Volodymyr Ilchenko | National Academy of Fine Arts and Architecture (Kyiv, Ukraine) (original) (raw)
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Papers by Volodymyr Ilchenko
Experimental Thermal and Fluid Science, 2002
ABSTRACT An investigation on forced convective subcooled boiling of water was carried out using o... more ABSTRACT An investigation on forced convective subcooled boiling of water was carried out using optical measurement techniques. An experimental facility was constructed and built up for water at low system pressure. The test section consists of a horizontal rectangular channel heated from one side by a copper strip. The imaging and observation techniques presented in [1], were further developed by combining the high speed camera with an additional low speed, high resolution CCD camera. The view parallel to the heated surface records the dynamics of bubble growth, the bubble detachment and collapse while the low speed data from the perpendicular view delivers additional data like the number of bubbles, the bubble size and density distribution, the average spacing of the bubbles and the average local vapor content. The first part of this paper concentrates on the measurement techniques and the development of the image processing and analysing algorithms for a statistical evaluation of the high speed films. Secondly, results of the bubble characteristics and the vapor distribution obtained with the combined camera system are presented for various heat fluxes in the range of 0.2 to 1.1 MW/m2 and different liquid mass fluxes (250–2000 kg/m2 s) at a constant subcooling rate of 20 K. Finally, a model is presented to predict the local void fraction as a function of the height above the heated surface assuming a spherical form of the bubbles.
International Journal of Heat and Fluid Flow, 2004
Subcooled flow boiling is a commonly applied technique for achieving efficient heat transfer. In ... more Subcooled flow boiling is a commonly applied technique for achieving efficient heat transfer. In the study, an experimental investigation in the nucleate boiling regime was performed for water circulating in a closed loop at atmospheric pressure. The testsection consists of a rectangular channel with a one side heated copper strip and a very good optical access. For the optical observation of the bubble behaviour the high-speed cinematography is used. Automated image processing and analysis algorithms developed by the authors were applied for a wide range of mass flow rates and heat fluxes in order to extract characteristic length and time scales of the bubbly layer during the boiling process. Using this methodology, a huge number of bubble cycles could be analysed. The structure of the developed algorithms for the detection of the bubble diameter, the bubble lifetime, the lifetime after the detachment process and the waiting time between two bubble cycles is described. Subsequently, the results from using these automated procedures are presented. A remarkable novelty is the presentation of all results as distribution functions. This is of physical importance because the commonly applied spatial and temporal averaging leads to a loss of information and, moreover, to an unjustified deterministic view of the boiling process, which exhibits in reality a very wide spread of bubble sizes and characteristic times. The results show that the mass flux dominates the temporal bubble behaviour. An increase of the liquid mass flux reveals a strong decrease of the bubble life-and waiting time. In contrast, the variation of the heat flux has a much smaller impact. It is shown in addition that the investigation of the bubble history using automated algorithms delivers novel information with respect to the bubble lift-off probability.
A computer holography is the optical hologram recording on the CCD-matrix with digital reconstruc... more A computer holography is the optical hologram recording on the CCD-matrix with digital reconstruction of the 2Dimages for the different volume object cross-sections. The possibility to use compact semiconductor laser diodes in the computer holography for 3D-scene registration is experimentally proved in the D. Gabor's scheme. For off axis hologram recording the S. Benton's scheme for holography using is suggested.
Experimental Thermal and Fluid Science, 2002
ABSTRACT An investigation on forced convective subcooled boiling of water was carried out using o... more ABSTRACT An investigation on forced convective subcooled boiling of water was carried out using optical measurement techniques. An experimental facility was constructed and built up for water at low system pressure. The test section consists of a horizontal rectangular channel heated from one side by a copper strip. The imaging and observation techniques presented in [1], were further developed by combining the high speed camera with an additional low speed, high resolution CCD camera. The view parallel to the heated surface records the dynamics of bubble growth, the bubble detachment and collapse while the low speed data from the perpendicular view delivers additional data like the number of bubbles, the bubble size and density distribution, the average spacing of the bubbles and the average local vapor content. The first part of this paper concentrates on the measurement techniques and the development of the image processing and analysing algorithms for a statistical evaluation of the high speed films. Secondly, results of the bubble characteristics and the vapor distribution obtained with the combined camera system are presented for various heat fluxes in the range of 0.2 to 1.1 MW/m2 and different liquid mass fluxes (250–2000 kg/m2 s) at a constant subcooling rate of 20 K. Finally, a model is presented to predict the local void fraction as a function of the height above the heated surface assuming a spherical form of the bubbles.
International Journal of Heat and Fluid Flow, 2004
Subcooled flow boiling is a commonly applied technique for achieving efficient heat transfer. In ... more Subcooled flow boiling is a commonly applied technique for achieving efficient heat transfer. In the study, an experimental investigation in the nucleate boiling regime was performed for water circulating in a closed loop at atmospheric pressure. The testsection consists of a rectangular channel with a one side heated copper strip and a very good optical access. For the optical observation of the bubble behaviour the high-speed cinematography is used. Automated image processing and analysis algorithms developed by the authors were applied for a wide range of mass flow rates and heat fluxes in order to extract characteristic length and time scales of the bubbly layer during the boiling process. Using this methodology, a huge number of bubble cycles could be analysed. The structure of the developed algorithms for the detection of the bubble diameter, the bubble lifetime, the lifetime after the detachment process and the waiting time between two bubble cycles is described. Subsequently, the results from using these automated procedures are presented. A remarkable novelty is the presentation of all results as distribution functions. This is of physical importance because the commonly applied spatial and temporal averaging leads to a loss of information and, moreover, to an unjustified deterministic view of the boiling process, which exhibits in reality a very wide spread of bubble sizes and characteristic times. The results show that the mass flux dominates the temporal bubble behaviour. An increase of the liquid mass flux reveals a strong decrease of the bubble life-and waiting time. In contrast, the variation of the heat flux has a much smaller impact. It is shown in addition that the investigation of the bubble history using automated algorithms delivers novel information with respect to the bubble lift-off probability.
A computer holography is the optical hologram recording on the CCD-matrix with digital reconstruc... more A computer holography is the optical hologram recording on the CCD-matrix with digital reconstruction of the 2Dimages for the different volume object cross-sections. The possibility to use compact semiconductor laser diodes in the computer holography for 3D-scene registration is experimentally proved in the D. Gabor's scheme. For off axis hologram recording the S. Benton's scheme for holography using is suggested.