避免结露和下降气流的方法:用对长波具有高透过性的薄膜密封包裹冷却顶板,该薄膜和冷却顶板下表面之间保留一空气或真空夹层。实验测试了办公室内的温度场、速度场和CO2浓度场,结果显示薄膜的温度等于或大于冷却顶板下表面和室内空气温度的平均值,薄膜表面和冷却顶板不可能结露,下降气流也相应减少,冷却顶板的制冷量基本保持不变。     

上海体育馆置换通风系统设计研究

介绍了上海体育馆置换通风设计,采用相同的原始数据与设计参数,按照现行的暖通规范与混合通风设计作了比较。计算显示出置换通风在室内空气品质和节能上的优势及其在应用场所上的局限性。     

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.     

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。     

Chilled ceiling and displacement ventilation aided with personalized evaporative cooler

This paper aims at studying the energy impact of a chilled ceiling displacement ventilation CC/DV system aided with a personalized evaporative cooler (PEC) directed towards the occupant trunk and face. A simulation model is developed for integrating the personalized cooler with the ascending thermal plume. The thermal model of the conditioned room air around the person is integrated with a segmental bioheat and thermal comfort model to predict the human thermal comfort.The model is validated with experimental data on the vertical temperature distribution in the room, and the recorded overall comfort perceived by surveyed subjects. Experimental results agreed well with predicted values of temperature and comfort level. When using personalized cooling, the DV supply air temperature can be as high as 24 °C while the PEC at flow rates of 3–10 l/s achieved similar comfort with a DV system at supply temperature of 21 °C. At equal thermal comfort level, the integrated CC/DV system, PEC model resulted in up to 17.5% energy savings compared to the CC/DV system without a PEC. When mixed air is used in the CC/DV system additional 25% savings in energy is realized when compared with energy used for the 100% fresh air without the PEC.     

Performance of a solar-regenerated liquid desiccant ventilation pre-conditioning system

A solar-regenerated liquid desiccant ventilation pre-conditioning system has been proposed for use in hot and humid climates. The system aims to dehumidify the ventilation air which is the major source of latent load. A heat exchanger is used to cool the dehumidified air instead of typical evaporative cooling to maintain the dryness of the air. The use of solar energy at the regeneration process and cooling water from a cooling tower makes the system more passive. The simulation procedure for the proposed system has been presented. By inputting the climatic data and the physical parameters of all equipments, the operating parameters at each equipment and the performance parameters of the system can be evaluated. The simulation procedure is demonstrated by showing the daily profiles of the operating and performance parameters on a typical day as well as investigating the influence of the selected operating parameters on the system performance. The results suggest that the most influential parameters are solar radiation, ventilation rate, and desiccant solution concentration. The balance between the water removed at the dehumidifier and that evaporated at the regenerator needs to be considered to maintain uniform performance during continuous operation.     

一种新型液体除湿空调的应用

分析了常规液体除湿空调的不足,开发了一种新型液体除湿空调装置,介绍了其系统原理及流程。在上海高温高湿的气候条件下的实际应用表明该系统在节能和低品位能源利用方面有重要意义。     

溶液调湿技术在既有建筑空调系统改造中的应用

针对既有建筑空调系统改造中存在的问题,提出采用溶液调湿空调系统的改造方案,以达到降低改造难度,保证改造后空调系统节能、舒适的目的.以某大型三甲医院综合服务楼为例,对其空调效果不佳的现象进行了测试分析,对溶液调湿空调改造方案和传统改造方案进行了分析比较,指出了溶液调湿空调在既有建筑改造中应用的可行性和优势.     

溶液除湿空调新风机组冬季工况性能研究

提出了一种由溶液除湿新风机组和空气源热泵装置组合的新系统,利用MATLAB语言对该系统进行数值模拟计算和分析,结果表明:在西安地区冬季空调室外计算参数下,新风机组性能系数COP,TCOP和COPh分别为0.5,0.65和5.1。     

Performance analysis of a liquid desiccant and membrane contactor hybrid air-conditioning system

The present study examines the performances of a hybrid air-conditioning system in which a vapour-compression inverse cycle is integrated with an air dehumidification system working with hygroscopic solution and hydrophobic membrane. This model may be a valid alternative to traditional summertime air-conditioning system, in which the air is cooled to below its dew-point temperature and subsequently reheated.The proposed hybrid system involves simultaneously cooling and dehumidifying the air conveyed to the conditioned ambient in an air-solution membrane contactor. An LiCl solution is cooled by means of a vapour-compression inverse cycle using the refrigerant KLEA 407C. The solution is regenerated in another membrane contactor by exploiting the heat rejected by the condenser.A SIMULINK calculation programme was designed in order to simulate the system under examination in steady-state conditions. The performances of the system were analysed on varying a few significant operating parameters, and were compared with those of a traditional direct-expansion air-conditioning plant in typical summertime conditions. The results of the simulations revealed significant energy savings, which, in particular operating conditions, may exceed 50%.     

置换通风与混合送风供冷季运行能耗比较

根据置换通风和混合送风设计及运行的特点，以DeST为模拟工具，分析了北京某写字楼分别采用置换通风和混合送风方式供冷季空调系统的运行情况，讨论了两种送风方式在定风量或变风量运行时系统的逐时能耗及在室外新风利用上的特点。结果表明，置换通风比混合送风节省10％以上的运行费用。     

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。