Search Results (27)

Turbine inlet air cooling (TIAC) is a well-established approach for enhancing the performance of gas turbine power plants operating in hot climates. However, single air-cooling methods have shown limitations mainly in harsh and severe climates. In this work, nine hybrid TIAC configurations integrating two different cooling technologies are proposed and systematically analyzed. The hybrid systems are grouped into three main configurations based on the arrangement of evaporative and refrigerated cooling: Configuration I, where media evaporative cooling is followed in series by refrigerated cooling; Configuration II, where refrigerated cooling precedes evaporative cooling; and Configuration III, where both systems operate in parallel and are then mixed. Each configuration is evaluated through thermodynamic and thermo-economic analyses, considering the performance of a typical 85 MW General Electric (GE) PG7121EA gas turbine unit under the harsh climate conditions of Riyadh, Saudi Arabia. Simulations were carried out using the Engineering Equation Solver (EES) software. This study provides a comprehensive framework for selecting hybrid TIAC configurations based on an overall thermo-economic assessment that considers additional power generation, water consumption, and economic performance. The results reveal that all hybrid TIAC systems substantially reduce the inlet air temperature below ISO reference conditions, with Configuration I providing the best overall balance between technical and economic performance. In terms of cost-effectiveness, Configuration II–Hybrid VI (single-effect H₂O–LiBr absorption refrigeration followed by evaporative cooling) demonstrates improved economic performance over the standalone single-effect H₂O–LiBr absorption system. The findings underscore that hybrid TIAC systems can significantly enhance gas turbine output while achieving favorable payback periods, making them a promising solution for desert climates. Full article

This investigation introduces a conceptual configuration for an innovative combined cooling and power (CCP) arrangement that harnesses waste thermal energy from a supercritical carbon dioxide (sCO₂) power loop through integration with a cascading transcritical CO₂ cycle coupled with a lithium bromide–water vapor absorption chiller (tCO₂/LiBr-H₂O VAR). A systematic comparative assessment of thermodynamic behavior and exergoeconomic characteristics was executed across three configurations: the newly proposed CCP scheme, a hybrid sCO₂/tCO₂ power system, and a conventional standalone sCO₂ engine. Parametric sensitivity analyses were conducted to evaluate how various operating parameters influence overall system effectiveness, while particle swarm optimization (PSO) was employed to determine the optimal exergetic efficiency peaks and minimum unit product costs for each architecture. Findings demonstrate that the proposed CCP topology delivers exergy efficiency enhancements of 8.46% and 1.65% relative to the standalone sCO₂ configuration and the combined sCO₂/tCO₂ arrangement, respectively. Correspondingly, reductions in total product unit costs reach 2.80% and 0.80% for the same comparisons. These outcomes confirm that employing a cascading tCO₂/LiBr-H₂O VAR subsystem as the bottoming cycle represents a compelling solution for cooling and power production. Full article

We present the first comprehensive study on effluent water from mining, oil, natural gas, and geothermal operations in Poland. In 2019, we explored chemical composition of effluent samples collected from 67 locations in Poland representing various oil and gas, mining, and geothermal operations. It has been found that the effluents contained large amount of various elements. Those elements are critical and indispensable for the European Union industry and renewable energy technologies. Thus, the recovery opportunity of critical elements from the effluent water was discussed. We highlighted the main needs and directions for further development of desalination technologies for effluent water. The majority of the analyzed water samples were characterized by high concentration levels of total dissolved solids in the range from 5 to 150 g/L. The highest concentrations of elements in investigated water samples, from several tens to hundreds of mg/L, were observed for K, Mg, Br, Ba, B, Mn, Li, SiO₂, and Sr. Additionally, most of the mine and geothermal water samples contained several tens of g/L NaCl. The most valuable element found in the investigated water samples was lithium. Desalted fresh water can be reused in agriculture or industry. Thus, desalination and extraction of critical elements from effluent water is a sustainable solution to the water scarcity problem in Poland caused by climate warming as well as a means to strengthen resilience of the resources supply for agriculture, industry, and renewable energy technologies. Full article

This study presents a comprehensive thermodynamic simulation and parametric analysis of a single-effect lithium bromide–water (LiBr–H₂O) vapour absorption refrigeration system (VARS) to assess the influence of key operating parameters on its performance, which is primarily measured by the coefficient of performance. The thermodynamic properties of the LiBr–H₂O solution are assessed using P-T-x diagrams to establish the operational limits of the cycle for given constraints, such as the absorber and the generator temperatures and the cycle’s operating pressures. The analysis includes the effects of generator temperature ($T_{gen}$), evaporator pressure ($P_{evap}$), and solution heat effectiveness ($\eta$) on the cycle performance. Additionally, exergy analyses of the cycle’s major components are performed. Simulation results demonstrate that $T_{gen}$ is the most dominant parameter that increases the COP non-linearly from 0.35 at 85 °C to 0.73 at 110 °C (for $\eta$ = 0.5, $T_{cond}$ = 40 °C), while the circulation ratio decreases sharply. Moreover, higher evaporator pressure positively influences the COP; for instance, increasing the evaporator pressure from 0.8 kPa to 1.2 kPa raised the COP from 0.71 to 0.76. This is directly correlated with the increased concentration difference between the strong and weak solutions. The heat recovery effectiveness proved vital for energy optimisation: increasing the recovery effectiveness from 0.5 to 0.9 improved the COP from approximately 0.72 to 0.82 at a fixed $T_{gen}$ of 100 °C. Absorber temperatures limit the minimum operating temperatures of the generator for the vapour production of the refrigerant (water). Moreover, the higher condenser/absorber temperatures significantly deteriorate the performance of the cycle; for instance, raising the operating temperature of the condenser/absorber from 40 °C to 45 °C results in the COP value dropping by up to 35% at a generator operating temperature of nearly 100 °C. Among all cycle components, the generator exhibits the highest exergy loss, especially at lower generator temperatures. These findings provide essential optimisation strategies for designing and operating solar or waste heat-driven LiBr–H₂O VARS units efficiently. Full article

This work mainly focuses on the energy and exergy analysis of a single-effect absorption cooling system operating with the couple H₂O-LiBr, under different climatic conditions in Senegal and France. A simulation model was developed, using the Engineering Equation Solver V10 (EES) software. Results indicate that the system can achieve a maximum COP of 0.76 and an exergy efficiency of 56%, which decreases as the generator temperature increases. Increasing the generator temperature from 87 to 95 °C significantly improves COP, but gains become marginal beyond 100 °C. The highest exergy destruction occurs in the generator, followed by the absorber, condenser, and evaporator. A temperature difference above 44 °C between the generator and the absorber is required to maintain H₂O-LiBr solution stability. Optimal temperatures for hot climates like Senegal are 90 °C (generator), 42 °C (absorber/condenser), and 7 °C (evaporator), while maximum exergy efficiency (56%) is reached at 81 °C, typical of moderate climates (France). Evaporator exergy efficiency increases from 16 to 52% with rising ambient temperature, while absorber and condenser efficiencies drop. Increasing the cooling water flow rate from 0.2 to 1.4 kg/s reduces exergy losses in the absorber and the condenser by up to 36%. The solution heat exchanger (SHE) optimal effectiveness of 0.75 reduces exergy consumption in the absorber and the generator. Full article

In sorption cooling systems, an important stage of the thermodynamic cycle is the separation of the refrigerant fluid from the absorbent mixture. This process is called “regeneration” or “desorption,” and it is similar to thermal desalination, where water is separated from an aqueous saline solution. However, since sorption systems utilize high salt concentration solutions, conventional desalination techniques such as reverse osmosis are not suitable. In this regard, membrane devices can enhance heat and mass transfer processes in compact sizes. In the present paper, a membrane device with an air gap membrane distillation configuration was evaluated, operating with the H₂O/LiBr + LiCl solution (with a mass ratio of 2:1, LiBr:LiCl), to assess the produced distilled water flux. Among the operating parameters analyzed (solution temperature, cooling water temperature, salt concentration, and membrane pore size), solution temperature had the highest impact on the distilled water flux, while the membrane pore size had the lowest impact. The maximum distilled water flux was 7.63 kg/h·m² with a solution temperature of 95.3 °C, a cooling water temperature of 25.1 °C, a salt concentration of 44.99% w/w, and a membrane pore size of 0.45 μm. On the other hand, the minimum distilled water flux was 0.28 kg/h·m² with a solution temperature of 80.3 °C, a cooling water temperature of 40.1 °C, a salt concentration of 50.05% w/w, and with a membrane pore size of 0.22 μm. Full article

Rationally designing and synthesizing chemosensors capable of simultaneously detecting both anions and cations via water content modulation is challenging. In this study, we synthesized and characterized a novel triazine calixarene derivative-based iodide and copper ion-selective fluorescent “turn-off” sensor. This dual-channeled fluorescent probe is able to recognize Cu²⁺ and I⁻ ions simultaneously in aqueous systems. The fluorescent sensor s4 was synthesized by displacement reaction of acridine with 1, 3-bis (dichloro-mono-triazinoxy) benzene in acetonitrile. Mass spectrometry (MS), UV-vis, and fluorescence spectra were acquired to characterize the fluorescence response of s4 to different cations and anions, while infrared (IR) spectroscopy and isothermal titration calorimetry (ITC) were employed to study the underlying selectivity mechanism of s4 to Cu²⁺ and I⁻. In detail, s4 displayed extremely high sensitivity to Cu²⁺ with over 80% fluorescence decrement caused by the paramagnetic nature of Cu²⁺ in the aqueous media. The reversible fluorescence response to Cu²⁺ and the responses to Cu²⁺ in the solution of other potential interferent cations, such as Li⁺, Na⁺, K⁺, Ca²⁺, Cd²⁺, Zn²⁺, Sr²⁺, Ni²⁺, Co²⁺ were also investigated. Probe s4 also exhibited very good fluorescence selectivity to iodide ions under various anion (F⁻, Cl⁻, Br⁻, NO₃⁻, HSO₄⁻, ClO₄⁻, PF₆⁻, AcO⁻, H₂PO₄⁻) interferences. In addition to the fluorescent response to I⁻, s4 showed a highly selective naked-eye-detectable color change from colorless to yellow with the other tested anions. Full article

In this article, we present a method for extracting the complex permittivity of high-conductivity solutions up to 9 GHz. Microwave measurements were performed using a low-cost SMA connector, employed as an open-circuit coaxial probe, which was subsequently brought into contact with the liquids under characterization. Compared to state-of-the-art techniques, this method offers the advantage of good accuracy while remaining simple to implement with a low-cost sensor. The affordability of the sensor is crucial because the sensor must operate in a corrosive environment. The use of existing but expensive commercial solutions is prohibitive. Therefore, sensor replacement must be straightforward and inexpensive in case of damage. Two permittivity extraction methods were studied, both relying on a straightforward experimental approach and knowledge of the complex permittivity of reference liquids (deionized water, ethanol, methanol). The technique was initially validated on saline solutions (NaCl) known from the literature before being applied to aqueous lithium bromide (LiBr water) solutions. Eight LiBr water solutions, known to be highly corrosive, were measured for LiBr mass concentrations ranging from 1% to 54% and for conductivities up to 14 S/m. The high conductivity of these solutions brings challenges to extract the real part of the permittivity, which is underestimated by both methods. In contrast, the imaginary part exhibits consistent results with variations strongly correlated to the concentration. Notably, an inversion of the direction of variation was observed for mass concentration in LiBr exceeding 35% aligning with the conductivity curve. Full article

The desalination of aquifers and seawaters is a viable choice to meet primarily domestic and industrial global water requirements. It removes salts from seawater to obtain freshwater with sufficient quality for different purposes, as well as a highly salt-concentrated waste stream known as brine. This residue is usually returned to the ocean, provoking, among other impacts, changes in temperature, salinity and oxygen and overall local aquatic ecosystem stress, as well as social rejection. Desalination in inland aquifers is more complicated because brine disposal is complicated or impossible. The current study presents a new zero-brine discharge technology able to achieve ecological liquid purification through distillation for the separation of the dissolved solids as crystallized salts (Adiabatic Sonic Evaporation and Crystallization, ASE&C). This new technology was used with seawater and three types of brine to test how it would work when coupled with reverse osmosis desalination plants. Analysis of the byproducts after treatment of the seawater and the different brines are presented here. A basic economic approach to calculating potential revenues is also presented. The results of the analyses revealed a complete depuration of water as distilled water, and crystallized solids with highly concentrated commercial salts (with different composition depending on their origin). The estimated economic value of annual revenue (taking into account only seven element recoveries and treatment of a volume of 1000 m³/d) for three types of brines ranged between 1 and 11 million euros, compared to between 3.6 and 9.3 million euros when ASE&C is employed with seawater. The treatment of greater volumes for seawater desalination would increase these numbers significantly. ASE&C supposes a solution coupled (or not) to desalination plants to reduce the ecological impacts associated with brine discharges to zero, obtaining two significant commercial byproducts: (seawater: freshwater and commercial elements Br, Ca, Cs, Cl, NaOH, Mg, N, K, Rb, Na, Sr, Li, U, B, Sr, Ga, etc.; aquifers: a larger list than for saltwater, depending on the nature of the water body). It can solve environmental issues associated with brine discharge, with null CO₂ emissions (renewable energy) and profitable (i.e., with no costly pretreatment) technology. Full article

The Reshui area, located to the northeast of the Qinghai–Tibet Plateau, exhibits complex geological conditions, well-developed structures, and strong hydrothermal activities. The distribution of hot springs within this area is mainly controlled by faults. In this paper, five hot springs from the area were taken as the research object. We comprehensively studied the geochemical characteristics and genetic mechanism of the geothermal water by conducting a field investigation, hydrogeochemistry and environmental isotopic analysis (⁸⁷Sr/⁸⁶Sr, δ²H, δ¹⁸O, ³H). The surface temperature of the geothermal water ranges from 84 to 91 °C. The geothermal water in the area exhibits a pH value ranging between 8.26 and 8.45, with a total dissolved solids’ (TDS) concentration falling between 2924 and 3140 mg/L, indicating a weakly alkaline saline nature. It falls into the hydrochemical type CI-Na and contains a relatively high content of trace components such as Li, Sr, B, Br, etc., which are of certain developmental value. Ion ratio analysis and strontium isotope characteristics show that the dissolution of evaporite minerals and carbonate minerals serves as a hot spring for the main source of solutes. Hydrogen and oxygen stable isotope characteristics findings indicate that the geothermal water is primarily recharged via atmospheric precipitation. Moreover, the tritium isotopic data suggest that the geothermal water is a mixture of both recent water and ancient water. Moreover, the recharge elevation is estimated to be between 6151 and 6255 m. and the recharge area is located in the Kunlun Mountains around the study area. The mixing ratio of cold water, calculated using the silicon enthalpy equation, is approximately 65% to 70%. Based on the heat storage temperature calculated using the silicon enthalpy equation and the corrected quartz geothermal temperature scale, we infer that the heat storage temperature of geothermal water in the area ranges from 234.4 to 247.8 °C, with a circulation depth between 7385 and 7816 m. The research results are highly valuable in improving the research level concerning the genesis of high-temperature geothermal water in Reshui areas and provide essential theoretical support for the rational development and protection of geothermal resources in the area. Full article

Polyamic acid (PAA) is the precursor of polyimide (PI), and its solution’s properties have a direct influence on the final performances of PI resins, films, or fibers. The viscosity loss of a PAA solution over time is notorious. A stability evaluation and revelation of the degradation mechanism of PAA in a solution based on variations of molecular parameters other than viscosity with storage time is necessary. In this study, a PAA solution was prepared through the polycondensation of 4,4′-(hexafluoroisopropene) diphthalic anhydride (6FDA) and 4,4′-diamino-2,2′-dimethylbiphenyl (DMB) in DMAc. The stability of a PAA solution stored at different temperatures (−18, −12, 4, and 25 °C) and different concentrations (12 wt% and 0.15 wt%) was systematically investigated by measuring the molecular parameters, including M_w, M_n, M_w/M_n, R_g, and [η], using gel permeation chromatography coupled with multiple detectors (GPC-RI-MALLS-VIS) in a mobile phase 0.02 M LiBr/0.20 M HAc/DMF. The stability of PAA in a concentrated solution decreased, as shown by the reduction ratio of M_w from 0%, 7.2%, and 34.7% to 83.8% and that of M_n from 0%, 4.7%, and 30.0% to 82.4% with an increase of temperature from −18, −12, and 4 to 25 °C, respectively, after storage for 139 days. The hydrolysis of PAA in a concentrated solution was accelerated at high temperatures. Notably, at 25 °C, the diluted solution was much less stable than the concentrated one and exhibited an almost linear degradation rate within 10 h. The M_w and M_n decreased rapidly by 52.8% and 48.7%, respectively, within 10 h. Such faster degradation was caused by a greater water ratio and less entanglement of chains in the diluted solution. The degradation of (6FDA-DMB) PAA in this study did not follow the chain length equilibration mechanism reported in literature, given that both M_w and M_n declined simultaneously during storage. Full article

Absorption cooling technologies converting excess heat and renewable heat resources to cooling energy have shown progress in recent years. In this study, two 400 kW LiBr solution absorption chiller types with series and parallel connected are analyzed over a range of parameter values to better understand their applicability for different uses. Thermodynamic models for the components were constructed and validated. The performance of the chillers related to heat transfer, energy, exergy, and economy performance was comprehensively analyzed. The operating performance was investigated by considering the external variables, including inlet cooling water, chilled water, and inlet steam temperatures and the solution allocation ratio. The results indicate that the parallel connected chiller reaches higher energy and exergy performance than the series-connected chiller, but the heat transfer and economic performance was lower. The coefficient of performance and the exergy efficiency of the parallel chiller were for the reference system 1.30 and 24.42%, respectively. Except for the exergy efficiency, the inlet steam and inlet chilled water temperature had positive impact on the heat transfer, energy, and economic performance, while the inlet cooling water temperature trends the opposite. The sensitivity analysis on solution allocation ratio showed that a higher ratio decreases the heat transfer and economic performance, but considering the energy and exergy performance, a suitable allocation ratio would be 0.54. Full article

For absorption cooling cycles using water as a refrigerant, H₂O/LiCl mixtures are suitable for replacing conventional H₂O/LiBr mixtures. In addition, membrane devices can be used to develop compact and lighter absorption systems, and they can operate with H₂O/LiCl mixtures. The present paper describes an experimental evaluation of a membrane desorber/condenser operating at atmospheric pressure. Two operation modes were analyzed: continuous cycle operation and intermittent operation. For the first operation mode, the maximum desorption rate was 3.49 kg/h·m², with a solution temperature of 90.3 °C and a condensation temperature of 25.1 °C. The lowest desorption rate value was 0.26 kg/h·m², with a solution temperature of 75.4 °C and a condensation temperature of 40.1 °C. In the second mode, after three operating hours, the refrigerant fluid produced, per 1 m² of membrane area, 7.7, 5.6, 4.3, and 2.2 kg, at solution temperatures of 90.3, 85.3, 80.4, and 75.4 °C, respectively. A one-dimension heat and mass transfer model is presented. The calculated values of desorption rate and outlet temperatures were compared with the experimental data; a square correlation coefficient of 0.9929 was reached for the desorption rate; meanwhile, for the outlet solution temperatures and the outlet cooling-water temperatures, a square correlation coefficient up to 0.9991 was achieved. The membrane desorber has the advantages of operating at atmospheric-pressure conditions, high condensation temperature, the ability to use different saline solution working mixtures, and different operation methods. These advantages can lead to new absorption systems. Full article

In membrane distillation, the vapor pressure difference is the driving force of mass transfer. The vapor pressure is generally assumed by the saturation pressure and calculated by the Antoine equation. However, in the actual operation process, the feed solutions usually flow in a non-equilibrium state, which does not meet the theoretical and measurement conditions of the vapor-liquid equilibrium (VLE) state. This study tested the actual water vapor pressure of the pure water, lithium bromide (LiBr) solution, lithium chloride (LiCl) solution, and calcium chloride (CaCl₂) solution under different flow conditions. The results showed that the actual water vapor pressure was lower than the saturation pressure overall, and the difference increased with temperature but decreased with the mass concentration. Therefore, in vacuum membrane distillation (VMD), air gap membrane distillation (AGMD), and sweeping gas membrane distillation (SGMD), the membrane flux calculated by water vapor saturation pressure was higher than the actual membrane flux, and the relative difference decreased and was less than 10% after 60 °C. In direct contact membrane distillation (DCMD), the water vapor pressure difference on both membrane sides was almost the same by using the saturation vapor pressure or the tested data since the pressure errors were partially offset in parallel flow or counter-flow modes. Full article

Polyhemiaminal (PHA) polymers are a new class of thermosetting polymers that have recently gained attention owing to their high mechanical strength and excellent recycling behavior. However, low thermal stability is a common issue in PHA polymers due to the thermally labile crosslinked knots. Herein, crosslinked PHA polymer composites were synthesized by reacting formaldehyde with a precursor solution of 4,4ʹ-oxydianiline (ODA) and cyclodextrins (CDs) (α-, β-, and γ-). The material obtained under optimal conditions (ODA:CD molar ratio of 1:0.5, 37% aqueous solution of formaldehyde (formalin)) exhibited good film formability and high thermal stability with two characteristic decomposition phenomena and a high char yield. The early decomposition of CDs and char formation led to high thermal stability. Time-resolved NMR analysis was conducted to study hemiaminal bond formation via a condensation reaction between ODA and formaldehyde. Furthermore, PHA matrix formation was confirmed by the dissolution of the deposited CD layer in a solution of N-methyl-2-pyrrolidinone containing 8–9 wt.% LiBr at 80 °C and FTIR analysis. Based on the elemental analysis results, PHA network formation was confirmed by considering a single unit of the PHA network with CD composition, including the solvent and water. Full article