Gas turbine waste heat driven multiple effect absorption system

In this article, two arrangements of the multiple effect absorption (MEA) type are presented. They are using LiBr-H₂O and are powered by the exhaust of gas turbines. The first arrangement (MEA-I) is used as a cooling device and is coupled to an engine that drives a VC cooling unit. The other one (MEA-II) is used as a solution concentration machine and is coupled to an engine that drives a RO unit.Thermodynamic analysis for MEA-I showed a COP_t of 1.31 and 2.18 for evaporation temperatures of 5°C and 14°C respectively. Relative to the VC, the MEA-I increased the cooling capacity by 65% and 77% with payback periods of 35 months and 29 months for evaporation temperatures of 5°C and 14°C respectively.The MEA-II is analyzed using sea water as an example for a water based solution. Relative to a gas turbine driven RO desalination unit the MEA-II increased the fresh water produced by 13.5%. As a solution concentration machine the MEA-II requires 28% of the heat of evaporation with a solution top temperature of 36°C which makes it equivalent to a machine with five evaporators, where the solution top temperature reaches 66°C. Based on selling the released solvent byproduct water alone, the MEA-II would have a payback period of 77 months.     

Refuse-fired,pressurized, fluidized-bed combustion combined cycle analysis

Use of pressurized, fluidized-bed combustion (PFBC) has given a new opportunity to use municipal refuse as fuel for combined gas and steam power cycles keeping the pollutants of sulphur and nitrogen oxides to a minimum at reduced capital cost.In combined gas and steam power cycles, the heat energy in the exhaust gases of a simple gas turbine cycle is used to generate steam in a waste-heat boiler and the generated steam is used in the steam turbine for power generation.The effects of gas turbine pressure ratio and inlet temperature on the main parameters of refuse-fired, pressurized, fluidized-bed combustion combined cycles are determined.The results indicate a maximum combined cycle thermal efficiency and work output at a possible range of optimum pressure ratios between 10 and 12 for a range of gas turbine inlet temperatures of 750–1000°C.     

Experiments on an absorption refrigeration system powered by a solar pond

A heat source at temperatures not higher than 80°C was used to simulate the heat input to an absorption refrigerator from a solar pond. A laboratory model of an absorption refrigerator, using an ammonia-water solution at 52% concentration by weight, was operated intermittently using this heat source. Generation temperatures as high as 73°C and evaporation temperatures as low as −2°C were obtained. Tap water was used to remove the heat generated from the condensation of the ammonia vapour and the absorption of the refrigerant in the water. The temperature of the tap water was near the ambient laboratory temperature of 28°C. The COP for this unit working under such conditions was in the range 0.24–0.28.     

Messung der spezifischen Wärme und der Fehlordnungsenergie von amorphen Blei-Wismut-Schichten

Amorphous Pb-Films with a 30 atomic-% Bi-content are produced by evaporation onto a cooled Be-foil at 20 °K in high vacuum. The specific heat of these films in the temperature range from 5–8 °K is found to be 1.6 times larger than after crystallization, which takes place during warming up between 30 and 40 °K. The stored energy released during this crystallization amounts to 1.5 kcal/mol.     

Enhancing gas turbine performance by intake air cooling using an absorption chiller

The performance of gas turbines, operated either as a simple cycle or a combined cycle, is critically constrained by the prevailing ambient temperature, particularly in arid and tropical climates. This paper investigates the option of cooling the intake air to the compressor of the gas-turbine system using an absorption chiller in order to increase the gas turbine capacity. High-temperature waste heat from the exhaust gas may be utilized to produce steam in a recovery boiler. Part of the steam produced could then be used to drive a lithium-bromide double-effect absorption chiller which in turn could cool the incoming air. An analysis carried out by taking the weather data of Bangkok (Thailand) indicates that reducing the temperature from ambient condition to 15°C could help to increase the instantaneous power output between 8 and 13%. As an outcome, as much as 11% additional electricity could be generated from the same gas turbine power plant.A simple economic assessment indicates that the proposed scheme will require a minimal investment as compared to the commissioning cost of a new gas turbine unit to meet the corresponding capacity increment. The latter will need nearly four times higher initial cost than the amount estimated for the proposed scheme. Thus, implementation of such a system would significantly abate the negative impact of the ambient temperature, while providing an economically and environmentally attractive option for energy producers in most developing nations of the world which are located in arid and tropical zones.     

On the disintegration energies of174Lu isomers

The cross section of⁴He for elastic electron scattering has been measured relative to that of the proton using a gas target with helium, hydrogen or a mixture of both gases. Scattering angles were between 56° and 130°, and the energy varied from 30 to 59 MeV. A model independent rms charge radius of (1.63 ± 0.04) fm has been evaluated for the α-particle.     

Modeling the Water Droplet Evaporation Processes with Regard to Convection,Conduction and Thermal Radiation

A predictive model was developed for investigation of high-temperature heating and evaporation of water droplets. The model takes into account the basic interrelated processes of heat transfer and phase transitions. Typical velocity and temperature profiles were found in the high-temperature gas–water droplet system with external gas medium temperature varied from 100 to 800°C. Various formulations of the problem, significantly different in the type of considered processes and factors, are considered.We analyzed temperature conditions of heating and evaporation of water droplets, which allow the use of simplified models and which need consideration of all complex interrelated processes of heat and mass transfer (including convection, conduction and radiant heat transfer in droplets, and also in the surface vapor–gas layer).     

Flow patterns and heat-transfer characteristics of a top heat mode closed-loop oscillating heat pipe with check valves (THMCLOHP/CV)

The aim of this research was to investigate the flow patterns and heat transfer of a top heat mode closed-loop oscillating heat pipe with check valves (THMCLOHP/CV). In this study, the heat pipe was made of a high-quality glass capillary tube with an inner diameter of 2.4 mm bent into 10 meandering turns. The number of check valves was 2 and the tube was filled with R141b at a filling ratio of 50% of internal volume of the tube. The combined lengths of the evaporator, adiabatic and condenser sections were equal to 50 mm. The pipe was operated at the top heat mode, and the angles of inclination were 20°, 40°, 60°, 80°, and 90°. The heat applied at the evaporator section was controlled at 85°Cto 105°C, and 125°C. The results show that in the evaporator section, bubbles are produced and grow as a result of the continuous nucleate boiling. They coalesced and their volume expanded. Similarly, in the condenser section the vapor plug condensate caused the bubbles to collapse and accumulate as a liquid mass at the lower section of the U-bend tube. A new slug then developed and the bubbles coalesced in an upward flow. Heat flux increased when the evaporator temperature and inclination angle increased causing the average length of the vapor plug to decrease and the average velocity of vapor plug to increase. The maximum heat flux occurred at an evaporator temperature of 125°C and an inclination angle of minus 90°.     

Energy conservation in the refinery by utilizing reformed fuel gas and furnace flue gases

Decrease of fuel supplies and cost increases make it vital for industries, especially energy intensive ones, to consider conserving available sources and convert losses into sources of energy.In this paper, a gas turbine-based cogeneration system is suggested to utilize a refinery's reformer gas in the gas turbine, and furnaces flue gases together with the engine exhaust gases in a heat recovery steam generator, HRSG. This is proposed as an alternative to the currently used system where the gas turbine and the steam generator are used separately. Operating variables comprising compressor pressure ratio and turbine inlet temperature are varied widely to evaluate performance; namely power, SFC, overall efficiency and annual fuel savings at design and off-design loading conditions using a dedicated computer program.Results show that the proposed system offers 100% higher overall efficiency and $5.25 million annual fuel saving for a 12 MW_e gas turbine.     

A mass spectrometric line for tritium analysis of water and noble gas measurements from different water amounts in the range of microlitres and millilitres

This paper describes the procedure followed for noble gas measurements for litres, millilitres and microlitres of water samples in our laboratory, including sample preparation, mass spectrometric measurement procedure, and the complete calibrations. The preparation line extracts dissolved gases from water samples of volumes of 0.2 μ l to 3 l and it separates them as noble and other chemically active gases. Our compact system handles the following measurements: (i) determination of tritium concentration of environmental water samples by the ³He ingrowth method; (ii) noble gas measurements from surface water and groundwater; and (iii) noble gas measurements from fluid inclusions of solid geological archives (e.g. speleothems). As a result, the tritium measurements have a detection limit of 0.012 TU, and the expectation value (between 1 and 20 TU) is within 0.2 % of the real concentrations with a standard deviation of 2.4 %. The reproducibility of noble gas measurements for water samples of 20–40 ml allows us to determine solubility temperatures by an uncertainty better than 0.5 °C. Moreover, noble gas measurements for tiny water amounts (in the microlitre range) show that the results of the performed calibration measurements for most noble gas isotopes occur with a deviation of less than 2 %. Theoretically, these precisions for noble gas concentrations obtained from measurements of waters samples of a few microlitres allow us to determine noble gas temperatures by an uncertainty of less than 1 °C. Here, we present the first noble gas measurements of tiny amounts of artificial water samples prepared under laboratory conditions.     

Selection of alloys and their influence on the operational characteristics of a two-stage metal hydride heat transformer

A heat transformer can upgrade heat to a higher temperature. A two-stage heat transformer has a greater temperature upgrading potential than a single-stage heat transformer, e.g. heat can be upgraded from a level of about 130–140°C to temperatures of about 200°C. A practical method to select suitable hydrides to be used in a two-stage heat transformer is presented. The example discussed shows that the selected alloys result in a reasonable operation of the two-stage heat transformer. Three different evaluation criteria viz. coefficient of performance, alloy output and temperature output, are introduced to compare the operational characteristics of heat transformers with different alloys; the influence of some metal hydride properties on the operational characteristics is also discussed.     

Enthalpy determination of order in poly(vinyl chloride)

Enthalpy measurements by means of solution microcalorimetry were obtained on a PVC resin in the temperature range 37-110°C. Enthalpy measurements above T_g detect a heat of fusion of about 1.5 cal/g of polymer and thereby demonstrate the presence of a soluble ordered structure in PVC. Enthalpy measurements on samples quenched and slow-cooled from within the temperature interval 37-220°C confirm the value of 1.5 cal/g for the heat of fusion as well as demonstrate a broad melting range of 130-200°C.     

Comparison of light-induced degradation and regeneration in P-type monocrystalline full aluminum back surface field and passivated emitter rear cells

This paper reports on a systematic and quantitative assessment of light induced degradation (LID) and regeneration in full Al-BSF and passivated emitter rear contact cells (PERC) along with the fundamental understanding of the difference between the two. After LID, PERC cells showed a much greater loss in cell efficiency than full Al-BSF cells (∼0.9% vs ∼0.6%) because the degradation in bulk lifetime also erodes the benefit of superior BSRV in PERC cells. Three main regeneration conditions involving the combination of heat and light (75 °C/1 Sun/48 h, 130 °C/2 Suns/1.5 h and 200 °C/3 Suns/30 s) were implemented to eliminate LID loss due to BO defects. Low temperature/long time (75 °C/48 h) and high temperature/short time (200 °C/30s) regeneration process was unable to reach 100% stabilization. The intermediate temperature/time (130 °C/1.5 h) generation achieved nearly full recovery and stabilization (over 99%) for both full Al-BSF and PERC cells. We discussed the effect of temperature, time and suns in regeneration mechanism for two cells.     

Study on the concentration difference heat pump using fusion and freezing processes of acetic acid-acetamide system

The concentration difference heat pump using fusion and freezing processes to generate a cold fluid has been investigated. This heat pump system utilizes the acetic acid-acetamide pair as working material, and consists of a cold fluid generating and a separation process. The operation at the cooling capacity of 3.52 kW (1 ton of refrigeration) has been investigated in this study. At the cold fluid generating process, solid acetic acid at 15°C is fused into an acetamide solution at 15°C, such that the temperature and the concentration of acetamide of the solution decreases. This dilute solution at lower temperature can be used to generate a cold fluid. The lowest attainable temperature of the solution has been investigated experimentally, and also calculated from the energy balance equation. The decreasing rates of the temperature have also been studied. At the separation process, continuous distillation is adopted to concentrate the dilute solution sent from the cold fluid generating process. The data which support the possibility of separation by continuous distillation are presented. The energy demand at the separation process is investigated theoretically.     

Gas turbine exhaust gas heat recovery at South Baghdad (Iraq) power plant

Gas turbine exhaust is usually relatively clean, especially the exhaust from natural gas turbines. The use of such gases to improve the overall thermal efficiency of a steam power plant has the advantage of reducing the cost of cleaning the equipment and reducing the maintenance costs of the heat recovery equipment used in the application.In this paper, two proposals for recovering the waste energy of the exhaust gases from a gas turbine unit, fuelled by natural gas at south Baghdad Power Plant (Iraq) are discussed. The proposals cover improvements to the thermal efficiency of a steam power plant installed near the gas turbine unit. The first proposal is to use the exhaust gases to preheat the feed water at four feed water heaters, in order to increase the power output. This arises because of the savings in the amount of steam extracted at a different level used for preheating the feed water line. The second proposal is to use the thermal energy in the exhaust gases to reheat the extracted stream, at five points at a high thermal potential, to increase the thermal gain at the preheating feed water line. This avoids the complexity associated with rejection of the extracted steam. The first roposal shows that a 1.22–14.9% saving in fuel consumption is achievable and the overall thermal efficiency of the steam power plant becomes 29–34% (at different gas turbine plant loads). The second proposal shows that a 2.3–7.35% saving in fuel consumption can be attained and the corresponding thermal efficiency will be 30.3–32%.     

Natural Convection from a Corrugated Heated Surface at the Bottom of Vented Rectangular Enclosure

Natural convection heat transfer characteristics enclosures from a tilted rectangular enclosure heated at the corrugated bottom wall and vented by uniform slots opening at the top wall are experimentally investigated. The experiments were carried out to study the effects of the angle of opening of the corrugated surface, opening ratio, enclosure's tilt angle, and Rayleigh number on the passive cooling of the enclosure. The experiments were carried out at Rayleigh numbers ranging from 2 × 10⁸ to 1.52 × 10⁹ for enclosure tilt angles ranging from 0° to 90° and angle of opening of corrugated surface ranging from 0° to 25°. The top venting arrangement was studied at different opening ratios of 1, 0.75, 0.5, and 0.25. The results gave an optimum angle of opening of the corrugated surface at which Nusselt number is maximum.     

Hybrid inorganic–organic proton conducting membranes for fuel cells and gas sensors

We developed new fast proton conducting membranes based on a hybrid inorganic–organic phosphosilicate polymer synthesized from othophosphoric acid, dichlorodimethylsilane, and tetraethoxysilane. The membranes were amorphous, translucent, and flexible. A high concentration of –OH groups and short distances between them promoted fast proton conductivity in dry atmosphere at increased temperatures. The proton conductivity was measured using the electrochemical impedance spectroscopy. Its value increased with rising temperature following the Arrhenius dependence with the activation energy 20 kJ/mol. In dry conditions at 120 °C, the conductivity was 1.6 S/m. The tests in a H₂/O₂ fuel cell confirmed that the membrane was able to operate at temperatures from 100 to 130 °C using dry input gas streams. The cell performance significantly improved with increasing temperature. The membrane was also tested in a potentiometric gas sensor with the TiH_x reference electrode and the Pt sensing electrode. The sensor exhibited fast, stable, and reproducible response to dry H₂ and O₂ gases at temperatures above 100 °C. We expect the application of our membrane in intermediate temperature fuel cells and gas sensors operating in dry conditions.     

Laboratory investigations of back discharge in multipoint–plane geometry in flue gases

The paper presents investigations of back discharge occurring in air and flue gases produced by the process of burning of LPG (Liquefied Petroleum Gas) or charcoal at temperature ranging from 20 to 120 °C. The discharge was generated between a charge-emitting multipoint electrode and a plate covered with fly-ash layer. Current–temperature characteristics were determined for this system. The aim of this work was to determine an effect of back discharge on morphology of fly-ash layer and gas composition. It was noticed that flue gases leaving the back-discharge zone contains increased amount of NO_x and CO compounds.     

Flow on blades of wells turbine for wave power generation

Wells turbine has the cascade whose stagger angle is 90°, namely the blades are perpendicular to the axial velocity. Good performance is required from 0° to 90° angle of attack because the turbine is operated in the oscillating airflow produced with wave energy. Furthermore, very interesting and complex flows are experimentally observed by the oil film method for large angles of attack where the performance is strongly influenced, especially, the self-starting. This paper tries to analyze the mechanism of these three-dimensional flows around the turbine with the flow visualization and the numerical analysis, focusing on the off-design condition.     

Effect of Coolant Temperature on the Condensation Heat Transfer in Air-Conditioning and Refrigeration Applications

This article directly investigates the effect of a cooling medium's coolant temperature on the condensation of the refrigerant R-134a. The study presents an experimental investigation into condensation heat transfer, vapor quality, and pressure drop of R-134a flowing through a commercial annular helicoidal pipe under the severe climatic conditions of a Kuwait summer. The quality of the refrigerant is calculated using the temperature and pressure obtained from the experiment. Measurements were performed for refrigerant mass fluxes ranging from 50 to 650 kg/m²s, with a cooling water flow Reynolds number range of 950 to 15,000 at a fixed gas saturation temperature of 42°C and cooling wall temperatures of 5°C, 10°C, and 20°C. The data shows that with an increase of refrigerant mass flux, the overall condensation heat transfer coefficients of R-134a increased, and the pressure drops also increased. However, with the increase of mass flux of cooling water, the refrigerant-side heat transfer coefficients decreased. Using low mass flux in a helicoidal tube improves the heat transfer coefficient. Furthermore, selecting low wall temperature for the cooling medium gives a higher refrigerant-side heat transfer coefficient.