Novel Twofold Use of Photographic Technique for Simultaneous Flow Boiling Image Recording and Void Fraction Computation in a Mini-Channel Experiment

Abstract

The paper presents a novel twofold use of the photographic technique for flow boiling heat transfer investigation in the horizontal mini-channel. The dedicated measurement system was constructed to record basic thermal and flow parameters, i.e., boiling liquid inlet and outlet temperatures and pressures, and also temperatures inside the heating block to calculate heat flux going into the liquid. A high-speed video camera equipped with synchronous movement system was applied to combine the recording of two-phase flow images with simultaneous local void fraction measurements both based on the same photographic data set. The data were collected, managed, and refined with the scripts developed in the MathWorks Matlab 2019b environment. The synchronous use of two intelligent techniques in the scripts, i.e., the background subtraction technique and the statistical analysis of individual pictures allowed obtaining reliable experimental results. The proposed method of the void fraction determination ensures high measurement accuracy.

Flow Structure Investigations during Novec Refrigerant Condensation in Minichannels

“…Based on this value, the vapor quality x was determined. A very similar method in the study of the flow structures during boiling was used by Płaczkowski et al [38].…”

Numerical Analysis of the Boiling Heat Transfer Coefficient in the Flow in Mini-Channels

“…Images of two-phase flow structures recorded by a high-speed camera were used to determine the local void fraction in the channel, as mentioned in papers [3,7]. This was achieved by a specially developed procedure based on image analysis on the MatLab environment.…”

“…Boiling heat transfer in mini-channel flow has been the subject of extensive experimental and numerical research presented in the literature [1][2][3][4][5][6][7][8][9][10][11]. Due to the complexity of the process, the development of comprehensive correlations and/or flow boiling models based solely on experimental data is not possible.…”

“…In the presented experimental research, the new approach concerning high-speed filming with a high-resolution camera, specific photographic data reduction and experimental errors analysis of the observed two-phase boiling flow structures in a horizontal, rectangular mini-channel [3] was applied. This technique allowed simultaneous boiling two-phase flow visualisation and local void fraction measurement.…”