LiBr Solution Research Articles

Experimental Study on the Filtration Efficiency of Structured Packing Air Handling Processors

Air handling processors with structure packing are widely utilized in the air-conditioning system, in which coupled heat and mass transfer occurs between air and water/desiccant. As an additional benefit, the processor could remove particles at the same time. An experimental setup for a cross-flow packed processor was established to investigate the filtration efficiency, in which air-water and air-desiccant were chosen as flow media. Effects of air and water/desiccant parameters on the filtration performance were experimentally analyzed. The results show that for typical air-to-liquid flow rate ratio (≈1), PM5 arrestance efficiency of packed processor with water is 40%∼50% while that with LiBr solution is 20%∼30%. The filtration efficiency with LiBr solution is higher than that with water when splash effect of liquid is omitted.

Experimental study of evaporation of horizontal films of water–salt solutions

The present studies were carried out for the horizontal films (thin layers) of water and water solutions of NaCl, CaCl2 , LiCl, and LiBr with different solubility characteristics, as well as with specific features of formation and decay of water hydrates. Required volume of solution V o of given weight concentration ξo , preliminary heated to the working surface temperature, was put in one step on the horizontal bottom of the bowl, heated to working temperature t CT , by means of volume batchers Thermo Scientific. After evaporation completion, the final mass of solution and form of their residue were registered. At the final stage of evaporation formation of NaCl crystals and water hydrates of CaCl2 · 2H2 O, LiCl · H2 O, and LiBr · 2H2 O occurred.

1024 吸収冷凍機の吸収器内の可視化

Compression type refrigerator has been used as automotive air conditioner, so we need additional fuel for air conditioning. Absorption chiller is heat driven type refrigerator, so when we adapt it for automotive air conditioner and use with waste heat, it will reduce the fuel consumption. We are developing the absorption chiller for automobile which have the tolerance for unique environment of automobile. In this work, we propose new type absorber which has heat exchanger smeared lithium-bromide(LiBr) solution by rotors with brushes. And now, wet area of heat exchanger is important factor for the performance. In this paper, the method to visualize the liquid film flow of solution is established by using laser and fluorescent agent, and wet area of surface of heat exchanger is quantified.

Pipeline Corrosion Failure in an Absorption Chiller

Absorption chillers generate chilled water by employing as refrigerant water which is evaporated at low pressure. The steam produced is then absorbed by a concentrated LiBr solution. The materials employed for the construction of this kind of plant are usually copper and stainless steel. Despite their good corrosion resistance, the environment rich of halogen ions can lead in some cases to severe corrosion attacks.This paper describes a complex case of corrosion that produced the failure of an absorption chiller pipelines. The failure involved in different steps both copper and stainless steel pipes.

Design and Performance Study of a Hot Water Driven 5 TR Capacity Absorption Cooling System

Use of high grade electrical energy, generated from fossil fuels, for cooling has increased environmental concerns like global warming and ozone layer depletion. Hence, there is a need to reduce dependence on them and explore potential environmental friendly options. In this aspect, vapor absorption system has scope of utilizing low grade energy source i.e. hot water from solar panel, to generate cooling effect and are environment friendly as no chloro-floro-carbons are used. The most usual combination of absorber refrigerant pair in such system is lithium bromide water (LiBr–H2O), where water vapor is the refrigerant. In present work, a hot water driven, single stage, absorption cooling system, using a lithium bromide water solution, is analyzed for determining the effect of various parameters on coefficient of performance (COP). Four basic stages in the absorption cycle are generation, condensation, evaporation and absorption with ideally no moving part. A configuration of theses four stages, having 5 TR cooling capacity is determined and examined for the variation in COP corresponds to the change in pressure and concentration. The pressure parameter is varied in condenser and evaporator, resulting graph shows that the increment in pressure of evaporator increases the COP whereas increment of pressure in condenser decreases the COP. At lower inlet concentration of LiBr solution to the absorber gives increment in COP.

LiBr treated porous silicon used for efficient surface passivation of crystalline silicon solar cells

A simple but effective passivation method of both front and rear surfaces using porous silicon (PS) has been developed. This paper investigates the effect of LiBr on the passivation of PS. The immersion of as-etched PS in dilute LiBr solution followed by an annealing in an infrared furnace, under a controlled atmosphere at different temperatures, led to the passivation of the PS layer and the improvement of the electronic properties of the crystalline silicon substrates. The influence of substrate temperature was investigated, since the processed wafers were found to be sensitive to heat, which in turn was optimized to have a gettering effect. The bromide of lithium can effectively saturate dangling bonds and hence contributed to the formation of a stable passivation film, at both front and back surfaces. Such a reaction was found to have a beneficial effect on the passivation process of the PS layer grown on both sides. The obtained results exhibited a significant improvement of the minority carrier lifetime, which is an important parameter that defines the quality of crystalline silicon substrates, and an apparent enhancement of its photoluminescence (PL). The internal quantum efficiency was investigated and found to be significantly improved. The qualitative effect of the above-mentioned procedure proved a significant enhancement of the electronic quality of the treated substrates.

A study of the coupled heat and mass transfer during absorption process in a spiral tubular absorber

In this study, a fine local modeling of the coupled heat and mass transfer during absorption process of water vapor by a LiBr solution in a spiral tubular absorber of an absorption chiller was made. We have taken into account of the real hydrodynamics of the liquid solution that reveals the presence of three different flow regimes: a falling film region existing on the tube in which circulates the cooling water, a droplet formation region at the tube's bottoms and a droplet free fall region between the spaced tubes. The equations governing the coupled heat and mass transfer are established for the three flow regimes. The numerical simulation has given the distributions of different absorption parameters along the absorber tubes. This numerical simulation has shown up the relationship between the heat and the mass transfers and also highlighted the importance of the droplet formation and fall regimes in improving the absorption process, when the droplets are considered fully mixed. The validity of the model was improved using experimental data performed on a spiral tubular absorber of a double effect absorption chiller.

Theoretical analysis of the thermal performance of a plate heat exchanger at various chevron angles using lithium bromide solution with nanofluid

Nanofluids technology has been rapidly developing over the last two decades. In this paper, the performance of a lithium bromide (LiBr) solution with and without nanoparticles in plate heat exchanger (PHE) for various chevron angles and mass flow rates was investigated. As a result, the heat transfer rate and the overall heat transfer coefficient in 60°/60° PHE is over 100% higher than that of 30°/30° PHE, and the effectiveness of the PHE in 60°/60° PHE is about 70% higher than that of 30°/30° PHE. By using nanoparticle in the working fluid, the heat transfer performance can increase significantly. The heat transfer rate of 3 vol.% nanofluids increased about 3–8% compare to that of LiBr solution for all chevron PHEs. Besides, the 60°/60° PHE using 3 vol.% nanofluids produced the largest heat transfer rate and heat exchange effectiveness under given operating conditions.

Comparison Study on the Corrosion Resistance of Stainless Steel and Copper Tubes in LiBr Solution in Heat Pump

Cooling water surplus heat utilization by lithium bromide absorption heat pump is a significant measure of energy saving in thermal power plants, however, lithium bromide corrosion on tubes seriously affects the reliability of heat pump absorbers. Through weight loss methods and electrochemical polarization methods, corrosion resistance of copper tube and five types of stainless steel tubes 304,316 L,436L,444 and 445J2 have been studied under absorber conditions. The results reveal that the corrosion resistance of five types of stainless steel tubes is significantly better than copper tubes in 62wt-% LiBr solution, and the corrosion resistance of the order of tubes is 316L>445J2≈444>304≈436L>>TP2. Inhibition effect of lithium molybdate is a little better than sodium molybdate at the same weight concentration.

Influence of heated surfaces and fluids on pool boiling heat transfer

The influence of heated surfaces and fluids on pool boiling heat transfer was investigated experimentally. As the test specimen, Plain Surface (PS) and Nano-Structured Surface (NSS) were used. As the test fluid, pure water, an aqueous Lithium Bromide (LiBr) solution, and an aqueous Sodium Dodecyl Sulfate (SDS) solution were tested. Under the saturated water and aqueous LiBr solution conditions, the NSS showed a lower Onset of Nucleate Boiling (ONB) and higher Nucleate Boiling Heat Transfer Coefficient (NBHTC) than the PS. On the other hand, under aqueous SDS boiling conditions, the NBHTC was increased on the PS, but decreased on the NSS, as compared with under pure water boiling conditions. It was found that the interaction and combination between the heated surface and fluid can be an important parameter affecting the boiling heat transfer performance, and both the surface tension and surface wettability (i.e., contact angle) should be taken into account. The change of water contact angle induced by the chemical reaction between the heated surface and fluid was examined and discussed. As the test surface, copper PS, titanium PS, and titanium dioxide NSS were prepared. Then, they were boiled under saturated water and butanol conditions for 8h, and their water contact angles were compared with the fresh (i.e., pre-boiled) surfaces. The water-boiling process remarkably decreased the water contact angles for all surfaces, as compared with the butanol-boiling process. This implies that the chemical reaction between the heated surfaces and boiling fluids affects the surface wettability, which can strongly influence the pool boiling heat transfer performance.

Simulation of Vapor Absorption of Aqueous Libr Solution on Alternate Heat and Mass Transfer Surfaces of Corrugated Plates and Mesh Pecking

The traditional tube-shell absorber is relatively too bulky to be used in a small absorption chiller for solar air conditioning. As the outer-surface of solution film on the traditional absorber surface is easier to be saturated, several alternate heat and mass transfer absorber schemes have been proposed. However, the film-inversion absorber uses only half surfaces while the dual-side film-inversion absorber scheme is of good performance but too complicated to fulfill. The scheme using stainless steel mesh packing as the film guider is much easier and more uniform in distributing film, and it can also act as the framework for exposing dual-side film to the vapor for adiabatic mass transfer. The alternate heat and mass transfer configurations with plate surfaces and mesh packing are of promising performance for small chiller absorbers.

Bromide and lithium transport in soils under long-term cultivation of alfalfa and wheat

The combined effects of two soil textures and two types of crop management were investigated using lithium and bromide tracers transport under saturated flow conditions. Leaching tests were carried out through intact columns of two soils, a clay loam (CL) and sandy loam (SL), each cropped with either wheat (Triticum aestivam) (W) or alfalfa (Medicago sativa) (A) for 11 years. A saturated steady state flow condition was established using tap water prior to injecting a pulse of 0.005M LiBr solution onto the surface of the soil columns. Breakthrough curves (BTCs) for leached Br− and Li+ in the soil columns (especially under alfalfa cultivation) exhibited an early arrival time and greater concentrations, indicating preferential flow effects. Relative 5% arrival times were 0.07, 0.11, 0.24 and 0.31 for CL-A, SL-A, CL-W, and SL-W, respectively; its smaller values confirmed the higher possibility of preferential flow under alfalfa than under wheat. The Br− concentration was higher than the Li+ concentration. With the exception of soils under alfalfa (CL-A and SL-A), the peak of the BTCs for Br− occurred earlier than that for Li+, by about 0.4 and 1.2 pore volumes for the CL-W and SL-W cases, respectively. Clay loam soil under alfalfa showed higher Br− and Li+ concentration levels when compared to sandy loam soil under alfalfa crop production. In the soils under alfalfa cultivation, structural cracks, root channels, and earthworm burrows were the cause of higher leached concentrations for both tracers when compared to the soil under wheat. Therefore, alfalfa-induced changes in soil structure lead to continuous macropores, a result of the decomposition of penetrating roots. Our results show that agricultural-management practices (i.e. the type of cropping) can play an important role in making groundwater vulnerable to leached solutes.

Effect of alloying elements on the electronic properties of thin passive films formed on carbon steel, ferritic and austenitic stainless steels in a highly concentrated LiBr solution

The influence of alloying elements on the electrochemical and semiconducting properties of thin passive films formed on several steels (carbon steel, ferritic and austenitic stainless steels) has been studied in a highly concentrated lithium bromide (LiBr) solution at 25°C, by means of potentiodynamic tests and Mott–Schottky analysis. The addition of Cr to carbon steel promoted the formation of a p-type semiconducting region in the passive film. A high Ni content modified the electronic behaviour of highly alloyed austenitic stainless steels. Mo did not modify the electronic structure of the passive films, but reduced the concentration of defects.

Cross-linking in the silks of bees, ants and hornets

Silk production is integral to the construction of nests or cocoons for many Aculeata, stinging Hymenopterans such as ants, bees and wasps. Here we report the sequences of new aculeate silk proteins and compare cross-linking among nine native silks from three bee species (Apis mellifera, Bombus terrestris and Megachile rotundata), three ant species (Myrmecia forficata, Oecophylla smaragdina and Harpegnathos saltator) and three hornets (Vespa analis, Vespa simillima and Vespa mandarinia). The well studied silks of spiders and silkworms are comprised of large proteins that are cross-linked and stabilized predominantly by intra and intermolecular beta sheet structure. In contrast, the aculeate silks are comprised of relatively small proteins that contain central coiled coil domains and comparatively reduced amounts of beta sheet structure. The hornet silks, which have the most beta sheet structure and the greatest amount of amino acid sequence outside the coiled-coil domains, dissolve in concentrated LiBr solution and appear to be stabilized predominantly by beta sheet structure like the classic silks. In contrast, the ant and bee silks, which have less beta sheet and less sequence outside the coiled-coil domains, could not be dissolved in LiBr and appear to be predominantly stabilized by covalent cross-linking. The iso-peptide cross-linker, ε-(γ-glutamyl)-lysine that is produced by transglutaminase enzymes, was demonstrated to be present in all silks by mass spectrometry, but at greater levels in silks of ants and bees. The bee silks and ant cocoons, but not the Oecophylla nest silks, appeared to be further stabilized by tanning reactions.

Experimental investigation of aqueous LiBr solution absorber bundle with horizontal elliptical tubes

This article reports on the results of experimental studies on combined heat and mass transfer in the absorption of water vapor by aqueous LiBr solution under laminar falling film flow on the horizontal elliptical tube (HET) bundle. The performance of the absorber with HET has been calculated based on the measured parameters. The outputs are shown with respect to absorbent inlet mass concentration and Reynolds Number (Re), coolant inlet temperature and flow rate, and absorber vapor pressure. The results are compared with the published experimental results on absorber bundle with horizontal circular tubes (HCT). The results show that the heat and mass transfer coefficients enhanced on HET at aspect ratio (Ar ) > 1 with respect to HCT and improve with the increase of absorbent mass flow rate, absorber vapor pressure, coolant flow rate, and also with the decrease of absorbent concentration and coolant inlet temperature. Because of film thickness increasing and droplet flying off from the tube bundle, the maximum heat transfer coefficient is attained in an optimum absorbent mass flow rate around Re = 45. Finally, the empirical correlations for outside Sherwood number (Sh) and Nusselt number (Nu) are found to depend on the Re, Schmidt number (Sc), mass concentration and absorber vapor pressure.

Experimental Methane Hydrate Dissociation Conditions in Aqueous Solutions of Lithium Salts

Gas hydrate dissociation pressures have been determined for methane in aqueous solutions of LiBr w = (0.05, 0.10, 0.15, and 0.2655) and LiCl w = (0.05, 0.10, 0.15, and 0.20) along the hydrate–liquid–gas equilibrium line in the temperature range (260 to 290) K and for pressures up to 22.5 MPa by applying an isochoric method. LiBr showed a more pronounced inhibition effect than LiCl as expected from the different degree of hydration caused by the different anion sizes.

Research on Ratio Selection of Mixed LiBr-CaCl<sub>2</sub> Solution for Liquid Desiccant Cooling System

In recent years, liquid desiccant cooling system has shown its potential research value for its low-grade heat using and energy-saving. Thermal properties of liquid desiccant, especially its vapor pressure greatly affects the dehumidification efficiency of this system. Here comes the problem to find a liquid desiccant with better dehumidification effect and lower cost. To solve this problem, a local composition model: nonrandom two-liquid (NRTL) theory could be used to calculate a mixed solution of LiBr-CaCl2, and calculates the ideal mixing ratio of this solution in a working environment. The best mixing ratio with cost-effectiveness can be worked out by taking into account the initial cost of the solution. Study shows that: compared to single LiBr solution, the dehumidification effect could be raised by more than 8.2% and the costs could be reduced by 20% with mixed LiBr-CaCl2 solution.

Heat Transfer and Thermodynamic Performance of LiBr/H2O Absorption Heat Transformer with Vapor Absorption Inside Vertical Spiral Tubes

In this paper, an absorption heat transformer (AHT) with falling film of aqueous LiBr solution inside vertical spiral tubes is installed and tested. The variations of coefficient of performance (COP), thermal efficiency (Eth ), and the heat transfer coefficient of the absorber at different falling film flow rates, hot water flow rates, and operating temperatures are investigated experimentally. The results demonstrated that the coefficient of performance and thermal efficiency of the system decrease with the increase in the flow rate of LiBr solution, and the influence of flow rate of hot water on COP and Eth is insignificant. The available COP in the experiments is higher than 0.4. The heat and mass transfer coefficients of the absorber increase with the increase of the flow rate of LiBr solution, up to 400W/m2/K and 0.013 kg/m2/s (temperature of waste heat is 90°C). The heat transfer coefficient of the absorber increases with the increase of the temperature of waste heat, and decreases with the increase of the cooling water temperature. Meanwhile, the computer code ABSIM (Absorption Simulation) is used to simulate the AHT systems, and the simulated results are compared with the experimental data.

The Electrochemistry Behaviour of Carbon Steel in 55% LiBr Solution with A-Mo Inhibitor

The inhibition effects of A-Mo inhibitor on corrosion of carbon steel in 55% LiBr solution were investigated using cyclic potentiodynamic polarization curves EIS experiments, Mott-Schottky analysis, SEM, EDAX and XRD methods. The results revealed that A-Mo inhibitor was capable of inhibiting the corrosion of carbon steel in 55%LiBr solution, exhibiting high inhibition efficiencies around 99.7%. A-Mo inhibitor promoted the formation of a protective passive film composed of Fe, Mo and O elements. The passive film improved the electrochemistry performance and enhanced corrosion resistance of carbon steel.

Passive Behavior and Passivity Breakdown of AISI 304 in LiBr Solutions through Scanning Electrochemical Microscopy

The passive behavior and passivity breakdown of AISI 304 stainless steel in LiBr solutions has been investigated by means of scanning electrochemical microscopy (SECM). The sample generation – tip collection (SG-TC) mode was used to operate the SECM and the tip potential was biased to detect the electroactive species. The evolution of the current at the ultramicroelectrode tip with the applied potential within the passive range was followed at different LiBr concentrations. Results show that the absolute value of the current at the tip increases with the applied potential. Additionally, SECM was also used to detect stable pits formed on the stainless steel surface in a 0.2 M LiBr solution. The results show clear evidence of the presence of high amounts of other reducible species (metal cations) apart from oxygen. Also, the dish-shape morphology of the pits observed using Confocal Laser Scanning Microscopy will be discussed in relation to the kinetics of the reactions observed using SECM.