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Numerical investigation of inlet pressure effects on condensation flow regime in a supersonic nozzle

  • Yu Qian EMAIL logo
Published/Copyright: February 19, 2025
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Abstract

Non-equilibrium condensation (NEC) is a prevalent phenomenon in various industrial equipment, and it can substantially affect their operational efficiency and overall performance. Droplet nucleation and growth is one of the important aspects of NEC and needs to be investigated and studied, whatever affects these parameters. On the other hand, NEC has a considerable impact on the flow pattern and condensation shock causes a sudden change in flow parameters. This study has been conducted with the aim of investigating the impact of inlet pressure (IP) on the flow pattern and two-phase flow parameters. The values of 90 kPa, 95 kPa, 99.98 kPa, 105 kPa, and 110 kPa are considered as the nozzle IP for this investigation, and its impact on the parameters of pressure, temperature, speed, density, droplet radius, liquid mass fraction (LMF), nucleation rate, Number of drops and condensed mass rate. According to the results, as the IP increases, the condensation shock occurs earlier and the LMF in the nozzle increases. As the pressure increases from 90 kPa to 110 kPa, the amount of LMF increases by about 5.7 %, and more LMF is produced in the nozzle. This study provides a good understanding of the impact of IP on NEC.


Corresponding author: Yu Qian, Fushun Vocational Technology Institute, Fushun 113122, Liaoning, China, E-mail:

Funding source: the National Natural Science Foundation of China

Award Identifier / Grant number: 52106208

Funding source: the Natural Science Foundation of Sichuan Province

Award Identifier / Grant number: 2023NSFSC0924

Acknowledgments

I would like to take this opportunity to acknowledge that there are no individuals or organizations that require acknowledgment for their contributions to this work.

  1. Research ethics: Research involving Human Participants and Animals: The observational study conducted on medical staff needs no ethical code. Therefore, the above study was not required to acquire ethical code.

  2. Informed consent: This option is not necessary due to that the data were collected from the references.

  3. Author contributions: All authors contributed to the study’s conception and design. Data collection, simulation and analysis were performed by “Yu Qian”. The first draft of the manuscript was written by “Yu Qian”.

  4. Use of Large Language Models, AI and Machine Learning Tools: To ensure the integrity of my research, I affirm that this study does not utilize any large language models, AI, or machine learning tools in its methodology or analysis.

  5. Conflict of interest: The authors declare no competing of interests.

  6. Research funding: This work was supported by the National Natural Science Foundation of China (grant number 52106208), and the Natural Science Foundation of Sichuan Province (2023NSFSC0924).

  7. Data availability: The authors do not have permissions to share data.

Appendix A

NEC in supersonic nozzle

As illustrated in Figure A1, a typical CD nozzle experiences expansion of the working fluid. This expansion process is accompanied by a phase change, starting with superheated dry steam and progressing towards a state containing both vapor and liquid (wet steam). As depicted in Figure A1, at Point 1, the stream enters the channel or nozzle as superheated dry vapor. The vapor expands towards sonic conditions at the throat due to the divergent shape of the channel. Between Points 1 and 2, the steam maintains its superheated dry state, signifying that it has not yet reached the conditions where condensation begins. The saturation line, marking the onset of liquid phase formation, is crossed at Point 3. The precise place of this transition (after of before the throat) is influenced by the particular geometry of the channel and the extent to which the steam is expanded. In this region, liquid droplets begin to form and dissipate within the vapor, but their nucleation rate is initially quite low. Consequently, the vapor continues to expand as a dry stream in a metastable condition. A significant increase in the nucleation rate occurs, culminating at spot 4. Beyond this spot, the rate of droplet formation becomes constant, leading to a stable number of droplets within the flow. These droplets subsequently experience rapid growth between Points 4 and 5, facilitating the progression towards a state where the flow is in thermodynamic balance. The expansion of the stream between spots 5 and 6 happens close to equilibrium states. As the system reaches thermodynamic stability through a condensation, latent heat is released from the liquid state to the steam state. This heat emission results in a shock of pressure between spots 5 and 4, revealing the taking place of the condensation process within the expanding flow [54].

Figure A1: 
NEC in supersonic nozzle [54].
Figure A1:

NEC in supersonic nozzle [54].

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Received: 2024-03-30
Accepted: 2025-02-02
Published Online: 2025-02-19

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