Energy and exergy analysis and optimization of a gas turbine cycle coupled by a bottoming organic Rankine cycle

Journal of Thermal Analysis and Calorimetry - In this study, the numerical analysis of energy and exergy has been performed for a gas turbine cycle coupled with an ORC cycle. Validation of current...     

Design and analysis of a hybrid concentrated photovoltaic thermal system integrated with an organic Rankine cycle for hydrogen production

Journal of Thermal Analysis and Calorimetry - Solar is one of the most promising energy sources because of the abundance of solar radiation in certain parts of the world. One of the main limiting...     

Energy,exergy, and sensitivity analyses of a new integrated system for generation of liquid methanol,liquefied natural gas,and crude helium using organic Rankine cycle,and solar collectors

Journal of Thermal Analysis and Calorimetry - The increasing growth of helium consumption in industries and the limited resources of this element are the challenges that industries will face in the...     

Energy and exergy analyses of nanofluid-filled parabolic trough solar collector with acentric absorber tube and insulator roof

Journal of Thermal Analysis and Calorimetry - Increasing the energy demands has encouraged the development of novel archetypes solar receiver employed in sustainable energies. Parabolic trough...     

Thermodynamic analysis of waste heat recovery from hybrid system of proton exchange membrane fuel cell and vapor compression refrigeration cycle by recuperative organic Rankine cycle

Journal of Thermal Analysis and Calorimetry - According to day-by-day consumption increase, energy high costs and nonrenewable energy destroying effects, clean technologies such as fuel cells lead...     

Performance analysis and multi-objective optimization of an organic Rankine cycle with binary zeotropic working fluid employing modified artificial bee colony algorithm

From a thermal point of view, zeotropic mixtures are likely to be more efficient than azeotropic fluids in low-temperature power cycles for reduction in exergy destruction occurring during heat absorption/rejection processes due to their suitable boiling characteristics. In this study, comprehensive energetic and exergetic analyses are mathematically performed for an organic Rankine cycle (ORC) system employing a potential binary zeotropic working fluid, namely R717/water. For this purpose, initially mass, energy, and exergy balance equations are derived. With regard to the similarity in molar mass of R717 (17.03 g mol^?1) and water (18.01 g mol^?1), there is no need to alter the size of the ORC components such as turbine and pump. In order to achieve the optimal thermal and exergy efficiencies of the ORC system, modified version a powerful and relatively new optimization algorithm called artificial bee colony (ABC) is used taking into account different effective constraints. The main motivation behind using ABC lies on its robustness, reliability, and convergence rate speed in dealing with complicated constrained multi-objective problems. Convergence rates of the algorithm for optimal calculation of the efficiencies are presented. Subsequently, due to the importance of exergy concept in ORC systems, exergy destructions occurring in the components are computed. Finally, the impacts of pressure, temperature, mass fraction, and mass flow rate on the ORC thermal and exergy efficiencies are discussed.

     

Sampling and gas chromatographic analysis of volatile organic compounds in hot and extremely humid emissions

Adsorptive enrichment on hydrophobic adsorbents, thermal desorption, and capillary gas-chromatographic analysis have been used to determine volatile organic compounds in extremely humid stack-gas emissions from the residential burning of brown-coal briquets. One hundred and fifty two compounds were identified and quantified. Quantitative emission factors were determined for the identified individual compounds in relation to the amount of the fuel used. These factors enable a first assessment of the pollution of the city of Leipzig with volatile organic compounds resulting from the burning of indigenous lignite.     

Experimental analysis and exergetic assessment of the solar air collector with delta winglet vortex generators and baffles

Journal of Thermal Analysis and Calorimetry - To increase the efficiency of solar air collectors (SACs), the combined effects of baffles and delta winglet vortex generator (DWLVG) on the...     

Energy and exergy analysis of solar energy-integrated,geothermal energy-powered Organic Rankine Cycle

Journal of Thermal Analysis and Calorimetry - In this study, the energy and exergy analysis of the solar- and geothermal energy-powered Organic Rankine Cycle was made for different system...     

Large-bore coated columns for sampling and concentration of organic volatiles in air, headspace and water analysis

Large-bore coated (LBC) columns were used as sampling and concentrating traps in analyses for traces of organic volatiles in air and water. This simple technique utilizes long metal columns thinly coated with SE-30 for direct trapping of the organics. The sample is simply passed through the LBC column; the trapped organics are then thermally desorbed onto a conventional porous polymer pre-column or onto a second LBC column. If desired, this can be shorter or narrower bore than the initial LBC sampling column. The sample is finally desorbed onto the gas chromatographic column for analysis. Multiple transfers between LBC columns are possible, with increased concentration at each transfer, resulting in a "concentration pump" effect. The technique offers the advantages of great simplicity, efficiency and ease of sample transfer. Samples are obtained with low back-pressure and minimal interfering artifacts. The system shows almost complete imperturbability to moisture. Indifference to moisture and the low back-pressure enable direct sampling of very large volumes of air and even breath. Direct sampling of aqueous systems was also possible. The latter area was not fully investigated but offers potential for water pollution analysis and in direct examination of biological fluids and aqueous flavor extracts where heat sensitivity is a problem. With LBC columns the sampling and concentration sequence exposes the substances sought to no more drastic conditions than those they will be subjected to in the process of gas chromatographic analysis.     

The analysis of 1-propanol and 2-propanol in humid air samples using selected ion flow tube mass spectrometry

Following the observation that propanol is present in the breath samples of cystic fibrosis (CF) patients infected by Pseudomonas aeruginosa (PA), a study of the reactions of H(3)O(+), NO(+) and O(2) (+.) with 1-propanol and 2-propanol has been conducted using selected ion flow tube mass spectrometry (SIFT-MS). In this study the number and the distribution of the product ions from NO(+) reactions with the two propanol isomers under humid air conditions were able to differentiate between the two isomers. The reaction mechanisms and the structures of the product ions for these reactions, especially those with H(3)O(+) and NO(+), have been proposed. As an example, 2-propanol was shown to be present in a breath sample from one CF patient infected with PA, and also in a PA isolate from another CF patient grown on Pseudomonas-selective media. The results of this study allow an analytical procedure to be advanced for the analysis of the two propanol isomers, which can also be utilised in other applications.     

Sampling and analysis of volatile organic compounds in air using a dualsorbent trap

Summary A dualsorbent trap containing graphitized carbon blacks was used for the collection of volatile and semi-volatile organic pollutants from the atmosphere of different workplaces and from an above-ground parking lot. The method proved to be sensitive, simple and reliable. Thermal desorption and solvent extraction methods followed by GC-MS analysis were employed.     

Evaluation of tetraglyme for the enrichment and analysis of volatile organic compounds in air

A recently developed method for the sampling and analysis of volatile organic compounds in air has been evaluated. The system is based on the enrichment of analytes in tetraethylene glycol dimethyl ether or tetraglyme, a water-soluble organic liquid. The subsequent analysis consists of dispersion of a sample aliquot in water followed by purge-and-trap and gas chromatographic separation. Physico-chemical data were investigated for 10 volatile organic compounds, providing information on the possibilities and limitations of the tetraglyme method. The target analytes included chlorinated alkanes and alkenes, and monocyclic aromatic hydrocarbons. Air/tetraglyme partition coefficients Kat were determined over an environmental relevant temperature range of 2-25 degrees C to evaluate sorption efficiencies and estimate breakthrough volumes at the sampling stage. At 2 degrees C breakthrough volumes (allowing 5% of breakthrough) ranged from 5.8 (1,1-dichloroethane) to 312 l (1,1,2-trichloroethane) for 20 ml of tetraglyme. With regard to the desorption stage, the effect of tetraglyme on the air/water partition of organic compounds was investigated through the measurement of air/tetraglyme-water partition coefficients Kat-w for 2-31% (v/v) tetraglyme in water. Finally a clean-up procedure for tetraglyme was evaluated. Analysis of a blank tetraglyme-water (17:83, v:v) mixture by gas chromatography-flame ionization detection/mass spectrometry showed minor background signals. None of the target compounds were detected.     

Sample preparation for the analysis of volatile organic compounds in air and water matrices

This review summarizes literature data from the past 5 years on new developments and/or applications of sample preparation methods for analysis of volatile organic compounds (VOC), mainly in air and water matrices. Novel trends in the optimization and application of well-established airborne VOC enrichment techniques are discussed, like the implementation of advanced cooling systems in cryogenic trapping and miniaturization in adsorptive enrichment techniques. Next, focus is put on current tendencies in integrated sampling-extraction-sample introduction methods such as solid phase microextraction (SPME) and novel in-needle trapping devices. Particular attention is paid to emerging membrane extraction techniques such as membrane inlet mass spectrometry (MIMS) and membrane extraction with a sorbent interface (MESI). For VOC enrichment out of water, recent evolutions in direct aqueous injection (DAI) and liquid-liquid extraction (LLE) are highlighted, with main focus on miniaturized solvent extraction methods such as single drop microextraction (SDME) and liquid phase microextraction (LPME). Next, solvent-free sorptive enrichment receives major attention, with particular interest for innovative techniques such as stir bar sorptive extraction (SBSE) and solid phase dynamic extraction (SPDE). Finally, recent trends in membrane extraction are reviewed. Applications in both immersion and headspace mode are discussed.     

Adsorption of water vapour from humid air in carbon molecular sieves: carbosieve S-III and carboxens 569, 1000 and 1001

The adsorption of water vapour in carbon molecular sieves (CMS) used to determine volatile organic compounds (VOCs) in air was investigated. The CMS mass in the trap was found not to affect the mass of retained water under conditions of incomplete saturation of the adsorbent bed with water. Thus, the restrictions commonly imposed on the CMS mass are not necessary. The usefulness of four different CMSs to sample large volumes of humid air was estimated. Carboxen 1000 exhibited the best performance. To assess the magnitude of CMS mass in the trap in dependence on the volume, the relative humidity and the temperature of the sample, the use of a novel parameter, called the water vapour interference factor, was suggested.     

Thermal and spectroscopic characterization of several derivatives containing a new organic ring system

Several derivatives containing a new organic ring system, the tropane-6-spiro-5-hydantoin structure (namely 8-alkyl-8-azabicyclo [3.2.1.] octane-6-spiro-5-imidazoline-2,4-diones) have been characterized by thermal (DSC and simultaneous DTA-TG-DTG) and spectroscopic techniques (IR,¹ H-NMR,¹³ C-NMR). X-ray powder diffraction and elemental analysis were applied for structural and molecular characterization. All the compounds melt in the range 160–250°C and undergo decomposition with progressive mass loss after the solid-liquid thermal transition with molecular degradation. It was found that tropane-6-spiro-5-hydantoin derivatives with the hydantoin ring in position are thermally less stable than those containing this ring in position.One of the authors (Dr. M.V.) thanks partial financial support from CICYT through research project PA 86-0317. Thanks are extended to Ms. A. García and Mr. J. C. Rivero for artwork.     

Comparative analysis and multi-criteria optimization of a supercritical recompression CO2 Brayton cycle integrated with thermoelectric modules

Journal of Thermal Analysis and Calorimetry - Regarding the high expense of the exploiting energy from energy resources, each innovation or modification on the energy systems with the aim of...     

A versatile and uncomplicated method for the analysis of volatile organic compounds in ambient urban air

A method was developed for sampling and selective quantitative determination of typical volatile organic compounds (VOCs) in ambient urban air. A mobile and self-contained dual-channel air sampling tool based on solid phase adsorption was constructed. A simple calibration procedure circumventing the adsorption/desorption process was designed. The method was validated for seven “key-analytes”: n-hexane, 3-methyl-2-pentene, benzene, tetrachloroethene, styrene, 1,2,4-trimethylbenzene and acetophenone. The complete air sampling equipment is easily accommodated in a business suitcase. The lower limits of the practical working ranges are between 0.1 μg m^–3 (tetrachloroethene) and 1.2 μg m^–3 (benzene). Air samples were collected at a location in Salzburg with heavy motor vehicle traffic and measured in order to prove a satisfactory method performance under practical monitoring conditions.     

A versatile and uncomplicated method for the analysis of volatile organic compounds in ambient urban air

A method was developed for sampling and selective quantitative determination of typical volatile organic compounds (VOCs) in ambient urban air. A mobile and self-contained dual-channel air sampling tool based on solid phase adsorption was constructed. A simple calibration procedure circumventing the adsorption/desorption process was designed. The method was validated for seven “key-analytes”: n-hexane, 3-methyl-2-pentene, benzene, tetrachloroethene, styrene, 1,2,4-trimethylbenzene and acetophenone. The complete air sampling equipment is easily accommodated in a business suitcase. The lower limits of the practical working ranges are between 0.1 μg m^–3 (tetrachloroethene) and 1.2 μg m^–3 (benzene). Air samples were collected at a location in Salzburg with heavy motor vehicle traffic and measured in order to prove a satisfactory method performance under practical monitoring conditions. Received: 4 January 1998 / Revised: 14 September 1998 / Accepted: 21 October     

Capillary columns in series for GC analysis of volatile organic pollutants in atmospheric and alveolar air

Analysis of volatile organic compounds in air samples requires high resolution capillary gas chromatography. When the sample contains both polar and non-polar compounds, use of only one type of stationary phase can be unsuitable if it leads to the preferential separation of one kind of component having the same polarity at the expense of the separation of other classes of component. This paper describes the coupling of fused silica capillary columns of different polarity and length in order to achieve the separation of such complex mixtures. The combination is evaluated with a 42 component standard mixture and then applied to various atmospheric air samples and alveolar air of exposed subjects to demonstrate the capabilities of the complete sampling and separation technique.