空氣調節
维库，知识与思想的自由文库
空氣調節，在中國大陸簡稱空調，其他華語地區稱為冷氣，而產生這種效果的，是一種電器、系統或機制，以冷凍循環把空氣中的熱力抽出。在建築學上，一個完整的暖氣，通風及空氣調節系統被稱為HVAC（英語：Heating, Ventilation, Air-conditioning and Cooling）。
目录 |
[编辑] 歷史
在超過一千年前，波斯已發明一種古式的空氣調節系統，利用裝置於屋頂的風桿，以外面的自然風穿過涼水並吹入室內，令室內的人感到涼快。[1]
19世紀，英國科學家及發明家麥可·法拉第(Michael Faraday)，發現壓縮及液化某種氣體可以將空氣冷凍，此現象出現在液化亞摩尼亞蒸發時，當時其意念仍流於理論化。
1842年，佛羅里達州醫生約翰·哥里(John Gorrie)以壓縮技術製造出冰塊，並使用作冷凍空氣以吹向瘧疾與黃熱病的病人。[2] 他想到使用其製冰機以管理大廈的環境，並想像到可令整個城市涼快的中央空氣調節系統[3]。哥里在1851年為其製冰機取得美國專利(#8080)。此技術受到北方一些商人及宗教領袖的攻擊，因此技術威脅這些商人從北方運送冰塊至南方出售的生意。當哥里及其生意夥伴在1855年去世後，空氣調節的意念亦隨之消失。
空氣調節其中一個供個人舒適的應用是在1902年，當時紐約證券交易所落成的新大樓設有中央空调。一名新澤西州Hoboken的工程師Alfred Wolff協助設計此嶄新的空氣調節系統，並把技術由紡織廠遷移至商業大廈，他被認為是令工作環境變得涼快的先驅之一。
1902年後期，首個現代化，電力推動的空氣調節系統由韋利士·夏維蘭·加利亞(1876年-1950年)發明。其設計與Wolff的設計分別在於並非只控制氣溫，亦控制空氣的濕度以提高紐約布克林一間印刷廠的製作過程質素。此技術提供了低熱度及濕度的環境，令紙張面積及油墨的排列更準確。其後，加利亞的技術開始用於在工作間以提升生產效率，開利工程公司亦在1915年成立以應付激增的需求。在逐漸發展下，空氣調節開始用於提升在家居及汽車的舒適度。住宅空調系統的銷量到1950年代才真正起飛。建於1906年，位於北愛爾蘭貝爾法斯特的皇家維多利亞醫院，在建築工程學上具有特別意義，被稱為世界首座設有空氣調節的大廈。
1906年，美國北卡羅萊納州夏洛特的Stuart W. Cramer正找尋方法增加其南方紡織廠的空氣濕度。Cramer把技術命名為空氣調節，並在同年將其用於專利申請中，作為水調節(water conditioning)的代替品。水調節當時是一個著名的程序，令紡織品的生產較容易。他把水氣與通風系統結合以「調節」及轉變工廠裡的空氣，控制紡織廠中極重要的空氣濕度。韋利士·加利亞使用此名稱，並把它放進其1907年創辦的公司名稱：「美國加利亞空氣調節公司」 (今開利公司)。
最初的空调、电冰箱使用氨、氯甲烷之类的有毒气体。这类气体泄露后会酿成重大事故。Thomas Midgley, Jr.在1928年发明了氯氟碳气体（chlorofluorocarbon gas）， 并将其命名为氟利昂。 这种制冷剂对人类安全得多，但是对大气臭氧层有害。 氟利昂是杜邦公司CFC、HCFC或HFC类冷冻剂的商标，其中每一类冷冻剂名称还包括一个数字，以表示其成分的分子组成(例如R-11, R-12, R-22, R-134)。其中，在直接蒸发式适度冷却产品领域应用最广的R-22 HCFC制冷剂将于2010年起停止用于新生产的设备中，并于2020年彻底停止使用。R-11和R-12在美国已经停产。作为替代品，一些对臭氧层无害的制冷剂已投入使用， 包括商品名为“Puron”的制冷剂R-410A。
[编辑] 空氣調節的應用
空调工程师们通常把空气调节的应用大致分为“舒适性应用”和“工艺过程性应用”。
Comfort applications aim to provide an indoor environment that remains relatively constant in a range preferred by humans despite changes in external weather conditions or in internal heat loads. Some have claimed that comfort air conditioning increases worker productivity but this claim is disputed, one counter argument being that apparent increases in productivity can be explained as resulting from workers perceiving that their employer shows an interest in their welfare. (See Hawthorne effect). What is certain is that comfort air conditioning makes deep plan buildings feasible. Without air conditioning, buildings must be built narrower or with light wells so that inner spaces receive sufficient fresh air. Air conditioning also allows building to be taller since wind speed increases significantly with altitude making natural ventilation impractical for very tall buildings.
Process applications aim to provide an indoor environment suit a process being carried out that remains relatively constant despite changes in external weather conditions or in internal heat loads. Although often in the comfort range it is the process that determines conditons not human preference. Process applications include:
- Hospital operating theatres in which air is filtered to high levels to reduce infection risk and the humidity controlled to limit patient dehydration. Although temperatures are often in the comfort range, some specialist procedures such as open heart surgery require low temperatures (about 18°C, 64°F) and others such as neonatal relatively high temperatures (about 28°C, 82°F).
- Cleanrooms for the production of integrated circuits, pharmaceuticals and the like in which very high levels of air cleanliness and control of temperature and humidity are required for the success of the process.
- Facilities for breeding laboratory animals. Since many animals normally only reproduce in spring, holding them in rooms at which conditions mirror spring all year can cause them to reproduce year round.
- Aircraft air conditioning. Although nominally aimed at providing comfort for passengers and cooling of equipment, aircraft air conditioning presents a special process because of the low air pressure outside the aircraft.
In both comfort and process applications not only is the objective to control temperature (although in some comfort applications this is all that is controlled) but other factors including humidity, air movement and air quality.
[编辑] 效率評估 (SEER)
Some countries set minimum requirements for energy efficiency. The efficiency of air conditioners are often (but not always) rated by the SEER (Seasonal Energy Efficiency Ratio). The SEER rating is calculated by dividing the total number of BTUs of heat removed from the air by the total amount of energy required by the air conditioner in watt-hours. The higher the ratio, the more energy efficient the air conditioner.
On a power basis, the SEER ratio relates the cooling power of the air conditioner (in BTU per hour) to the electrical power consumption (in watts). For example, if an air conditioner has a cooling power of 5000 BTU/hour, and an SEER rating of 10, then on average it will consume 500 watts of electric power (5000 divided by 10).
Note: SEER is very similar to the "coefficient of performance" commonly used in thermodynamics, except COP is a unitless parameter. (To convert SEER to COP, multiply by 0.293 or (1055 / 3600). In theory, a SEER of 13 is equivalent to a COP of 3.8. This means that 3.8 units of heat energy are pumped per unit of work energy.)
Today, it is rare to see systems rated below SEER 9 in the United States, since older units are being replaced with higher efficiency units. The United States [4] now requires that residental systems manufactured in 2006 have a minimum SEER rating of 13 (although window-box systems are exempt from this law, so their SEER is still around 10). Substantial energy savings can be obtained from more efficient systems. For example by upgrading from SEER 9 to SEER 13, the power consumption is reduced by 30% (equal to 1 - 9/13). It is claimed that this can result in an energy savings valued at up to $US 300 per year (depending on the usage rate and the cost of electricity). In many cases, the lifetime energy savings is likely to surpass the higher initial cost of a high-efficiency unit.
A common misconception is that the SEER rating system also applies to heating systems; however, SEER ratings only apply to air conditioning.
Air conditioners (for cooling) and heat pumps (for heating) both work similarly in that heat is transferred or "pumped" from a cooler "heat-source" to a warmer "heat-sink". (Note: This process requires energy input according to the second law of thermodynamics.) Air conditioners and heat pumps usually operate most effectively at temperatures around 50-55 degrees Fahrenheit. Typically when the heat source temperature falls below 40 deg F, the system begins to reach a point called the "balance point", where the system is not able to "pull" any more heat out of the heat-source. Similarly, when the heat-sink temperature rises to about 120 deg F, the system will operate less effectively, and will not be able to "push" out any more heat.
[编辑] 空氣調節的種類
[编辑] 冷凍循環
在冷凍循環中，熱泵把熱力由一個低溫熱源傳送到另一個較高溫的散熱裝置，熱力會自然地以相反方向流動。這是最普遍的空氣調節方式。冰箱的運作原理與此相當接近，把熱力由冰箱內部傳送至冰箱外的空氣中。
此循環使用了普適氣體定律(universal gas law) PV = nRT，P代表氣壓，V代表體積，而R則代表普適氣體常數，T代表溫度，n則是氣體的摩尔數量 (1 摩尔 = 6.022×1023 粒子)。
最常見的冷凍循環使用電動馬達推動一個壓縮機。在汽車上，壓縮機是由引擎的曲軸透過滑輪推動，兩者皆使用電動馬達作空氣循環。由於熱力被吸收時會產生蒸發現象，而熱力釋放時會產生凝結，空氣調節機使用壓縮機在兩個間隔之間造成壓力的轉變，並以泵令冷凍劑流動。冷凍劑將被泵入較冷的間隔(蒸發盤管)，而低壓及低溫令冷凍劑蒸發成蒸氣，並吸取熱量。在另一間隔(凝結器)，冷凍劑的蒸氣被壓縮並經過另一熱力交換盤管，凝結成為液體，並釋放出先前在冷間隔中所吸收的熱量。
[编辑] 濕度
冷凍空氣調節器材通常會降低已處理空氣的濕度。比較冷(低於露点)的蒸發盤管把已處理空氣的水蒸氣凝結，正如冷飲品會令容器外空氣中的水蒸氣凝結一樣，水份將經過污水管流走，如此會去除了冷凍空間中的水蒸氣，並使相對濕度降低。由於人體會自然地透過蒸發排出的汗水以降低體溫，較乾燥的空氣會提高人體的舒適度。舒適的空氣調節系統通常設計成可排放出相對濕度介乎40%至60%的空氣。在食品零售商的物業中，大型開放式冷凍櫃可作為高效率的空氣抽濕器材。
一些空氣調節器材只會令空氣乾燥而不會降低其溫度，其運作方式與一般空氣調節器材相似，只是在空氣抽入口與排放口之間加入一個熱力交換器，加上對流式風扇，在熱帶潮濕的氣候下可達到與冷氣機相近的舒適程度，但只消耗約1/3的電力。這種空調機亦適合一些對較冷空氣感到不舒服的人。
[编辑] 制冷劑(冷媒)
氟利昂(Freon，氯氟甲烷)是一系列由杜邦化工及其他公司生產的氯氟烴化學品的商標名稱。這些冷凍劑因具有很高的穩定性及安全性而被廣泛使用。但有證據顯示這些含有氯成份的冷凍劑在釋放出大氣時會升到大氣層的上層，其化學作用尚未清楚，但被認為是CFC在同溫層被紫外線照射而分解，放出氯氣粒子。氯粒子成為使臭氧分解的催化劑，令為地球防止紫外線照射的臭氧層被嚴重破壞。氯氣會繼續成為催化劑，直至其與其他粒子組成穩定狀態為止。少見但已被禁止生產的CFC冷凍劑包括R-11及R-12。逐漸禁止生產的冷凍劑包括HCFC (R-22，普遍用於家居中) 及 HFC (R-134a，用於汽車上) 已完全取代CFC。而根據蒙特利爾協定(Montreal Protocol)，HCFC亦已逐漸被淘汰，由氫氟碳化物(hydrofluorocarbons，HFC)如 R-410A,R404 代替，並無氯化物成份。
除了化學制冷劑或化學混和制冷劑的使用之外，傳統使用天然制冷劑(冷媒)氨氣來製作冰塊，但是因氨氣物理特性之影響(如可燃性、毒性、惡臭及腐蝕性)，並不適合於家用傳統空調環境使用。多使用於漁船或工業製冰使用。另一發展中之天然制冷劑(冷媒)為二氧化碳。因其超臨界壓縮特性，使用於熱水熱泵有極佳的優勢。
[编辑] 蒸發冷凍機
The aforementioned Persian cooling systems were evaporation coolers. In very dry climates, such affectionately called "swamp coolers" are popular for improving comfort during hot weather. The evaporative cooler is a device that draws outside air through a wet pad. The sensible heat of the incoming air, as measured by a dry bulb thermometer, is reduced. The total heat (sensible heat plus latent heat) of the entering air is unchanged. Some of the sensible heat of the entering air is converted to latent heat by the evaporation of water in the wet cooler pads. If the entering air is dry enough, the results can be quite comfortable. These coolers cost less and are mechanically simple to understand and maintain.
An early type of cooler, using ice for a further effect, was patented by John Gorrie of Apalachicola, FL in 1842, who used the device to cool the patients of his malaria hospital.
There is a process called absorptive refrigeration) which uses heat to produce cooling. In one instance, a three-stage absorptive cooler first dehumidifies the air with a spray of salt-water or brine. The brine osmotically absorbs water vapor from the air. The second stage sprays water in the air, cooling the air by evaporation. Finally, to control the humidity, the air passes through another brine spray. The brine is reconcentrated by distillation. The system is used in some hospitals because, with filtering, a sufficiently hot regenerative distillation removes airborne organisms.
[编辑] 吸收式冷冻机
一些建筑采用燃气锅炉来发电. 锅炉产生的热废气可以用来驱动一种叫“吸收式冷冻机组”的设备来制取冷水。制取出来的冷水可以通过末端散热设备来冷却空气，达到空调的目的。 这种既发电又制冷的能源双重利用技术很有吸引力，尤其是在燃油价格很合适并且有多种使用要求的地区。这种同时产热，电，冷的系统目前叫“三联供”系统。
[编辑] 功率
空调设备的功率在美国通常用一个专业名词“冷吨”来表达. 一“冷吨”的定义为：冷却一“短吨” （ short ton，等于 2000 磅或者907 千克)的冰用24小时的时间来溶解所需要的制冷功率。它等于12,000 英热单位/小时 或 3510 瓦(http://physics.nist.gov/Pubs/SP811/appenB9.html)。 民宅(独立别墅式建筑)的中央空调系统通常容量为1到5冷吨。
The use of electric/compressive air conditioning puts a major demand on the nation's electrical power grid in warm weather, when most units are operating under heavy load. In the aftermath of the 2003 North America blackout locals were asked to keep their air conditioning off. During peak demand, additional power plants must often be brought online, usually 天然气 fired plants because of their rapid startup. A 1995 study of various utility studies of residential air conditioning concluded that the average air conditioner wasted 40% of the input energy. This energy is lost in the form of heat, which must be pumped out. There is a huge opportunity to reduce the need for new power plants and to conserve energy.
在汽车里空调需要消耗交直流系统转换中大约5马力(4千瓦)的功率。
The Association of Home Appliance Manufacturers (AHAM) offers a worksheetthat can help you estimate how powerful an air conditioner you need. The worksheet guides you through the measurements needed to calculate the size of the air conditioner, and then it automatically calculates the final answer for you.
[编辑] 隔熱
隔熱可減低空氣調節系統所需要的能量。較厚的牆、反射性的屋頂物料、窗簾及建築物隔鄰的樹木，皆可減低系統的能源需求，耗用較少電費。
[编辑] 各國的家居空氣調節系統
家居空氣調節系統在東亞地區的國家最為常見與普及，包括日本、南韓、中國內地大城市、香港及台灣等。由於夏季氣候炎熱，而生活水平亦較高，空氣調節成為一種生活必需品。日本及鄰近地區製造的空調系統多數為窗口式（窗型）或分體式（分離式），以分體式較為先進及昂貴。隨著生活水平的提升，空調在熱帶氣候的東南亞地區如馬來西亞、新加坡與菲律賓等地亦逐漸普及。
在美國，家居空調系統在東岸及南部較為常見，部份地區的普及程度與東亞地區不遑多讓。中央空調系統在美國較常見，並成為佛羅里達州新建住宅的非正式標準。
在歐洲，家居空調系統則較為罕見，部份原因是歐洲較為溫和的氣候及社會原因，如西班牙人傳統上會進行午睡(siesta)，及到法國渡過漫長的暑假；但世界氣候暖化的現象可能令空調系統更為普及。住宅、老人院及醫療設施皆欠缺空調設備，可能是歐洲在2003年熱浪侵襲中造成35,000人死亡的原因之一。
[编辑] 健康影響
雖然空氣調節的其中一個用途是淨化空氣，例如加入空氣過濾器以防止致敏源進入一個封閉的環境，以避免過敏反應，空氣調節被認為會引起哮喘(vasomotor asthma或vasomotor rhinitis)，是在轉換氣壓或氣溫的情況下通常會引起的反應。
另外，由於空氣調節帶來的人造環境，部份人，尤其是一些喜歡適應環境的人，並不喜歡空氣調節，而把它與都市化及城市的過份產生熱量扯上關係。例如treehugger.com。
[编辑] 參看
[编辑] 外部連結
[编辑] 空调技术
[编辑] 消费指南
- 计算器 计算您需要的制冷系统规格]
- 制冷计算器
- 空调资料 aircondition-units.com
- 空调计算器
- 免费制冷制热量计算程序和数据表格
[编辑] 維修資料
[编辑] 能源效益
- 消费者家庭节能向导-中央空调 美国能源效率经济委员会(ACEEE)
- 能源效率项目数据库 ACEEE
- 制热和制冷 美国能源部－能源效率和可再生能源署
- 获得能源之星的中央空调
- 英国ECA：英国政府计划，为使用ECA认证产品的公司提供税收折扣。
- www.doityourself.com上关于空调的内容
- 国际能源组织 - 建筑和社区系统的节能
- AHAM认证
