A study of a bubble absorber using a plate heat exchanger with NH3–H2O, NH3–LiNO3 and NH3–NaSCN

Abstract

There is a continuous research effort being carried out worldwide on the development of absorption cooling systems with the objective of increasing their performance, one important area is the search for more efficient heat exchangers and alternative working fluids that can improve the performance of NH 3 –H 2 O and H 2 O–LiBr that are commonly used in commercial absorption refrigeration machines. In this work the study of a plate heat exchangers used as bubble absorbers with NH 3 –LiNO 3 and NH 3 –NaSCN as alternative working fluids is carried out. A mathematical model was developed in order to analyze the absorption process in a bubble absorber with NH 3 –H 2 O, NH 3 –LiNO 3 and NH 3 –NaSCN as working fluids using a plate heat exchanger at refrigeration conditions and low generator temperatures. The results show that NH 3 –H 2 O and NH 3 –NaSCN working fluids obtained higher absorber thermal loads and absorbed vapor mass values than NH 3 –LiNO 3 , the lower values for the latter were caused mainly by the high solution viscosity that decreases the efficiency of the absorption process. On the other hand, NH 3 –LiNO 3 obtained the highest COP value from a single effect absorption refrigeration system simulation, however, NH 3 –NaSCN obtained a higher COP than NH 3 –H 2 O; therefore NH 3 –NaSCN seems to be a good working fluid to be tested in an absorption machine. ► A bubble absorber is simulated with NH 3 –H 2 O, NH 3 –LiNO 3 and NH 3 –NaSCN working fluids. ► The analysis is realized with a plate heat exchanger at different working conditions. ► The NH3–LiNO 3 obtains lower absorption performance than NH 3 –H 2 O and NH 3 –NaSCN. ► The NH 3 –LiNO 3 has problems in the absorption process, due to the high viscosity. ► The NH 3 –NaSCN obtains better performance in an absorption cycle than NH 3 –H 2 O.