A basis for the development of new ammonia–water–sodium hydroxide absorption chillers

Adding NaOH to ammonia/water improves the separation of ammonia in the generator and reduces both chiller driving temperature and rectification losses. In this paper the main disadvantages for the implementation of these new mixtures are addressed: a) few experimental data or reliable correlations of the fluid mixture properties exist; b) selection of an adequate system for separating the hydroxide; and c) evaluation of potential corrosion problems. Our results show that the separation of NaOH from an ammonia/water solution with a maximum approximate mass fraction of 0.05 (5% weight) is viable when reverse osmosis is used with membranes BW30 and SW30HR LE. Cycle simulation using experimental data to calculate the vapour–liquid equilibrium properties shows that the COP is approximately 20% higher than with a conventional ammonia/water chiller working under the same conditions and using a hydroxyl separation efficiency of 99% for NaOH, which is feasible according to the experimental tests.