Study On New Working Pairs Based On Absorption Heat Pump Cycle

Absorption heat pump which can be driven by low grade industrial waste heat or renewable energy sources such as solar heat is an effective way to achieve energy saving and emission reduction.To solve the problems of crystallization and strong corrosivity for the traditional LiBr/H2O working pair,several new working pairs were proposed at different situations.By measuring the thermophysical properties include crystallization temperature,saturated vapor pressure,specific heat capacity,etc.and corrosivity of the new working pairs systematically,the performance of the absorption cycles based on these new working pairs were analyzed and compared with LiBr/H2O.The results showed that CaCl2-LiCl(2:1)/H2O has better absorption refrigeration characteristics and lower corrosivity.At the same refrigeration conditions,the generation temperature of a single-effect absorption refrigeration cycle using CaC12-LiCl(2:1)/H2O was 5.8? lower than LiBr/H2O.The COP for refrigeration was 0.441 higher than LiBr/H2O,and the exergy efficiency was also 0.052 higher.The corrosion rates for carbon steel and copper in CaCl2-LiCl(2:1)/H2O at 80? were 18.5 ?m·y-1 and 2.8 ?m·y-1 respectively without localized corrosion.As the working pair of multi-effect absorption heat pump cycle,LiNO3-LiBr(1:1)/H2O has good absorption characteristic and corrosivity.By using LiNO3-LiBr(1:1)/H2O as the working pair,the double-effect or triple-effect absorption heat pump can achieve cooling and heating together.At the same conditions,the generation temperature of a double-effect absorption cycle using LiNO3-LiBr(1:1)/H2O was 9.5 0C lower than LiBr/H2O,and the COP was 0.22 higher.The corrosivity of LiNO3-LiBr(1:1)/H2O was obviously lower than LiBr/H2O.For a triple-effect absorption cycle,at the conditions of 7? refrigeration and 53? hot water,the high-pressure generation temperature was 230.3? for LiNO3-LiBr(1:1)/H2O and 15.3? lower than LiBr/H2O.In comparison with a corrosion rate of 80.1?m·y-1 with heavy localized corrosion for 316L stainless steel in LiBr/H2O,the corrosion rate for LiNO3-LiBr(1:1)/H2O was 10.5 ?m·y-1 without localized corrosion.Thus 316L stainless steel could be used as the structure and heat exchange materials in the high-pressure generator using LiNO3-LiBr(1:1)/H2O as the working pair,the highest hot water temperature for LiNO3-LiBr(1:1)/H2O was 58? as the highest applicative temperature for 316L stainless steel is 240?.Furthermore,the crystallization temperature of the working fluid in the evaporator was decreased by adding some[BMIM]NO3 or KNO3 with a little vapor pressure changing.The crystallization temperatures for 6%KNO3/H2O and 6%[BMIM]NO3/H2O were-9.2 and-7.7?,respectively.The absorption cycle could make the refrigeration below 0? with these new working pairs.At the same conditions of TE=-5?,the generation temperatures for LiBr/H2O-KNO3 and LiBr/H2O-[BMIM]NO3 were 84.1? and 81.4?,respectively.The absorption heat pump with these new working pairs could also be used for heating by using cold air as low temperature heat source.At the conditions of getting 45? hot water,the generation temperatures for LiBr/H2O-KNO3 and LiBr/H2O-[BMIM]NO3 were 94.4? and 91.9?,respectively.