International Journal of Advanced Engineering Research and Science (IJAERS) Peer-Reviewed Journal ISSN: 2349-6495(P) | 2456-1908(O) Vol-9, Issue-6; Jun, 2022 Journal Home Page Available: https://ijaers.com/ Article DOI: https://dx.doi.org/10.22161/ijaers.96.31 www.ijaers.com Page | 295 A CHF Model for Pool Boiling on Rough Surface under Exponential Heat Supply Avdhoot Walunj 1 , Alangar Sathyabhama 2 , Amol Mande 3 , Ravindra Kolhe 4 , Dattatray Palande 4 1 Department of Farm Machinery and Power Engineering, Mahatma Phule Krishi Vidyapeeth, Rahuri-413722, India Email: aawalunj@gmail.com , avdhoot.walunj@nic.in 2 Department of Mechanical Engineering, National Institute of Technology Karnataka, Surathkal-575025, India Email : bhama72@gmail.com 3 Department of Mechanical Engineering, Sanjivani College of Engineering, Kopargaon-423603, India Email : mandeamolmech@sanjivani.org.in 4 Department of Mechanical Engineering, Sanjivani College of Engineering, Kopargaon-423603, India Email : kolheravindramech@sanjivani.org.in 5 Department of Mechanical Engineering, Matoshri College of Engineering and Research Center, Nashik -422105, India Email : dpalande@gmail.com Received: 10 May 2022, Received in revised form: 02 Jun 2022, Accepted: 07 Jun 2022, Available online: 15 Jun 2022 ©2022 The Author(s). Published by AI Publication. This is an open access article under the CC BY license (https://creativecommons.org/licenses/by/4.0/). Keywords— surface roughness, transient heat transfer, heat transfer coefficient, hydrodynamic model Abstract— In present study, the experiments are carried on sample of different surface roughness to investigate the transient heat transfer phenomenon at the saturated condition of the distilled water. The surface roughness (Ra) ranges from 0.106 μm to 4.03 μm. The boiling crisis is observed during each transient heat supply. The high-speed camera of 1000 fps is used to observe the stages of boiling during different transient and to confirm the moment of critical heat flux (CHF). The empirical relation is presented for transient CHF and corresponding heat transfer coefficient (HTC). It is found that transient CHF is a function of both Ra and γ. The hydrodynamic model is developed for prediction of CHF at different rate of exponential heat supply for the wide range of Ra by incorporating γ. I. INTRODUCTION The knowledge of boiling crisis in the nuclear reactors during exponential heat supply is important for the safety and efficient performance. The moment of critical heat flux (CHF) after which sharp reduction in heat transfer coefficient (HTC) is observed may lead to the rapid surge in the core temperature. Thus the formation of vapor blanket at CHF may lead to core meltdown accident. Hence understanding of the mechanism of transient CHF during exponential power escalation is of paramount importance. Researchers have contributed to explaining the CHF mechanisms by various approach viz. (i) Kelvin– Helmholtz instability between the upward flow vapor columns and downward flow liquid, (ii) dry-out of the liquid layer i.e. micro/macrolayer dry-out. Kutateladze [1] and Zuber [2] considered the Kelvin-Helmholtz instability as surface-fluid interaction fails due to relative motion between vapor column and surrounding liquid. Chang [3] considered the forces acting on the bubble during lift off from the horizontal surface and claimed that the critical velocity of the upward moving bubble is responsible for CHF. Haramura and Katto [4] stated near field evaporation phenomena through the macrolayer evaporation model and estimated CHF at the dry-out condition of macrolayer. Lay and Dhir [5] and Pasamehmetoglu et al. [6] developed the theoretical model based on microlayer