【正文】 lr are in equilibrium at pressure Pm： Then strong solution returns to the LP absorber to form the lowpressure cycle.Highpressure cycleThe strong solution Xhr in the HP absorber from the HP generator through the HP solution heat exchanger absorbs vapor generated in the LP generator. The weak solution) (ha is then pumped to the HP generator through the HP solution heat exchanger. Similarly, Xh, and Th2 are determined by the temperature Twi of the cooling water and Pro： The weak solution in the HP generator is heated to Th4 by the heat source and concentrated to strong solution Xhr. Th4 and Xhr are in equilibrium at pressure Pc： The strong solution concentrated in the HP generator then returns to the HP absorber, forming the high pressure cycle.Mass and energy balanceEvaporator： LP absorber： LP generator： LP heat exchanger： (19)HP absorber： HP generator： HP solution exchanger： (26)Condenser： Total input heat： Total output heat： Total energy balance： Coefficient of performance (COP)： State variables, temperatures, concentrations and enthalpies of LiBr aqueous solution at points 19 were calculated by literature 1319.The temperature differences (ΔT) between two fluids at the exits of the heat exchangers in the system were determined based on the operating parameters and heat exchanger structure in different heat exchangers. For example, in the evaporator, the temperature differences between the chilled water and refrigerant at the entrance。C chilled water in the evaporator.Theoretical analysis of the absorption cycleLowpressure cycleWater vaporized in the evaporator is absorbed by the concentrated solution of LiBr from the LP generator through the LP solution heat exchanger。C 7. Therefore a twostage LiBr/H20 absorption refrigeration system is useful and significant in recovering low temperature waste heat in industries, and in applying solar energy and geological heat. Research work for simulating singlestage absorption refrigeration systems, doubleeffect absorption refrigeration systems and absorption heat pumps has been reported by a number of researchers, including Bogart 8, Vilest et al 9, and Grossman et al 1176。C and the chilled water supply temperature is 9176。C, such as waste heat in industries, solar energy and geological heat. If these low temperature heat sources can be used or reused, it will not only improve the overall system energy efficiency, but decrease the heat pollution to the environment as well.A twostage LiBr/H20 absorption refrigeration system, with water as refrigerant and lithium bromide as absorbent, can however be operated with a lower temperature heat source from 75 to 86176。 and adsorption systems, using ammonia calcium chloride (CaCI2/NH3), watersilicagel, water zealot, activated charcoalmethanol (CH3OH). However, only absorption refrigeration systems using water lithium bromide as working fluid have been operated successfully and have found mercial applications.A singlestage LiBr/H20 absorption refrigeration system generally consists of an evaporator, absorber, generator, condenser and solution heat exchanger. This system operates with water as refrigerant and lithium bromide as absorbent, and the heat source required to run such a system should have at least a temperature of over 86176。 Road, Guangzhou, ChinaS. M. DengDepartment of Building Services Engineering, The Hong Kong Polytechnic University, Hung Hom, Kowloon, Hong KongReceived 19 December 1994。然而，這種即時(shí)分析方法在雙級溴化鋰吸收式制冷系統(tǒng)中認(rèn)識熱量與質(zhì)量進(jìn)行熱質(zhì)交換方面，以及在為實(shí)現(xiàn)系統(tǒng)的最高效率而進(jìn)行的系統(tǒng)設(shè)計(jì)中都很有用。同初步試驗(yàn)結(jié)果比較可得出，雙級溴化鋰吸收式制冷系統(tǒng)的理論分析可以準(zhǔn)確合理的代替實(shí)際的系統(tǒng)。根據(jù)圖6與初步實(shí)驗(yàn)試驗(yàn)結(jié)果進(jìn)行比較可知,由理論分析獲得的制冷系數(shù)比實(shí)際的大10%13%.人們普遍相信偏差的主要原因很可能是在分析過程中忽略了熱損失,在加上這個(gè)熱損失之后,計(jì)算結(jié)果與試驗(yàn)結(jié)果非常吻合,由圖6上的短線段可知,偏差的其它可能原因可能是由于計(jì)算過程中的假定,然而這種差異可以在有充分的試驗(yàn)數(shù)據(jù)之后得以識別。冷卻水溫度的影響(Twi)（圖5），與初步的實(shí)驗(yàn)結(jié)果進(jìn)行對比。C時(shí)制冷系統(tǒng)的冷卻水溫度為32176。冷凍水溫度的影響(Tch0)176。C和87176。,系統(tǒng)熱損失也在增加,對于雙級溴化鋰吸收式制冷系統(tǒng)熱源溫度Thi高于87176。雙級溴化鋰吸收式制冷系統(tǒng)的制冷系數(shù)是隨著熱水的溫度增加而增加的,但當(dāng)該溫度Thi高于87176。C.,這時(shí)雙級溴化鋰吸收式制冷系統(tǒng)在熱水溫度Thi低于73176。176。結(jié)論利用低溫?zé)崴鳛闊嵩吹姆治鼋Y(jié)論和討論如下:熱水溫度的影響圖形3顯示了熱水溫度對制冷系數(shù)(COP)的影響，很顯然雙級溴化鋰吸收式在高壓發(fā)生器和低壓發(fā)生器中的溴化鋰水溶液的出口溫度低于58176。質(zhì)量和能量守恒蒸發(fā)器:質(zhì)量守恒: (10)能量守恒: (11)低壓吸收器:質(zhì)量守恒: (12)能量守恒: (13)低壓發(fā)生器: 質(zhì)量守恒: (14)能量守恒: (15)質(zhì)量守恒: (16)低壓熱交換器: 質(zhì)量守恒: （17) （18)能量守恒: （19)高壓吸收器:質(zhì)量守恒: (20)能量守恒: (21) 高壓發(fā)生器: 質(zhì)量守恒: (22)能量守恒: (23)高壓溶液熱交換器:質(zhì)量守恒: (24) (25)能量守恒: (26)冷凝器: 質(zhì)量守恒: (27)能量守恒: (28)總輸入熱量: (29)總輸出熱量: (30)總能量守恒: (31)制冷系數(shù):