食品專業(yè)畢業(yè)論文外文翻譯--制冷劑的利用發(fā)展過程

1、<p><b>　　外文文獻(xiàn)：</b></p><p>　　Refrigerant History</p><p>　　The first practical refrigerating machine was built by Jacob Perkins in 1834; it used ether in a vapor-compression cycle

2、. The first absorption machine was developed by Edmond Carr? in 1850, using water and sulfuric acid. His brother, Ferdinand Carr? demonstrated an ammonia/water refrigeration machine in 1859. A mixture called chemogene, c

3、onsisting of petrol ether and naphtha, was patented as a refrigerant for vapor-compression systems in 1866. Carbon dioxide was introduced as a refrigerant in th</p><p>　　Nearly all of the early refrigerants

4、were flammable, toxic, or both, and some also were highly reactive. Accidents were common. The task of finding a nonflammable refrigerant with good stability was given to Thomas Midgley in 1926. He already had establishe

5、d himself by finding tetraethyl lead, to improve the octane rating of gasoline.</p><p>　　With his associates Henne and McNary, Midgley observed that the refrigerants then in use comprised relatively few chem

6、ical elements, clustered in an intersecting row and column of the periodic table of elements. The element at the intersection was fluorine, known to be toxic by itself. Midgley and his collaborators felt, however, that c

7、ompounds containing it should be both nontoxic and nonflammable.</p><p>　　Their attention was drawn to organic fluorides by an error in the literature. It showed the boiling point for tetrafluoromethane (car

8、bon tetrafluoride) to be high compared to those for other fluorinated compounds. The correct boiling temperature later was found to be much lower. Nevertheless, the incorrect value was in the range sought and led to eval

9、uation of organic fluorides as candidates. The shorthand convention, later introduced to simplify identification of the organic fluorides for a sys</p><p>　　Within three days of starting, Midgley and his col

10、laborators had identified and synthesized dichlorodifluoromethane, now known as R-12.</p><p>　　The first toxicity test was performed by exposing a guinea pig to the new compound. Surprisingly, the animal was

11、 completely unaffected, but the guinea pig died when the test was repeated with another sample. Subsequent examination of the antimony trifluoride, used to prepare the dichlorodifluoromethane from carbon tetrachloride, s

12、howed that four of the five bottles available at the time contained water. This contaminant forms phosgene (COCl2) during the reaction of antimony trifluoride with carb</p><p>　　The development of fluorocarb

13、on refrigerants was announced in April 1930. To demonstrate the safety of the new compounds, at a meeting of the American Chemical Society, Dr. Midgley inhaled R-12 and blew out a candle with it. While this demonstration

14、 was dramatic, it would be a clear violation of safe handling practices today.</p><p>　　CFC Refrigerants</p><p>　　Commercial chlorofluorocarbon (CFC) production began with R-12 in early 1931, R-

15、11 in 1932, R-114 in 1933, and R-113 in 1934; the first hydrochlorofluorocarbon (HCFC) refrigerant, R-22, was produced in 1936. By 1963, these five products accounted for 98% of the total production of the organic fluori

16、ne industry. Annual sales had reached 372 million pounds, half of it R-12. These chlorofluorochemicals were viewed as nearly nontoxic, nonflammable, and highly stable in addition to offering good ther</p><p>

17、;　　"Ideal" Refrigerants</p><p>　　In addition to having the desired thermodynamic properties, an ideal refrigerant would be nontoxic, nonflammable, completely stable inside a system, environmentally

18、 benign even with respect to decomposition products, and abundantly available or easy to manufacture. It also would be self-lubricating (or at least compatible with lubricants), compatible with other materials used to fa

19、bricate and service refrigeration systems, easy to handle and detect, and low in cost. It would not require extreme </p><p><b>　　Toxicity</b></p><p>　　A fundamental tenet of toxicolo

20、gy, attributed to Paracelsus in the 16th century, is "dosis solo facit venenum", the dose makes the poison. All substances are poisons in sufficient amounts. Toxic effects have been observed for such common sub

21、stances as water, table salt, oxygen, and carbon dioxide in extreme quantities. The difference between those regarded as safe and those viewed as toxic is the quantity or concentration needed to cause harm and, in some c

22、ases, the duration or repetition of exp</p><p>　　There are multiple reasons that toxicity concerns have surfaced with the introduction of new refrigerants. First, they are less familiar. Second, public consc

23、iousness of health hazards is growing. Manufacturer concerns with liability also have increased. Third, few refrigerant users fully understand the measures and terminology used to report the extensive toxicity data being

24、 gathered. And fourth, the new chemicals are somewhat less stable when released and exposed to air, water vapor, other atm</p><p>　　Concerns with refrigerant safety have been heightened by negative marketing

25、 by competing equipment vendors. Frequent overstatement, to influence customer perceptions, coupled with contradictions have fueled discomfort in refrigerant choices for all of the alternative refrigerants.</p>&l

26、t;p>　　Acute versus Chronic Risks</p><p>　　Acute toxicity refers to the impacts of single exposures, often at high concentrations. It suggests the possible risk levels for the consequences of accidental re

27、leases, such as from a spill or rupture. It also is a gauge for service operations in which high exposures may be experienced for brief periods, such as upon opening a compressor or removing a gasket that may have refrig

28、erant trapped under it.</p><p>　　Chronic toxicity refers to the effects of repeated or sustained exposures over a long period, such as that experienced in a lifetime of working in machinery rooms. Few techni

29、cians actually spend their full day in machinery rooms and concentrations may fluctuate. Most chronic exposure indices, therefore, are expressed as time-weighted average (TWA) values.</p><p>　　The nature of

30、chronic effects is such that most can be anticipated and/or monitored, and occupational safety measures can be taken to minimize their impacts. As an example, refriger- ant concentrations can be lowered by designing equi

31、pment with reduced leakage and promptly repairing leaks that do occur. Refrigerant sensors can be used to sense and warn technicians of concentration increases. Further measures are identified below, in the discussion of

32、 safety standards.</p><p>　　From a safety perspective, the goal is to reduce both acute and chronic risks.</p><p>　　PAFT Tests</p><p>　　The Programme for Alternative Fluorocarbon To

33、xicity Testing (PAFT) is a cooperative effort sponsored by the major producers of CFCs from nine countries. PAFT was designed to accelerate the development of toxicology data for fluorocarbon substitutes, as refrigerants

34、 and for other purposes. Examples of the other uses include as blowing agents, aerosol propellants, and solvents. The PAFT research entails more than 100 individual toxicology tests by more than a dozen laboratories in E

35、urope, Japan, a</p><p>　　These PAFT studies investigate acute toxicity (short-term exposures to high concentrations, such as from accidental releases), subchronic toxicity (repeated exposure to determine any

36、 overall toxicological effect), and chronic toxicity and carcinogicity (lifetime testing to assess late-in-life toxicity or potential to cause cancer). The experiments also gauge genotoxicity (effects on genetic material

37、, an early screen for possible cancer-inducing activity), reproductive and developmental toxicity </p><p>　　A new program, initiated in 1994, is addressing the mechanistic causes of tumors and other effects

38、observed in other programs. PAFT M was spurred by findings of benign tumors in earlier tests of R-123, R-134a, and R-141b. Although the tumors occurred late in life and were neither cancerous nor life threatening, a bett

39、er understanding of causal effects is being sought.</p><p><b>　　中文譯文：</b></p><p>　　制冷劑的利用發(fā)展過程</p><p>　　在1834年雅各布·珀金斯建造了第一個(gè)具有實(shí)際意義的冷藏的機(jī)器；它在一個(gè)蒸汽壓縮系統(tǒng)里使用乙烯。在1850年，埃德蒙

40、83;卡爾開發(fā)了利用水和硫酸制造的第一個(gè)吸收機(jī)器。他的兄弟，費(fèi)迪南·卡爾，在1859年證明氨水/水冷藏機(jī)器，叫chemogene的混合物，由乙烯和石油汽油組成，作為適合1866系統(tǒng)蒸汽壓縮而取得專利權(quán)。二氧化碳同年被作為一種新的致冷劑介紹。在1873氨水首先在蒸汽壓縮系統(tǒng)使用，二氧化硫和乙烯在1875被使用，甲基氯化物在1878內(nèi)使用。威尼斯搬運(yùn)工迪克第一個(gè)使用離心式壓縮機(jī)，并且在1926替換氯化物。 </p>

41、<p>　　幾乎所有早的制冷劑是易燃，有毒，或者兩的都有的，并且一些事故是很容易發(fā)生的。 1926年麥迪格雷告訴托馬斯他發(fā)現(xiàn)的這種物質(zhì)不易燃解而且穩(wěn)定性好。他通過tetraethyl發(fā)現(xiàn)的結(jié)果指導(dǎo)自己，以便改進(jìn)汽油的辛烷額定值。隨著他同事亨和麥克納里，麥迪格雷觀察到制冷劑中很少使用相對(duì)的化學(xué)元素。通過元素周期表他發(fā)現(xiàn)十字路口的元素是氟，而大家讀知道知道氟單獨(dú)是有毒的。可是麥迪格雷和他合作者感到，包含氟的化合物既無毒又不易燃。&

42、lt;/p><p>　　通過一個(gè)在文學(xué)方面的錯(cuò)誤，他們的注意力被轉(zhuǎn)移到了有機(jī)的氟化物。它發(fā)現(xiàn)氟與碳結(jié)合的化合物的沸點(diǎn)為與其他氟化的化合物的那些相比是很高的。沸騰的溫度過后被發(fā)現(xiàn)低得多。就是如此，錯(cuò)誤的尋找從而導(dǎo)致有機(jī)的氟化物成為制冷劑的替換物。作為制冷劑的表示方法，今天一直使用一些數(shù)字標(biāo)記符號(hào)，以表明化學(xué)的成分和結(jié)構(gòu)。</p><p>　　在發(fā)現(xiàn)氟化物可以成為制冷劑后的3天內(nèi)，麥迪格雷和他的合

43、作者鑒定并且合成新的制冷劑，現(xiàn)在被稱為R-12.</p><p>　　第一個(gè)毒性試驗(yàn)是把一只幾尼豬放在這種新化合物中進(jìn)行的。令人吃驚的是，動(dòng)物完全未受影響，但是當(dāng)試驗(yàn)被另一種樣品重復(fù)時(shí)，幾尼豬死了。對(duì)銻化物的隨后檢查顯示，用碳四氯化物準(zhǔn)備的活潑化合物，顯示在時(shí)間可提供的5個(gè)瓶子中的4個(gè)包含水。這種污染物與銻和碳四氯化物發(fā)生化學(xué)反應(yīng)形成二氯化碳(COCl2)。 如果最初試驗(yàn)使用其它樣品的話，有機(jī)氟化物制冷劑的發(fā)現(xiàn)會(huì)

44、可能推遲多年。碳氟化合物制冷劑的發(fā)展被在1930年4月宣布。證明新化合物是安全的，在一個(gè)美國(guó)化學(xué)協(xié)會(huì)的會(huì)議上，米奇利博士吸入R-12并且用它吹滅一支蠟燭。當(dāng)這次帶有戲劇性的游戲結(jié)束時(shí)，這也說明了新化合物的安全可利用性。 </p><p>　　CFC制冷劑—商業(yè)氯氟烴(CFC)從1931年開始生產(chǎn)，R-11在1932年，R-114在1933年，R-113年在1934年的早些時(shí)候，用R-12解熱的HCFC，R-22，

45、在1936生產(chǎn)。到1963年，這5種產(chǎn)品占有機(jī)的氟工業(yè)的總產(chǎn)量的98%。全年銷售額已經(jīng)達(dá)到3.72億磅，它的一半是R-12。這些制冷劑被作為幾乎無毒，不易燃，成本低并且提供好熱力學(xué)的特性和材料兼容性之外還具有非常穩(wěn)定的特性。半個(gè)世紀(jì)中從CFCs的產(chǎn)生和發(fā)現(xiàn)他們對(duì)環(huán)境的危害在什么時(shí)候釋放人們不停的研究著。具體的與人類環(huán)境相關(guān)最大的是這些化合物對(duì)臭氧層的破壞性，和對(duì)作為溫室氣體而可能導(dǎo)致的全球變暖。具有諷刺意義的是，CFCs的高穩(wěn)定性使他們

46、能夠把平流層中的臭氧層耗盡。相同的穩(wěn)定延長(zhǎng)他們的大氣的壽命，因此他們是主要的溫室氣體。</p><p><b>　　"理想"的制冷劑</b></p><p>　　除有被期望的熱力學(xué)的特性之外，理想的制冷劑應(yīng)在一個(gè)系統(tǒng)里面無毒，不易燃，完全穩(wěn)定，甚至在分解產(chǎn)品環(huán)境上無污染，并且可充分提供或者容易生產(chǎn)。它也將是潤(rùn)滑自我(或者與潤(rùn)滑劑至少相容)，與常常建

47、立的其他材料相容和服務(wù)制冷系統(tǒng)，易于處理和發(fā)現(xiàn)并且費(fèi)用低。它將不需要極端壓力，或者高或者低。有另外的標(biāo)準(zhǔn)，但是沒有當(dāng)今的制冷劑理想甚至基于部分目錄。而且，現(xiàn)在沒有理想的制冷劑將來很可能被發(fā)現(xiàn)。 </p><p><b>　　毒性 </b></p><p>　　一種毒理學(xué)的基本的原則，在16世紀(jì)對(duì)于制冷劑要求沒有毒。全部物質(zhì)在足夠的數(shù)量上是毒藥。有毒效應(yīng)適合水、食、氧和

48、二氧化碳在極端數(shù)量?jī)?nèi)這樣的普通物質(zhì)觀察。其中的那些差別認(rèn)為是安全和那些觀看為有毒在需要引起危害的那些數(shù)量或者集中和，有時(shí)候暴露的持續(xù)或者重復(fù)。 有小的數(shù)量造成高的危險(xiǎn)的物質(zhì)，即使用短暫的暴露，被認(rèn)為是非常有毒的。實(shí)際的暴露沒有引起危害的那些被視為安全。</p><p>　　有的毒性關(guān)系到的多個(gè)原因已經(jīng)與新制冷劑的介紹同時(shí)出現(xiàn)。首先，不那么熟悉他們。 其次，對(duì)健康的危害的公開意識(shí)正增長(zhǎng)，制造商關(guān)心責(zé)任也已經(jīng)增加。第

49、三，很少用戶完全理解議案和專有名詞用來報(bào)告廣大的毒性數(shù)據(jù)。第四，當(dāng)釋放時(shí)，新化學(xué)制品有一些物質(zhì)不那么穩(wěn)定和暴露在空氣中，水蒸汽，其他大氣的化學(xué)制品和陽光。因此降低達(dá)到臭氧層的散發(fā)物的小部分或者那堅(jiān)持空氣作為一種溫室氣體。當(dāng)毒性經(jīng)常用更高的速度增加時(shí)，與大氣的湍流層不一定有關(guān)。最有毒化合物那些有進(jìn)入身體然后分解或者破壞性在一個(gè)批判性的器官內(nèi)分解的足夠的穩(wěn)定。作為例子，大多數(shù)CFCS是在空氣里的很穩(wěn)定，比或者在制冷系統(tǒng)內(nèi)HCFCS或者HFC

50、S較少通常穩(wěn)定，和一般有可比較或者偉大厲害毒性HCFCS或者HFCS。涉及解熱安全一直被以競(jìng)爭(zhēng)賣主設(shè)備被負(fù)銷售增大。頻繁的夸張，影響用戶知覺，加上矛盾已經(jīng)為所有其它的制冷劑把不安給在解熱的選擇過程中加燃料。</p><p><b>　　對(duì)慢性危險(xiǎn)的敏銳性</b></p><p>　　一些應(yīng)用服務(wù)器為歸類資源提供支持進(jìn)一步使用分布的交易。 在包括JMS 交易在一筆分配的

51、交易內(nèi)，應(yīng)用服務(wù)器要求交易API(JTA)有能力的JMS 提供者。 JMS 提供者暴露它JTA 支持使用JMS XA聯(lián)合生產(chǎn)，應(yīng)用服務(wù)器使用創(chuàng)造XA聯(lián)合機(jī)。XA聯(lián)合生產(chǎn)提供與普通聯(lián)合生產(chǎn)相同的驗(yàn)證選擇。 XA聯(lián)合生產(chǎn)的賓語是給予物體的JMS，正如普通物體一樣。預(yù)計(jì)應(yīng)用服務(wù)器將通過使用JNDI找到他們。 在機(jī)器房間和集中里的他們的整天可能波動(dòng)。大多數(shù)慢性照射指標(biāo)，因此，被以表示時(shí)間加權(quán)平均數(shù)(TWA) 估價(jià)。 慢性效應(yīng)的自然是如此以至最可

52、能被預(yù)期和/或監(jiān)控，并且職業(yè)的安全措施可能被花費(fèi)使他們的影響減到最小。 作為一個(gè)例子，螞蟻的集中可能降低在設(shè)計(jì)與泄露并且迅速修理一起的設(shè)備時(shí)漏發(fā)生的事故。 解熱的傳感器能習(xí)慣于感覺并且警告技師濃度增加。 更進(jìn)一步的措施在下面被鑒定，在安全標(biāo)準(zhǔn)的討論過程中。 </p><p><b>　　PAFT測(cè)試</b></p><p>　　其它的碳氟化合物毒性的計(jì)劃測(cè)試(PAFT

53、) 來自9 個(gè)國(guó)家的CFCs的主要的生產(chǎn)者發(fā)起的一次合作的努力。 PAFT用于加速毒理學(xué)碳氟化合物的數(shù)據(jù)的發(fā)展代替，作為制冷劑和適合其他目的。其它用途的例子作為吹代理人，煙推進(jìn)者和溶劑包括。PAFT 研究需要100 個(gè)別毒理學(xué)超過以12實(shí)驗(yàn)室在歐洲，日本和美國(guó)內(nèi)超過測(cè)試。 第一個(gè)試驗(yàn)在1987年被啟動(dòng)，以便處理R-123 和R- 134a(PAFT I)。 隨后的計(jì)劃被為R-141b(PAFT II)起動(dòng)， R-124和R-125(PA

54、FT III)，R-225ca和R-225cb(PAFT IV) ，以及R-32(PAFT V)。 因?yàn)槊糠N化合物是100萬-500萬美元的試驗(yàn)費(fèi)和持續(xù)是2-6 年， 取決于認(rèn)為必要或者通過最初結(jié)論表明的具體的試驗(yàn)。 這些PAFT 研究調(diào)查厲害的毒性( 對(duì)高的集中的短期的暴露， 自事故釋放起的這些)，循環(huán)毒性(重復(fù)暴露確定任何總的毒物的效應(yīng))， 以及慢性毒性和潛在毒性(一生評(píng)價(jià)在生活過程中后期的毒性或者潛能測(cè)試引起癌癥)。實(shí)驗(yàn)也估計(jì)毒性