Numerical approaches for moist air condensing flows modelling in the transonic regime

Wiśniewski, Piotr; Dykas, Sławomir; Yamamoto, Satoru; Pritz, Balázs

doi:10.1016/j.ijheatmasstransfer.2020.120392

Cited by 23 publications

(8 citation statements)

References 16 publications

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“…The nucleation process is based on the classical theory extended with the Kantrowitz correction, whereas the droplet growth model is based on the Knudsen number (Kn) [5]. Details about the condensation model implementation can be found in previous works of the authors [15,16,17,21,22]. This figure presents the structure of condensation and the aerodynamic waves arising in the expanding flow with a supersonic outlet.…”

Section: Numerical Studymentioning

confidence: 99%

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Analysis of the moist air transonic flow in the symmetric and asymmetric nozzle of the low expansion

Wiśniewski

Dykas

Majkut

et al. 2022

J. Phys.: Conf. Ser.

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Condensation has a negative impact on turbomachinery efficiency in many energy processes. This paper compares the expansion of moist air in symmetric and asymmetric nozzles with a low expansion rate. The presented numerical study is supported by analytical and experimental research. The experimental tWesting was carried out using an in-house experimental test rig where two nozzles were examined for moist air with relative humidity of about 25%. The nozzles were tested for a supersonic outlet, as well as for the outlet condition with elevated pressure, which resulted in the occurrence of a normal shock in the test section. The asymmetric nozzle profile is congruent with the symmetric nozzle. However, the nozzle walls are shifted linearly in the flow direction. The Schlieren photography technique and static pressure measurements on the nozzle wall were used for qualitative identification of both condensation and shock waves. The presented numerical modelling was conducted using commercial computational fluid dynamics software extended with an in-house condensation model. The code was validated against in-house experiment as well as against the data available in the literature. The analysis of the flow in the considered two types of nozzles with a very low expansion rate revealed very interesting structures of pressure waves. The impact of the linear shift of the nozzle walls on the condensation process and the interaction of the condensation wave with aerodynamic oblique as well as normal shock waves were investigated.

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Section: Numerical Studymentioning

confidence: 99%

“…An in-house code was developed by Dykas et al [8,9,10,11], who studied the condensation in nozzles with high expansion rate [12,13]. This code became the basis of the model implemented to commercial software ANSYS Fluent and is presented in this study [14,15,16,17].…”

Section: Introductionmentioning

confidence: 99%

Analysis of the moist air transonic flow in the symmetric and asymmetric nozzle of the low expansion

Wiśniewski

Dykas

Majkut

et al. 2022

J. Phys.: Conf. Ser.

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“…The most popular and the one most often used by researchers is the continuous droplet growth model developed by Gyarmathy [2], which is applied for a bigger size of droplets: (15) where λv is thermal conductivity of vapour.…”

Section: Numerical and Mathematical Modelsmentioning

confidence: 99%

“…1) was applied to investigate moist air condensing flows using different droplet growth models. This nozzle was previously used in our numerical as well as experimental research [13,15]. The 2D mesh presented on Figure 1 was created and it has ~21 000 elements, the boundary layer with growth rate equal to 1.2 was introduced to obtain y + = 1.…”

Section: Numerical Studymentioning

confidence: 99%

“…The functionality of the model implemented in the commercial software was extended by allowing slip velocity consideration, i.e. investigation of the difference between liquid and gaseous phase velocities, which is especially important if droplets reach a relatively large size or if the flow has a significant swirl [14,15]. Valuable techniques for condensation simulation in complex 3D structures were introduced by Yamamoto [16,17].…”

Section: Introductionmentioning

confidence: 99%

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Assessment of condensation models for moist air transonic flow prediction

et al. 2021

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The aim of this article is to thoroughly analyse the influence of condensation models on the modelling of condensation phenomena in transonic flow of moist air. The reason for the study was the fact that different condensation models are used by researchers to obtain satisfactory results of numerical modelling. The condensation models tested herein differ in the nucleation rate formula and the droplets growth equation. Four most often used condensation models were selected for detailed investigations. The results obtained from each model were compared with experiments for the nozzle flow. The main focus was on the location of the onset of the nucleation process. Moreover, the droplets growth intensity was compared and discussed. The nozzle flow CFD calculations were performed using the ANSYS Fluent commercial tool. Finally, the condensation model which is the most suitable for the moist air transonic flow was recommended.

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Modeling condensing flows of humid air in transonic nozzles

Hertwig

Wittmann

Wiśniewski

et al. 2023

Exp. Comput. Multiph. Flow

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The ability to accurately model condensing flows is crucial for understanding such flows in many applications. Condensing flows of pure steam have been studied extensively in the past, and several droplet growth models have been derived. The rationale for the choice of growth models for condensation in humid air is less established. Furthermore, only a few validation cases for condensation in such flows exist. This paper aims to identify existing limitations of common droplet growth laws. The Hertz—Knudsen model is compared to heat-transfer-based models by Gyarmathy and Young, using an Euler—Lagrange approach in Ansys Fluent. For this, an adaption for Young’s growth law is introduced, allowing its application in condensation of different gas mixtures. The numerical model has been validated and applied to flows in nozzles and turbines in previous publications. The accuracy of the droplet growth models is investigated in transonic nozzle test cases. A case with pure steam and a case with humid air at two different humidity values are considered. Finally, the influence of humidity, Knudsen number, and droplet radius on the growth rate of each model is shown analytically. Flows at lower humidity values with longer condensation zones are shown to benefit from the higher sensitivity of the Hertz—Knudsen model to the mass fraction of water vapor in the flow. Heat-transfer-based models tend to overestimate condensation in such flows. However, the ability to empirically adapt the growth model by Young and its applicability in different Knudsen numbers results in good agreement with validation data over a wide range of cases.

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Numerical approaches for moist air condensing flows modelling in the transonic regime

Cited by 23 publications

References 16 publications

Analysis of the moist air transonic flow in the symmetric and asymmetric nozzle of the low expansion

Analysis of the moist air transonic flow in the symmetric and asymmetric nozzle of the low expansion

Assessment of condensation models for moist air transonic flow prediction

Modeling condensing flows of humid air in transonic nozzles

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