多区域变风量空调系统及其分配控制研究

在多区域变风量空调及其控制系统的分析研究基础上,根据ASHRAE通风标准对新风量的要求,针对混合送风系统仿真分析了4种新风及其分配的控制方案,综合考虑了各方案的新同分配以及系统能耗。结果表明,通过VAV末端再热控制并结合AHU送风温度优化的控制方案,可以较好地解决多区域VAV空调系统新风分配问题,同时能有效地降低系统的能耗。     

变风量空调系统新风量控制策略对比试验研究

介绍了变风量空调系统常用的新风控制策略,分析了基于CO_2浓度模型的新风量计算方法。通过对比试验研究了定新风比与变新风比控制策略在系统新风量及各区域新风量分配方面的控制效果,结果表明,2种控制策略均存在新风分配不均的问题。在此基础上,试验研究了变新风比控制策略对室内空气品质的控制效果及节能性。结果表明,在实现相同室内空气品质控制效果的前提下,与基于max Y方程的变新风比策略(max Y-V)相比,基于MSE方程的变新风比策略(MSE-V)能够更大程度地降低能耗,相同工况下,MSE-V策略的空调系统能耗较max Y-V策略低6.76%。     

关键区温度重设定的自适应按需新风控制

针对多区域变风量空调系统,提出一种关键区温度重设定的自适应按需新风控制策略,以最少的能耗满足各区的室内空气质量要求。该策略实时检测各区人员负荷,识别关键区,充分考虑关键区的新风需求,在进行新风设定时充分考虑循环空气中没有使用完的新风。关键区的温度重设定可以加大输送到关键区的送风量从而加大关键区的新风量,新风比减小,从而达到节能目的。利用多区域变风量空调系统的动态仿真平台对该控制策略进行了测试,对其动态控制性能、能耗特性及空气质量特性进行了评估,同时将该控制策略与其他按需新风控制策略进行了比较。     

基于新风阀静压差控制的VAV系统新风量变设定值在线控制方法

针对在多区域变风量空调系统中新风量供给与需求不匹配的问题,在新风阀静压差控制法的基础上,提出了一种将室内CO_2体积分数变化、系统末端需求总风量作为新风量设定值确定和控制约束条件的新风量变设定值在线控制方法,并通过试验对其可行性进行了分析。试验结果表明,该方法能够与空调系统中其他控制回路很好地拟合在一起共同实现控制,以保证室内新风量的需求且更加节能,适合于在线应用。     

变风量多分区空调系统新风量计算

介绍了变风量多分区系统的区域新风需求、新风分布、通风效率和单/双通道多分区循环系统,借鉴ANSI/ASHRAE标准62.1-2004提出的系统新风量计算方法给出了变风量多分区空调系统的新风量计算方法.该方法有助于在新风节能方面拓展设计思路.     

基于独立新风系统的新风量保障方法及经济性研究

介绍了不同传统变风量空调系统新风量控制方法的控制及节能效果,详细分析了变风量空调系统各个区域新风供给量及其需求量之间不匹配的问题。提出了基于独立新风系统的新风量保障方法。通过对比试验研究,分析了该新风量保障方法的经济性。结果表明:基于独立新风系统的新风量保障方法可以很好地实现新风量的按需分配;在大连地区,空调系统使用年限在12 a以上时,采用独立新风系统可以达到很好的节能效果。     

北京大兴国际机场航站楼过渡季新风系统运行策略调适与优化

北京大兴国际机场航站楼核心区内区新风系统设计采用新风机组+全空气处理机组组合的方式进行新风供应。经实测发现，过渡季时室内新风量严重不足，室内效果无法达到设计预期。针对这一问题对机组运行方式展开调适优化并进行分组实测，验证不同运行模式下的室内CO₂浓度，分析结果表明，过渡季新风系统新风量不足是其设计策略导致的。同时根据分析结果对过渡季新风系统运行策略进行修正，并得到了不同区域变频新风机组(OAU)和空调机组(AHU)运行频率的搭配。在该运行模式下，过渡季新风系统既可以满足室内需求，又兼顾节能效果，为后续北京大兴国际机场过渡季OAU-AHU新风系统的实际运行提供了运行依据。     

变风量空调系统的新风问题

以某写字楼为例,分析了变风量系统中不同分区形式对各朝向房间的人均新风量分配的影响,认为新风量分配不均的情况主要出现在冬季和过渡季,提出满足所有朝向房间人员健康要求同时能实现过渡季利用新风节能的新风量设计标准;建议在建筑设计中增加新风竖井面积,在空调外区适当增加最小新风量的取值。     

基于预测稳态时房间CO_2浓度的新风量控制策略

变风量空调系统新风量控制中,传统的控制策略不能兼顾既满足多房间室内空气质量又充分减少新风负荷的要求。针对多房间CO2浓度的控制要求,提出了一种通过在线预测稳态时房间CO2浓度控制新风量的方法。通过实时预测各个空调房间稳态时的CO2浓度,选择CO2浓度最高的房间作为检测房间,控制其CO2浓度为设定值,其他房间的CO2浓度都小于设定值。给出了其理论依据和在线稳态预测的步骤。与新风比修正新风量控制方法的对比结果表明,该方法在保证多房间CO2浓度满足要求的基础上有效减少了新风负荷。     

医用空调新风独立除湿系统变工况运行控制特性研究

本文结合医院手术室空调系统特点对新风独立除湿系统进行建模,并通过VBA编写程序进行模拟计算,研究以普通冷水机组为冷源的新风独立除湿系统的可行性,以及不同的室外环境温湿度、室内设计温湿度、新风量及冷冻水供水温度对新风独立除湿系统的能耗、运行特性及控制的影响,并提出使得系统较节能且稳定地运行的控制策略。研究结果表明,适当地增加新风量会提高新风机器露点温度,有利于系统的安全运行;室内设计温湿度的高低不仅会影响系统的能耗,而且会影响到新风机器露点温度,从而影响系统的稳定性;合理匹配室内设计温湿度和新风量,就能保证系统的稳定运行。     

Fault-tolerant control for outdoor ventilation air flow rate in buildings based on neural network

This paper describes a supervisory control scheme that adapts to the presence of the measurement faults in outdoor air flow rate control using sensor-based demand-controlled ventilation, maintains an adequate indoor air quality and minimizes the resulting increase in energy consumption. A strategy, which is based on neural network models, is employed to diagnose the measurement faults of outdoor and supply flow sensor, and accomplishes the fault-tolerant control of outdoor air flow when faults occur. The neural network models are trained using the data collected under various normal conditions. The residuals between the measurements of flow sensors and the outputs of the neural network models are used to diagnose the faults. When the fault of outdoor or supply air flow sensor occurs, the recovered estimate of outdoor or supply air flow rate obtained on the basis of the neural network models is used in the feedback control loop to regain the control of outdoor air flow. Tests using dynamic system simulation are conducted to validate the strategy. The control, IAQ and energy performances of the system under fault-tolerant control strategy in the presence of the faults in air flow sensor are also presented.     

A new operating strategy for economizer dampers of VAV system

The paper proposes a new operating strategy for the outdoor, discharge, and recirculation air dampers of the economizer in VAV system, called split-signal damper control strategy. The strategy controls the outdoor air by only one damper while keeping the remaining dampers full open. The discharge or recirculation air damper is modulated to control the amount of outdoor air introduced into the system while keeping the two remaining dampers full open. Since at least two dampers are always kept fully open during the occupied times, the strategy can provide a minimum static pressure drop in economizer dampers and results in minimum energy use in return and supply fans. An additional advantage is that the proposed strategy prevents reverse airflow through the discharge air damper of a VAV system that uses a volume matching control strategy. The proposed strategy along with the existing strategies such as the three-coupled dampers used in most existing system and the two-coupled dampers are evaluated on an existing system using 1-year long measured data set, along with an economizer damper model developed and validated in this paper. The simulation results show that the annual energy savings in supply and return fans of an existing system, compared to the traditional strategy of three-coupled dampers, are 12% and 5%, respectively.     

Outdoor Air Contaminants and Indoor Air Quality under Transient Conditions

The indoor concentrations of contaminants originating from outdoor sources have been measured and calculated under transient conditions. The results show that contaminants that are supplied to an office building via the ventilation system can reach considerably high concentration levels. The indoor/outdoor concentration ratio and time lag are dependent on the air change rate. In buildings with low air change rates the indoor concentration variations are smoothed out compared to buildings with high air change rates. The results from the theoretical model are compared to the results from both laboratory and field measurements and the model is verified for well mixed conditions in a 20 m³ test chamber. The model can be used to simulate different control strategies for reduction of indoor contaminant concentrations related to outdoor sources. One such control strategy is based on reduction of the outdoor air change rate during periods with peak outdoor contaminant concentrations.     

Proposal for a new hybrid control strategy of a solar desiccant evaporative cooling air handling unit

Correctly controlled solar desiccant evaporative cooling is an interesting option for achieving savings in building air-conditioning consumption. The operation of this system (open loop cooling cycle) is strongly influenced by indoor and outdoor air conditions. This influence is characterized using numerical simulations. First the air conditioned room and the cooling system are simulated using a validated model of the desiccant wheel. Then the influence of each parameter of the desiccant air handling unit is evaluated. The third step is to assess the system cooling power for each operating mode with fluctuating outdoor and indoor air conditions. This allows for making relevant choices for a new control strategy taking into account both indoor and outdoor air conditions. This control strategy is tested for a whole cooling season and compared to a reference compression system with promising results, allowing for energy savings of about 40% for French climate.     

热回收型多元变制冷剂流量空调系统控制策略实验研究

阐述了多元变制冷剂流量(MVRV)空调系统的自治协调控制(SRI)思想，指出室外机叠加循环原理是自治协调控制的核心内容；自行研制出热回收型MVRV空调系统实验装置并建立实验台，对上述策略进行验证。实验结果表明，所提出的控制策略切实可行，效果良好，适用于单冷、热泵以及热回收型MVRV空调系统。     

Prediction-based online optimal control of outdoor air of multi-zone VAV air conditioning systems

An optimal strategy for outdoor air control is developed using a system approach based on prediction to minimize energy consumption. ARMA model is used to predict the energy performance which is expressed by an energy-increment equation. The energy-increment equation is formed to involve the real-time variations of AHU load and energy use of reheaters of VAV terminals. To minimize the Energy-increment equation by genetic algorithm, the optimal settings of outdoor air ratio of AHU and reheating could be obtained. The strategy is tested and evaluated in a simulated environment under various outdoor and indoor conditions.     

我国西北地区涂装车间空调系统设计方案探讨

根据我国西北地区冬夏季独特的室外气候条件和空气质量,确定了不同区域新风空调机组的功能段布置,温湿度控制方案及设计要点。通过理论计算,对比分析了冬夏季新风与循环风空调的能源消耗,得出因地制宜的循环风空调系统选用原则,以最大限度的节能减排和降低运营成本。     

Optimization of a liquid desiccant based dedicated outdoor air-chilled ceiling system serving multi-zone spaces

A liquid desiccant based dedicated outdoor air-chilled ceiling (DOAS-CC) system is proposed to serve a multi-zone space. The outdoor airflow rate and the supply air humidity ratio are two crucial variables in such a system, which significantly influence indoor thermal comfort, indoor air quality and energy consumption. Two strategies are presented to optimize these two variables in the study. They are the demand-controlled ventilation (DCV) strategy and the supply air humidity ratio set-point reset strategy. To evaluate the performances of these two strategies, a basic control strategy, i.e., the strategy adopting constant ventilation flow rate and constant supply air humidity ratio, is selected as the benchmark. Performances of the two strategies in terms of indoor air temperature, relative humidity and CO₂ concentration as well as energy consumption are analyzed using simulation tests. The results show that the supply air humidity ratio set-point reset strategy is effective for the indoor air humidity control. It can save about 19.4% of total energy consumption during the whole year. The DCV-based ventilation strategy can further reduce about 10.0% of energy consumption.