煤气、空气预热的能和(火用)分析

一、概要用物理法或化学法回收余热来预热煤气和空气,可以显著地节约燃料,其节约值无论从能或(火用)的角度分析,均远超过回收值。为此,本文提出了燃料能节约增值率和(火用)节约增值率的概念,并予推导。燃烧低热值燃料时,用预热炉预热主炉用的煤气、空气,可以节省高热值燃料,同样有节约增值的现象,经济效益更为明显,     

火焰炉节能技术分析

介绍了我国火焰炉的能源消耗和节能状况,阐述了火焰炉的节能技术应用,包括优化燃料结构、改善燃料燃烧状况、优化炉衬结构、采取余热回收措施、采用先进的燃烧技术及提高控制水平等,探讨了火焰炉节能的发展方向。     

关于空气预热的燃料节约率

对无烟煤绝热燃烧过程空气预热的燃料节约进行了热力学分析，结果表明：在空气消耗系数。α＝１．０～１．３时，空气预热温度每提高１００℃，燃料节约率提高４．６％～５．９％，且α越大，预热空气的节能效果越显著。     

固定床玉米秸燃烧特性的实验研究

影响生物质燃烧特性的因素主要包括燃料长度、空气预热温度、送风量和燃料含水量。研究了上述因素对玉米秸的燃烧特性，包括指燃料失重率、炉内温度以及炉内的气体成分的影响，并对影响的机理进行了相应的分析。     

空气预热可以节约燃料

<正> 锅炉、加热炉以及各种工业炉窑,燃烧空气预热是提高燃烧效率的手段。这时由于空气预热燃料节约率的求法表示如下: (1) 式为空气不预热时燃料的消耗量; (2) 式为空气预热时燃料的消耗量; (3) 式为窄气预热时燃料的节约率。     

大容量锅炉火焰动态响应特性及红外探测技术

根据火焰辐射与量子光学辐射理论，阐述了大容量锅炉炉内燃烧过程着火区火焰辐射光谱频率与光强的关系。介绍了各种燃料火焰的动态响应特性，红外火焰探测技术的特点和系统功能以及实际应用效果。     

燃油室式少无氧化加热炉的设计

文中简述了采用轻柴油在α=0.5条件下的燃烧实现工件少无氧化加热。在炉型结构的设计中利用了空气动力学分区原理,实现了燃料在炉膛内分层燃烧,并且达到了快速加热,提高了炉子热效率的目的。选择合理的燃烧装置,结合预热助燃空气的办法,提高了燃料的理论燃烧温度,满足工艺的要求,同时也回收了热量,节约了燃料。经生产的实际使用和热工测试表明炉子的各项技术经济指标比较先进。     

无焰燃烧发展及研究现状

无焰燃烧是一种同时具备高效和低排放特点的燃烧技术,然而传统实现无焰燃烧所需的高温预热空气及高速射流两大重要条件,提高了整体工业设备实现无焰燃烧的复杂性,限制了该技术在更广阔领域的发展。本文综述了无焰燃烧燃烧机理与特性的研究发展,并提出了未来可能的发展趋势。分析发现：高温预热空气并不是实现无焰燃烧的必要条件,而通过高速射流提高炉内烟气循环率却必不可少;使用EDC模型结合GRI 3.0反应机理能在数值模拟中得到贴合实验数据的结果;气体、液体及固末燃料均可实现无焰燃烧,使用CH4/H2混合气体实现无焰燃烧可在提升燃烧稳定性的同时依旧保持低排放的特点;炉膛结构可很大程度上影响炉内流场进而影响无焰燃烧效果。因此,研究无需预热的无焰燃烧系统在降低工业成本的同时可增大燃料种类的选择性,通过设计合理的炉膛结构,营造良好的炉内流场在强化无焰燃烧效果的同时可一定程度降低对初始射流速度的要求,研究CH4/H2混合气体的燃烧机理具有十分重要的意义。     

地沟油生物柴油与正丁醇/乙醇混合燃料燃烧火焰特性

为研究不同配比下生物柴油混合燃料燃烧特性,设计了一套生物质液体燃料雾化蒸发燃烧系统,该系统可产生生物柴油及其混合燃料层流预混火焰,结合OH-PLIF平面激光诱导荧光技术测定并分析燃烧火焰的高度和锋面面积以及层流预混火焰的传播速度和OH-PLIF总信号强度等燃烧特性.结果表明随着正丁醇或乙醇添加比例的增大,两种混合燃料燃烧火焰高度、火焰锋面面积呈下降趋势;火焰传播速度呈上升趋势.在混合燃料中,正丁醇的体积分数越大,燃烧火焰OH-PLIF总信号强度越大,而乙醇的体积分数越大,混合燃料燃烧火焰OH-PLIF总信号强度越小.     

应用通气性固体提高加热炉的辐射热效率

以往的燃料加热炉多采用低空气比燃烧强化燃烧管理、提高炉壁绝热性能防止热损失、延长预热区或采用交换器回收余热等节能技术,目前在技术上已达到相当水平。因此,为进一步推进节能,应注重提高炉内     

Quantitative analysis of fuel-saving potential for waste heat recovery system integrated with hybrid electric vehicle

Hybrid electric vehicles (HEVs) with low fuel consumption, low emissions, and long driving range are the ideal transition models between conventional fuel vehicles and pure electric vehicles. The growing demand for increased vehicle efficiency has motivated the introduction of waste heat recovery (WHR) technology in the automotive industry, with the organic Rankine cycle (ORC) as the most promising measure for recycling waste energy. Currently, only a few studies have been conducted to couple HEV and WHR systems. These studies have mainly focused on the hybrid powertrain control strategy, but lack quantitative methods to comprehensively analyze the fuel-saving potential due to the WHR system. In this study, an HEV-WHR integrated system that includes a mechanism-based dynamic model of ORC and a hybrid diesel-electric truck model is established. Further, a quantitative evaluation method that simultaneously considers the negative integrated effects (increased vehicle weight and increased exhaust back pressure) and the positive impact values of the engine, motor, and WHR system on the fuel-saving potential is proposed. Finally, the influence of two environmental factors (wind speed and ambient temperature) on the fuel-saving performance is analyzed. The results reveal that under the standard highway driving cycle (HWY), the negative integrated effects reduce the ideal fuel-saving potential of the HEV-WHR system from 6.10% to 5.42%. However, the optimized performances of the engine, motor, and WHR system improve the fuel-saving rate by 0.39%, 1.81%, and 3.22%, respectively. The results also indicate that the fuel-saving potential increases from 1.62% to 8.60% with increasing wind speed and decreases from 6.70% to 4.25% with increasing ambient temperature.     

Searching for hidden costs: A technology-based approach to the energy efficiency gap in light-duty vehicles

The benefit-cost analysis of standards to reduce vehicle greenhouse gas emissions and improve fuel economy by the U.S. Environmental Protection Agency (EPA) and the Department of Transportation (DOT) displays large net benefits from fuel savings for new vehicle buyers. This finding points to an energy efficiency gap: the energy-saving technology provided in private markets appears not to include all the technologies that produce net private benefits. The gap exists if the costs of energy-saving technologies are lower than the present value of fuel reductions, and “hidden costs” – undesirable aspects of the new technologies – do not exceed the net financial benefits. This study examines the existence of hidden costs in energy-saving technologies through a content analysis of auto reviews of model-year 2014 vehicles.Results suggest that it is possible to use fuel-saving technologies on vehicles without imposing hidden costs. For each technology examined, reviews with positive evaluations outnumbered those with negative evaluations. Evidence is scant of a robust relationship between vehicles’ use of energy-saving technologies and negatively rated operational characteristics, such as handling or acceleration. Results do not provide evidence for hidden costs as the explanation of the efficiency gap for vehicle fuel-saving technologies.     

Hydrogen technology for supply chain sustainability: The Mexican transportation impacts on society

This study sheds light on the Hydrogen technology in transportation for reaching the sustainability goals of societies, illustrated by the case of Mexico. In terms of the affected supply chains the study explores how the packaging and distribution of a fuel-saving tool that allows the adoption of hydrogen as complementary energy for maritime transportation to improve economic and environmental performance in Mexico. This exploratory study performs interviews, observations, simulations, and tests involving producers, suppliers, and users at 26 ports in Mexico. The study shows that environmental and economic performance are related to key processes in Supply Chain Management (SCM) in which packaging and distribution are critical for achieving logistics and transportation sustainability goals. Reusable packaging and the distribution of a fuel-saving tool can help decrease costs -, of transport, and downstream/upstream processes in SCM while at the same time increasing the environmental performance.     

Design of thermoelectric heat pump unit for active building envelope systems

Active building envelope (ABE) systems represent a new thermal control technology that actively uses solar energy to compensate for passive heat losses or gains in building envelopes or other enclosures. This paper introduces initial steps in exposing the community to this new technology, and explores an optimization based design strategy for its feasible application. We discuss the overall ABE system, and focus on the design and analysis of a key component—the thermoelectric heat pump unit, or the TE unit. This unit becomes an integral part of the generic enclosure, and is a collection of thermoelectric coolers, or heaters. As a critical component of the optimization based design strategy, computationally inexpensive approximate analytical models of generic TE coolers/heaters (referred to as TE coolers) are developed. A multi-objective optimization technique is implemented to design and evaluate different design configurations of the TE unit. The multi-objective optimization simultaneously minimizes two design objectives: (1) the total input power required to operate the TE unit and (2) the number of TE coolers for economic considerations. Preliminary results indicate that the total input power required to operate the TE unit decreases as the distribution density of the TE coolers increases. In addition, the thermal resistance of the heat sink (attached to the TE cooler) plays a key role in determining the number of TE coolers required. These preliminary findings may have practical implications, influencing the implementation of the ABE system.     

Research Needs in Low Reynolds Number Flow Heat Exchangers

Low Reynolds number flows prevail in some process, power, automotive, aircraft, and other industrial heat exchangers such as shell-and-tube, plate, and compact heat exchangers. Laminar or low Reynolds number turbulent flows are the results of either high viscosity fluids, compact flow passages (i.e., small hydraulic diameter), or low fluid velocities. Significant advancements have been made in the past 100 years in understanding and predicting flow and heat transfer in such internal flows. This paper summarizes the research needs to further advance the science of low Reynolds number flow heat exchangers. Emphasis is primarily given to the thermal design aspects; research needs related to mechanical design, manufacturing, material selection, and other nonthermal design aspects are not covered. Also the coverage is restricted primarily to single-phase applications. The outlined research needs are based on the input from invited lecturers and some participants, experts in the field, at the Fourth NATO Advanced Study Institure in Ankara, Turkey, July 1981.     

A Principal Component Analysis and neural network based non-iterative method for inverse conjugate natural convection

Inverse Heat Transfer Problems (IHTP) are characterized by estimation of unknown quantities by utilizing any given information of the system. In this study, the inverse problem of estimation of boundary heat flux for a given temperature distribution on the walls of a two dimensional square cavity with a finite wall thickness is considered. A non-iterative method is applied utilizing Artificial Neural Network (ANN) and Principal Component Analysis (PCA) to estimate the parameters that define the boundary heat flux. The forward model is numerically solved with Fluent 6.3 for known values of a linearly varying boundary heat flux and the temperature distribution thus obtained is utilized to train the ANN for the inverse model. A parametric study is carried out to determine the effect of the thermal conductivity of the top and bottom walls on the flow and temperature distribution in the cavity. PCA analysis is carried out to reduce the dimensions of the input data set for the inverse model. These reduced dimensions are used to train the network and due to low dimensionality of the input, the effort required to train the network is considerably less. The trained networks are finally used to estimate boundary heat flux for any desired temperature distribution on the top and bottom walls. Additionally, covariance analysis is carried out in order to estimate the required number of temperatures during an experiment, on the top and bottom walls for the prediction of heat flux with a reasonable accuracy. The inverse model with covariance analysis is compared with the inverse model with PCA and both the methods are found to be equally potent.     

Investigation on the effect of filling ratio on the steady-state heat transfer performance of a vertical two-phase closed thermosyphon

Filling ratio of the working fluid has a predominant effect on the heat transfer characteristics of a two-phase closed thermosyphon (TPCT). A comprehensive model is developed to investigate the effect of filling ratio on the steady-state heat transfer performance of a vertical TPCT. Three types of flow pattern and two types of transition, according to the distribution of liquid film and liquid pool, are considered in this model, while other models generally focus on only one or two types of them. The total heat transfer rate of liquid pool, including those of natural convection and nucleate boiling, is calculated by combination of their effective areas and heat transfer coefficients. New correlations of the effective area are proposed based on the experimental results from other study. Two different geometries of the TPCT with nitrogen as working fluid are performed experimentally, and the evaporator temperatures accord well with the theoretical calculation. And the calculated results are compared with those by other empirical heat transfer correlations for liquid pool. The range of filling ratio, which can keep a TPCT steady and effective, is proposed based on analysis and comparison. The effects of heat input, operating pressure and geometries of the TPCT on the range are also discussed.     

Multi-pressure absorption cycles in solar refrigeration:: A technical and economical study

A technical and economical study of regenerative absorption chillers with multi-pressure cycle has been undertaken as solar operated refrigeration systems. Referred to as advanced absorption chillers they represent one of the new technology options that are under development. Advanced absorption cooling technology offers the possibility of chillers with thermal COPs of 1.5 or greater at driving temperatures of 140°C, which reduces the collector area and the heat rejection requirements compared to current absorption cooling technology. Two different absorption systems have been considered. The first is an advanced, double-effect regenerative absorption cooling system, driven at 140°C, whose efficiency is about 55% of the Carnot efficiency. The second is an ideal, single-effect regenerative absorption system that achieves 70% of the Carnot efficiency driven at 140°C or 200°C. To evaluate the solar performance of a thermally driven chiller requires a separate analysis of the solar availability for a given location compared to the required monthly average solar input. In this analysis different systems, including the vapour compression chillers, have been compared in terms of the thermal and electrical energy input. An effective electrical COP may be computed assuming that the ratio of electrical energy cost to thermal energy cost is four, which is typical of today’s fossil fuel costs. The effective electrical COPs of different technical options can then be compared. Those systems with higher electrical COPs will have lower energy costs. If solar is to be competitive, then the cost of delivered solar thermal energy should be less than the cost of delivered fossil thermal energy.     

Numerical modelling of boiling heat transfer in microchannels

In this paper we report the results of our modelling studies on two-phase forced convection in microchannels using water as the fluid medium. The study incorporates the effects of fluid flow rate, power input and channel geometry on the flow resistance and heat transfer from these microchannels. Two separate numerical models have been developed assuming homogeneous and annular flow boiling. Traditional assumptions like negligible single-phase pressure drop or fixed inlet pressure have been relaxed in the models making analysis more complex. The governing equations have been solved from the grass-root level to predict the boiling front, pressure drop and thermal resistance as functions of exit pressure and heat input. The results of both the models are compared to each other and with available experimental data. It is seen that the annular flow model typically predicts higher pressure drop compared to the homogeneous model. Finally, the model has also been extended to study the effects of non-uniform heat input along the flow direction. The results show that the non-uniform power map can have a very strong effect on the overall fluid dynamics and heat transfer.     

阳极焙烧炉热平衡分析

阳极焙烧炉的热平衡计算与分析对工程实际有非常重要的意义。给出了包括热收入、热支出这些重要经济技术指标的计算结果。通过这些计算结果分析了阳极焙烧炉在运行过程和生产管理方面存在的问题,并提出了解决方案。