High-speed visualization and image processing of sub-atmospheric water boiling on a transparent heater
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R E G UL A R P A P E R
Vladimir Serdyukov
•
Ivan Malakhov • Anton Surtaev
High-speed visualization and image processing of subatmospheric water boiling on a transparent heater
Received: 24 December 2019 / Revised: 12 April 2020 / Accepted: 2 May 2020 The Visualization Society of Japan 2020
Abstract The paper is devoted to the processing and analysis of the high-speed visualization data on water pool boiling in the pressure range of 5.5–103 kPa. The study of the vapor bubbles dynamics and evolution of void fraction near a heated wall during boiling was performed using a special design of a transparent heating element and high-speed visualization from its bottom side. To analyze the wide array of video data, automatic image processing programs were developed. As a result, a detailed statistical analysis of the growth curves and departure diameters of vapor bubbles during boiling at different pressures was carried out. It was shown that at ultra-low pressure 5.5 kPa after the departure of massive vapor bubbles the pulsating boiling regime was occurred. A method based on the estimation of void fraction near a heated wall was proposed and implemented for the description of this cyclic boiling regime at low sub-atmospheric pressure. Keywords Sub-atmospheric boiling Vapor bubbles evolution High-speed visualization Image processing Transparent heater design
1 Introduction Today, the high-speed video (HSV) recording has become an almost inalienable part of experimental studies of the process of liquid boiling. Starting from the first papers (Gunter 1951; Lubuntsov et al. 1964; Mamontova 1966; Abdelmessih et al. 1972), the researchers have obtained the video data on the growth dynamics and departure of vapor bubbles, their interaction and the features of crisis phenomena development during boiling of various liquids at different pressures. The obtained information allowed to significantly improve the understanding of nucleation and bubble dynamics and to create new theoretical approaches to describe the bubble growth rate, bubble departure diameter, etc. In addition, the usage of high-speed visualization as a rule allows to analyze and to identify the mechanisms of heat transfer enhancement during boiling using various functional modified surfaces (Zupancˇicˇ et al. 2017; Surtaev et al. 2018a; Dedov et al. 2019; Sadaghiani et al. 2020). High-speed video recording of liquid boiling traditionally is performed from the side of heating element. However, as noted by many researchers, such format of visualization has shortcomings. In particular, the V. Serdyukov (&) I. Malakhov A. Surtaev Novosibirsk State University, Novosibirsk, Russia E-mail: [email protected] V. Serdyukov I. Malakhov A. Surtaev Kutateladze Institute of Thermophysics, Novosibirsk, Russia V. Serdyukov Chinakal Institute of Mining, Novosibirsk, Russia
V. Serdyukov et al.
activation of numerous nucleation sites at relatively low heat fluxes makes it difficult to identify individual vapor bubbles. More recently, various researchers (Nishi
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