喷射渗透式布袋风管送风系统送风特性分析

根据能量守恒及质量守恒方程构建了喷射渗透式布袋风管送风系统内部压力分布的数学模型,利用该模型分析了不同结构及不同送风量下布袋风管内部压力及送风特性的变化情况.结果表明,沿着气流方向,风管内部全压、动压呈下降趋势,静压逐渐增加;各送风参数中布袋风管的管径及送风量对喷射和渗透出风都有较大影响,布袋渗透率对喷射送风影响较大.     

某阅览室地板送风设计与实测

介绍了某阅览室地板送风的设计计算、模拟结果以及竣工后的实测数据。通过对室内热环境、空气品质等测试数据及问卷调查结果的分析,介绍了地板送风末端装置在阅览室的应用效果及设计要点。     

Numerical study on temperature stratification in a room with underfloor air distribution system

In this study, numerical prediction using computational fluid dynamics (CFD) was utilized to investigate air temperature stratification in a room with an underfloor air distribution (UFAD) system. The numerical modeling using CFD computation was validated with physical test in a full size experimental room with an UFAD system. The different supply air conditions and heat loads were discussed. The results show that the effect of three parameters, heat load, supply volume flux and supply air velocity, on room air temperature would be expressed by the length scale of the floor supply jet. When the length scale increased from 0.8 to 1.56 m, the ratio of vertical temperature difference between 2.5 and 0.1 m at the occupied zone to the difference between return and supply air temperature decreased from 0.62 to 0.25. When there was only one local heat source in the room, there was a thermal stratified interface at the occupied zone. The interface height was about 1.42 times the length scale. The results may suggest ways to optimize UFAD design and operation.     

Thermal comfort and IAQ assessment of under-floor air distribution system integrated with personalized ventilation in hot and humid climate

The potential for improving occupants’ thermal comfort with personalized ventilation (PV) system combined with under-floor air distribution (UFAD) system was explored through human response study. The hypothesis was that cold draught at feet can be reduced when relatively warm air is supplied by UFAD system and uncomfortable sensation as “warm head” can be reduced by the PV system providing cool and fresh outdoor air at the facial level. A study with 30 human subjects was conducted in a Field Environmental Chamber. The chamber was served by two dedicated systems – a primary air handling unit (AHU) for 100% outdoor air that is supplied through the PV air terminal devices and a secondary AHU for 100% recirculated air that is supplied through UFAD outlets. Responses of the subjects to the PV-UFAD system were collected at various room air and PV air temperature combinations. The analyses of the results obtained reveal improved acceptability of perceived air quality and improved thermal sensation with PV-UFAD in comparison with the reference case of UFAD alone or mixing ventilation with ceiling supply diffuser. The local thermal sensation at the feet was also improved when warmer UFAD supply air temperature was adopted in the PV-UFAD system.     

送风量对渗透式纤维空气分布系统送风特性影响的实验研究

采用现场实验的方法研究了送风量对渗透式纤维空气分布系统送风时表面空气流速和纤维空气分布系统空腔内部轴向空气压力分布的影响。实验结果表明：送风量对渗透式纤维空气分布系统对空气的“自整流”作用影响较小,与空气渗透流速大小成线形关系。随着送风量的增加,渗透式纤维空气分布系统空腔内部空气总压和静压值逐渐增加,静压增加梯度和动压衰减梯度越来越大,末端处静压复得现象愈明显。研究结果可为相应的数值模拟及工程设计提供参考。     

独立新风系统(DOAS)研究(2):设计方法

介绍了低温送风独立新风系统的组成及全热交换器、新风机组、末端设备、风道的设计计算，分析了其热湿平衡，给出了一个工程设计实例。     

Thermal comfort and indoor air quality in the lecture room with 4-way cassette air-conditioner and mixing ventilation system

We performed the experimental and the numerical studies on thermal comfort (TC) and indoor air quality (IAQ) in the lecture room with cooling loads when the operating conditions are changed. Predicted mean vote (PMV) value and CO₂ concentration of the lecture room were measured and compared to the numerical results. Both of them showed a reasonable agreement with each other and then we applied the numerical model to analyze TC and IAQ for a couple of different operating conditions. From the results we found that the increment of the discharge angle of 4-way cassette air-conditioner makes uniformity of TC worse, but rarely affects IAQ. It turned out that TC and IAQ are hardly affected by the variation of the discharge airflow. Finally TC was merely affected by the increment of the ventilation rate, but when the ventilation rate is more than 800 m³/h, the average CO₂ concentration can be satisfied with the standard limits of Japanese in our case studies.     

海南某数据中心空调系统设计

结合项目当地具体气候条件,综合对比多种空调系统方案,从节能效果、初投资、运行费用等各方面计算分析,找到适合本项目的 空调系统节能设计.空调设计从系统架构特点出发,利用备用机组的制冷能力,结合磁悬浮机组部分负荷效率高的优点,实际运行时冷水机组全部运行,主机负载率为70％～80％,磁悬浮主机的COP可达15以上,配合冷却塔...     

Measurements and predictions of the air distribution systems in high compute density (Internet) data centers

When equipment power density increases, a critical goal of a data center cooling system is to separate the equipment exhaust air from the equipment intake air in order to prevent the IT server from overheating. Cooling systems for data centers are primarily differentiated according to the way they distribute air. The six combinations of flooded and locally ducted air distribution make up the vast majority of all installations, except fully ducted air distribution methods. Once the air distribution system (ADS) is selected, there are other elements that must be integrated into the system design. In this research, the design parameters and IT environmental aspects of the cooling system were studied with a high heat density data center. CFD simulation analysis was carried out in order to compare the heat removal efficiencies of various air distribution systems. The IT environment of an actual operating data center is measured to validate a model for predicting the effect of different air distribution systems. A method for planning and design of the appropriate air distribution system is described. IT professionals versed in precision air distribution mechanisms, components, and configurations can work more effectively with mechanical engineers to ensure the specification and design of optimized cooling solutions.     

长三角地区某数据中心空调系统设计

介绍了长三角地区某数据中心空调冷源、空调水系统、空调风系统等的设计,并对机房的气流组织进行了CFD模拟和验证。该数据中心在空调冷源设计上采取了磁悬浮冷水机组、大温差高温供冷(18℃/28℃)、自然冷却及热通道封闭等措施,保证设计PUE<1.3。     

Saving energy in the heat-pump air conditioning system driven by gas engine

The main functions of the heat-pump air conditioning system driven by gas engine (GEHPAC) are to maintain the room temperature and control the humidity of the room. In summertime, the air can be reheated by the waste heat water from the gas engine, while the air can be reheated and humidified by the waste heat water in winter. Reducing or displacing electrical heating requirements can achieve the greatest opportunity for significant energy savings. This paper, therefore, aims to improve the energy performance of the AC system by using the waste heat from the gas engine. The mathematical model for the second heat exchanger, the sprayed room, the mixed air, was used to research the GEHPAC. Explicitly, we investigated the influence of various factors including the outdoor air temperature and humidity in summer and winter. Results from the analysis show that the GEHPAC can save more energy than the electricity engine heat pump. The GEHPAC runs beautifully in part load mode. PERx is higher in winter than in summer. The maximum PERx is over 1.6 in summer, while over 1.9 in winter. The GEHP which can control the room humidity can be used in more areas than the common GEHP.     

Intelligent system based on wavelet decomposition and neural network for predicting of fan speed for energy saving in HVAC system

In this study, a heating, ventilating and air-conditioning (HVAC) system with different zones was designed and tested. Its fan motor speed and damper gap rates were controlled by two controllers (i.e. a PID controller and an intelligent controller) in real time to minimize its energy consumption. The desired temperatures were realized by variable flow-rate by considering the ambient temperature for each zone and evaporator. The PID parameters obtained in our previous theoretical work using fuzzy logic were utilized in this study. The experimental data used in this study was collected using a HVAC system built in a laboratory environment. The fan motor speed and damper gap rates were predicted using wavelet packet decomposition (WPD), entropy, and neural network (NN) techniques. WPD was used to reduce the input vector dimensions of the intelligent model. The suitable architecture of the NN model is determined after certain trial and error steps. According to test results, the developed model performance is at desirable level. Efficiency of the developed method was tested and a mean 95.62% recognition success was obtained. This model is an efficient and robust tool to predict damper gap rates and fan motor speed to minimize energy consumption of the HVAC system.