Study on a Quaternary Working Pair of CaCl₂-LiNO₃-KNO₃/H₂O for an Absorption Refrigeration Cycle

• Main Authors: Yiqun Li, Na Li, Chunhuan Luo, Qingquan Su
• Format: Article
• Language: English
• Published: MDPI AG 2019-05-01
• Series: Entropy
• Subjects: absorption refrigeration; working pair; crystallization temperature; vapor pressure; COP; corrosivity
• Online Access: https://www.mdpi.com/1099-4300/21/6/546

When compared with LiBr/H₂O, an absorption refrigeration cycle using CaCl₂/H₂O as the working pair needs a lower driving heat source temperature, that is, CaCl₂/H₂O has a better refrigeration characteristic. However, the crystallization temperature of CaCl₂/H₂O solution is too high and its absorption ability is not high enough to achieve an evaporation temperature of 5 °C or lower. CaCl₂-LiNO₃-KNO₃(15.5:5:1)/H₂O was proposed and its crystallization temperature, saturated vapor pressure, density, viscosity, specific heat capacity, specific entropy, and specific enthalpy were measured to retain the refrigeration characteristic of CaCl₂/H₂O and solve its problems. Under the same conditions, the generation temperature for an absorption refrigeration cycle with CaCl₂-LiNO₃-KNO₃(15.5:5:1)/H₂O was 7.0 °C lower than that with LiBr/H₂O. Moreover, the cycle’s COP and exergy efficiency with CaCl₂-LiNO₃-KNO₃(15.5:5:1)/H₂O were approximately 0.04 and 0.06 higher than those with LiBr/H₂O, respectively. The corrosion rates of carbon steel and copper for the proposed working pair were 14.31 μm∙y^−1 and 2.04 μm∙y^−1 at 80 °C and pH 9.7, respectively, which were low enough for engineering applications.