数码涡旋空调系统节能分析

目前变制冷剂流量空调系统越来越受到广泛的关注，而数码涡旋空调系统是变制冷剂流量空调系统中的一种新兴技术。介绍了数码涡旋压缩机技术，分析了数码涡旋空调系统的特点和节能因素，并将其与VAV(Variable Air Volume)空调系统进行对比，指出了数码涡旋空调系统是目前中央空调尤其是小型的中央空调系统的一个发展方向。     

变风量空调系统

介绍了变风量空调系统（VAV系统）的特点、末端装置的型式以及最小送风量的确定方法，指出了VAV系统的研究重点和发展前景。     

对全空气定风量系统“可调新风比”的探讨与建议

<正>在公共建筑的空调设计中,常用的空调形式为全空气系统、风机盘管+新风系统、温湿度独立控制系统。无论采用哪种空调系统,都要根据建筑内的人员密度以及空调房间内的人数,确定空调房间的新风量。对于风机盘管+新风系统、温湿度独立控制系统,新风系统完全可以根据计算的新风量设计,相应的每层的新风机房、新风竖井、排风竖井、集中的新风热回收机组都按此新风量进行设计。那么对于全空气系统,又是如何规定的呢?1相关规范对伞空气定风培系统的可调新风比要求     

高层建筑空调节能设计的探讨

指出了空调系统耗能的两个方面，介绍了空调系统设计的几个节能措施，如合理降低室内温度湿度标准、控制与正确利用室外新风量等。     

直接蒸发式与串联式独立新风空调系统性能实验研究

通过建立空调系统测试实验台,就直接蒸发式与串联式独立新风空调系统进行性能研究。研究影响系统性能各因素,并分析两种空调系统在各因素下的运行性能,以及室内盘管保持干工况下运行的适用条件。得出当室内负荷显热比低于0.8,或者室外温度升高到35℃、相对湿度增大到65%的工况下,串联式系统比直接蒸发式系统更具结露的风险。且适当增加新风量有利于改善室内温湿度过高的现象,但新风量过大,容易造成室温偏高。     

吸湿供冷系统的空气处理方式分析

温度和新风量的大小在影响室内环境的舒适性方面起着重要的作用。为了改善室内空调环境，ASHRAB规定设计温度应该保持在30％-60％之间，且需要把原有的设计新风量增大2倍至4倍。显然，降低温度和增大新风会加大空调的冷负荷，传统的空调供冷系统在满足上述条件方面显示出了自身的一些缺点。吸温供冷系统把除温和冷却降温供冷解耦分开处理．不但能把空气温度处理到一个比较低的程度，而且在节能方面也显示出很大的潜力。对吸温供冷系统的几种空气处理方式进行了分析和比较，从而可根据不同的情况为吸温供冷系统的使用选择比较理想的空气处理方式，以达到节能目的。     

上海期货大厦变风量空调系统实际运行状况的初步分析

对上海期货大厦内变风量空调系统的实际运行状况,如室内空气品质,新风供给,吊顶回风、能耗等方面问题进行了初步分析。以期对今后VAV空调系统的应用有所借鉴。     

冬冷夏热地区户式空调设计与节能分析

以一单元式住宅的风道式户式空调系统为例，探讨了冬冷夏热地区户式空调的新风量确定方法，分析了户式空调的负荷特性，节能设计及户式空调系统的设计负荷与设计风量。     

空调系统的几种节能控制方式

介绍了四种空调系统的节能控制方式，即室内温度、湿度设定值控制，新风量控制，动力设备启停控制及空气处理工艺的控制。     

变风量空调系统模拟及能耗研究

应用DeST软件模拟分析了某大型办公建筑全年动态负荷 ,并对带有串联型末端装置的变风量系统及常规空调系统进行全年能耗计算。通过各系统能耗的比较 ,说明了该建筑使用VAV系统比常规空调系统具有良好的节能性及在系统的使用寿命内应用变风量空调系统是相当经济的。对变风量空调系统在国内的应用前景进行了合理评判。     

Design recommendations for heat discharge systems in walls

When the design of an in-wall heat discharge system (HDS) is inappropriate, the heat stored in the system is not completely discharged into the environment, therefore an excess flow of heat is transferred to the space where the internal temperature is to be modified. This study presents the results obtained by modifying the design conditions of an HDS, the purpose being to prevent the design of the system from contributing to the overheating of the controlled space. Considered in the design modifications was: the separation between the plates that form the air channel, height and width of the system, dimensions of the opening of the air channel intake and the heat storing capacity of the storage plate. After making these variations to the analytic model, this study concludes that it is advisable to increase both the width of the system and the opening of the air channel intake, thus allowing for a greater flow of ventilation air within the system without overheating either the heat storage plate or the interior of the controlled space.     

Neural computing thermal comfort index for HVAC systems

The primary purpose of a heating, ventilating and air conditioning (HVAC) system within a building is to make occupants comfortable. Without real time determination of human thermal comfort, it is not feasible for the HVAC system to yield controlled conditions of the air for human comfort all the time. This paper presents a practical approach to determine human thermal comfort quantitatively via neural computing. The neural network model allows real time determination of the thermal comfort index, where it is not practical to compute the conventional predicted mean vote (PMV) index itself in real time. The feed forward neural network model is proposed as an explicit function of the relation of the PMV index to accessible variables, i.e. the air temperature, wet bulb temperature, globe temperature, air velocity, clothing insulation and human activity. An experiment in an air conditioned office room was done to demonstrate the effectiveness of the proposed methodology. The results show good agreement between the thermal comfort index calculated from the neural network model in real time and those calculated from the conventional PMV model.     

重型燃气轮机高温部件试验全场主流空气系统仿真分析

为保证重型燃气轮机高温部件全场主流空气系统调节的全面性和灵活性,基于仿真技术实现了对燃气轮机高温部件试验设施空气系统的调节过程计算,得到了试验段与气源侧流量、压力和温度等状态参数的变化曲线,分析了气源温度、阀门开度及连锁控制对试验运行的影响,并确定了运行控制应对方案.结果表明:试验设施进气系统和排气系统并联的方案可以将...     

Hydronic heating systems: transient modelling,validation and load matching control

A dynamic model of a hydronic heating system is developed. The system consists of a boiler, baseboard terminal units, domestic hot water (DHW) heat exchanger coil and an environmental zone. The model is described by a set of time varying nonlinear coupled differential equations. Predicted responses from the model are compared with the measured data gathered on an on–off controlled hydronic heating system installed in an apartment building. Results show that the model predictions compare well with the field data. Using this validated model, feedback controllers are designed to achieve better regulation of zone air temperature, boiler water temperature and DHW temperature. A load tracking setpoint control strategy is proposed to regulate boiler temperature as a function of outdoor air temperature. Results showing the simulated responses of the system with the designed controllers subject to step changes in space heating and DHW loads are given. © 1998 John Wiley & Sons, Ltd.     

风冷式太阳能吸收式制冷机性能模拟研究

在环境温度和太阳辐射动态变化的情况下,对制冷量为5 kW的风冷式太阳能吸收式制冷机的性能进行了模拟,得出了集热器出口水温和热水储槽温度随时间变化的规律曲线以及在此规律的影响下吸收式制冷机的性能曲线.模拟结果表明风冷式太阳能吸收式制冷机在理论上是切实可行的,但是环境温度的变化以及风冷系统的散热能力对系统性能有较大的影响,环境温度的升高会使需要风冷降温的冷凝器、吸收器温度升高,从而提高了发生温度的要求,这不利于太阳能的利用和系统的制冷.为此需要强化冷凝器和吸收器的散热效果,来降低境温度对系统的不利影响.     

Synergistic integration of a gas turbine and solid oxide fuel cell for improved transient capability

A theoretical solid oxide fuel cell–gas turbine hybrid system has been designed using a Capstone 60 kW micro-gas turbine. Through simulation it is demonstrated that the hybrid system can be controlled to achieve transient capability greater than the Capstone 60 kW recuperated gas turbine alone. The Capstone 60 kW gas turbine transient capability is limited because in order to maintain combustor, turbine and heat exchangers temperatures within operating requirements, the Capstone combustor fuel-to-air ratio must be maintained. Potentially fast fuel flow rate changes, must be limited to the slower, inertia limited, turbo machinery air response. This limits a 60 kW recuperated gas turbine to transient response rates of approximately 1 kW s⁻¹. However, in the SOFC/GT hybrid system, the combustor temperature can be controlled, by manipulating the fuel cell current, to regulate the amount of fuel sent to the combustor. By using such control pairing, the fuel flow rate does not have to be constrained by the air flow in SOFC/GT hybrid systems. This makes it possible to use the rotational inertia of the gas turbine, to buffer the fuel cell power response, during fuel cell fuel flow transients that otherwise limit fuel cell system transient capability. Such synergistic integration improves the transient response capability of the integrated SOFC gas turbine hybrid system. Through simulation it has been demonstrated that SOFC/GT hybrid system can be developed to have excellent transient capability.     

Comparative study of room temperature control in buildings with and without the use of PCM in walls

The concept of thermal energy storage in building gains a specific importance in the present energy scenario related to energy consumption and indoor thermal comfort. The material used to store the thermal energy which undergoes a phase change referred as PCM and it is considered as a possible solution for reducing energy consumption in the building by storing and releasing heat within a certain temperature range; it raises the building inertia and also stabilizes indoor air temperature fluctuations. The room temperature is controlled by imposing PCM inside the walls. An attempt has been made to compare room air temperature with and without the use of PCM inside the walls of constructed modular building unit. The PCM imposed modular building shows the reduced temperature fluctuations in room, the PCM absorbs and liberates excess heat which is gained from the outer side of the room and maintains constant inner room temperature. The PCM imposed walls of modular building unit have an ability to reduce 10–30% of heat load in comparison with the plain wall. The results showed that reduction in room temperature is about 2–4°C and it has been concluded that the PCM imposed modular building unit has more energy saving opportunities than normal modular building unit.     

Numerical visualization of air intake induced by free surface vortex

Free surface vortex control is vital in a pump sump system because the air absorbed by free surface vortex induces noise,vibration,and cavitation corrosion on the pumping system.In this study,the change of free surface vortex and air absorption in a pump intake has been investigated by the Volume of Fraction (VOF) method with steady multiphase flow model in order to represent the behavior of the free surface vortex exactly.The homogeneous free surface model is used to apply interactions of air and water.The results show that air intake by the free surface vortex motion can be visualized using the iso-sufface of air volume fraction.The vortices make an air column from the free surface to the pump intake.Also,it was found that the free surface vortex can be controlled by installing curtain walls.     

Stabilized three-stage oxidation of DME/air mixture in a micro flow reactor with a controlled temperature profile

Ignition and combustion characteristics of a stoichiometric dimethyl ether (DME)/air mixture in a micro flow reactor with a controlled temperature profile which was smoothly ramped from room temperature to ignition temperature were investigated. Special attention was paid to the multi-stage oxidation in low temperature condition.Normal stable flames in a mixture flow in the high velocity region, and non-stationary pulsating flames and/or repetitive extinction and ignition (FREI) in the medium velocity region were experimentally confirmed as expected from our previous study on a methane/air mixture. In addition, stable double weak flames were observed in the low velocity region for the present DME/air mixture case. It is the first observation of stable double flames by the present methodology. Gas sampling was conducted to obtain major species distributions in the flow reactor. The results indicated that existence of low-temperature oxidation was conjectured by the production of CH₂O occured in the upstream side of the experimental first luminous flame, while no chemiluminescence from it was seen.One-dimensional computation with detailed chemistry and transport was conducted. At low mixture velocities, three-stage oxidation was confirmed from profiles of the heat release rate and major chemical species, which was broadly in agreement with the experimental results.Since the present micro flow reactor with a controlled temperature profile successfully presented the multi-stage oxidations as spatially separated flames, it is shown that this flow reactor can be utilized as a methodology to separate sets of reactions, even for other practical fuels, at different temperature.     

A study on the solar energy storing rock-bed to heat a polyethylene tunnel type greenhouse

A study was conducted to store solar energy in an underground rock-bed for greenhouse heating. Experiments were carried out in two identical polyethylene tunnel type greenhouses, each with 15 m² ground area. Rocks were filled in two canals excavated and insulated in the soil of one of the greenhouses. Greenhouse air was pushed through the rock-bed by a centrifugal fan with 1100 m³/h air flow rate and controlled by two thermostats when the energy storage or release was required. No crops were grown in the greenhouses and the vents were kept closed unless excessive condensation occurrence inside the greenhouses. The results of this study showed that the rock-bed system created an air temperature difference of about 10 °C at night, between the two greenhouses, the control one having the lower temperature. Furthermore, the rock-bed system kept the inside air temperature higher than that of outside air at night, even in an overcast day following a clear day. Whilst solar energy collection efficiency of the system was 34%, its energy recovery or release efficiency was higher than 80%. A numerical mathematical model considered here represented actual data well. An economic analysis indicated that the rock-bed system is more economical than the LPG or petroleum-based fuel burning heating systems widely used in Turkish greenhouses.