优化集中供暖散热器毕业论文外文文献翻译.doc

《优化集中供暖散热器毕业论文外文文献翻译.doc》由会员分享，可在线阅读，更多相关《优化集中供暖散热器毕业论文外文文献翻译.doc（28页珍藏版）》请在淘文阁 - 分享文档赚钱的网站上搜索。

1、中文译文:优化集中供暖散热器 阿尔斯兰蒂尔克和厄兹居奇机械工程学院，阿塔图尔克大学， 25240埃尔祖鲁姆，土耳其 学院：机械工程，伊斯坦布尔技术大学， Gumussuyu ， 80191伊斯坦布尔 ，土耳其 。 摘要 近似解析模型已经被用来评估集中供暖散热器的最佳尺寸。散热器的问题是被分为三个一维的问题，然后温度分布和来自散热器的热传输速率，得到了很好分析。优化热传输速率的几何最大限度，是为了给定散热器的数量和与生产技术相关的几何约束。并且对于热的限制，已经被发现。 现在介绍几何和热参数对散热器的性能的影响。 关键词：集中供热；优化；散热器 1 导言散热器是最受欢迎的集中采暖设备。作为散热器

2、，它比周围的空气热，此时一定数额的热量转移到空气，从而水在较低的温度下存在。对各种可用的设计通常配备对流散热，以改善其热输出，这些设计普遍应用于国内商业、工业领域。对于集中供暖散热器的使用主要形式是国内的家居采暖。尽管散热器被称为散热器，但他们中的大部分是以自然对流的形式输出的。由于集中采暖散热器的平均表面温度一般情况下低于80，所以辐射传热对于总热量的传输的贡献小于自然对流换热。由于表面温度较低，在对这种散热器的热分析中，对于辐射传热来说，在能量平衡方程中可以线性化。在本文中，假设的主要模型，传热是传导和对流，辐射对其的影响可以被忽略。为了测量温度分布和传热率，一种近似的数学模型被构建出来。

3、设计和优化这些散热器或散热器片，一般是基于两种方法，一种是为了某一特定数量的散热，尽量减少其数量或质量；另一种是为了某一特定的数量或质量，最大限度的增大热耗散。这里考虑的优化问题的重点是：根据给定的散热器材料的数量和几何限制、热限制，以找到能最大限度的发挥热传递的集中采暖散热器的最佳尺寸。 2 数学分析在图1中所显示的散热器，考虑到稳定状态的条件和忽略温度在整个厚度边界层上的变化，我们可以假定温度在散热器管的中心线上的分布是一维的。假设关于传热是传导和对流，以及可以忽略辐射对其的影响，这个结论是正确的。那么线性数学模型即被认可。由于平衡的条件，散热器的一部分显示在图1中已经足够了。这表明，为了

4、数学方便，这个问题在条款的三个领域内会被调查。Full-sizeimage(23K) 图1 散热器示意图对于散热器的每个部分，能量平衡方程都以以下形式给出 (1)目前在联结点对温度和热的连续性的引用，边界条件的方程可表示为： （2a）1(L1)=2(0) (2b) (2c) (2d) (2e) (2f) (3a) (3b)该方程给出了均衡器，（1）表示如下： (4)使用著名的Dittus-Boelter的相关性，为了选定内流速，传热系数、内管都以管半径的形式表示。hi=A(U)0.8(R)0.2 (5)在如（5）所示的系统图A里，可以计算出内部流体的热物理特性。运用边界条件给出了均衡器：(2a

5、),(2b),(2c),(2d)和(2f),未知系数 Cj,1 和 Cj,2 也在表里， （4）可以粗略地计算。3 优化程序这里的目的是最大限度地发挥传热率，为了达到散热器的体积分数和举例来校核其他的热工参数。总传热率，即目标函数，很容易计算，应用管与管内流体之间的牛顿冷却定律，式为： (6)散热器的体积分数被表示为一个相同的约束。 (7)散热器的正面尺寸，必须等于或者小于，由于生产技术，其正面尺寸受到限制，在图1中，以下等式约束可以写成： (8)为简单起见，选择1 = 2 = 3 = ，并应用相同的限制，给出了均衡器。一个客观的功能与一个独立的变量散热器管半径可以被发现，R。能最大限度地发挥

6、功能的R的价值被认可，它通过鉴别设置的结果归于零的这种功能表示出来。然后解决新产生的方程。4 结论在本文中，为了集中供暖散热器的优化设计，近似解析模型已被提出。散热器的问题，已分为三个一维的问题。为了评估散热器内温度分布，利用散热器的边界条件和连续性，该问题已经解决了。温度差异已被用于从散热器到环境的内部传热率中。通过使用近似解析模型，散热器最佳尺寸与最大限度传热率的优化已经获得。目前的优化技术，可以应用于集中采暖散热器与更复杂的几何形状。 外文文献二Choosing a Heating SystemBefore choosing a heater remember.The best way

7、to improve the comfort of your home in winter and spend less on heating is to reduce the heat losses from your home. Before you buy a heating system, we recommend the following: insulate ceilings (R3.5+), walls (R2+), and floors (R1.5+), where possible; seal off draughts; use insulating window cover

8、ings; and zone living and sleeping areas. For more information on the above, please see our Keeping Your Home Warm and Cavity Wall Insulation fact sheets. When building or renovating these improvements even allow you to buy a smaller heating system. Buying a heaterThe steps below give you a systemat

9、ic approach to addressing the above questions.How comfortable your body feels is not only dependent on the temperature in your home. When choosing a heating system, it is worth considering the following. Is it the appropriate size for the space to bheated? Does it have a range of heat settings? Is i

10、t thermostatically controlled? How much noise does it make? Can I zone it? Does it have a radiant heat component? How efficient is it? Cost? What are its greenhouse gas emissions? How quickly will it heat the area? How frequently am I going to use it?factors that contribute to human comfort.What mak

11、es us feel warm?Radiant energy: All materials, including people, give off radiant energy. The hotter something is, the more radiant energy it gives off. Examples of high emitters are the sun, fires, and hot radiators. Radiant energy is transferred by electromagnetic waves, which means it is not reli

12、ant on air movement. Radiant heat works best when the person to be heated is nearby. It is not as useful when people are moving about. About 50% of our experience of winter comfort depends on the amount of radiant energy reaching us.Convection/warm air: Convection relies on themovement of heat throu

13、gh gas (including air) or liquidto transfer heat from a warm area to a colder area. Being surrounded by warm air makes us feel warm asour rate of heat loss by conduction and convection isreduced, but too much convection can make us feeluncomfortable.Clothing/bedding: Surrounding the body with alayer

14、 of insulating clothing or bedding reduces theheat loss from a person, increasing the comfort levelwithout changing the environment. Activity level: The amount of heat generated by a person varies hugely depending on activity level. The amount of heating needed in an office is much greater than the

15、heating required in a busy warehouse or gym.What makes us feel cold?Moving air: Moving air increases the rate of evaporation a person experiences, which is the main mechanism the body has for losing heat. Even warm moving air, if close to the body, increases the heat loss from a person. For this rea

16、son, heaters that rely on moving air (fan heaters, central ducted systems) should be located to avoid excessive air movement where people are often sitting or standing.Cold surfaces: Cold floors make for cold feet and cold walls, ceilings and windows make the rest of you feel cold as your body radia

17、tes more heat to them than they radiate to you. Insulation and insulating curtains increase the temperature of the surrounding surfaces and make you feel comfortable at a lower air temperature.Step 2: Should I heat the whole house?Central heating or zoning:Heating unused areas in your home is a wast

18、e of heat and money. By closing off unused areas and ensuring your heater is only heating the used areas, you will save money and greenhouse gas emissions whilst still being comfortable. You can do this by closing doors as well as closing vents if you have a central heating system. In all but the mo

19、st open plan houses, this should be achievable. Central heating systems can be supplemented by high efficiency space heating when only small areas of the house are being used. The table below gives an idea of whether you are likely to get better value from central or space heating. However, note tha

20、t central heating systems can also be supplemented by installing a high efficiency space heater in the main living area, to be used when whole house heating is not required. If you are upgrading from space to central heating, consider retaining the existing space heater for this purpose. Space vs Ce

21、ntral HeatingHeating requiredSystem recommendedOnly heating living areasSpace heatingLiving areas and minimal heat to bedrooms Space heatingHeating several disconnected rooms Central heatingWhole houseCentral heating The tendency in Canberra in recent years has been to install central heating becaus

22、e of perceived greater comfort. Additionally, large ducted systems (gas or reverse cycle) are perceived to have higher efficiencies than smaller space heaters because their efficiency rating ignores the very large losses through the walls of the ducts even before any heat reaches you in your rooms.

23、Factors that are often ignored are the large initial cost of a central system Appliance emissions and running costs Heater typeGreenhouseemissions pekWhCost per kWh heat produced1Solar Air Heater0-0.1 kg0-1.5c2 star Gas (65%)0.28 kg7.9cents5 star Gas (88%)0.20 kg5.9Electric Heat Pump 5 star (COP2.02

24、)0.495.4cElectric Heat Pump 2 Star (COP1.4)0.707.8cElectricolumn,Convection, etc,0.98 kg10.9cOff Peak Electric0.98 kg7.5cStep 3: Types of heatingNow that you have some ideas of cost and whether to use central or space heating, here is a break down of the more common types of heaters and heating syst

25、ems: STOP PRESS: Solar air heaters to heat your home. An increasing range of solar air heaters, modular, space, and integrated into existing duct work are now available. While generally not designed to be the only heater in the house these heaters provide very low cost, low emissions heat, particula

26、rly in the shoulder seasons. Space heaters:3.1 Flued gas heaters have grown in size recently so that some of them almost qualify as central heating units, heating up to 150m2 of a well insulated home. They give off a mixture of radiant and convective heat and their efficiencies and cost vary widely.

27、 Limited ducting is possible for some units. Pros: Can be effective; low greenhouse gas emissions; medium cost; radiant heat; some have a visible flame. Cons: Efficiency highly dependent on initial cost.3.2 Unflued gas heaters are similar to flued units except that they tend to be smaller, cheaper,

28、and highly efficient. However they have a number of issues that make them less attractive. Cons: Internal air quality is reduced due to combustion products. This can exacerbate respiratory problems. Water vapour production also means that extra ventilation is necessary, reducing effective efficiency

29、 of the heater. Not recommended for Canberra conditions. 3.3 Electric fan forced heaters provide quick, even heating to small or moderate sized areas. Cons: High running costs; high carbon dioxide (CO2) emissions; high air flows can cause cooling and rapid heat loss in older leaky houses; often nois

30、y; heat losses when mounted in an external wall. 3.4 Electric column/radiant heaters provide radiant heat to small areas. When turned down very low they can provide adequate levels of comfort at low cost if the user is very close to the heater. Pros: High radiant heat content; low initial cost; can

31、be targeted to heat just the people. Cons: High running costs and high greenhouse gas emissions if they are the primary source of heat in a room.3.5 Off-peak electric storage heatersRadiant/convection heaters store off-peak electricity as heat in storage bricks. Storage fan heaters are available to

32、heat up to 50m2.The fan helps distribute the heat and control the heat delivery and temperature. Storage radiators deliver 24 hour background heat for areas up to 30m2.Pros: Off peak nature of electricity reduces cost; radiant heat component. Cons: High emissions; relatively high cost; diminishing p

33、ower as the evening wears on; lag time once stored heat is depleted.3.6 Electric thin film heating. Thin films are installed in the ceiling, in wall panels or under floor coverings to give radiant heat. They operate on peak rate electricity. Pros: can effectively heat an area using less electricity

34、than other peak rate electric heaters, especially if targeted (e.g. under-desk leg and feet warmers); thermostatically controlled. Cons: High initial installation cost; high running costs; massively inefficient if not mounted on the room side of high resistance insulation.Central Heating Systems3.7

35、Hydronic heating. Water is heated in a boiler and then circulated around the home to radiator panels, skirting board convectors or fan coil convectors that heat the room by convection and radiation. Natural gas, LPG or wood typically fuels hydronic heating, but it is also possible to use off-peak el

36、ectricity, solar energy and air or ground sourced heat pumps. Each panel usually has its own control valve or thermostat to give individual room control. Pros: Efficient; excellent zoning capability; silent; non-allergenic; high radiant heat component. Cons: High initial cost3.8 Ducted central heati

37、ng ：a) Gas: A gas furnace, usually located under the house or in the roof, heats air that is then circulated using a large fan and network of ducts. Zoning is possible but needs to be specified at the time of purchase. Pros: Efficient; low initial cost compared to other central heating systems. Cons

38、: Large air movement; temperature fluctuations limited zoning potential; warmest air is near the ceiling; duct losses.b) Electric reverse cycle (heat pump) A heat pump extracts heat from the outside air and de livers it into the home using a fan. It can be installed not only as central ducting, but

39、also in a wall or window, or as a splitsystem with the compressor outside and the console unitPros: Very high efficiency possible but decreases astemperature drops; low running costs; canuse for coolingin summer. Cons: High initial cost; higher CO2 emissions than gas;generally noisier for you and yo

40、ur neighbours; some short blasts of cold air during the de-ice cycle; airmovement; warmest air is near the ceiling;3.9 In-slab heating A concrete slab is heated by internal electric cables or hot water pipes. It is usually installed only in new homes or extensions before the concrete is poured. Typi

41、cally it is fuelled by off-peak electricity (for cables) or natural gas (for hot water pipes). Slow response time (6-8 hours) to changes in thermostat settings means systems should be set and left on for 24 hour heating. Pros: High radiant heat component; warm feet; non-allergenic; silent. Cons: Exp

42、ensive to run; very high greenhouse gas emissions when using electricity; slow response time; requires large amounts of additional under-slabinsulation.Wood fired heatersCan be used for both central and space heating. Open fireplaces are no longer allowed to be installed. Only sealed, high efficienc

43、y wood heaters that meet Australian Standard 4013 can be installed in houses. In urban areas, particulate emissions arising from wood fires are a serious concern and the ACT Government encourages householders to switch to other forms of heating. Pros: Can be very cheap to run; when used well can be

44、efficient and low greenhouse gas emissions. Cons: Some particulate emissions unavoidable; concerns about availability of sustainable firewood (e.g. plantation); very high greenhouse emi ssions and particulate emissions if burned poorly.外文文献三节选自James B. Bradford et al. “HVAC Equipment and Systems”.Ha

45、ndbook of Heating, Ventilation, and Air-Conditioning.Ed. Jan F. Kreider.Boca Raton, CRC Press LLC. 2001 Applications1Unlike chillers, pumps, and air handlers, the cooling tower must be installed in an open space with careful consideration of factors that might cause recirculation (recapture of a portion of warm and humid exhaust air by the same tower) or restrict air flow. A poor tower siting situation might lead to recirculation, a problem not restricted to wet cooling towers. Similar recirculation can occur with air-cooled condensing equipment as well. With cooling to