【正文】 the chiller. The 7 systems range in capacities from the smallest scroll (30 kW。 商業(yè)的建筑物從比較大的多層的辦公大樓到街角的便利商店，占地面積和類型差別很大，因此應(yīng)用于這類建筑的設(shè)備類型比較多樣，對(duì)于比較大型的建筑物，空調(diào)設(shè)備設(shè)計(jì)是總系統(tǒng)設(shè)計(jì)的一部分，這部分包括如下項(xiàng)目：例如 一個(gè)管道系統(tǒng)設(shè)計(jì)，空氣分配系統(tǒng)設(shè)計(jì)，和冷卻塔設(shè)計(jì)等。 冷凝器是一個(gè)熱交換器，用于將制冷劑的熱量傳遞到冷卻介質(zhì)中，制冷劑進(jìn)入冷凝器變成過冷液體，用于冷凝器中的典型冷卻介質(zhì)是空氣和水，大多數(shù)住宅建筑的冷凝器中使用空氣作為冷卻介質(zhì)，而大型系統(tǒng)的冷凝器中采用水作為冷卻介質(zhì)。 空調(diào)的制冷能力常用冷噸或千瓦 (千瓦 ) 來表示，冷噸是一個(gè)度量單位，它與制冰廠在 24小時(shí)內(nèi)使 1噸 (907 公斤 )的水結(jié)冰的能力有關(guān)，其值是 (12,000 Btu/hr)，空調(diào)的冷卻能力不要和產(chǎn)生冷量所需的電能相互混淆。 F), 產(chǎn)生了 7176。在 A1中的制冷劑通常用在建筑空調(diào)設(shè)備方面的，包括 R11， R12， R22，R134a,和 R410A。 2020年之后， R22不允許生產(chǎn) (環(huán)保署 ,1993b)。人們通常認(rèn)為碳化氫制冷劑易燃且比較危險(xiǎn)，但它在傳統(tǒng)的壓縮機(jī)中和有的工業(yè)設(shè)備中都可以被使用。吸收式制冷機(jī)在吸收循環(huán)中利用熱能（典型的是來自蒸汽或燃料燃燒）并利用氨－水或水－鋰溴化物制得冷凍水。接著，水用水泵打到冷卻塔中，水通過蒸發(fā)而降溫。 在建筑中所使用的制冷機(jī)組類型根據(jù)應(yīng)用場所來確定。制冷機(jī)的效率通常用輸入功（用 kw表示）與制冷量（用 tons 表示）的比值表示。圖 給出了往復(fù)式、螺桿式、旋渦式、帶葉片控制的離心式制冷機(jī)組、壓縮機(jī)頻繁啟動(dòng)的制冷 機(jī)組在滿負(fù)荷時(shí)的百分比下相應(yīng)的效率（用 kw/ton 表示）。而往復(fù)式是這四種類型中效率最低的。 蒸汽壓縮式制冷機(jī) 四種電啟動(dòng)的蒸汽壓縮式制冷機(jī)組的名義制冷量范圍。 制 冷機(jī)組名義制冷量為 30～ 18000kw（ 8～ 5100tons）。在換熱器中，空氣被冷凍水冷卻和加濕。而且，由于制冷機(jī)組通常安裝在較大的建筑中，在同一年里，制冷機(jī)組冷卻了多于 28％的商用建筑的地板空間（ DOE， 1998）。使用 R410A的系統(tǒng)運(yùn)作中，壓力大約比 R22高 50% (表 )；因此， R410A不能夠用于當(dāng)作速凍制冷劑來替代 R22。然而， R123有 B1安全等級(jí)，這就意謂它有一個(gè)比較低的毒性而勝于 R134a，如果一個(gè)使用 R123冷卻設(shè)備在一棟建筑物中被用，當(dāng)使用這些或任何其他有毒的或易燃的制冷劑時(shí)候，標(biāo)準(zhǔn) 15(ASHRAE,1992) 提供安全預(yù)防的指導(dǎo)方針。 F)，可以認(rèn)為接近 azeotropic混合制冷劑。這種現(xiàn)象被稱溫度的移動(dòng)，在大氣壓力下， R407 C的沸點(diǎn) (沸騰 )是 – 44 176。蒸汽的形成要以一定的足夠速度被壓縮機(jī)排出以維持在蒸發(fā)器中低壓和保持循環(huán)進(jìn)行。 蒸汽壓縮循環(huán) 雖然空調(diào)系統(tǒng)應(yīng)用在建筑物中有較大的尺寸和多樣性 ,大多數(shù)的系統(tǒng)利用蒸汽壓縮循環(huán)來制取需要的冷量和除濕，這個(gè)循環(huán)也用于制冷和冰凍食物和汽車的空調(diào)，在 1834年，一個(gè) 名叫 帕金斯 的人在倫敦獲得了機(jī)械制冷系統(tǒng)的第一專利權(quán)，在 1857年，詹姆士和 賽博 生產(chǎn)出第一個(gè)有活力的商業(yè)系統(tǒng)，除了蒸汽壓縮循環(huán)之外 , 有兩種不常用的制冷方法在建筑物中被應(yīng)用 : 吸收式循環(huán)和蒸發(fā)式冷卻，這些將在后面的章節(jié)中講到。在 1970 年的美國， 36% 的住宅不是全空氣調(diào)節(jié)就是利用一個(gè)房間空調(diào)器冷卻；到 1997年，這一數(shù)字達(dá)到了 77%，在那年作的第一次市場調(diào)查表明，在美國有超過一半的住宅安裝了中央空調(diào) (人口普查局 , 1999)。C, 10176。F) can be used to reduce costs for space heating. Capacities of air conditioning are often expressed in either tons or kilowatts (kW) of cooling. The ton is a unit of measure related to the ability of an ice plant to freeze one short ton (907 kg) of ice in 24 hr. Its value is kW (12,000 Btu/hr). The kW of thermal cooling capacity produced by the air conditioner must not be confused with the amount of electrical power (also expressed in kW) required to produce the cooling effect. Refrigerants Use and Selection Up until the mid1980s, refrigerant selection was not an issue in most building air conditioning applications because there were no regulations on the use of refrigerants. Many of the refrigerants historically used for building air conditioning applications have been chlorofluorocarbons (CFCs) and hydrochlorofluorocarbons (HCFCs). Most of these refrigerants are nontoxic and nonflammable. However, recent . federal regulations (EPA 1993a。 EPA 1993b) and international agreements (UNEP, 1987) have placed restrictions on the production and use of CFCs and HCFCs. Hydrofluorocarbons (HFCs) are now being used in some applications where CFCs and HCFCs were used. Having an understanding of refrigerants can help a building owner or engineer make a more informed decision about the best choice of refrigerants for specific applications. This section discusses the different refrigerants used in or proposed for building air conditioning applications and the regulations affecting their use. 4 The American Society of Heating, Refrigerating and Air Conditioning Engineers (ASHRAE) has a standard numbering system,for identifying refrigerants (ASHRAE, 1992). Many popular CFC, HCFC, and HFC refrigerants are in the methane and ethane series of refrigerants. They are called halocarbons, or halogenated hydrocarbons, because of the presence of halogen elements such as fluorine or chlorine (King, 1986). Zeotropes and azeotropes are mixtures of two or more different refrigerants. A zeotropic mixture changes saturation temperatures as it evaporates (or condenses) at constant pressure. The phenomena is called temperature glide. At atmospheric pressure, R407C has a boiling (bubble) point of –44176。F) that it is considered a nearazeotropic refrigerant mixture. ASHRAE groups refrigerants by their toxicity and flammability (ASHRAE, 1994).Group A1 is nonflammable and least toxic, while Group B3 is flammable and most toxic. Toxicity is based on the upper safety limit for airborne exposure to the refrigerant. If the refrigerant is nontoxic in quantities less than 400 parts per million, it is a Class A refrigerant. If exposure to less than 400 parts per million is toxic, then the substance is given the B designation. The numerical designations refer to the flammability of the refrigerant. The last column of Table shows the toxicity and flammability rating of mon refrigerants. Refrigerant 22 is an HCFC, is used in many of the same applications, and is still the refrigerant of choice in many reciprocating and screw chillers as well as small mercial and residential packaged equipment. It operates at a much higher pressure than either R11 or R12. Restrictions on the production of HCFCs will start in 2021. In 2021, R22 cannot be used in new air conditioning equipment. R22 cannot be produced after 2020 (EPA, 1993b). R407C and R410A are both mixtures of HFCs. Both are considered replacements for R22. R407C is expected to be a dropin replacement refrigerant for R22. Its evaporating and condensing pressures for air conditioning applications are close to those of R22 (Table ). However, replacement of R22 with R407C should be done only after consulting with the equipment manufacturer. At a minimum, the lubricant and expansion device will need to 5 be replaced. The first residentialsized air conditioning equipment using R410A was introduced in the . in 1998. Systems using R410A operate at approximately 50% higher pressure than R22 (Table )。在 1998年， 83%的新建住宅安裝了中央空調(diào) ( 人口普查局 , 1999)。對(duì)于蒸汽壓縮制冷循環(huán)，有一種叫制冷劑的工作液體，它能在適當(dāng)?shù)墓に囋O(shè)備設(shè)計(jì)壓力下蒸發(fā)和冷凝。 所有在生產(chǎn)中的機(jī)械冷卻產(chǎn)生的熱量必須經(jīng)過冷凝器散發(fā)， 在許多例子中，在冷凝器中這個(gè)熱能被直接散發(fā)到環(huán)境的空氣中或間接地散發(fā)到一個(gè)冷卻塔的水中。 C(– 47176。 14 ASHRAE組制冷劑 (表 )根據(jù)它們