The Experts below are selected from a list of 177 Experts worldwide ranked by ideXlab platform

Satha Aphornratana - One of the best experts on this subject based on the ideXlab platform.

  • Experimental study of a sliding vane expander in a micro-scale ORC system for utilizing low-grade heat
    Energy Procedia, 2017
    Co-Authors: Worakit Suankramdee, Tongchana Thongtip, Satha Aphornratana
    Abstract:

    Abstract In the other study of the authors, the sliding vane expander, was developed successfully. It was workable satisfactorily and provided an acceptable performance for a certain working condition. In this present study, performance of the sliding vane expander with a wider range of operating conditions is observed and examined. The Boiler Temperature is varied from 70 to 90°C while the condensation Temperature is varied between 34 to 42°C. This range of condensation Temperature is consistent with hot climate such as Thailand. The results show that at the Boiler Temperature of 90°C and condensation Temperature of 34°C, torque of the expander increases with a decrease in the rotational speed. The shaft power and efficiency initially increase with a decrease in the rotational speed until reaching the optimal point. Later, they decrease as the rotational speed continue to decrease. The optimal point indicates the highest possible shaft power and efficiency at which the expander is able to produce for one particular operating condition. It is also found that an increase of condensation Temperature and decrease in Boiler Temperature cause the optimal point of shaft power and efficiency reducing. The mass flow rate increases with rotational speed. At identical rotational speed, a decrease in the Boiler Temperature results in a decrease of torque, shaft power, mass flow rate, and efficiency. An increase of the condenser Temperature causes a decrease of torque, shaft power, and efficiency. Meanwhile, the mass flow rate is kept constant. The maximum power output of 185W and efficiency of 1.57% are obtained at the 4,100 rpm.

  • investigation and improvement of ejector refrigeration system using computational fluid dynamics technique
    Energy Conversion and Management, 2007
    Co-Authors: Kulachate Pianthong, Wirapan Seehanam, Masud Behnia, Thanarath Sriveerakul, Satha Aphornratana
    Abstract:

    Abstract Ejector refrigeration systems are usually designed to utilize low grade energy for driving the cycle. They also have low maintenance cost because they operate without a compressor. Mainly, the ejector performance directly affects the refrigerating performance. Therefore, an investigation on the characteristics and an efficient design of the ejector are important to improve ejector refrigeration systems. In this study, the computational fluid dynamics (CFD) code, FLUENT, is employed to predict the flow phenomena and performance of CPM and CMA steam ejectors. The ejector refrigeration system, using water as the working fluid, is operated at 120–140 °C Boiler Temperature and 5–15 °C evaporator Temperature. CFD can predict ejector performance very well and reveal the effect of operating conditions on an effective area that is directly related to its performance. Besides, it is found that the flow pattern does not depend much on the suction zone because the results of axisymmetric and 3D simulation are similar. This investigation aids the understanding of ejector characteristics and provides information for designing the ejector to suit the optimum condition.

  • experimental investigation of an ejector refrigerator effect of mixing chamber geometry on system performance
    International Journal of Energy Research, 2001
    Co-Authors: Satha Aphornratana, Supachart Chungpaibulpatana, Pongsid Srikhirin
    Abstract:

    This paper describes an experimental study of an ejector refrigeration cycle using R11 as the working fluid. The system was tested with Boiler Temperature from 100 to 110°C, the condenser Temperature from 35 to 41°C, and the evaporator Temperature up to 12°C. Two different mixing chambers with throat diameter of 8 mm were used. Choking of the fluid was always found in the first mixing chamber, but not in the second one. The system was more flexible to operate when there was no choking in the mixing chamber. A cooling Temperature as low as −5°C could be obtained with COP between 0.1 and 0.25 and cooling capacity between 500 and 1700 W. Copyright © 2001 John Wiley & Sons, Ltd.

Saffa Riffat - One of the best experts on this subject based on the ideXlab platform.

  • theoretical studies of a hybrid ejector co2 compression cooling system for vehicles and preliminary experimental investigations of an ejector cycle
    Applied Energy, 2013
    Co-Authors: Xiangjie Chen, Siddig Omer, Mark Worall, Saffa Riffat
    Abstract:

    This paper presents theoretical investigations into a hybrid ejector and CO2 vapour compression (VC) system for road transport cooling. The purpose is to utilise the waste heat from exhaust gas and the VC sub-system to drive the ejector system, whose cooling effect will be employed to subcool the VC sub-system. Exploitation of the energy consumption ratio between ejector sub-system and CO2 VC sub-system indicated that the more energy obtained from exhausted gas, the better system performance could be achieved for CO2 VC sub-system, and hence higher cooling capacity of the VC sub-system at the same compression power. Thermodynamic simulations of two sub-systems and the hybrid system were presented. The results indicated that, at Boiler Temperature of 120°C, evaporator Temperature of 10°C, a COP of 0.584 was achieved for hybrid system, with 22% improvement over a single ejector cycle. Preliminary experimental studies were carried out on a single ejector cycle, with Boiler Temperatures between 115°C and 130°C, and evaporator Temperatures between 5°C and 10°C. The effects of various operation conditions on the overall ejector operation were coherently analysed. The COP of the ejector sub-system from experimental results was approximately 85% compared with simulation results, which showed a good agreement between theoretical analysis and experimental results.

  • Experimental investigation of a novel steam ejector refrigerator suitable for solar energy applications
    Applied Thermal Engineering, 2010
    Co-Authors: Xiaoli Ma, Wei Zhang, Siddig Omer, Saffa Riffat
    Abstract:

    Abstract The paper presents the results of an experimental investigation of a novel steam jet refrigerator suitable for solar energy applications. The primary flow of the ejector is controlled using a spindle in order to provide fine tuning and for ejector operation as well as optimum coefficient of performance. The influence of the spindle position, and the Boiler Temperature, as well as that of evaporating Temperature which denotes the cooling load Temperature, on the performance of the ejector is assessed.

Husain Mohammed Almuslim - One of the best experts on this subject based on the ideXlab platform.

  • thermodynamic analysis of reheat cycle steam power plants
    International Journal of Energy Research, 2001
    Co-Authors: Ibrahim Dincer, Husain Mohammed Almuslim
    Abstract:

    In this study, a thermodynamic analysis of a Rankine cycle reheat steam power plant is conducted, in terms of the first law of thermodynamic analysis (i.e. energy analysis) and the second law analysis (i.e. exergy analysis), using a spreadsheet calculation technique. The energy and exergy efficiencies are studied as 120 cases for different system parameters such as Boiler Temperature, Boiler pressure, mass fraction ratio and work output. The Temperature and pressure values are selected in the range between 400 and 590°C, and 10 and 15 MPa, being consistent with the actual values. The calculated energy and exergy efficiencies are compared with the actual data and the literature work, and good agreement is found. The possibilities to further improve the plant efficiency and hence reduce the inefficiencies are identified and exploited. The results show how exergy analysis can help to make optimum design decisions in a logical manner. Copyright © 2001 John Wiley & Sons, Ltd.

Moed D.h. - One of the best experts on this subject based on the ideXlab platform.

  • Organic Contaminants and Treatment Chemicals in Steam-Water Cycles: Thermal stability, decomposition products and flow-accelerated corrosion
    2015
    Co-Authors: Moed D.h.
    Abstract:

    Boiler feedwater and steam have to be of high purity, because of the susceptibility of the steam-water cycle to corrosion. Organic contaminants break down in Boilers by hydrothermolysis, leading to the formation of organic acid anions, which are suspected to cause corrosion of steam-water cycle components. The impact and behavior of organic decomposition products in the steam-water cycle are not well understood. While guidelines for organic contaminants are becoming stricter, organic treatment chemicals are gaining popularity. Some alkalizing amines show potential for protecting steam-water cycles against corrosion, but their thermal stability is limited and acidic decomposition products are a concern. There are no official guidelines for the application of alkalizing amines in fossil-fired plants, because their thermal stability in the hottest sections of the plant is unknown. This thesis aims to contribute to well-founded guidelines for organic contamination and amine application in steam-water cycles to facilitate effective water treatment and chemical dosing. It does so by investigating the thermal decomposition of organic contaminants and treatment chemicals and using results to conduct corrosion experiments. To investigate hydrothermal reactions both batch and continuous flow reactors were tested, and it was concluded that the latter are better at investigating (hydro)thermolysis of organic treatment chemicals. A flow reactor gives precise control over retention time, Temperature and pressure and these parameters can be changed much faster than with a batch reactor. The flow reactor was the basis for virtually all thermal stability and decomposition experiments described in this thesis. It was found that lower heating rates give more organic acid anions as degradation products of organic carbon, both in quantity and species variety. Thermal stability of the decomposition products determines which of these products is most prevalent. As Boiler Temperature increased, acetate became the dominant degradation product, due to its higher thermal stability. Shorter retention times led to more variety and quantity of organic acid anions, due to a lack of time for the thermally less stable ones to degrade. The absence of oxygen increased the thermal stability of decomposition products. The (hydro)thermolysis of monoethylene glycol and slurry oil produced up to a few hundred ppb acetate and formate. The (hydro)thermolysis of polyethylene glycol produced a high variety and quantity of organic acid anions, that could only partially be determined to be in the lower ppm range. The (hydro)thermolysis of the water dissolvable fraction of gasoil, naphtha and hydro wax did not lead to an increase in organic acid anions. Methyl ethyl ketoxime thermally degraded into several organic acid anions and nitrite in the higher ppb or lower ppm range. By using the flow reactor to investigate amine thermal stability, it was concluded that thermolysis under superheater conditions was more rapid than hydrothermolysis under Boiler conditions. Anionic decomposition products increased linearly over time, while the thermal decomposition of morpholine followed first order kinetics. Metal catalysis of amine thermolysis caused by oxides on the inner surface of superheater tubes was investigated by using varying sizes and elemental composition. Kinetics of morpholine and ethanolamine thermolysis decreased as the tube size increased. The relation between the surface:volume ratio and the degradation rate constant was linear. Although results varied between the two applied tubing materials, there is no consistent trend that can link thermolysis kinetics to tube wall composition. The thermolysis of five alkalizing amines and two organic acids was comprehensively tested at superheater conditions. Morpholine, ethanolamine, cyclohexylamine, dimethylamine, 3-methoxypropylamine and acetic acid were shown to undergo thermolysis according to first order kinetics. The activation energy, prefactor and activation volume were obtained from the experimental data for all investigated amines. Dimethylamine did not fully degrade, in spite of longer retention times being applied, suggesting synthesis may occur. Formic acid is very unstable under steam water cycle conditions. It is still found in high Temperature and pressure steam-water cycles, though, and therefore it could be hypothesized that it is synthesized in the condensing stages. Acetic acid has higher thermal stability than all other tested compounds and is therefore the dominant organic acid anion at high Temperatures. Cationic degradation products were ammonia and some amines, meaning that the complete thermolysis of an amine does not necessarily lead to acidic conditions, as the formed ammonia also provides protection. A model was constructed to predict the thermal stability of the amines in steam-water cycle. More plant data is necessary to fully validate the model. Runs conducted with an experimental two-phase flow-accelerated corrosion loop showed a linear relation between liquid film pH and obtained corrosion rates for the same steam quality. The tested steam quality was not high enough to create the conditions in which ammonia provides insufficient protection against acetic acid, but expanding the liquid film pH model to higher steam qualities does give an idea of the dangers of high acetate concentrations in a steam-water cycle. The models for calculating the pH of the liquid film in two-phase flow and amine thermolysis (if validated) could be connected to assess if alkalizing amine application is recommended for a specific steam-water cycle. In general, it can be concluded from the results that ethanolamine provides better protection against two-phase flow-accelerated corrosion in the presence of organic acid anions, so there is a maximum superheater Temperature for each amine at which it can be applied. When ammonia is the only volatile treatment chemical protecting the steam-water cycle, organic acid anions in the plant should be reduced until theoretical pH drop of the two-phase liquid film is acceptable

  • Organic Contaminants and Treatment Chemicals in Steam-Water Cycles: Thermal stability, decomposition products and flow-accelerated corrosion
    2015
    Co-Authors: Moed D.h.
    Abstract:

    Boiler feedwater and steam have to be of high purity, because of the susceptibility of the steam-water cycle to corrosion. Organic contaminants break down in Boilers by hydrothermolysis, leading to the formation of organic acid anions, which are suspected to cause corrosion of steam-water cycle components. The impact and behavior of organic decomposition products in the steam-water cycle are not well understood. While guidelines for organic contaminants are becoming stricter, organic treatment chemicals are gaining popularity. Some alkalizing amines show potential for protecting steam-water cycles against corrosion, but their thermal stability is limited and acidic decomposition products are a concern. There are no official guidelines for the application of alkalizing amines in fossil-fired plants, because their thermal stability in the hottest sections of the plant is unknown. This thesis aims to contribute to well-founded guidelines for organic contamination and amine application in steam-water cycles to facilitate effective water treatment and chemical dosing. It does so by investigating the thermal decomposition of organic contaminants and treatment chemicals and using results to conduct corrosion experiments. To investigate hydrothermal reactions both batch and continuous flow reactors were tested, and it was concluded that the latter are better at investigating (hydro)thermolysis of organic treatment chemicals. A flow reactor gives precise control over retention time, Temperature and pressure and these parameters can be changed much faster than with a batch reactor. The flow reactor was the basis for virtually all thermal stability and decomposition experiments described in this thesis. It was found that lower heating rates give more organic acid anions as degradation products of organic carbon, both in quantity and species variety. Thermal stability of the decomposition products determines which of these products is most prevalent. As Boiler Temperature increased, acetate became the dominant degradation product, due to its higher thermal stability. Shorter retention times led to more variety and quantity of organic acid anions, due to a lack of time for the thermally less stable ones to degrade. The absence of oxygen increased the thermal stability of decomposition products. The (hydro)thermolysis of monoethylene glycol and slurry oil produced up to a few hundred ppb acetate and formate. The (hydro)thermolysis of polyethylene glycol produced a high variety and quantity of organic acid anions, that could only partially be determined to be in the lower ppm range. The (hydro)thermolysis of the water dissolvable fraction of gasoil, naphtha and hydro wax did not lead to an increase in organic acid anions. Methyl ethyl ketoxime thermally degraded into several organic acid anions and nitrite in the higher ppb or lower ppm range. By using the flow reactor to investigate amine thermal stability, it was concluded that thermolysis under superheater conditions was more rapid than hydrothermolysis under Boiler conditions. Anionic decomposition products increased linearly over time, while the thermal decomposition of morpholine followed first order kinetics. Metal catalysis of amine thermolysis caused by oxides on the inner surface of superheater tubes was investigated by using varying sizes and elemental composition. Kinetics of morpholine and ethanolamine thermolysis decreased as the tube size increased. The relation between the surface:volume ratio and the degradation rate constant was linear. Although results varied between the two applied tubing materials, there is no consistent trend that can link thermolysis kinetics to tube wall composition. The thermolysis of five alkalizing amines and two organic acids was comprehensively tested at superheater conditions. Morpholine, ethanolamine, cyclohexylamine, dimethylamine, 3-methoxypropylamine and acetic acid were shown to undergo thermolysis according to first order kinetics. The activation energy, prefactor and activation volume were obtained from the experimental data for all investigated amines. Dimethylamine did not fully degrade, in spite of longer retention times being applied, suggesting synthesis may occur. Formic acid is very unstable under steam water cycle conditions. It is still found in high Temperature and pressure steam-water cycles, though, and therefore it could be hypothesized that it is synthesized in the condensing stages. Acetic acid has higher thermal stability than all other tested compounds and is therefore the dominant organic acid anion at high Temperatures. Cationic degradation products were ammonia and some amines, meaning that the complete thermolysis of an amine does not necessarily lead to acidic conditions, as the formed ammonia also provides protection. A model was constructed to predict the thermal stability of the amines in steam-water cycle. More plant data is necessary to fully validate the model. Runs conducted with an experimental two-phase flow-accelerated corrosion loop showed a linear relation between liquid film pH and obtained corrosion rates for the same steam quality. The tested steam quality was not high enough to create the conditions in which ammonia provides insufficient protection against acetic acid, but expanding the liquid film pH model to higher steam qualities does give an idea of the dangers of high acetate concentrations in a steam-water cycle. The models for calculating the pH of the liquid film in two-phase flow and amine thermolysis (if validated) could be connected to assess if alkalizing amine application is recommended for a specific steam-water cycle. In general, it can be concluded from the results that ethanolamine provides better protection against two-phase flow-accelerated corrosion in the presence of organic acid anions, so there is a maximum superheater Temperature for each amine at which it can be applied. When ammonia is the only volatile treatment chemical protecting the steam-water cycle, organic acid anions in the plant should be reduced until theoretical pH drop of the two-phase liquid film is acceptable.WatermanagementCivil Engineering and Geoscience

Robert T. Dobson - One of the best experts on this subject based on the ideXlab platform.

  • Steam jet ejector cooling powered by waste or solar heat
    Renewable Energy, 2009
    Co-Authors: A.j. Meyer, T.m. Harms, Robert T. Dobson
    Abstract:

    Abstract A small scale steam jet ejector experimental setup was designed and manufactured. This ejector setup consists of an open loop configuration and the Boiler operate in the Temperature range of Tb = 85–140 °C. The typical evaporator liquid Temperatures range from Te = 5 °C to 10 °C while the typical water-cooled condenser pressure ranges from Pc = 1.70 kPa to 5.63 kPa (Tc = 15–35 °C). The Boiler is powered by two 4 kW electric elements while a 3 kW electric element simulates the cooling load in the evaporator. The electric elements are controlled by means of variacs. Primary nozzles with throat diameters of 2.5 mm, 3.0 mm and 3.5 mm are tested while the secondary ejector throat diameter remains unchanged at 18 mm. These primary nozzles allow the Boiler to operate in the Temperature range of Tb = 85–110 °C. When the nozzle throat diameter is increased, the minimum Boiler Temperature decreases. A primary nozzle with a 3.5 mm throat diameter was tested at a Boiler Temperature of Tb = 95 °C, an evaporator Temperature of Te = 10 °C and a critical condenser pressure of Pcrit = 2.67 kPa (22.6 °C). The system's COP is 0.253. In a case study the experimental data of a solar powered steam jet ejector air conditioner is investigated. Solar powered steam ejector air conditioning systems are technical and economical viable when compared to conventional vapour compression air conditioners. Such a system can either utilise flat plate or evacuated tube solar thermal collectors depending on the type of solar energy available.