A COMPARISON BETWEEN LITHIUM BROMIDE - WATER AND IONIC LIQUID - WATER AS WORKING SOLUTION FOR ABSORPTION REFRIGERATION CYCLES

摘要

Reliable Vapour-Liquid-Equilibria (VLE) measurements are required for the estimation of the performance of an absorption chiller. Thus the water partial pressure of a mixture of water and a room temperature ionic liquid (RTIL) was measured in two different ways: Via Fourier-Transform-Infrared (FT-IR) Spectroscopy in a dynamic cell and via Raman-Spectroscopy in a static cell. Additional mixture properties as viscosity and specific heat capacity were measured as a function of concentration. An absorption chiller designed for LiBr - water with a nominal cooling capacity of 10 kW was operated with a mixture of diethylmethylammonium methanesulfonate (DEMA MeSO_3) and water in order to demonstrate the performance of new working solutions with RTILs. Although the measured Coefficient of Performance (COP) is comparable to the one of lithium bromide (LiBr) - water, the higher viscosities of working solutions with RTILs cause an insufficient heat and mass transfer which leads to a low refrigeration output.