Molecular dynamics study of the water vapor absorption into aqueous electrolyte solutions

Conference · Thu Jul 01 04:00:00 EDT 1999

OSTI ID:20034243

Daiguji, Hirofumi; Hihara, Eiji

Water-lithium bromide (H{sub 2}O-LiBr) is the most popular working fluid pair in absorption refrigeration. However, it has certain limitations including crystallization and low diffusivity. The crystallization of LiBr aqueous solution is the serious problem to be solved for the development of the air-to-air residential refrigeration of higher efficiency. The low absorption rate due to the low diffusivity of LiBr aqueous solution is the critical problem for the coefficient of performance of this machine. Recent topics of the research in H{sub 2}O-LiBr type absorption refrigeration technology are solubility elevation by additive and absorption enhancement by surfactant. In order to overcome these problems, various kinds of additives and surfactants are attempted to the H{sub 2}O-LiBr system. For the research on the effective working fluid pair, or the correct prediction and control of the dynamic process accompanying phase change phenomenon, it is so much important to understand the thermophysical properties and the dynamic processes from molecular scale. In the present study, the molecular dynamics simulations were carried out under nonequilibrium condition in order to investigate the dynamic process of water vapor absorption into aqueous electrolyte solution. The two boxes at liquid-vapor equilibrium at different saturation pressure are coupled. One box contains water and the other box contains aqueous electrolyte solution. The variables are temperatures of water, temperature and concentration of aqueous electrolyte solution and pressure difference between two boxes. The absorption rate calculated and some molecular pictures were reported. On the molecular scale, ions are negatively adsorbed at the surface particularly in weak aqueous electrolyte solution and highly concentrated aqueous electrolyte solution is effectively frozen and cannot rapidly adjust to the incident water vapor molecules. These structural and dynamical properties affect the absorption rate.

• Research Organization: Univ. of Tokyo (JP)
• OSTI ID: 20034243
• Country of Publication: United States
• Language: English

Related Subjects

32 ENERGY CONSERVATION, CONSUMPTION, AND UTILIZATION
ABSORPTION
ABSORPTION REFRIGERATION CYCLE
AQUEOUS SOLUTIONS
HEAT TRANSFER
LITHIUM BROMIDES
MOLECULAR DYNAMICS METHOD
REFRIGERATING MACHINERY
WATER VAPOR
WORKING FLUIDS