发动机余热回收技术的研究现状及发展趋势

综述了国内外发动机余热回收技术的研究现状和发展趋势.从用途上把发动机余热利用技术分为废气涡轮增压、制冷空调、发电、采暖和改良燃料等五种,并分别探讨这些技术的可行性.阐述了有关余热回收的新技术及新理论.最后指出了利用有机工质循环系统将废气余热转化为电能,是汽车余热利用的发展趋势.     

Investigation of prototype thermoelectric domestic-ventilator

Applications of thermoelectrics had been enlarged from conventional single refrigeration or generation to waste heat recovery with tough energy consumption of the world. With improvement of living standard more and more domestic air-conditioners are used in Chinese families now. Percentage of power consumption of domestic air-conditioner caused by heat load of fresh air supply increased after SARS, which could be prevented efficiently with sufficient fresh air supply, broke out in China in 2003. A novel prototype thermoelectric domestic-ventilator with heat recovery of exhaust of air-conditioned room had been made in Hunan University thermoelectric lab. A thermoelectric heat exchanger and a flat-fin cross flow heat exchanger were integrated in this ventilator. This ventilator was investigated and its cooling (and heating) performance were evaluated in terms of the coefficient of performance, cooling and heating powers, and being handled temperature difference of fresh air. The coefficient of performance of this ventilator was found to be over 2.5 in the whole experiment. The optimal working parameters of this ventilator were studied in this paper. The potential improvements in performances and market prospects were also discussed in this work.     

燃气-超临界CO2联合循环发电系统

  [目的]  燃气轮机排气温度高,可增加底循环,利用排气的余热发电,从而提高燃料总的能量利用率。鉴于超临界CO₂循环热效率高,并且具有系统简单、结构紧凑、运行灵活等潜在优势,可与燃气轮机组成新型的燃气-超临界CO₂联合循环。  [方法]  为了充分利用燃气轮机排气余热,提出在简单回热超临界CO₂循环的基础上,再嵌套一个简单回热循环的布置方式,并以PG9351(FA)型燃气轮机为例,对其热效率进行了计算分析。同时,在系统中增加余热利用装置,可将剩余热量用于供热、转换为冷量或发电。  [结果]  结果表明:对于选定的燃气轮机,超临界CO₂循环最高温度可达约600 ℃,循环发电效率约32%,获得余热温度为170 ℃以上,余热热量占燃气轮机排气热量9%,联合循环发电效率约54%。  [结论]  燃气-超临界CO₂联合循环发电系统具有较高的热效率,并且保留部分较高品位的余热,可进一步用于电厂运行。     

基于CO2热泵的产消型数据中心能效联动优化

  目的  随着数字经济的发展,数据中心的“规模”将不断扩大,“算力”不断提高,随之带来的“能耗”及“运行成本”也将不断攀升。为实现数据中心余热的有效利用,并实现能效的联动优化,构建了一种基于CO₂热泵的产消型数据中心能源系统。  方法  将数据中心视为产消者,耗电的同时将制冷系统的余热回收,用于住宅供暖。产消型数据中心能源系统采用空气直接冷却、直膨式地埋管冷却和建筑供暖末端冷却三种方式实现数据中心全年的冷却,最大程度利用自然冷却,降低系统电耗。CO₂作为余热回收用热泵的工作介质,能够提高系统紧凑性与环境友好性。  结果  本系统可有效削减冷负荷,进而在平均占用率较低时,实现制冷电耗的降低。当平均占用率为0.6时,与常规房间级风冷空调机组相比,本系统可降低全年冷负荷108 MWh,节约电耗制冷电耗167 MWh,为建筑供热290 MWh,获得年收益4.23万元。  结论  本系统可实现数据中心余热回收用于建筑供暖,实现了数据中心非供暖期余热的有效利用。并通过地源热泵系统实现了数据中心余热与建筑热负荷的协调,为产消型数据中心的能效联动优化提供了借鉴。     

Integration of Kalina cycle in a combined heat and power plant,a case study

This paper presents the integration of the Kalina cycle process in a combined heat and power plant for improvement of efficiency. In combined heat and power plants, the heat of flue gases is often available at low temperatures. This low-grade waste heat cannot be used for steam production and therefore power generation by a conventional steam cycle. Moreover, the steam supply for the purpose of heating is mostly exhausted, and therefore the waste heat at a low-grade temperature is not usable for heating. If other measures to increase the efficiency of a power plant process, like feed-water heating or combustion air heating, have been exhausted, alternative ways to generate electricity like the Kalina cycle process offer an interesting option. This process maximizes the generated electricity with recovery of heat and without demand of additional fuels by integration in existing plants. The calculations show that the net efficiency of an integrated Kalina plant is between 12.3% and 17.1% depending on the cooling water temperature and the ammonia content in the basic solution. The gross electricity power is between 320 and 440 kW for 2.3 MW of heat input to the process. The gross efficiency is between 13.5% and 18.8%.     

Research on a Refrigeration Dehumidification System with Membrane-Based Total Heat Recovery

An independent air dehumidification system is helpful to improve indoor air quality and decrease energy consumption by heating, ventilation, and air conditioning (HVAC). A refrigeration dehumidification system with membrane-based total heat recovery is the key equipment to realize this goal. The system comprises two subsystems: a membrane total heat recovery and a direct expansion refrigeration system. The total heat exchanger has a membrane core where the incoming fresh air exchanges moisture and temperature simultaneously with the exhaust air. In this manner, the total heat or enthalpy from the exhaust air is recovered. Then the fresh air flows through a cooling coil where it is dehumidified below the dewpoint. Finally, the cold and dry air is supplied to indoors. A prototype of practical application is designed and fabricated. Experiments are conducted under variable operating conditions in the psychrometric calorimeter chamber. The effects of varying operating conditions like temperature and air humidity on the air dehumidification rate, cooling power, coefficient of performance, and compressor power are evaluated with indoor exhaust air dry bulb 27°C, wet bulb 19°C, and fresh air flow rate 200 m³/h. In comparison with a conventional refrigeration dehumidification system, the coefficient of performance and air dehumidification rate of the prototype are 2.3 times and 3 times higher, respectively. The performance of the prototype is rather robust under a hot and humid environment.     

AE94.3A型燃气轮机进气冷却的应用可行性研究

对AE94.3A型燃气轮机燃气-蒸汽联合循环热力系统平衡进行研究进而发现,与同类型、同等级不同型号机组相比,AE94.3A型联合循环机组余热锅炉的排烟温度较高,排烟余热仍有进一步利用的空间。通过设计优化,扩大省煤器受热面,回收烟气余热加热给水,驱动热水型溴化锂制冷机制冷,用于机组满负荷调峰时的压气机进气冷却或厂房及办公区域空调供冷,对改善燃气轮机联合循环的运行性能,实现能源梯级利用,提高能源利用率和机组经济性运行起到了很大作用。     

Energy recovery from diesel engine exhaust gases for performance enhancement and air conditioning

The utilisation of exhaust waste heat is now well known and the forms the basis of many combined cooling and power installations. The exhaust gases from such installations represent a significant amount of thermal energy that traditionally has been used for combined heat and power applications. This paper explores the theoretical performance of four different configurations of a turbocharger diesel engine and absorption refrigeration unit combination when operating in a high ambient day temperature of 35 °C. The simulation is performed using “SPICE”, a well known programme commonly used for engine performance predictions. The paper examines the interfacing of the turbocharged diesel engine with an absorption refrigeration unit and estimates the performance enhancement. The influence of the cycle configuration and performance parameters on the performance of the engine operating as a power supply with an auxiliary air conditioning plant is examined. It is demonstrated that a pre- and inter-cooled turbocharger engine configuration cycle offers considerable benefits in terms of SFC, efficiency and output for the diesel cycle performance.     

Experimental study of hydrogen storage with reaction heat recovery using metal hydride in a totalized hydrogen energy utilization system

Experimental results for hydrogen storage tanks with metal hydrides used for load leveling of electricity in commercial buildings are described. Variability in electricity demand due to air conditioning of commercial buildings necessitates installation of on-site energy storage. Here, we propose a totalized hydrogen energy utilization system (THEUS) as an on-site energy storage system, present feasibility test results for this system with a metal hydride tank, and discuss the energy efficiency of the system. This system uses a water electrolyzer to store electricity energy via hydrogen at night and uses fuel cells to generate power during the day. The system also utilizes the cold heat of reaction heat during the hydrogen desorption process for air conditioning. The storage tank has a shell-like structure and tube heat exchangers and contains 50 kg of metal hydride. Experimental conditions were specifically designed to regulate the pressure and temperature range. Absorption and desorption of 5,400 NL of hydrogen was successfully attained when the absorption rate was 10 NL/min and desorption rate was 6.9 NL/min. A 24-h cycle experiment emulating hydrogen generation at night and power generation during the day revealed that the system achieved a ratio of recovered thermal energy to the entire reaction heat of the hydrogen storage system of 43.2% without heat loss.     

Integration of a molten carbonate fuel cell with a direct exhaust absorption chiller

A high market value exists for an integrated high-temperature fuel cell-absorption chiller product throughout the world. While high-temperature, molten carbonate fuel cells are being commercially deployed with combined heat and power (CHP) and absorption chillers are being commercially deployed with heat engines, the energy efficiency and environmental attributes of an integrated high-temperature fuel cell-absorption chiller product are singularly attractive for the emerging distributed generation (DG) combined cooling, heating, and power (CCHP) market. This study addresses the potential of cooling production by recovering and porting the thermal energy from the exhaust gas of a high-temperature fuel cell (HTFC) to a thermally activated absorption chiller. To assess the practical opportunity of serving an early DG-CCHP market, a commercially available direct fired double-effect absorption chiller is selected that closely matches the exhaust flow and temperature of a commercially available HTFC. Both components are individually modeled, and the models are then coupled to evaluate the potential of a DG-CCHP system. Simulation results show that a commercial molten carbonate fuel cell generating 300 kW of electricity can be effectively coupled with a commercial 40 refrigeration ton (RT) absorption chiller. While the match between the two “off the shelf” units is close and the simulation results are encouraging, the match is not ideal. In particular, the fuel cell exhaust gas temperature is higher than the inlet temperature specified for the chiller and the exhaust flow rate is not sufficient to achieve the potential heat recovery within the chiller heat exchanger. To address these challenges, the study evaluates two strategies: (1) blending the fuel cell exhaust gas with ambient air, and (2) mixing the fuel cell exhaust gases with a fraction of the chiller exhaust gas. Both cases are shown to be viable and result in a temperature drop and flow rate increase of the gases before the chiller inlet. The results show that no risk of cold end corrosion within the chiller heat exchanger exists. In addition, crystallization is not an issue during system operation. Accounting for the electricity and the cooling produced and disregarding the remaining thermal energy, the second strategy is preferred and yields an overall estimated efficiency of 71.7%.     

Thermodynamic analysis of an existing coal-fired power plant for district heating/cooling application

In a conventional coal-fired power plant, which is only designed for electricity generation, 2/3 of fuel energy is wasted through stack gases and cooling water of condensers. This waste energy could be recovered by trigeneration; modifying the plants in order to meet district heating/cooling demand of their locations. In this paper, thermodynamical analysis of trigeneration conversion of a public coal-fired power plant, which is designed only for electricity generation, has been carried out. Waste heat potentials and other heat extraction capabilities have been evaluated. Best effective steam extraction point for district heating/cooling system; have been identified by conducting energetic and exergetic performance analyses. Analyses results revealed that the low-pressure turbine inlet stage is the most convenient point for steam extraction for the plant analyzed.     

Power generation and cooling capacity enhancement of natural gas processing facilities in harsh environmental conditions through waste heat utilization

Most natural gas (NG) producers in the Persian Gulf face increasing challenges in meeting their domestic gas demands and therefore seek to reduce their NG consumption. Concurrently, the on‐site power generation and cooling capacities of local NG processing facilities are constrained by extreme climatic conditions. A combined cooling and power scheme based on gas turbine (GT) waste heat‐powered absorption refrigeration is techno‐economically assessed to reduce the NG consumption of a major gas processing plant in the Persian Gulf. The scheme utilizes double‐effect water‐lithium bromide absorption refrigeration activated by steam generated from GT exhaust gas waste heat to provide both GT compressor inlet air and process gas cooling. Based on a thermodynamic analysis, recovery of 150 MW of GT waste heat is found to enhance the plant cooling capacity by 195 MW, thereby permitting elimination of a 32.6 MW GT and existing cooling equipment. On‐site power generation is enhanced by 196 GWh annually through GT compressor inlet air cooling, with energy efficiency (i.e., 64%) improved by 35% using cogeneration relative to the existing power generation plant. The overall net annual operating expenditure savings contributed by the combined cooling and power system are of $US13 million to 34 million based on present and projected local utility prices, with an economic payback period estimated at 2 to 5 years. These savings translate to approximately 94 to 241 MMSCM of NG per year, highlighting the potential of absorption refrigeration to both enhance the power generation and cooling capacity of hydrocarbon processing plants exposed to harsh environmental conditions and to realize substantial primary energy savings. Copyright © 2014 John Wiley & Sons, Ltd.     

Stockholm CHP potential—An opportunity for CO2 reductions?

The potential for combined heat and power (CHP) generation in Stockholm is large and a total heat demand of about 10 TWh/year can be met in a renewed large district heating system. This model of the Stockholm district heating system shows that CHP generation can increase from 8% in 2004 to 15.5% of the total electricity generation in Sweden. Increased electricity costs in recent years have awakened an interest to invest in new electricity generation. Since renewable alternatives are favoured by green certificates, bio-fuelled CHP is most profitable at low electricity prices. Since heat demand in the district heating network sets the limit for possible electricity generation, a CHP alternative with a high electricity to heat ratio will be more profitable at when electricity prices are high. The efficient energy use in CHP has the potential to contribute to reductions in carbon dioxide emissions in Europe, when they are required and the European electricity market is working perfectly. The potential in Stockholm exceeds Sweden's undertakings under the Kyoto protocol and national reduction goals.     

A review on solar cold production through absorption technology

Recently, the traditional energy types have failed to satisfy the human needs because of their limited quantity as well as their negative environmental impacts. Conventional cold producing machines that are based on vapor compression principle are primary electricity consumers and their working fluids are being banned by international legislation. From this perspective, solar powered cooling systems as a green cold production technology are the best alternative. Absorption refrigeration is a mature technology that has proved its applicability with the possibility to be driven by low grade solar and waste heat. In this study, we present a comprehensive literature review on absorption based refrigeration and air conditioning systems that are powered by solar energy. Various systems along with their thermodynamic operating principle are presented. Moreover, the previous experimental and numerical simulation studies for these systems are discussed.     

基于有机朗肯循环的APU余热回收系统性能分析

为有效利用飞机辅助动力装置（Auxitlary Power Unit , APU）排气余热,基于有机朗肯循环（Organic Rankine Cycle, ORC）发电系统,构建了APU余热回收系统。系统以APU排气余热为输入,驱动ORC做功,输出电能,为机载设备提供二次能源。结合工程热力学原理,建立系统热力学模型,并通过Matlab编程对余热回收系统进行了仿真计算及性能分析。仿真结果表明,系统功率及效率随飞行马赫数增加而降低;APU余热回收系统在飞机低音速飞行时有良好的性能;马赫数小于1时,系统功率在12 kW以上,效率在11%以上,耗气率低于0.0262 kg/kJ。     

Operational aspects of adsorption air‐conditioner used in diesel locomotive

A locomotive cabin adsorption air‐conditioner has been equipped in #DF4B‐2369 locomotive; and has been successfully run for 2 years. It is powered by waste heat from the exhaust of the diesel engine. The influence on heat transfer is described by the equivalent heat transfer coefficient or thermal resistance of components inside the adsorber. The variation of adsorption capacity is expressed by a non‐equilibrium adsorption function. The dynamic heat transfer process of adsorption air‐conditioning system is treated with the lumped parameter method. Some typical running experimental results are present. The diesel engine rotating speed and locomotive speed influenced on the refrigeration system are discussed. The maximum mean refrigeration power is regarded as an objective function. Based on experiments and theoretical analysis, the running characteristics of the air‐conditioning system are optimized. Some techniques of performance improvement are suggested as well. Copyright © 2006 John Wiley & Sons, Ltd.     

Theoretical Investigation of Waste Heat Recovery from an IC Engine Using Vapor Absorption Refrigeration System and Thermoelectric Converter

This study proposes the preliminary simulation of a single cylinder spark ignition engine with waste heat recovery system. To harvest waste heat energy from the engine exhaust a thermoelectric generator coupled to a vapor absorption refrigeration (VAR) system was proposed in this simulation work. Parametric simulation of engine, thermoelectric generator and VAR using thermodynamic relations was carried out in MATLAB – Simulink software. An attempt has been made mathematically to integrate engine, thermoelectric generator and VAR system to study the effect of engine load, speed, equivalence ratio on thermoelectric output and coefficient of performance (COP) of a VAR system. In this study, the VAR system runs by taking heat energy from the exhaust gas and the electric power produced by a thermoelectric generator was utilized to run the pump of the refrigeration system. It was found that COP of the absorption refrigeration system depends on engine load, speed and air fuel equivalence ratio. The study also reveals that about 10% to 15% of the total exhaust energy can be harvested using this system.     

Performance characterization of gas engine generator integrated with a liquid desiccant dehumidification system

Combined heat and power (CHP) involves on-site or near-site generation of electricity along with utilization of thermal energy available from the power generation process. CHP has the potential of providing a 30% improvement over conventional power plant efficiency and a CO₂ emissions reduction of 45% or more as compared to the US national average. In addition, an overall total system efficiency of 80% can be achieved because of the utilization of thermal energy that would be wasted if only the electric power were utilized, and because of the reduction of transmission, distribution, and energy conversion losses. The current research is being carried out in a four-story educational office building. This research focuses on the design, installation, and analysis of a modular CHP system consisting of a natural gas fired reciprocating engine generator with a liquid desiccant dehumidification system. The engine generator provides 75 kW of electric power to the building load bus while the combined waste heat from the exhaust gases and jacket water are used to regenerate the liquid desiccant. The liquid desiccant unit dehumidifies and cools the ventilation air to the building and supplies it to the mixed air section of the roof top unit. This paper discusses the various aspects involved in the design and installation of the system such as the heat recovery loop design and the electrical interconnection with the building load bus. Test results are also presented and the performance is compared to a traditional power plant with a conventional heating, ventilating, and air-conditioning system.     

可再生能源应用的重要领域

建筑能源具有品位低,温度范围窄,与自然能源的温度接近三大特点,这三大特点决定了可再生能源是建筑用能的首选。通过热泵的提升,可以将土壤能、地表水能、海洋能应用到建筑中,这一技术已在国外得到大规模利用。太阳能热发电是另一种最有希望与传统发电方式竞争的可再生能源发电方式。     

Recent developments of refrigeration technology in fishing vessels

Modern large and fast ocean fishing vessels include mechanical refrigeration, but all of them consume precious fuel or electricity to achieve refrigeration. Fishing vessels with tonnage at about 100 tons cannot attach compressor-icemaker onboard because of their small horsepower of diesel engine. These vessels always have to carry a lot of ice for caught fish preservation. At the same time, waste heat dissipated in the hot exhaust gases in most of the fishing vessels is rejected to the atmosphere. At present, some effort has been devoted to the utilization of the vast amount of the waste energy for refrigeration. In this paper, several types of refrigeration technology in fishing vessels are introduced, such as vapor-compression refrigeration systems, heat recovery systems to power absorption refrigeration plant, adsorption systems for producing chilled water, and adsorption icemaker systems, especially an adsorption icemaker prototype in our laboratory. The better perspectives of applications for the lattermost exist in fishing vessels.