The Adsorption Refrigeration Characteristics Of Alkaline-earth Metal Chlorides And Its Composite Adsorbents

摘要

A study was conducted on the adsorption characteristics of the adsorption refrigeration working pairs using alkaline-earth metal chlorides as adsorbents and ammonia as refrigerant. The adsorption isotherms between alkaline-earth metal chlorides and nitrogen were studied. The study shows that the adsorbents of CaCl_2, SrCl_2 provide better adsorption capability associated with ammonia when compared to that of MgCl_2, BaCl_2. CaSO_4 was added into the CaCl_2, SrCl_2 with a mass ratio 20%, respectively, in order to solve the swelling and smashing problems encountered with CaCl_2, SrCl_2 adsorbent particles. The adsorption refrigeration experiments of composite adsorbents were investigated. The results show that the refrigeration capacity of the unit adsorbent of CaCl_2/CaSO_4 is 1.26 times higher than that of CaCl_2, and SrCl_2/CaSO_4 is 1.6 times higher than that of SrCl_2 at 100 ℃. The mechanism of NH_3 adsorption and the gelatification of CaSO_4 were also discussed. BET (Brunauer-Emmett-Teller) specific surface area and pore structure of adsorbents were examined. Results show that the BET specific surface area and pore structure of composite adsorbents are retained well. This study indicates that the refrigeration capacity could be enhanced by compositing the adsorbents which indicates that composite adsorbents can perform better in adsorption refrigeration, and can be employed in adsorption refrigeration system using low-grade heat source.