Experimental Study of Water Vapor Absorption Into Lithium Bromide (LiBr) Solution Constrained by Superhydrophobic Porous Membranes

2013 ◽  
Author(s):  
Rasool Nasr Isfahani ◽  
Saeed Moghaddam
Keyword(s):  
Experimental Study ◽  
Water Vapor ◽  
Absorption Rate ◽  
Waste Heat ◽  
Water Vapor Pressure ◽  
Lithium Bromide ◽  
Small Scale ◽  
Solution Flow ◽  
Libr Solution ◽  
Channel Thickness

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.

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.

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.

Experimental study of small scale and high expansion ratio ORC for recovering high temperature waste heat

Energy ◽  
2020 ◽  
Vol 208 ◽  
pp. 118321 ◽  
Author(s):  
Antti Uusitalo ◽  
Teemu Turunen-Saaresti ◽  
Juha Honkatukia ◽  
Radheesh Dhanasegaran
Keyword(s):  
Experimental Study ◽  
High Temperature ◽  
Waste Heat ◽  
Expansion Ratio ◽  
Small Scale

Experimental study of ZrF62– stability in hydrothermal solutions at 90–255 ᵒC

2019 ◽  
pp. 107-111
Author(s):  
M. E. Tarnopolskaya ◽  
A. Yu. Bychkov
Keyword(s):  
Experimental Data ◽  
Experimental Study ◽  
Water Vapor ◽  
Vapor Pressure ◽  
Dissociation Constants ◽  
Water Vapor Pressure ◽  
Hydrothermal Solutions ◽  
Free Energies ◽  
Saturated Water Vapor ◽  
Saturated Water

The solubility of fluorite in HCl and HF solutions with a variable concentration of Zr at 90, 155, 205 and 255 ᵒC and the pressure of saturated water vapor were investigated. The results showed that the solubility of fluorite increases with increasing concentration of zirconium. Using the OptimA program, the free energies of the ZrF62– complex were determined from the experimental data, from which the dissociation constants of the reaction ZrF62– =Zr4+ + 6F- were calculated. The pK values were 29,86±0,13; 34,03±0,062; 38,28±0,033; 40,94± 0,079 at 90, 155, 205 and 255 ᵒС (saturated water vapor pressure).

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.

Physics of Membrane-Based Desorption Process From LiBr Solution Flow in Microchannels

2013 ◽  
Author(s):  
Rasool Nasr Isfahani ◽  
Saeed Moghaddam
Keyword(s):  
Wall Temperature ◽  
Lithium Bromide ◽  
Heated Wall ◽  
Inlet Temperature ◽  
Desorption Rate ◽  
Vapor Pressures ◽  
Solution Flow ◽  
Water Desorption ◽  
Desorption Process ◽  
Libr Solution

This study investigates the physics of water desorption from a lithium bromide (LiBr) solution film. The study was conducted on a membrane-based desorber in which the solution flows through an array of microchannels capped by a porous membrane. The membrane allows the vapor to exit the flow and retains the liquid. The solution film velocity and thickness as well as the solution and vapor pressures are independently controlled. Effects of different parameters such as wall temperature, solution and vapor pressures, solution flow velocity, and the solution inlet temperature on desorption rate were studied. Two different mechanisms of desorption are observed and analyzed. These mechanisms consisted of: (1) direct diffusion of water molecules out of the solution and their subsequent flow through the membrane and (2) formation of water vapor bubbles within the solution and their exit through the membrane. Direct diffusion was the dominant desorption mode at low surface temperatures and its magnitude was directly related to the vapor pressure, the solution concentration, and the heated wall temperature. Desorption at the boiling regime was predominantly controlled by the solution flow pressure. Overall, an order of magnitude higher desorption rate compare to a previous study on a membrane-based desorber was achieved.

scholarly journals The Initial Oxidation of HfNiSn Half-Heusler Alloy by Oxygen and Water Vapor

Materials ◽  
2021 ◽  
Vol 14 (14) ◽  
pp. 3942
Author(s):  
Oshrat Appel ◽  
Shai Cohen ◽  
Ofer Beeri ◽  
Yaniv Gelbstein ◽  
Shimon Zalkind
Keyword(s):  
Water Vapor ◽  
Photoelectron Spectroscopy ◽  
Elevated Temperatures ◽  
Surface Composition ◽  
Waste Heat ◽  
Water Vapor Pressure ◽  
Formation Enthalpy ◽  
Environmental Stability ◽  
Initial Oxidation ◽  
Practical Applications

The MNiSn (M = Ti, Zr, Hf) n-type semiconductor half-Heusler alloys are leading candidates for the use as highly efficient waste heat recovery devices at elevated temperatures. For practical applications, it is crucial to consider also the environmental stability of the alloys at working conditions, and therefore it is required to characterize and understand their oxidation behavior. This work is focused on studying the surface composition and the initial oxidation of HfNiSn alloy by oxygen and water vapor at room temperature and at 1000 K by utilizing X-ray photoelectron spectroscopy. During heating in vacuum, Sn segregated to the surface, creating a sub-nanometer overlayer. Exposing the surface to both oxygen and water vapor resulted mainly in Hf oxidation to HfO2 and only minor oxidation of Sn, in accordance with the oxide formation enthalpy of the components. The alloy was more susceptible to oxidation by water vapor compared to oxygen. Long exposure of HfNiSn and ZrNiSn samples to moderate water vapor pressure and temperature, during system bakeout, resulted also in a formation of a thin SnO2 overlayer. Some comparison to the oxidation of TiNiSn and ZrNiSn, previously reported, is given.

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