Pool Nucleate Boiling - Non-orthogonal Empirical Functions
The analysis of spatio-temporal data and the physical understanding of the systems generating them are often limited by the available techniques. These limitations are especially evident in nucleate boiling.
The movie on the left shows a sequence of temperature fields
obtained from a pool nucleate boiling experiment. Spatio-temporal data
for the wall temperature in pool nucleate boiling of water on a thin,
horizontal, stainless steel plate were obtained by liquid crystal
thermography and high speed video recording.
A previous analysis provided examples of the
thermal conditions for activation of individual nucleation sites, for the
heat transfer mechanisms during bubble growth and for the consequent
interactions between adjacent sites.
Principal Component Analysis (PCA) is shown to provide a reconstruction of the temperature fields that is accurate in the root mean square sense but which obscures information about the underlying physics, such as positions of the nucleation sites.
In contrast, the movie on the left shows a new approach using non-orthogonal
empirical functions (NEFs) which encodes the relevant physical constraints (e.g. each NEF has a
radially symmetrical form as suggested by the pattern of cooling during
bubble growth). NEFs provide an efficient identification of the positions
of active sites in successive frames; they are better suited to the
analysis of non-stationary dynamics than PCA and allow for information
compression.
See references below for more details.
[1] P.E. McSharry, J.H. Ellepola, J. von Hardenberg, L.A. Smith, D.B.R. Kenning, K. Judd (2002), Spatio-temporal analysis of nucleate pool boiling: identification of nucleation sites using non-orthogonal empirical functions. International Journal of Heat and Mass Transfer, 45(2): pp. 237-253.
[2] J. von Hardenberg, T. Kono, D.B.R. Kenning, P.E. McSharry, L.A. Smith (2002), Identification of boiling nucleation sites by non-orthogonal empirical functions (NEF) analysis of thermographic data in Proceedings of 12th International Heat Transfer Conference: Grenoble, France. pp. 377-382.
[3] P.E. McSharry, L.A. Smith, T. Kono, D.B.R. Kenning (2000), Nonlinear analysis of site interactions in pool nucleate boiling in Proceedings of 3rd European Thermal Sciences Conference, Spindler, ETS, Pisa: Heidelberg, Germany.
[4] J.H. Ellepola, P.E. McSharry, D.B.R. Kenning (1996), Is Nucleate Boiling Chaotic? (And Who Cares?) in Proceedings Eurotherm Seminar No. 48 Pool Boiling, Marvillet, EFS, Pisa: Paderborn, Germany. pp. 17-24.