Design of a compact absorber with a hydrophobic membrane contactor at the liquid–vapor interface for lithium bromide–water absorption chillers

In this study, analytical investigation at off-design conditions on performance of a plates-and-frames absorber with hydrophobic microporous membrane contactor at aqueous solution-water vapor interface are carried out. The absorber is a component of a single-effect lithium bromide-water absorption chiller with a hot water thermally driven generator and water-cooled absorber and condenser. Integrating the absorber model with the chiller model is used to evaluate the absorber performance at off-design conditions corresponding to different inlet both driving hot water and cooling water (coolant) temperatures. For the same cooling capacity of the chiller and referring to design point values, the results indicate that, increasing the inlet driving hot water temperature results in an increase in the required absorber size, consequently, a decrease in the absorber performance. While, decreasing the cooling water (coolant) inlet temperature leads to slightly decreases in the required absorber size, consequently, an increase in the absorber performance.

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00/03651 Second-law analysis of multi-effect lithium bromide/ water absorption chillers

Fuel and Energy Abstracts ◽

10.1016/s0140-6701(01)80015-1 ◽

2000 ◽

Vol 41 (6) ◽

pp. 409

Keyword(s):

Water Absorption ◽

Lithium Bromide ◽

Second Law ◽

Absorption Chillers ◽

Second Law Analysis

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Molecular Dynamics Simulation for the Impact of N-Decanol Surfactants on the Liquid-Vapor Interface of Lithium Bromide Aqueous Solution

2010 14th International Heat Transfer Conference, Volume 3 ◽

10.1115/ihtc14-22746 ◽

2010 ◽

Author(s):

Beibei Zhu ◽

Hongtao Gao

Keyword(s):

Molecular Dynamics ◽

Aqueous Solution ◽

Molecular Dynamics Simulation ◽

Electrolyte Solution ◽

Dynamic Process ◽

Lithium Bromide ◽

Dynamics Simulation ◽

Vapor Interface ◽

The Impact ◽

Liquid Vapor

In order to investigate the effect of n-decanol, a kind of alcohol surfactants, on the absorption of water vapor into lithium bromide aqueous solution, this study focused on microscopic structure of the liquid-vapor interface of the electrolyte solution, the impact of n-decanol molecules on the interfacial properties and the absorption dynamic process employing the method of molecular dynamics simulation. The liquid-vapor configuration of lithium bromide aqueous solution added with four concentration of n-decanol can be analyzed by examining the density profile, the radial distribution functions and orientational order parameter. The computed results revealed that n-decanol molecules tended to adsorb at the interface with the methyl group pointing into the vapor phase and hydrophilic hydroxyl group pointing into the liquid phase which do much help to form a hydrogen bond network with water, and the tendency of this kind of preferred orientation became distinct with the increase of the amount of n-decanol. The hydrocarbon chains of n-decanol molecules were inclined to close to stay upright near the interface while the monolayer of n-decanol came into being near the interface. Ions were repelled from the surface. The direct interactions between hydroxyl hydrogen of n-decanol and anion exist, and there are much stronger electrostatic interactions between oxygen of n-decanol and cation. The dynamic process of the absorption of water into aqueous electrolyte solution with or without n-decanol was explored by molecular dynamics simulation under non equilibrium conditions. The simulation results showed that in comparison to the lithium bromide aqueous solution without n-decanol, the electrolyte aqueous solution with n-decanol can absorb more water molecules distinctly for 100 ps.

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Performance of an Absorber With Hydrophobic Membrane Contactor at Aqueous Solution-Water Vapor Interface

Journal of Thermal Science and Engineering Applications ◽

10.1115/1.4003067 ◽

2010 ◽

Vol 2 (3) ◽

Cited By ~ 1

Author(s):

Ahmed Hamza H. Ali

Keyword(s):

Aqueous Solution ◽

Water Vapor ◽

Water Temperature ◽

Cooling Water ◽

Cooling Capacity ◽

Hot Water ◽

Membrane Contactor ◽

Water Coolant ◽

Hydrophobic Membrane ◽

Vapor Interface

In this study, a detailed modeling of the heat and mass transfer processes inside a plate-and-frame absorber with hydrophobic microporous membrane contactor at aqueous solution-water vapor interface as a part of a chiller model is developed. The absorber is a component of a 5 kW cooling capacity single effect lithium bromide-water absorption chiller with a hot water thermally driven generator, a water-cooled absorber, and a condenser. The model is used to investigate the performance of the absorber in case the chiller operates at different values of the inlet driving hot water and cooling water (coolant) temperatures. The results clearly indicate that for the same cooling capacity of the chiller and compared with the performance at the design point value, increasing the inlet driving hot water temperature results in an increase in the required absorber size and consequently a decrease in the absorber performance, while decreasing the cooling water (coolant) inlet temperature leads to slight decreases in the required absorber size and consequently an increase in the absorber performance. The effect is prominent and can be used to decrease the absorber size for chillers work in places where the option of lower inlet coolant temperature is available with normal driving hot water temperature.

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