【正文】 制冷循環(huán)是常規(guī)的 ，從冷凝器來(lái)的高壓制冷劑進(jìn)入接收器，接著通過(guò)膨脹閥和發(fā)生吸熱過(guò)程的蒸發(fā)器 。而且，腐蝕所形成的碎片使噴淋水頭，換熱器等的通道變窄。 Some disadvantages associated with lithium bromide absorption refrigeration systems are: the risk of crystallization of solution at high concentrations。用像城市煤氣這樣的高溫?zé)嵩磥?lái)加熱發(fā)生器，在吸收過(guò)程中被逐級(jí)吸收，所以其熱力系數(shù)或制冷系數(shù)比雙效的高。所以來(lái)自第一級(jí)的熱量在第二級(jí)中被回收和利用了。但是雙效要求由氣體 火焰或高壓 蒸氣 直接驅(qū)動(dòng)。多效吸收裝置中，在被排放到環(huán)境之前，這些熱量中的一些用來(lái)產(chǎn)生更多的制冷劑蒸氣。間接加熱的裝置用外部鍋爐或發(fā)生系統(tǒng)產(chǎn)生的 蒸氣 或熱水。 kgkJh /25104 ? In the processes from point 5 to point 10, the working substance is LiBrH2O solution, therefore the enthalpies can be found from , 由點(diǎn) 5到點(diǎn) 10的過(guò)程中，工質(zhì)為 LiBrH2O溶液，因此焓可以由表 56查得 kgkJhh /15465 ??? 。 , specific enthalpy of solutions of LiBr in water 圖 溴化鋰水溶液的比焓 (3) Steadyflow analysis (3) 穩(wěn)流分析 Assume a lithium bromide system operating at the following conditions: 假設(shè)溴化鋰系統(tǒng)在以下工況下運(yùn)行： Evaporation: 5℃ (pe= mbar), Condensation: 50℃ (pc= mbar), Generator: 110℃ , Absorption: 40℃ . 蒸發(fā)器： 5℃ (pe= mbar): 冷凝器 : 50℃ (pc= mbar), 發(fā)生器 : 110℃ , 吸收器 : 40℃ . Assuming equilibrium states leaving the generator and the evaporator, no pressure drops, and plete heat exchange, . the strong solution leaves the exchanger at 40℃ . 假設(shè)發(fā)生器和蒸發(fā)器處于平衡狀態(tài)，沒(méi)有壓降，并且熱交換完全，也就是說(shuō)，濃溶液離開(kāi)換熱器時(shí)是 40℃ 。由于在吸收過(guò)程中，溶液中的溴化鋰質(zhì)量不變，因此有以下關(guān)系存在： ? ? ws ???? 1?? (59) Hence: 因此： wsw?? ?? ?? (510) For example, if ?w? and ?s? , the circulation factor λ is , by eq. (510). 比如說(shuō)，如果 ?w? ， ?s? ，由式 510可得循環(huán)倍率 λ為 。以溴化鋰吸收系統(tǒng)為例，吸收前后的質(zhì)量分?jǐn)?shù)分別表示為 s? 和 w? 。濃溶液由閥 (RV2)離開(kāi)發(fā)生器流回吸收器，狀態(tài)從 9點(diǎn)變到 10點(diǎn)，從而完成溶液循環(huán)。高溫高壓的制冷劑蒸氣以狀態(tài)點(diǎn) 1離開(kāi)發(fā)生器流入冷凝器，并在冷凝器中冷卻和冷凝。在吸收過(guò)程中放的熱 (Qa)被排向環(huán)境。溴化鋰 —水吸收式制冷基本循環(huán)包括 8個(gè) 主要部分，除了在機(jī)械驅(qū)動(dòng)制冷循環(huán)中可以見(jiàn)到的蒸發(fā)器，冷凝器和膨脹閥，其余五個(gè)部分是完成熱壓縮的溶液泵，吸收器，發(fā)生器，換熱器和一個(gè)閥 , a scheme of a basic absorption refrigeration system 圖 54, 基本吸收式制冷系統(tǒng)體系 In the evaporator, the heat (Qe) from low temperature source (To) is transferred to the refrigerant which changes its state from liquid to vapor at low pressure from state 3 to state 4. The vapor is then absorbed by the absorbent LiBr in the absorber at low pressure and temperature. During the absorption, the vapor changes into liquid state 5. The absorption is an exothermic process. The heat (Qa) released during the absorption process is rejected to the surroundings. The weak solution is delivered by the pump to the generator (G) at high pressure at the state 7. The solution in the generator is heated to boil off the refrigerant (water) with heat (Qb) from the high temperature source so that the solution is concentrated. Solution in the generator bees strong and leaves the generator at state 8. The high pressure and temperature refrigerant vapor at state 1 leaves the generator and flows to the condenser where the refrigerant is cooling down and condensed. The condensing heat (QC) is rejected to the surroundings. The liquid refrigerant then expands through the expansion valve (RV1) from state 2 to state 3. This pletes the refrigerant cycle. The strong solution leaving the generator flows back to the absorber after passing through the valve (RV2) and changing its state from state 9 to 10 to plete the solution circulatio n. It worth noting that the pression done by the pump in the absorption system only consumes a small amount of mechanical work (Wp). 在蒸發(fā)器中，制冷劑在低壓下吸收低溫?zé)嵩?(To)的熱量 (Qe)，并由狀態(tài)點(diǎn) 3 的液態(tài)變?yōu)闋顟B(tài)點(diǎn)4的蒸氣。從右邊的刻度可以看出，與蒸氣壓力相的純水的溫度大概為 5℃ 。在圖表中同樣可以看見(jiàn)純水線，即相當(dāng)于 0?? 的溶液，右邊不管是橫坐標(biāo)還是縱坐標(biāo)，在純水線上的點(diǎn)都有相同的溫度。由混合前后 LiBr 質(zhì)量不變可得 ： ? ? 2211321 ??? mmmm ??? (57) And: 321321 ?? ?? ???mm (58) 3. Vapor pressure of LiBrwater solution 3. LiBrwater溶液的蒸氣壓力 The vapor pressure of aqua lithium bromide solution is determined by its temperature and mass fraction. Their relationship is shown in . The abscissa is temperature in linear scale。而在運(yùn)行工況下，溴化鋰（一種吸濕性鹽）是幾乎不揮發(fā)的，所以不需要精餾。這是溴化鋰吸收式系統(tǒng)的低溫要控制在 0186。 In lithium bromidewater absorption refrigeration systems, water is the refrigerant and lithium bromide is the absorbent. This explains that the lithium bromide absorption system is strictly limited to evaporation temperatures above 0186。在發(fā)生器，濃溶液被加熱至沸騰，放出的蒸氣被精餾至幾乎為純氨蒸氣并被送入冷凝器。 In an ammoniawater absorption system, ammonia is used as the refrigerant and water as the absorbent. The absorber is fed with weak solution rich with water which absorbs the ammonia vapor. The absorption of ammonia by water is an exothermic process. The strong solution formed in the absorber is pumped to the generator at higher pressure. In the generator, the strong solution is boiled by heating, and the vapor given off is rectified to nearly pure ammonia and delivered to the condenser. There is a heat exchanger interposed between the generator and absorber. The hot weak solution from the generator transfers the heat to the strong solution from the absorber. To maintain the difference in pressures between the generator and absorber, a valve is installed in the pipe [4, 5] 在氨水吸收式系統(tǒng)中，氨做制冷劑，水做吸收劑。而在吸收式系統(tǒng)中，由另一種叫做吸收劑的液體來(lái)產(chǎn)生制冷循環(huán)所需的壓差。 1937年， . Berestneff研制了水 /氯化鋰制冷系統(tǒng)。 —Vapor Absorption Refrigeration Refrigeration plants based on the principles of vapour absorption have been around for many years. The early development on this system can be dated back over 100 years ago. In 1823, J. Leslie constructed a vacuum/absorption freezing apparatus in England. And in 1878, the first refrigerated mue was built in Paris using F. Carr233。它們是：吸收式制冷系統(tǒng)，吸附式制冷系統(tǒng)和蒸氣 噴射式制冷系統(tǒng)。這個(gè)問(wèn)題可以通過(guò)用選擇制冷和空調(diào)系統(tǒng)能源替代物的方法來(lái)緩解。 the refrigerants used in the cycle in Chapters 7 and 8. 機(jī)械驅(qū)動(dòng) 蒸氣 壓縮制冷循環(huán)是本書(shū)最主要的內(nèi)容， 蒸氣 壓縮制冷的循環(huán)分析將在第六章予以討論，循環(huán)的主要部件，包括壓縮機(jī)、冷凝設(shè)備、蒸發(fā)器以及流量控制閥將會(huì)在第十章到第十三章進(jìn)行討論。單位質(zhì)量制冷量可按下式求出： kgkJhhq 1e / ??? (53) The coefficient of performance of the cycle can be calculated as: 循環(huán)的性能系數(shù)（ COP）可以按下面計(jì)算： ?????? kgkJ kgkJhh hhwqC