Performance Analysis of an Absorption Cycle with a Separable Ionic Liquid and Reverse Osmosis Process

Abstract

Summary The objective of this study is to examine the new absorption refrigeration cycle using ionic liquid with LCST-type phase transition. This study selected [P4444][CF3COO] as the ionic liquid. The solution of the ionic liquid separates water from itself over the temperature of 55℃ and solve it under the temperature. This ionic liquid allows the separation process of refrigerant from the working fluid at heat source temperature of 60℃, which implies effective utilization of low temperature heat sources. The new absorption refrigeration cycle involves reverse osmosis process. This study investigates the behavior of the proposed cycle from the viewpoints of cooling output, COP, required pressure for the reverse osmosis to transfer the refrigerant of water from the absorbent to the ionic liquid solution, an area of membrane, mass transfer coefficient by cycle simulation. It is also discussed that the possibility of power recovering when the absorbent solution passes between reverse osmosis process and the absorber. The results of the cycle calculation and the sensitivity analysis show that there exists a mass flow rate of the ionic liquid which maximizes the cooling capacity with respect to the mass flow rate of the absorbent. The COP is expected to be 0.46 or more when sufficient area of the membrane is provided. On the other hand, high pressure of 33 MPa is required for the reverse osmosis process.