The Experts below are selected from a list of 333 Experts worldwide ranked by ideXlab platform
Jeng Shiun Lim - One of the best experts on this subject based on the ideXlab platform.
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Organic rankine cycle and Steam turbine for intermediate temperature waste heat recovery in total site integration
Malaysian Journal of Fundamental and Applied Sciences, 2019Co-Authors: Norhafiza Kamarudin, Liew Peng Yen, Nurfatehah Wahyuny Che Jusoh, Jeng Shiun LimAbstract:The utilization of waste heat for heat recovery technologies in process sites has been widely known in improving the site energy saving and energy efficiency. The Total Site Heat Integration (TSHI) methodologies have been established over time to assist the integration of heat recovery technologies in process sites with a centralized utility system, which is also known as Total Site (TS). One the earliest application of TSHI concept in waste heat recovery is through Steam turbine using the popular Willan’s line approach. The TSHI methodologies later were extended to integrate with wide range of heat recovery technologies in many literature, whereby Organic Rankine Cycle (ORC) has been reported to be the one of the beneficial options for heat recovery. In general, the medium to high temperature waste heat is recovered via Condensing/backpressure Steam turbine, whereas ORC is targeted for recovering the low temperature waste heat. However, it is known that Condensing turbine is also able to generate power by Condensing low grade Steam to sub-ambient pressure, which is comparable with ORC integration. In this work, the integration of ORC and Condensing turbine are considered for a multiple-process system to recover intermediate temperature waste heat through utility system. This study presents a numerical methodology to investigate the performance analysis of integration of ORC and Condensing turbine in process sites for recovering waste heat from a centralized utility system. A modified retrofit case study is used to demonstrate the effectiveness application of the proposed methodology. The performance of ORC and Condensing Steam turbine are evaluated with the plant total utility costing as the objective function.
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Organic rankine cycle and Steam turbine for intermediate temperature waste heat recovery in total site integration
'Penerbit UTM Press', 2019Co-Authors: Kamarudin Norhafiza, Liew Peng Yen, Che Jusoh, Nurfatehah Wahyuny, Shin Ho Wai, Jeng Shiun LimAbstract:The utilization of waste heat for heat recovery technologies in process sites has been widely known in improving the site energy saving and energy efficiency. The Total Site Heat Integration (TSHI) methodologies have been established over time to assist the integration of heat recovery technologies in process sites with a centralized utility system, which is also known as Total Site (TS). One of the earliest application of TSHI concept in waste heat recovery was through Steam turbine using the popular Willan’s line approximation. The TSHI methodologies later were extended to integrate with wide range of heat recovery technologies in many literatures, whereby Organic Rankine Cycle (ORC) has been reported to be the one of the beneficial options for heat recovery. In general, the medium to high temperature waste heat is recovered via Condensing/backpressure Steam turbine, whereas ORC is targeted for recovering the low temperature waste heat. However, it is known that Condensing turbine is also abled to generate power by Condensing low grade Steam to sub-ambient pressure, which is comparable with ORC integration. In this work, the integration of ORC and Condensing turbine was considered for a multiple-process system to recover intermediate temperature waste heat through utility system. This study presented a numerical methodology to investigate the performance analysis of integration of ORC and Condensing turbine in process sites for recovering waste heat from a centralized utility system. A modified retrofit case study was used to demonstrate the effectiveness application of the proposed methodology. The performances of ORC and Condensing Steam turbine were evaluated with the plant total utility costing as the objective function. The turbine integration was found to be more beneficial in the modified case study with lower utility cost involved. However, the capital cost has not been considered in the analysis
Stine Tveitan - One of the best experts on this subject based on the ideXlab platform.
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thermo economic study of waste heat recovery from Condensing Steam for hydrogen production by pem electrolysis
Energy Conversion and Management, 2019Co-Authors: Norbert Lummen, Assma Karouach, Stine TveitanAbstract:Abstract The hydrogen production potential and cost from waste heat recovered from Condensing Steam in a combined heat and power facility has been calculated. Two different concepts for using the recovered energy by an organic Rankine cycle in PEM water electrolysis have been developed and compared. Thermo-economic analysis has been employed to calculate the exergetic unit cost of the produced hydrogen as function of ORC working fluid, Steam Condensing pressure and hours of available waste heat per year for a mass flow rate of 10 kg/s of Condensing Steam between 80 kPa and 200 kPa condenser pressure in the Steam cycle. Hydrogen production rates in the range from 0.647 to 1.27 g H2/kg Steam were obtained. The exergetic unit cost of uncompressed, compressed (350 bar) and liquefied hydrogen were calculated. Costs as low as $3.06/kg H2 (uncompressed) could be achieved, when the use of waste heat was maximised. The lowest cost of compressed (350 bar) and liquefied hydrogen were $4.11/kg H2 and $16.53/kg H2, respectively. Depending on the chosen scenario, between 186 and 364 tonne hydrogen can be produced annually.
Teemu Turunensaaresti - One of the best experts on this subject based on the ideXlab platform.
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influence of turbulence modelling to Condensing Steam flow in the 3d low pressure Steam turbine stage
Volume 8: Microturbines Turbochargers and Small Turbomachines; Steam Turbines, 2016Co-Authors: Yogini Patel, Giteshkuma Patel, Teemu TurunensaarestiAbstract:With the tremendous role played by Steam turbines in power generation cycle, it is essential to understand the flow field of Condensing Steam flow in a Steam turbine to design an energy efficient turbine because condensation at low pressure (LP) turbine introduces extra losses, and erosion in turbine blades. The turbulence has a leading role in Condensing phenomena which involve a rapid change of mass, momentum and heat transfer. The paper presents the influence of turbulence modelling on non-equilibrium Condensing Steam flows in a LP Steam turbine stage adopting CFD code. The simulations were conducted using the Eulerian-Eulerian approach, based on Reynolds-averaged Navier-Stokes equations coupled with a two equation turbulence model, which is included with nucleation and droplet growth model for the liquid phase. The SST k-ω model was modified, and the modifications were implemented in the CFD code. First, the performance of the modified model is validated with nozzles and turbine cascade cases. The effect of turbulence modelling on the wet-Steam properties and the loss mechanism for the 3D stator-rotor stage is discussed. The presented results show that an accurate computational prediction of Condensing Steam flow requires the turbulence to be modelled accurately.© 2016 ASME
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influence of turbulence modelling on non equilibrium Condensing flows in nozzle and turbine cascade
International Journal of Heat and Mass Transfer, 2015Co-Authors: Yogini Patel, Giteshkuma Patel, Teemu TurunensaarestiAbstract:Abstract The accurate analysis of a Condensing flow plays an important role in the development of high-efficiency Steam turbines. This paper presents an investigation of turbulence modelling influence on non-equilibrium Condensing Steam flows in a Laval nozzle and in a stationary cascade of turbine blades using a commercial computational fluid dynamics (CFD) code. The calculations were conducted by employing 2D compressible Reynolds-averaged Navier–Stokes (RANS) equations coupled with a two equation turbulence model. The condensation phenomena were modelled on the basis of the classical nucleation theory. The standard k – e turbulence model was modified, and the modifications were implemented in the CFD code. The influence of inlet flow turbulence on Condensing process was discussed. The impact of turbulence modelling on wet-Steam flow was examined based on the experimental data available in the literature. The cascade loss coefficients were calculated numerically as well. The presented study of losses that occur due to the irreversible heat and mass transfer during the condensation process emphasised the importance of turbulence modelling for wet-Steam flows in turbines. The paper demonstrates that the accurate computational prediction of Condensing Steam flow requires the turbulence to be modelled accurately.
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numerical investigation of turbulence modelling on Condensing Steam flows in turbine cascade
Volume 1B: Marine; Microturbines Turbochargers and Small Turbomachines; Steam Turbines, 2014Co-Authors: Yogini Patel, Giteshkuma Patel, Teemu Turunensaaresti, Aki GronmaAbstract:Understanding the condensation process at the low-pressure (LP) turbine is important because condensation introduces extra losses, and erosion caused by the droplets wear turbine blades. The paper presents an investigation of the turbulence modelling on the non-equilibrium homogeneous Condensing Steam flow in a stationary turbine cascade employing 2D compressible Navier-Stokes (NS) equations. The classical nucleation theory is utilized to model the condensation phenomena. The performance of various turbulence models (i.e., the Spalart-Allmaras, the k-ω, the k-e, the RNG k-e, the Realizable k-e, and the SST k-ω) in Condensing Steam flows is discussed. The SST k-ω model is modified and implemented into a commercial computational fluid dynamics (CFD) code. Substantial improvements in the prediction accuracy are observed when compared with the original SST k-ω model. Overall, the modified model is in excellent agreement with the measurements in all studied test cases of the turbine cascade. The qualitative and quantitative analysis illustrates the importance of turbulence modeling in wet-Steam flows.Copyright © 2014 by ASME
Dirk Lucas - One of the best experts on this subject based on the ideXlab platform.
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poly disperse simulation of Condensing Steam water flow inside a large vertical pipe
International Journal of Thermal Sciences, 2016Co-Authors: Yixiang Liao, Dirk LucasAbstract:Abstract The condensation of saturated Steam bubbles in sub-cooled water inside a vertical pipe was studied by poly-disperse CFD simulations. Six test cases with varied pressure, liquid sub-cooling and diameter of the gas injection orifices were simulated. Baseline closures presented for non-drag forces in previous work were found to be reliable also in non-isothermal cases. The effect of bubble coalescence and breakup is over-weighting in the region close to Steam injection in case of small orifice diameter. With the increase of orifice diameter, breakup becomes dominant in determining bubble size change. The effect of interphase heat transfer coefficient correlations was investigated. The widespread Ranz–Marshall correlation was found to under-estimate the condensation rate, especially at high pressure levels. In contrast, satisfying agreement with the experimental data was obtained by the Tomiyama correlation.
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application of new closure models for bubble coalescence and breakup to Steam water vertical pipe flow
Nuclear Engineering and Design, 2014Co-Authors: Yixiang Liao, Dirk Lucas, Eckhard KrepperAbstract:Abstract New closure models for bubble coalescence and breakup proposed in Liao et al. (2011) , Nucl. Eng. Des. 241, 1024, are assessed for the case of Condensing Steam–water pipe flows. Steady-state CFD calculations are performed employing the commercial CFD solver ANSYS CFX. Predicted evolution of cross-section averaged bubble size and gas volume fraction distribution along the pipe is compared with the measurements provided by the TOPFLOW facility ( Lucas et al., 2010 . CFD4NRS-3, Int. Workshop on Experimental Validation and Application of CFD and CMFD Codes to Nuclear Reactor Safety Issues, Paper 13.1, 14.16.09, Washington D.C., USA.). It is shown that for cases with small initial bubble size and low gas volume fraction, bubble coalescence and breakup can be taken to be nearly negligible and the change of bubble size is primarily due to condensation. Nevertheless, with the increase of initial bubble size or gas volume fraction, bubble coalescence and breakup become more prevalent. Performance of new and standard closure models of bubble coalescence and breakup is investigated It is shown that both models overestimated the breakup rate; in particular, the standard model. The numerical results are also found to be dependent on the inlet liquid temperatures and inter-phase heat transfer models have a significant impact on the results.
Jose Maria Martinez-val - One of the best experts on this subject based on the ideXlab platform.
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Integration between direct Steam generation in linear solar collectors and supercritical carbon dioxide Brayton power cycles
International Journal of Hydrogen Energy, 2015Co-Authors: L. Coco-enríquez, J. Muñoz-antón, Jose Maria Martinez-valAbstract:Direct Steam Generation in Parabolic Troughs or Linear Fresnel solar collectors is a technology under development since beginning of nineties (1990's) for replacing thermal oils and molten salts as heat transfer fluids in concentrated solar power plants, avoiding environmental impacts. In parallel to the direct Steam generation technology development, supercritical Carbon Dioxide Brayton power cycles are maturing as an alternative to traditional Rankine cycles for increasing net plant efficiency and reducing balance of plant equipments dimensions and cots. For gaining synergies between these two innovative technologies, in this paper, Direct Steam Generation and Brayton power cycles are integrated in line-focusing solar power plants. Four configurations are studied: Configuration 1 consists on installing a condenser between solar field and power cycle; Condensing the heat transfer fluid (Steam water) with the balance of plant working fluid (carbon dioxide). The condenser would be a shell & tubes type. Along tubes carbon dioxide flows, and Steam water condensates at shell-side. Main advantage of the condenser equipment is the high heat transfer coefficient at water Condensing-side, reducing condenser dimension and weight. The main disadvantage of this configuration is the high operating pressure required in solar field for Condensing Steam into liquid water. This pressure should be between 150 bar and 175 bar for obtaining 400 °C at turbine inlet. In the Configuration 2, the superheated Steam delivered by solar collectors transfers the heat energy in a primary heat exchanger to the balance of plant working fluid. In this configuration the Steam not condensate into liquid water, and only reduces the temperature from 550 °C-560 °C to 420 °C. The Steam pressure drops in solar field along receivers, headers and heat exchangers are compensated by means of Steam compressors. This second solution is compatible with higher turbine inlet temperatures, up to 550 °C. The keystones of this second configuration are the Steam conditions at compressor inlet, pressure ∼175 bars and temperature ∼420 °C, for minimizing Steam compressor electrical consumption. The third design solution (Configuration 3) includes a solar field with direct Steam generation in solar collectors with boiling recirculation mode, but the balance of plant is integrated by two Brayton power cycles in cascade. The first power cycle operating at 550 °C turbine inlet, and the second cycle at 410 °C turbine inlet. Main advantage is the integration between a validated direct Steam generation technology (recirculation boiling mode) with the Brayton power cycles avoiding Steam compressors, a technology not yet commercially available, and main drawback of this design is the increasing number of balance of plant equipments. The Configuration 4 is very similar to the Configuration 2, with the same direct Steam generation solar field with superheated Steam without Condensing, and a single reheating stage solar field with molten salt as heat transfer fluid. The Configuration 1 provides similar efficiency and net power output, for similar solar field effective aperture area, as obtained with molten salt solar collectors with supercritical carbon dioxide power cycle (recompression with main compression intercooling cycle provides 36.6% net efficiency, for a maximum 400 °C turbine inlet). The second design solution (Configuration 2) net efficiency is not very much impacted for Steam compressor electrical consumption recompression cycle net efficiency is 43.6% with Steam solar field, versus 45.16% with molten salt solar field, in both cases with 550 °C turbine inlet. The Configuration 3 performance is ∼39.7% with two cascade Brayton power cycles with recompression and main compression intercooling. Finally, the Configuration 4 optimum plant performance is obtained for the recompression cycle with a net efficiency ∼45.77%, and is constrained by the molten salt drawbacks (material corrosion, material cost, environmental impact, etc).