冷热电联供系统中“以热定电”与“以电定热”的分析研究

为平衡冷热电联供系统中负荷变化,解决冷热电供需不平衡的问题,对燃气轮机冷热电联供的运行方式进行了优化选择。根据系统规模及容量,选择燃气轮机作为联供系统的原动机,同时选用了冷热电联供系统常用的两种运行模式:"以热定电"和"以电定热"。本文从热电输出和燃料消耗量两个方面比较分析了联供系统在两种运行模式中的性能差异,通过冷热电联产公式计算及Aspen Plus软件建模分析表明:当实际的热电输出等于终端的热电需求时,其最佳热电比HPR为1.75;当热电需求比在1≤HPR<1.75区间时,"以热定电"为最佳的系统运行方式;当热电需求比在1.75相似文献   

分布式热电联供技术在宾馆建筑中的应用

分布式热电联供是一项备受关注的重要技术,通过对宾馆建筑导入热电联供系统的运行状况分析,提出了改进方案,并就根据“以热定电”与“以电定热”两种系统的特点,得出了在现行分时电价和上网电价的条件下,准确预测用电用热负荷,采用分布式热电联供系统和运行技术能够获得较高的一次能源利用率。     

焦炉煤气热电联供方案的比较

介绍了利用焦炉煤气实现热电联供的工艺流程,包括燃气锅炉 汽轮机热电联供、燃气轮机热电联供.分析了两种工艺的优缺点.在焦化厂无蒸汽源的情况下,宜采用燃气锅炉 汽轮机热电联供系统,在有蒸汽源且焦炉煤气外供的情况下,宜采用燃气轮机热电联供系统.利用焦炉煤气实现热电联供为焦化厂焦炉煤气的利用提供了良好的解快方案,特别是环境保护效果明显.     

荷兰热—电联供的应用

简介热电联供就是同时供热和电。这看上去很简单,其实从许多方面来看,它确实如此。在发电的过程中必然产生热量。热电联供(Cogen)就是找到了一种如何去利用这一副产品的方法。实际上,Cogen或CHP     

燃气内燃发电机热电冷联供系统

介绍了燃气内燃发电机三联供系统的工作原理及3种系统形式,着重阐述了热电一体式联供系统,提出了发展燃气热电冷联供遇到的问题和对今后发展的建议。     

热电联供系统复合除湿空调系统动态仿真

将燃气内燃机热电联供系统(CHP)与热湿独立处理空调系统(采用固体除湿转轮)组成复合空调系统.供冷期,利用燃气内燃机余热再生除湿转轮.供暖期,利用燃气内燃机余热加热新风与供暖.针对上海某超市建筑,使用动态仿真方法对常规分供系统(采用热湿联合处理,配置电制冷机、燃气锅炉)、复合空调系统的一次能源利用率、静态投资回收期、二...     

中国城市热电厂区域热制冷对温室气体减排的作用

一些欧洲与亚洲国家已发展了满足建筑冬季供暖的区域供热系统,并以独立的电力压缩式制冷用于夏季空调的使用.存在两套并行的供暖与制冷空调系统意味着需要大量的初期投资.因此城市能源系统规划建设应考虑保持城市热电厂在夏季仍采用热电联产生产,实现热电厂区域热制冷以满足建筑在夏季的空调供冷,以使热电厂全年以高效率的热电联产方式运行.这种热电厂冷热联供系统为建筑提供了可持续的能源供应方案.本文以2004年的热电联产实际数据为依据,综合考虑我国的社会与经济发展趋势,对三种不同发展情景下通过发展热电厂夏季热制冷可实现的温室气体减排能力进行了分析预测.     

某医院建筑应用冷热电三联供系统的可行性分析

本文以上海某医院建筑作为冷热电三联供系统计算与分析为基础,对医院建筑的能耗特性进行了深入探讨,引入热电比、热电比频数和热电比时间数的概念,用以反映该医院建筑的冷、热、电负荷特性,得出医院建筑是冷热电三联供系统较合适用户的结论。     

冷热联供系统的能耗估算

阐述了利用热电联产热、锅炉房供热和房热驱动的各种冷热联供系统的能耗估算方法,对热电联产情况考虑了汽轮机进排气参数等条件的变化对供热供冷能耗的影响,给出了一定条件下各种系统包括热泵系统的供热供冷一次能耗率,并与常规系统作了比较。     

热电冷联供系统方案综合评价——某大学能源系统方案分析

为满足某大学热、电、冷负荷需求,提出了四种能源供应方案,即常规的燃气锅炉方案、燃气-蒸汽联合循环热电冷联供方案、热泵型热电冷联供方案和自备式热电冷联供方案.从经济性、能源利用效率和环保等角度进行了分析评价,认为采用自备式热电冷联供方案最合适.     

PEMFC系统天然气重整工艺条件热力学分析

对质子交换膜燃料电池（PEMFC）系统中天然气重整的工艺条件进行了热力学分析,考察了操作温度、操作压力、水碳比对天然气重整性能的影响,对PEMFC系统推荐了适宜的操作参数。     

热网循环水泵变频运行的变温差控制

在分析供热系统变流量运行调节的基础上,提出了变温差控制并给出了控制方案.变温差控制过程不仅具有负反馈,而且具有正反馈,能较好地适应外界气候条件的变化.比较分析了变温差控制、定温差控制、定压差控制、变压差控制的节能性,结果表明,变温差控制的节能潜力最大.     

外墙外保温系统对室内热环境的影响

采用对比试验的方法,建立采用外墙外保温系统的试验房间和不保温的对比试验房间,利用自动数据采集系统连续采集两房间不同部位的实时温湿度,分析外墙外保温系统的隔热保温性能。试验结果显示,外墙外保温系统具有优异的隔热保温性能。在相同的空调温控设定条件下,采用外保温的房间室内温度基本不受外界温度变化的影响。保温房间室内温度分布均匀。使用外墙外保温系统能营造良好的室内热环境。     

零排放燃料电池发动机

介绍了加拿大Ballard公司开发的离子交换膜燃料电池动力系统的工作原理及其尾气零排放的优越性能。该系统已应用在欧、美及日本的一些著名汽车制造厂商的车辆上。     

Comparison of FDS predictions by different combustion models with measured data for enclosure fires

The performance of mixture fraction models FDS4 and FDS5 is investigated under different global equivalence ratios (GER). Predictions of heat release rate (HRR), upper-layer temperature, and CO yield are compared with measurements considering their sensitivities to the lower limit of fuel, mixing time scale, and turbulence model constants. When using FDS4, the inclusion of an extinction model can result in significant variations in both total and volumetric HRR prediction. When using FDS5, the mixing model constant has significant effects on volumetric HRR prediction. At low GER (<0.23), the prediction of upper-layer temperature shows dependency on both the lower fuel limit and the mixing model constant, but the predicted temperature is always lower than measured temperature, with deviations in excess of 30%. At higher GER (0.53<GER<0.81), the upper-layer temperature prediction shows significant dependency on the mixing model constant but can be over-predicted, with deviations up to 24%. The variations of CO yield prediction with lower fuel limit or with the mixing model constant show an opposite trend to that of upper-layer temperature. Furthermore, the prediction of CO yield shows a much greater dependency on the Smagorinsky constant and on the turbulent Schmidt number than do those of HRR and upper-layer temperature.     

A novel on-off TRV adjustment model and simulation of its thermal dynamic performance

Field test results show that about 15% to 40% of building heat loss in China is attributable to poor heating systems regulation. The current method for addressing this problem is to install thermostatic radiator valves (TRVs) to the ends of radiators, a method adapted from northern Europe. However, this method has resulted in poor performance from delayed controlling action due to thermal inertia as well as insufficient system control accuracy. This is further compounded by incorrect operation by system users and a lack of financial incentives to regulate the system if users are not billed for their heat consumption. We present a new method for simultaneously heat controlling and metering. The core challenge is to design a control strategy that will maintain the room’s temperature. Thus, we established dynamic heat transfer models for water flow, the radiator and the building so as to obtain the optimal heating strategy. We also simulated the indoor thermal dynamic performance of the heating system with different heating loads, supply water temperatures, and supply water flow rates using three methods: a continuously changing flow rate (Method 1), a step-change flow rate based on temperature deviation (Method 2) and an intelligent step-change flow rate (Method 3) which predicts the duty cycle of the valve in the proceeding period and controls the valve’s on-time. The simulation results indicate the performance of these three methods. For Method 1, as the room temperature is above the set point, the flow rate can be automatically reduced to a level which is proportional to the room temperature deviation. Further, the scale factor of the flow rate is designed according to the +2°C deviation, so it is accepted that the room temperature is higher than the set point by +2°C using this method. However, this low control precision is unsatisfactory. The mean temperature is higher than the set point and greatly affected by the heating load and supply water’s temperature and flow rate. For Method 2, the controlling action is delayed by thermal inertia, the room temperature fluctuates between the highest and lowest levels, and the temperature deviation can be greater than the set value. For Method 3, both the simulation and field test results showed that room temperature deviation was maintained within a ±0.5°C range under the various conditions. This method appears relatively robust and adaptable, and was the best control strategy of the three methods.     

District heating system design for a university campus

İzmir Institute of Technology campus is in use since 2000 and still under development. At present, heating is provided by individual fuel boilers. On the other hand, the campus has a geothermal resource in its borders with a temperature of 33 °C. Because of this low geothermal fluid temperature; heat pump district heating system is considered for the campus. As an alternative, fuel boiler district heating system is studied. Each heating system is simulated using hourly outdoor temperature data. For the simulations, a control system with constant flow rate and variable return water temperature is used and the main control parameter is the indoor temperature. Various heating regime alternatives have been studied for heat pump district heating system for the various condenser outlet temperature and geothermal fluid flow rate, and two of these alternatives are given in this study. Furthermore, economic analysis has also been done for each heating system alternative based on investment and operational costs. Results indicate that heat pump district heating system has the highest investment but lowest operational cost.The alternatives are evaluated according to internal rate of return method, which shows the profit of the investment and resulted that, the heat pump district heating system has minimum 3.02% profit comparing with the fuel boiler district heating system at the end of the 20-year period.     

An investigation of propeller performance and machinery applications in wind assisted ships

An assessment is made of propeller performance for wind assisted ships and hence power/ rev requirements in different modes of wind assist operation, such as constant ship speed or constant power.

Problems of matching the propulsion engine(s) with the propeller are addressed including practical operating regions, power margins, operation off-design and its influences on propeller efficiency and specific fuel consumption.

Alternative suitable engine/gearbox and propeller arrangements are considered and compared for chosen ship types.     

亚洲金融大厦标准办公单元变风量空调系统自控策略分析

重点分析了幕墙侧风机盘管结合变风量空调系统在主风管变静压调节过程中有效实现整体控制的运行策略。将幕墙侧风机盘管纳入变风量空调自控系统进行整体控制,避免了以往项目中同一区域2种系统独立控制时容易产生的温度失调问题,同时,采用静压设定值定步长调整法,通过简单有效的控制逻辑实现了主风管变静压调节。经过冬、夏季的运行测试,结果显示上述空调自控系统达到了变静压调节的要求,并且实现了幕墙侧风机盘管与变风量空调系统的整体控制。     

Experimental Study on Fire Behaviors of Kerosene/Additive Blends

The widely used fuels in practical are blended fuel whose combustion characteristics is more complex than those of the single-component fuel in real fire scenarios. The fire behaviors of aviation kerosene/diethylene glycol dimethyl ether (DGM) blends (R-D) and aviation kerosene/ethanol (R-E) blends were studied using a cone calorimeter. The parameters of pool fires, including the ignition time, burning rate, fuel temperature, heat release rate and combustion yield, were investigated. Janssens’ method was adopted to analyze the ignition times of the two blends. Two types of representative burning processes for blended fuel pool fires were identified. For R-D blends, the burning process is similar to that for typical pure fuels. The process for R-E blends, however, is novel, having two obvious burning processes due to the appearance of an intermediate decay stage. The fuel exhaust mass fraction (approximately 15%) was found to be almost constant throughout the intermediate decay stage. The fuel temperature during the experiment indicated that the liquid surface boiling temperature of R-D blends ranges from 162°C to 200°C depending upon the composition of these blends. For R-E blends, the initial boiling temperature is affected by the ethanol ratio, while the boiling temperature in the second process is equal to the boiling temperature of pure RP-3 kerosene. When the ethanol ratio is lower than 40%, the initial boiling temperature of R-E blends is approximately 120°C; when the ethanol ratio is higher than 40%, the boiling temperature is equal to the boiling point of ethanol. A method for calculating the burning rate of each component in the burning processes of the two blends is put forward, with the results agreeing well with the interpretation of the two burning processes. The ratio of the combustion yield CO₂/CO and the carbon conversion ratio increase with the oxygenated fuel ratio, indicating that the combustion is more complete when oxygenated fuel is added. These results will be useful for fire hazard assessment and firefighting in terms of fuel storage and transportation.