【正文】 及自動復疊式 蒸氣 壓縮系統(tǒng)也將會在第六章進行 討論。在世界上有大量不同形式的熱能，比如太陽能，地熱能，各種廢熱和生物能等。‘s absorption machine. In 1937, . Berestneff developed water/ lithium chloride absorption refrigerating system. [13] —蒸氣吸收式制冷 利用蒸氣吸收原理的制冷設備已經(jīng)存在了很多年。 , essential ponents of the vapor absorption cycle 圖 52, 蒸氣吸收循環(huán)的主要部分 The main ponents of a basic absorption system are shown diagrammatically in Comparing the left part of , it can be seen that the condenser, expansion valve and evaporator in these two cycles are the same, the mechanical pressor, however, is replaced by a thermal pressor which consists of absorber, solution pump, generator (or boiler) and liquid valve. This group of ponents ?sucks‘ vapor from the evaporator, and delivers high pressure vapor to the condenser, just as the mechanical pressor does but the vapor is actually absorbed by a liquid absorbent . Aqua ammonia and aqua lithium bromide solutions are monly used in vapor absorption refrigeration systems 基本吸收式系統(tǒng)的主要組成部分如圖 52所示，和圖 51的左半部分相比可以看到在兩種循環(huán)中冷凝器，膨脹閥和蒸發(fā)器是相同的，而機械式壓縮機被一個熱壓縮機所代替了，這個熱壓縮機包括吸收器，溶液泵，發(fā)生器（或鍋爐）和液體閥。在發(fā)生器和冷凝器之間有一個換熱器。C以上；而氨水吸收式制冷循環(huán)可以在 0186。 the ordinate on the lefthand is vapor pressure in logarithmic scale。從表 51中可以看到 5176。稀溶液被泵以高壓送到發(fā)生器，狀態(tài)為 7點。在吸收式制冷系統(tǒng)中，泵所做的壓縮功只消耗很少的一部分機械功。 (2) Enthalpy of liquid and vapor (2) 液體和氣體的焓 shows the enthalpy of solutions of lithium bromide in water, which is based on Lower‘s values. [9] The figure is based on the enthalpies of liquid water and solid anhydrous lithium bromide each being zero at 0℃ .From this chart, the enthalpies of the LiBrwater solution may be obtained, if the temperature and the mass fraction of solutions are given. 圖 56顯示了由 Lower 的數(shù)據(jù)提供的水中溴化鋰溶液的焓。 kgkJh /138 ?? 。單位熱或燃料產(chǎn)生的蒸氣越多，冷卻能力越大，總體的運行效率就越高。所以，雙效吸收式循環(huán)比單效吸收式循環(huán)有更高的效率。 the corrosion in the system can occur. Lithium bromide, a highly corrosive brine, readily attacks ferrous metals such as steel. The corrosion process generates hydrogen gas that reduces the internal vacuum inside the evaporator, which results in the unit operating poorly. In addition, the debris resulting from the corrosion fouls narrow openings in spray headers, heat exchangers, etc. In order to enhance the performance of the working fluid, over the past 40 years a series of elaborate proprietary formulations have been built around the lithium bromidewater system so that its crystallization temperature can be lowered and its corrrosivity to metals can be reduced. Some anic salts of sodium and potassium such as potassium formate can be added to the lithium bromide water system and it has been proved that it can improve the characteristics and the efficiency of the refrigeration cycle. 溴化鋰吸收式制冷系統(tǒng)的不利因素有：高濃度溶液的結晶風險，蒸發(fā)器中可能會發(fā)生腐蝕。系統(tǒng)的剩余部分取代常規(guī)壓縮機分以下三步來完成熱壓縮： 1) Absorption of the ammonia vapor in a weak ammoniawater solution at evaporation pressure. 1) 稀氨水溶液在蒸發(fā)壓下吸收氨蒸氣的過程 2) Transport of the strong ammonia water solution from evaporator pressure to condenser pressure by a pump. 2) 泵將濃氨。腐蝕過程中產(chǎn)生的氫氣可以減小蒸發(fā)器的內(nèi)部真空度，使機組的運行工況變差。除了增加了一個發(fā)生器外，其結構和普通的雙效系統(tǒng)一樣。單效裝置可以在 75℃ 到 150℃ 之間的熱水驅(qū)動。直接加熱的制冷裝置包括一個燒天然氣或其他燃料的 燃燒器，燃燒器是用來產(chǎn)生吸收過程所需的熱量的。在表中，如果溫度和溶液的質(zhì)量分數(shù)給出，則可以查到 LiBrH2O的焓。 , a singleeffect lithium bromidewater absorption refrigeration system [8] 圖 55單 效溴化鋰吸收式系統(tǒng) 5. Analysis for a basic absorption refrigeration system (1) Circulation factor (1) 循環(huán)因素 In an absorption refrigeration system, the solution changes its mass fractions in the absorption process. For the lithium bromide absorption system, the mass fractions before and after absorption are denoted by s? and w? , respectively. An important quantity in the calculation of an absorption system is the mass flow rate of the strong solution which is needed to absorb unit mass flow rate of vapor from the evaporator. This quantity is called the circulation factor λ. It can be determined by the concentrations of the strong and weak solutions. From the definition of the circulation factor, after absorption, λ mass flow rate of the solution bees λ+1. Since the mass of lithium bromide in the solution does not change in the absorption process, therefore, the following equation exists 在吸收式制冷系統(tǒng)的吸收過程中，溶液的質(zhì)量分數(shù)發(fā)生改變。發(fā)生器中的溶液變濃并以狀態(tài)點 8離開發(fā)生器。 , the vapor pressure of solutions of LiBr in water [6] 圖 53, 溴化鋰水溶液的蒸氣壓力 , the saturated vapor pressure table of pure water [7] 表 51, 水的飽和 蒸氣 壓力表 Temperature Co Saturated Pressure mbar Temperature Co Saturated Pressure mbar Temperature Co Saturated Pressure mbar Temperature Co Saturated Pressure mbar 1 11 21 31 2 12 22 32 3 13 23 33 4 14 24 34 5 15 25 35 6 16 26 36 7 17 27 37 8 18 28 38 9 19 29 39 10 20 30 40 50 4. Basic Lithium bromidewater absorption refrigeration system —水吸收式制冷基本循環(huán) The diagram shown in is a basic lithiumbromide vapor absorption refrigeration system. A basic H2O–LiBr absorption refrigeration system consists of 8 main ponents. Apart from the evaporator, the condenser and the expansion valve which are found in a mechanical powered vapor pression refrigerator, other five ponents, namely, a pump, and absorber, a generator, a heat exchanger and a valve fulfill the function of ―thermal pressor‖: 圖 54所示是溴化鋰 —水吸收式制冷基本循環(huán)。橫坐標是以線性刻度表示的溫度；左邊的縱坐標是以對數(shù)刻度表示的 蒸氣 壓力；右邊的縱坐標是以線性刻度表示的溫度，顯示了純水的飽和溫度，此時， LiBr 溶液的溫度由橫坐標給定，而純水有和此溫度下 LiBr溶液相同的蒸氣壓力。在氨水吸收式系統(tǒng)中，水作為制冷劑會蒸發(fā)，所以要用精餾除去。為了維持發(fā)生器和吸收期間的壓差，在管路中裝了一個閥。在 蒸氣 吸收式制冷系統(tǒng)中常用的工質(zhì)是氨水溶液和溴化鋰溶液。1823年， J. Leslie 在英國制造出一臺真空 /吸收式冷凍裝置。 There are three kinds of vapor pression refrigeration cycles that can be driven by thermal energy. They are: the absorption refrigeration cycle, the adsorption refrigeration cycle and vapor jet refrigeration cycle. These cycles share similar technologies that are used in the vapor pression refrigeration cycle, ., throttling evaporating and condensing. but t