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

2009 ◽  
Author(s):  
Ahmed Hamza H. Ali ◽  
Mahmoud Ahmed
Keyword(s):  
Aqueous Solution ◽  
Water Vapor ◽  
Lithium Bromide ◽  
Cooling Water ◽  
Hot Water ◽  
Inlet Temperature ◽  
Membrane Contactor ◽  
Water Coolant ◽  
Hydrophobic Membrane ◽  
Vapor Interface

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.

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

2010 ◽  
Vol 2 (3) ◽  
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.

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

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.

Absorption Characteristics of Multilayered Thin Lithium Bromide (LiBr) Solution Film

2015 ◽  
Author(s):  
Mehdi Mortazavi ◽  
Rasool Nasr Isfahani ◽  
Sajjad Bigham ◽  
Saeed Moghaddam
Keyword(s):  
Absorption Rate ◽  
Numerical Models ◽  
Water Vapor Pressure ◽  
Lithium Bromide ◽  
Cooling Water ◽  
Solution Flow Rate ◽  
Inlet Temperature ◽  
Pressure Potential ◽  
Solution Flow ◽  
Uniform Solution

In this study, an alternative absorber design suitable for the plate-and-frame absorber configuration is introduced. The design utilizes a fin structure installed on a vertical flat plate to produce a uniform solution film and minimize its thickness and to continuously interrupt the boundary layer. Using numerical models supported by experiments employing dye visualization, the suitable fin spacing and size and wettability are determined. The solution flow thickness is measured using the laser confocal displacement measurement technique. The new surface structure is tested in an experimental absorption system. An absorption rate as high as 6×10−3 kg/m2s at a driving pressure potential of 700 Pa is achieved, which is considerably high in comparison with conventional absorption systems. The effect of water vapor pressure, solution flow rate, solution inlet concentration, cooling water inlet temperature and solution inlet temperature on the absorption rate is also investigated. The proposed design provides a potential framework for development of highly compact absorption refrigeration systems.

Absorption Characteristics of Thin Lithium Bromide (LiBr) Solution Film Constrained by a Porous Hydrophobic Membrane

2013 ◽  
Author(s):  
Rasool Nasr Isfahani ◽  
Saeed Moghaddam
Keyword(s):  
Water Vapor ◽  
Absorption Rate ◽  
Water Vapor Pressure ◽  
Lithium Bromide ◽  
Small Scale ◽  
Hydrophobic Membrane ◽  
Solution Flow ◽  
Libr Solution ◽  
Channel Thickness ◽  
Absorption Characteristics

An experimental study on absorption characteristics of water vapor into a thin lithium-bromide (LiBr) solution flow is presented. The LiBr solution flow is constrained between a superhydrophobic vapor-permeable wall and a solid surface that removes the heat of absorption. As opposed to conventional falling film absorbers, in this configuration, the solution film thickness and velocity can be controlled independently to enhance the absorption rate. The effects of water vapor pressure and cooling surface temperature on the absorption rate are studied. An absorption rate of approximately 0.005 kg/m2s was measured at a LiBr solution channel thickness and flow velocity of 160 μm and 4 mm/s, respectively. The absorption rate increased linearly with the water vapor driving potential at the tested solution channel thickness. The high absorption rate and the inherently compact form of the proposed absorber promise compact small-scale waste heat or solar-thermal driven cooling systems.

scholarly journals Feasibility Analysis of a Membrane Desorber Powered by Thermal Solar Energy for Absorption Cooling Systems

2020 ◽  
Vol 10 (3) ◽  
pp. 1110 ◽  
Author(s):  
Jonathan Ibarra-Bahena ◽  
Eduardo Venegas-Reyes ◽  
Yuridiana R. Galindo-Luna ◽  
Wilfrido Rivera ◽  
Rosenberg J. Romero ◽  
...  
Keyword(s):  
Experimental Data ◽  
Water Vapor ◽  
Solar System ◽  
Waste Heat ◽  
Cooling Water ◽  
Solution Temperature ◽  
Hydrophobic Membrane ◽  
Cooling Systems ◽  
Libr Solution ◽  
Absorption Cooling

In absorption cooling systems, the desorber is a component that separates the refrigerant fluid from the liquid working mixture, most commonly completed by boiling separation; however, the operation temperature of boiling desorbers is generally higher than the low-enthalpy energy, such as solar, geothermal, or waste heat. In this study, we used a hydrophobic membrane desorber to separate water vapor from an aqueous LiBr solution. Influencing factors, such as the H2O/LiBr solution and cooling water temperatures, were tested and analyzed. With the experimental data, a solar collector system was simulated on a larger scale, considering a 1 m2 membrane. The membrane desorber evaluation shows that the desorption rate of water vapor increased as the LiBr solution temperature increased and the cooling water temperature decreased. Based on the experimental data from the membrane desorber/condenser, a theoretical heat load was calculated to size a solar system. Meteorological data from Emiliano Zapata in Mexico were considered. According to the numerical result, nine solar collectors with a total area of 37.4 m2 provide a solar fraction of 0.797. The membrane desorber/condenser coupled to the solar system can provide an average of 16.8 kg/day of refrigerant fluid that can be used to produce a cooling effect in an absorption refrigerant system.

scholarly journals РЕЗЕРВИ ПІДВИЩЕННЯ ЕФЕКТИВНОСТІ ТРАНСФОРМАЦІЇ ТЕПЛОТИ УСТАНОВКИ АВТОНОМНОГО ЕНЕРГОЗАБЕЗПЕЧЕННЯ

2019 ◽  
pp. 25-30
Author(s):  
Сергій Георгійович Фордуй ◽  
Андрій Миколайович Радченко ◽  
Анатолій Анатолійович Зубарєв ◽  
Володимир Володимирович Бойчук ◽  
Олексій Валерійович Остапенко
Keyword(s):  
Thermal State ◽  
Cooling System ◽  
Lithium Bromide ◽  
Cooling Water ◽  
Cooling Capacity ◽  
Hot Water ◽  
Lubricating Oil ◽  
Air Conditioner ◽  
Piston Engine ◽  
Exhaust Heat

It is analyzed the efficiency of heat conversion in the integrated electricity, heat and cooling supply of the enterprise. The installation for energy supply includes two JMS 420 GS-N.LC GE Jenbacher cogeneration gas engines manufactured as cogeneration modules with heat exchangers for removing the heat of exhaust gases, scavenge gas-air mixture, cooling water of engine and lubricating oil. The heat of hot water is transformed by the absorption lithium-bromide chiller AR-D500L2 Century into the cold, which is spent on technological needs and for the operation of the central air conditioner for cooling the incoming air of the engine room, where from it is sucked by the turbocharger of the engine. The presence of significant heat losses, which account for about 30% of the total heat removed from the cogeneration gas piston module and is due to the inconsistency of the joint operation modes of the absorption lithium-bromide chiller and the gas piston engine, was revealed. This inconsistency is caused by the contradictory conditions of their effective operation according to the temperature of the return coolant at the outlet of the absorption lithium-bromide chiller and the entrance to the engine cooling system. The thermal state of the gas piston engine is ensured by maintaining the temperature of the return coolant at the entrance to it is not higher than 70 °C. At the same time, during the transformation of the heat of the coolant into the cold in an absorption lithium-bromide chiller, the temperature decreasing in the machine is no more than 10 ... 15 °С, that is, up to 75 ... 80 °С, if the temperature of the heat coolant outlet from the cogeneration gas piston module, i.e. at the inlet of the absorption lithium-bromide chiller, 90 °С. Therefore, the return coolant is additionally cooled in the "emergency heat release" radiator by removing its heat into surroundings. It is shown the possibility of increasing the cooling capacity of the system by conversion of the return coolant exhaust heat into cold in absorption lithium-bromide and ejector chillers through the data procession of monitoring the heat conversion system in the integrated energy plant.

A Hybrid Absorption Cycle for Water Heating, Dehumidification, and Evaporative Cooling

2015 ◽  
Author(s):  
Devesh Chugh ◽  
Rasool Nasr Isfahani ◽  
Kyle Gluesenkamp ◽  
Omar Abdelaziz ◽  
Saeed Moghaddam
Keyword(s):  
Water Vapor ◽  
Evaporative Cooling ◽  
Hot Water ◽  
Process Water ◽  
Coefficient Of Performance ◽  
Inlet Temperature ◽  
Thermal Coefficient ◽  
Water Heating ◽  
Air Stream ◽  
Absorption Cycle

In this study, development of a novel system for combined water heating, dehumidification, and space cooling is discussed. The system absorbs water vapor from an air stream into an absorbent. The latent heat of absorption, released into the absorbent, is transferred into the process water that cools the absorbent. The solution is regenerated in the desorber, where it is heated by a heating fluid. The water vapor generated in the desorber is condensed and its heat of phase change is also transferred to the process water. The condensed water is then used in an evaporative cooling process to cool the dehumidified air exiting the absorber. Essentially, this open-absorption cycle collects space sensible heat and transfers it to hot water. Another novel feature of the cycle is recovery of the heat energy from the solution exiting the desorber by heat exchange with process water rather than with the solution exiting the absorber. This approach has enabled heating the process water from an inlet temperature of 15°C to 57°C (conforming to the required DOE building hot water standard) and compact fabrication of the absorber, solution heat exchanger, and desorber in plate and frame configuration. The system under development currently has a water heating capacity of 1.5 kW and a thermal coefficient of performance (COP) of 1.45.

scholarly journals Surface behavior of amphiphiles in aqueous solution: a comparison between different pentanol isomers

2015 ◽  
Vol 17 (21) ◽  
pp. 14036-14044 ◽  
Author(s):  
M.-M. Walz ◽  
C. Caleman ◽  
J. Werner ◽  
V. Ekholm ◽  
D. Lundberg ◽  
...  
Keyword(s):  
Molecular Dynamics ◽  
Aqueous Solution ◽  
Water Vapor ◽  
Surface Structure ◽  
Photoelectron Spectroscopy ◽  
Md Simulation ◽  
Molecular Level ◽  
Vapor Interface ◽  
X Ray ◽  
Surface Behavior

Molecular-level understanding of concentration-dependent changes in the surface structure of different amphiphilic isomers at the water–vapor interface was gained by molecular dynamics (MD) simulation and X-ray photoelectron spectroscopy (XPS).

scholarly journals Thermodynamic Evaluation of LiCl-H2O and LiBr-H2O Absorption Refrigeration Systems Based on a Novel Model and Algorithm

Energies ◽  
2019 ◽  
Vol 12 (15) ◽  
pp. 3037 ◽  
Author(s):  
Ren ◽  
Qian ◽  
Yao ◽  
Gan ◽  
Zhang
Keyword(s):  
Cooling Water ◽  
Cooling Capacity ◽  
Calculation Model ◽  
Hot Water ◽  
Coefficient Of Performance ◽  
Inlet Temperature ◽  
Thermodynamic Evaluation ◽  
Absorption Refrigeration ◽  
Exergetic Efficiency ◽  
Absorption Chillers

An absorption refrigeration system (ARS) is an alternative to the conventional mechanical compression system for cold production. This study developed a novel calculation model using the Matlab language for the thermodynamic analysis of ARS. It was found to be reliable in LiCl-H2O and LiBr-H2O ARS simulations and the parametric study was performed in detail. Moreover, two 50 kW water-cooled single effect absorption chillers were simply designed to analyze their off-design behaviors. The results indicate that LiCl-H2O ARS had a higher coefficient of performance (COP) and exergetic efficiency, particularly in the lower generator or higher condenser temperature conditions, but it operated more restrictively due to crystallization. The off-design analyses revealed that the preponderant performance of LiCl-H2O ARS was mainly due to its better solution properties because the temperature of each component was almost the same for both chillers in the operation. The optimum inlet temperature of hot water for LiCl-H2O (83 °C) was lower than that of LiBr-H2O (98 °C). The cooling water inlet temperature should be controlled within 41 °C, otherwise the performances are discounted heavily. The COP and cooling capacity could be improved by increasing the temperature of hot water or chilled water properly, contrary to the exergetic efficiency.

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