1、大 连海洋大学 2012 届毕业设计 外文翻译（英文） DESIGN OF HEAT EXCHANGER FOR HEAT RECOVERY IN CHP SYSTEMS ABSTRACT The objective of this research is to review issues related to the design of heat recovery unit in Combined Heat and Power (CHP) systems. To meet specific needs of CHP systems, configurations can be altered
2、 to affect different factors of the design. Before the design process can begin, product specifications, such as steam or water pressures and temperatures, and equipment, such as absorption chillers and heat exchangers, need to be identified and defined. The Energy Engineering Laboratory of the Mech
3、anical Engineering Department of the University of Louisiana at Lafayette and the Louisiana Industrial Assessment Center has been donated an 800kW diesel turbine and a 100 ton absorption chiller from industries. This equipment needs to be integrated with a heat exchanger to work as a Combined Heat a
4、nd Power system for the University which will supplement the chilled water supply and electricity. The design constraints of the heat recovery unit are the specifications of the turbine and the chiller which cannot be altered. INTRODUCTION Combined Heat and Power (CHP), also known as cogeneration, i
5、s a way to generate power and heat simultaneously and use the heat generated in the process for various purposes. While the cogenerated power in mechanical or electrical energy can be either totally consumed in an industrial plant or exported to a utility grid, the recovered heat obtained from the t
6、hermal energy in exhaust streams of power generating equipment is used to operate equipment such as absorption chillers, desiccant dehumidifiers, or heat recovery equipment for producing steam or hot water or for space and/or process cooling, heating, or controlling humidity. Based on the equipment
7、used, CHP is also known by other acronyms such as CHPB (Cooling Heating and Power for Buildings), CCHP (Combined Cooling Heating and Power), BCHP (Building Cooling Heating and Power) and IES (Integrated Energy Systems). CHP systems are much more efficient than producing electric and thermal power se
8、parately. According to the Commercial Buildings Energy Consumption Survey, 1995 14, there were 4.6 million commercial buildings in the United States. These buildings consumed 5.3 quads of energy, about half of which was in the form of electricity. Analysis of survey data shows that CHP meets only 3.
9、8% of the total energy needs of the commercial sector. Despite the growing energy needs, the average efficiency of power generation has remained 33% since 1960 and the average overall efficiency of generating heat and electricity using conventional methods is around 47%. And with the increase in pri
10、ces in both electricity and natural gas, the need for setting up more CHP plants remains a pressing issue. CHP is known to reduce fuel costs by about 27% 15 CO released into the atmosphere. The objective of this research is to review issues related to the design of heat recovery unit in Combined Hea
11、t and Power (CHP) systems. To meet specific needs of CHP systems, configurations can be altered to affect different factors of the design. Before the design process can begin, product specifications, 大 连海洋大学 2012 届毕业设计 外文翻译（英文） such as steam or water pressures and temperatures, and equipment, such a
12、s absorption chillers and heat exchangers, need to be identified and defined. The Mechanical Engineering Department and the Industrial Assessment Center at the University of Louisiana Lafayette has been donated an 800kW diesel turbine and a 100 ton absorption chiller from industries. This equipment
13、needs to be integrated to work as a Combined Heat and Power system for the University which will supplement the chilled water supply and electricity. The design constraints of the heat recovery unit are the specifications of the turbine and the chiller which cannot be altered. Integrating equipment
14、to form a CHP system generally does not always present the best solution. In our case study, the absorption chiller is not able to utilize all of the waste heat from the turbine exhaust. This is because the capacity of the chiller is too small as compared to the turbine capacity. However, the need f
15、or extra space conditioning in the buildings considered remains an issue which can be resolved through the use of this CHP system. BACKGROUND LITERATURE The decision of setting up a CHP system involves a huge investment. Before plunging into one, any industry, commercial building or facility owner w
16、eighs it against the option of conventional generation. A dynamic stochastic model has been developed that compares the decision of an irreversible investment in a cogeneration system with that of investing in a conventional heat generation system such as steam boiler combined with the option of pur
17、chasing all the electricity from the grid 21. This model is applied theoretically based on exempts. Keeping in mind factors such as rising emissions, and the availability and security of electricity supply, the benefits of a combined heat and power system are many. CHP systems demand that the perfor
18、mance of the system be well tested. The effects of various parameters such as the ambient temperature, inlet turbine temperature, compressor pressure ratio and gas turbine combustion efficiency are investigated on the performance of the CHP system and determines of each of these parameters 1. Five m
19、ajor areas where CHP systems can be optimized in order to maximize profits have been identified as optimization of heat to power ratio, equipment selection, economic dispatch, intelligent performance monitoring and maintenance optimization 6.Many commercial buildings such as universities and hospita
20、ls have installed CHP systems for meeting their growing energy needs. Before the University of Dundee installed a 3 MW CHP system, first the objectives for setting up a cogeneration system in the university were laid and then accordingly the equipment was selected. Considerations for compatibility o
21、f the new CHP setup with the existing district heating plant were taken care by some alterations in pipe work so that neither system could impose any operational constraints on the other 5. Louisiana State University installed a CHP system by contracting it to Sempra Energy Services to meet the incr
22、ease in chilled water and steam demands. The new cogeneration system was linked with the existing central power plant to supplement chilled water and steam supply. This project saves the university $ 4.7 million each year in energy costs alone and 2,200 emissions are equivalent to 530 annual vehicul
23、ar emissions. 大 连海洋大学 2012 届毕业设计 外文翻译（英文） Another example of a commercial CHP set-up is the Mississippi Baptist Medical Center. First the energy requirement of the hospital was assessed and the potential savings that a CHP system would generate 10. CHP applications are not limited to the industrial
24、and commercial sector alone. CHP systems on a micro-scale have been studied for use in residential applications. The cost of UK residential energy demand is calculated and a study is performed that compares the operating cost for the following three micro CHP technologies: Sterling engine, gas engin
25、e, and solid oxide fuel cell (SOFC) for use in homes 9. The search for different types of fuel cells in residential homes finds that a dominant cost effective design of fuel cell use in micro CHP exists that is quickly emerging 3. However fuel cells face competition from alternate energy products th
26、at are already in the market. Use of alternate energy such as biomass combined with natural gas has been tested for CHP applications where biomass is used as an external combustor by providing heat to partially reform the natural gas feed 16. A similar study was preformed where solid municipal waste
27、 is integrated with natural gas fired combustion cycle for use in a waste-to-energy system which is coupled with a heat recovery steam generator that drives a steam turbine 4. SYSTEM DESIGN CONSIDERATIONS Integration of a CHP system is generally at two levels: the system level and the component leve
28、l. Certain trade-offs between the component level metrics and system level metrics are required to achieve optimal integrated cooling, heating and power performance 18. All CHP systems comprise mainly of three components, a power generating equipment or a turbine, a heat recovery unit and a cooling
29、device such as an absorption chiller. There are various parameters that need to be considered at the design stage of a CHP project. For instance, the chiller efficiency together with the plant size and the electric consumption of cooling towers and condenser water pumps are analyzed to achieve the o
30、verall system design 20. Absorption chillers work great with micro turbines. A good example is the Rolex Reality building in New York, where a 150 kW unit is hooked up with an absorption chiller that provides chilled water. An advantage of absorption chillers is that they dont require any permits or
31、 emission treatment 2 Exhaust gas at 800F comes out of the turbine at a flow rate of 48,880 lbs/h 7. One important constraint during the design of the CHP system was to control the final temperature of this exhaust gas. This meant utilizing as much heat as required from the exhaust gas and subsequen
32、tly bringing down the exit temperature. After running different iterations on temperature calculations, it was decided to divert 35% of the exhaust air to the heat exchanger while the remaining 65% is directed to go up the stack. This is achieved by using a diverter damper. In addition, diverting 35
33、% of the gas relieves the problem of back pressure build-up at the end of the turbine. A diverter valve can also used at the inlet side of the heat exchanger which would direct the exhaust gas either to the heat exchanger or out of the bypass stack. This takes care of variable loads requirement. Inside the heat exchanger, exhaust gas enter the shell side
