Effect of wall surface roughness on condensation shock

Pillai, Aditya; Prasad, B. V. S. S. S.

doi:10.1016/j.ijthermalsci.2018.06.028

Cited by 25 publications

(4 citation statements)

References 30 publications

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“…In Moses and Stein [52] experiments, the static pressure and the liquid fraction were measured in the supersonic nozzle. Dykas and Wroblewski [53], Pillai and Prasad [54], Mirhoseini and Boroomand [55] employed the experimental data of Moses and Stein [52] to validate their wet steam model. Moore et al [50] measured both the distributions of the static pressure and droplet dimension in their experiments.…”

Section: Steam Expansion and Mach Numbersmentioning

confidence: 99%

Performance of supersonic steam ejectors considering the nonequilibrium condensation phenomenon for efficient energy utilisation

et al. 2019

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Supersonic ejectors are of great interest for various industries as they can improve the quality of the low-grade heat source in an eco-friendly and sustainable way. However, the impact of steam condensation on the supersonic ejector performances is not fully understood and is usually neglected by using the dry gas assumptions. The non-equilibrium condensation occurs during the expansion and mixing process and is tightly coupled with the high turbulence, oblique and expansion waves in supersonic flows. In this paper, we develop a wet steam model based on the computational fluid dynamics to understand the intricate feature of the steam condensation in the supersonic ejector. The numerical results show that the dry gas model exaggerates the expansion characteristics of the primary nozzle by 21.95%, which predicts the Mach number of 2.00 at the nozzle exit compared to 1.64 for the wet steam model. The dry gas model computes the static temperature lower to 196 K, whereas the wet steam model predicts the static temperature should above the triple point due to the phase change process. The liquid fraction can reach 7.2% of the total mass based on the prediction of the wet steam model. The performance analysis indicates that the dry gas model overestimates a higher entrainment ratio by 11.71% than the wet steam model for the steam ejector.

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Section: Steam Expansion and Mach Numbersmentioning

confidence: 99%

Performance of supersonic steam ejectors considering the nonequilibrium condensation phenomenon for efficient energy utilisation

et al. 2019

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“…Researches demonstrate similar results in the investigation of roughness in blades and nozzles. In the study of Laval nozzle, Pillai and Prasad [26] indicated that condensation shock strength is adjusted due to increasing roughness, but the thickness of the boundary layer increases. Han et al [27] argued that increase in surface roughness, decreases Mach number and peak of nucleation rate in the turbine blade.…”

Section: Introductionmentioning

confidence: 99%

Numerical investigation of roughness effect on wet steam ejector performance in the refrigeration cycle

2022

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Machining operation and presence of water droplet cause increasing the surface roughness of wet steam ejector walls and changing its performance in the refrigeration cycle. The purpose of this work is to investigate the influences of the primary nozzle surface roughness on wet steam ejectors in the refrigeration cycle with steam water as a working flow. The flow is modeled by solving governed equations based on the Eulerian-Eulerian approach. The proposed model is validated by comparison numerical results with experimental data of the ejector and nozzle. Moreover, different surface roughness has been successfully applied to the primary nozzle and its effect on the entire flow is shown. Six properties of wet steam are selected, including pressure, temperature, Mach number, droplet average radius, droplet growth rate, and liquid mass fraction. The result shows, increase in the surface roughness resulted in a shift of the shock chain to the primary nozzle, damping shock strength, and increasing temperature in the diffuser. In addition, increment of the primary nozzle surface roughness decreases ER and COP of the refrigeration cycle by 3.67% and 3.8%, respectively. According to the important impact of the roughness on the liquid mass fraction, droplet average radius, droplet growth rate, ER, and COP, designers and operators should be considered the roughness effects in the design and operation of wet steam ejectors.

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“…White and Hounslow (2000) analyzed the shock structure in condensation flow and discussed the unsteady phenomena caused by condensation. Chandler et al (2014), Aditya and Prasad (2018), Dykas et al (2015Dykas et al ( , 2018, Starzmann et al (2018), Wang et al (2018), Yang et al ( 2019) and others have solved many basic problems, including the shock structure in condensation flow, distribution of condensation parameters, deposition of water droplets and formation mechanism of water films. Better simulation results can be obtained using the real steam equation and two-phase fluid model; however, the slip and temperature difference between phases are often neglected in most existing research.…”

Section: Introductionmentioning

confidence: 99%

Numerical investigation of the wet steam condensation flow characteristics in stator cascade with blade surface heating

Han

Yuan

Zhao

et al. 2020

Engineering Applications of Computational Fluid Mechanics

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The scientific and effective control of steam wetness in steam turbines is of great significance for improving power generation efficiency. Based on the research status of wet steam, the influence of different surface heating intensity in a stator cascade was studied. The distribution of condensation flow parameters in White cascade under 0-700 kW/m 2 surface heating intensity is calculated. On this basis, the positive heating intensity region was determined and refined to obtain the best heating condition with higher accuracy. The results show that the condensation is restrained and the outlet wetness is decreased as the blade surface heating intensity increases. The steam wetness and droplet diameter in the flow field can be controlled by adding heating intensity. Additionally, at the initial stage of applying heat to the blade, an increasing enthalpy drop occurs, and the entropy increase experiences a decline, while negative effects rapidly emerge if the heating intensity is too high. The optimum heating intensity is 120 kW/m 2. Compared with the 0 kW/m 2 , the average outlet wetness, total pressure loss coefficient and entropy increase of 120 kW/m 2 surface heating intensity can be reduced by 1.1266%, 15.5% and 1.7%, respectively, and the enthalpy drop can be increased by 1.7%.

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Effect of wall surface roughness on condensation shock

Cited by 25 publications

References 30 publications

Performance of supersonic steam ejectors considering the nonequilibrium condensation phenomenon for efficient energy utilisation

Performance of supersonic steam ejectors considering the nonequilibrium condensation phenomenon for efficient energy utilisation

Numerical investigation of roughness effect on wet steam ejector performance in the refrigeration cycle

Numerical investigation of the wet steam condensation flow characteristics in stator cascade with blade surface heating

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