Analytical study of the absorber performance of a Hygroscopic cycle for low concentrations of LiBr solutions

Abstract

Nowadays, higher ambient temperatures and water scarcity, primarily due to climate change, represent a challenge for the refrigeration systems of traditional thermodynamic power cycles. The novel Hygroscopic Cycle Technology arises as a solution to mitigate those drawbacks by means of hygroscopic compounds, which lead to a condensation process by absorption in a mixing chamber, called absorber. Consequently, heat rejection can be achieved at higher cold sink temperatures in a closed loop, avoiding water consumption. In this work, the influence of the concentration of the hygroscopic salt LiBr in the condensation process inside the absorber, key element of the cycle, has been analyzed with EES software. The analysis is divided into very low (0% to 0.01%) and low (0.01% to 5%) concentrations of LiBr-H2O solutions. Absolute pressure at the absorber ranges between 3 kPa and 21 kPa. Results show that properties of very low concentration mixtures can be approximated to those of pure water, showing errors lower than 0.11%. As concentration rises from 0.01 to 5 % specific enthalpy decreases, leading to lower consumption of the refrigeration system of the cycle.