Avinash Upadhyay

Doctoral Student, Indian Institute of Technology Patna

Research

Boiling Performance Enhancement with Soluble Additives

Efficient thermal management is vital for modern energy and electronic systems, where boiling heat transfer serves as one of the most effective mechanisms for dissipating high heat fluxes. However, the performance of such systems is often constrained by early dryout and unstable bubble dynamics. This field of research explores the use of soluble molecular and ionic additives to enhance boiling performance by improving the critical heat flux (CHF) and heat transfer coefficient (HTC) through interfacial and physico-chemical modifications of the boiling surface. These additives actively influence surface wettability, bubble departure frequency, and microlayer dynamics, offering a tunable strategy for improving boiling efficiency without relying on permanent surface coatings. Our recent studies have demonstrated that incorporating ionic liquids as co-surfactants in aqueous surfactant solutions can simultaneously enhance CHF and HTC by promoting stable in-situ deposition and improved liquid replenishment at the heated surface.

Related Publications

[1] Upadhyay, A., Kumar, B., & Raj, R. (2024). “Ionic Liquid as a Cosurfactant for Critical Heat Flux Enhancement during Boiling with Aqueous Surfactant Solutions”, Applied Thermal Engineering, 122962. Link

[2] Upadhyay, A., Kumar, B., Kumar, N., & Raj, R. (2023). “Simultaneous Enhancement of Critical Heat Flux and Heat Transfer Coefficient via In-Situ Deposition of Ionic Liquids during Pool Boiling”, International Journal of Heat and Mass Transfer, 208, 124066. Link

Decoding the Sound of Boiling: Acoustics of Gas and Vapor Bubble Departure

This research identifies the fundamental bubble dynamics responsible for sound generation during boiling and bubble departure processes using synchronized high-speed visualization, hydrophone measurements, analytical modeling, and numerical simulations. The study demonstrates that vapor bubble departure during boiling emits the dominant acoustic response, analogous to gas bubble departure from a submerged nozzle, wherein the rapid liquid-jet inrush during the neck-fracture (pinch-off) event excites bubble oscillations responsible for sound emission. Building upon this similarity, gas bubble acoustics are utilized as a simplified framework for understanding boiling acoustics. Interestingly, although gas and vapor bubbles exhibit nearly similar departure dynamics and damping behavior, vapor bubbles emit significantly lower acoustic frequencies due to interfacial heat and mass transfer effects, for which a modified natural frequency relation was developed.

Related Publications

[1] Suriyaprasaad, B., Upadhyay, A., Thakur, A., & Raj, R. (2026). “A Roadmap for Decoding the Sound of Boiling”, npj Thermal Science and Engineering, 1, 2. Link

[2] Upadhyay, A., Hazra, S. K., Alam, M. Q., & Raj, R. (2026). “Damped Harmonic Oscillator Framework for Boiling Acoustics: Insights from Single Vapor Bubble Experiments”, International Journal of Heat and Mass Transfer, 261, 128508: 1-13. Link

[3] Alam, M. Q., Upadhyay, A., Assam, A., & Raj, R. (2025). “On the origin and nature of acoustic emissions from bubbles departing an underwater nozzle”, Physics of Fluids, 37(4). Link

Adsorption Behavior of Ionic Liquids for Thermal Management Applications

The adsorption of amphiphilic molecules such as surfactants and ionic liquids at solid–liquid and liquid–vapor interfaces critically influences wetting, foaming, and interfacial heat-transfer characteristics. This research investigates how molecular structure, counter-ion type, and concentration govern adsorption behavior, dynamic surface tension, and interfacial transport phenomena. Through boiling experiments, wettability measurements, and surface characterization, it was demonstrated that ionic liquids actively adsorb over metallic surfaces and form micro-/nano-structured interfacial layers that modify bubble nucleation, bubble coalescence, and surface rewetting behavior, leading to simultaneous enhancement in critical heat flux (CHF) and heat transfer coefficient (HTC). More recently, these adsorption-driven surface modifications were extended toward scalable development of durable superhydrophobic and superhydrophilic surfaces for atmospheric water harvesting and broader thermal management applications, highlighting adsorption engineering as a versatile route for next-generation functional surface design.

Related Publications

[1] Shukla, A., Upadhyay, A., Qadeer, M., Thakur, A. D., & Raj, R. (2026). “Eco-friendly Immersion-Coating Strategy for Scalable and Durable Superhydrophobic Aluminum Surfaces”, Langmuir, 42, 8343: 1-15. Link

[2] Upadhyay, A., Kumar, B., & Raj, R. (2024). “Ionic Liquid as a Cosurfactant for Critical Heat Flux Enhancement during Boiling with Aqueous Surfactant Solutions”, Applied Thermal Engineering, 122962. Link

[3] Upadhyay, A., Kumar, B., Kumar, N., & Raj, R. (2023). “Simultaneous Enhancement of Critical Heat Flux and Heat Transfer Coefficient via In-Situ Deposition of Ionic Liquids during Pool Boiling”, International Journal of Heat and Mass Transfer, 208, 124066. Link

Boiling Acoustic-Based Deep Learning Strategies for Regime Prediction

This research develops and validates a deep-learning framework that interprets acoustic signatures from boiling processes to accurately predict regime transitions and thermal performance states. Using high-sensitivity hydrophones and spectrogram-based preprocessing, the approach converts underwater boiling sound into machine-learning-ready data. A convolutional neural model (YAMNET), enhanced with explainable AI techniques (e.g., Grad-CAM), identifies key features and spectral bands associated with specific boiling regimes such as nucleate boiling, transition, or film boiling. By combining signal processing, transfer-learning of pre-trained audio models, and domain-specific feature extraction, the method achieves robust regime classification and opens pathways for early detection of boiling crisis in thermal-fluid systems.

Related Publications

[1] Suriyaprasaad, B., Upadhyay, A., Thakur, A., & Raj, R. (2026). “A Roadmap for Decoding the Sound of Boiling”, npj Thermal Science and Engineering, 1, 2. Link

[2] Suriyaprasaad, B., Upadhyay, A., Thakur, A., & Raj, R. (2025). “Explainable boiling acoustics analysis using Grad-CAM and YAMNet for robust pool boiling regime classification”, Applied Thermal Engineering, 127220. Link

Computational Fluid Dynamics (CFD) Simulations for Multiphase Applications

This research leverages advanced CFD methods to investigate multiphase phenomena such as bubble formation, departure, and oscillation in submerged nozzle flows. By coupling detailed numerical modeling of the liquid–gas interface with experimental validation of acoustic emissions, the work elucidates key mechanisms behind bubble dynamics, interfacial stress waves, and the resulting acoustic signals. The simulations incorporate compressibility of the gas phase, rapid neck‐fracture events, and transient liquid inrush to reproduce observed acoustic frequency peaks and waveform signatures. These CFD studies not only bridge the gap between physical measurements and mechanistic insight but also provide a predictive framework to guide the design of multiphase flow systems, thermal‐fluid devices, and noise‐mitigation solutions.

Related Publication

[1] Alam, M. Q., Upadhyay, A., Assam, A., & Raj, R. (2025). “On the origin and nature of acoustic emissions from bubbles departing an underwater nozzle”, Physics of Fluids, 37(4). Link

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