Heat transfer modelling of an isolated bubble in sodium pool boiling
- Authors: Iyer, Siddharth , Kumar, Apurv , Coventry, Joe , Lipiński, Wojciech
- Date: 2022
- Type: Text , Journal article
- Relation: International Journal of Thermal Sciences Vol. 179, no. (2022), p.
- Full Text: false
- Reviewed:
- Description: Sodium tubular boiler receivers in concentrated solar thermal power plants are a viable option to provide near-isothermal heat for industrial applications. Accurately predicting the boiling behaviour in the receivers is imperative to improve the performance of these plants. A physics-based reduced-order bubble growth model is developed in this work to gain a fundamental understanding of the boiling process in the receiver. The model predicts the growth rate of an isolated bubble in a sodium pool based on heat transferred from the microlayer, the macrolayer, the thermal boundary layer and the bulk liquid surrounding the bubble. A transient 2D conduction equation is solved to model the cooling of the wall below the bubble due to evaporation of the microlayer and the macrolayer. The model is used to study the growth of a sodium bubble in a liquid pool and analyse the relative contribution of different heat transfer mechanisms to the growth process. It is found that the microlayer heat transfer is the dominant mechanism controlling bubble growth in sodium. Furthermore, a parametric study of the effect of wall superheat, contact angle and temperature of the bulk liquid on the bubble growth process in sodium shows that the bubble size increases with increasing superheat, contact angle and bulk liquid temperature. © 2022
Mechanistic modelling of bubble growth in sodium pool boiling
- Authors: Iyer, Siddharth , Kumar, Apurv , Coventry, Joe , Lipiński, Wojciech
- Date: 2023
- Type: Text , Journal article
- Relation: Applied Mathematical Modelling Vol. 117, no. (2023), p. 336-358
- Full Text: false
- Reviewed:
- Description: This work presents a mechanistic model to simulate the growth of a sodium bubble from nucleation to departure in sodium pool boiling. A previously developed and validated heat transfer sub-model is coupled to a force balance sub-model to predict the growth rate and departure radius of a sodium bubble. The model accounts for the change in the contact angle of a bubble as it grows, and the shrinkage of the bubble base prior to departure. The developed model is used to quantify and analyse the heat transfer from different regions, i.e. the microlayer, the macrolayer, the thermal boundary layer and the bulk liquid surrounding the bubble. In addition, bubble growth rate and departure radius are calculated for different values of wall superheat, rate of change of contact angle and bulk liquid temperature. It is found that the departure radius of a sodium bubble is on the order of a few centimetres and the wall superheat has a significant influence on the shape of a sodium bubble at departure. © 2022 Elsevier Inc.
Micro-scale heat transfer modelling of the contact line region of a boiling-sodium bubble
- Authors: Iyer, Siddharth , Kumar, Apurv , Coventry, Joe , Pye, John , Lipiński, Wojciech
- Date: 2020
- Type: Text , Journal article
- Relation: International Journal of Heat and Mass Transfer Vol. 160, no. (2020), p.
- Full Text: false
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- Description: The use of boiling liquid metals such as sodium is attractive for providing a near-isothermal heat source for engineering applications. However, previous use of boiling sodium as a coolant in nuclear reactors and as a heat transfer fluid in solar thermal applications has shown that the boiling process is unstable. To stabilise the flow, it is imperative to gain a better understanding of the boiling phenomena. An integral part of the boiling process is the evaporation of the region where the liquid-vapour interface meets the heater wall, referred to as the contact line region. The heat transfer modelling of this region formed below a single bubble in nucleate pool boiling of sodium is considered in this study. A contact line model previously developed for high Prandtl number flows is extended by including the effect of an electron pressure component which is unique to liquid metals. The assumptions made in the model are critically assessed to determine their validity for modelling micro-scale evaporation in sodium. The model was used to show that the evaporative heat flux from the contact line region in sodium can be up to six times larger compared to a high Prandtl number fluid FC-72 for a superheat of 15 K, owing to the high thermal conductivity of sodium. Furthermore, a study on the influence of specific characteristics of sodium — high boiling superheat and presence of an electron pressure — showed that the evaporative heat flux increases with increasing superheat and decreases with increasing electron pressure. © 2020 Elsevier Ltd
- Description: We gratefully acknowledge the financial support from the Australian Research Council (grant no. LP150101189 ). We thank our project partner Vast Solar Pty Ltd for their support and contributions.
Progress in heat transfer research for high-temperature solar thermal applications
- Authors: Lipiński, Wojciech , Abbasi-Shavazi, Ehsan , Chen,Jingjinga , Coventry, Joe , Hangi, Morteza , Iyer, Siddharth , Kumar, Apurv , Li, Lifeng , Li,Sha , Pye,John , Torres, Juan , Wang, Bo
- Date: 2021
- Type: Text , Journal article
- Relation: Applied Thermal Engineering Vol. 184, no. (2021), p.
- Full Text: false
- Reviewed:
- Description: High-temperature solar thermal energy systems make use of concentrated solar radiation to generate electricity, produce chemical fuels, and drive energy-intensive processing of materials. Heat transfer analyses are essential for system design and optimisation. This article reviews the progress, challenges and opportunities in heat transfer research as applied to high-temperature solar thermal and thermochemical energy systems. The topics discussed include fundamentals of concentrated solar energy collection, convective heat transfer in solar receivers, application of liquid metals as heat transfer media, and heat transfer in non-reacting and reacting two-phase solid–gas systems such as particle–gas flows and gas-saturated porous structures. © 2020 Elsevier Ltd.
- Description: High-temperature solar thermal energy systems make use of concentrated solar radiation to generate electricity, produce chemical fuels, and drive energy-intensive processing of materials. Heat transfer analyses are essential for system design and optimisation. This article reviews the progress, challenges and opportunities in heat transfer research as applied to high-temperature solar thermal and thermochemical energy systems. The topics discussed include fundamentals of concentrated solar energy collection, convective heat transfer in solar receivers, application of liquid metals as heat transfer media, and heat transfer in non-reacting and reacting two-phase solid–gas systems such as particle–gas flows and gas-saturated porous structures. © 2020 Elsevier Ltd. **Please note that there are multiple authors for this article therefore only the name of the first 5 including Federation University Australia affiliate “Apurv Kumar" is provided in this record**