https://orcid.org/0000-0002-2410-474X
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ABSTRACT
The paper presents the results of experimental and theoretical studies of temperature fluctuations at the surface of heaters in different heat transfer regimes. Developing several methods of treatment for the temperature fluctuations, we succeed in the diagnosing the onset of transient boiling regimes. The proposed methods are based on the statistical analysis of histograms and amplitude-frequency analysis of the spectra of temperature fluctuations. In addition, the study demonstrates and compares how these techniques may be utilized to predict the transitions from the convective heat transfer to the nucleate boiling and the film boiling regimes.
Nomenclature
| A, C, m | = | coefficients, exponents |
| As | = | asymmetry criterion |
| c | = | specific heat (J/(kg∙K)) |
| d | = | diameter(m) |
| f | = | number of values |
| G | = | flow rate (m3/sec) |
| h | = | heat transfer coefficient (W/(m2∙K)) |
| i | = | imaginary unit |
| N | = | number of points |
| q | = | heat flux (W/m2) |
| S | = | area (m2) |
| T | = | temperature (K) |
| ΔT | = | superheat (K) |
| V | = | volume (m3) |
Greek symbols
| α | = | exponent |
| β | = | index (Hz) |
| θ | = | subcooling relative to saturation temperature (K) |
| μ3 | = | third central moment (K3) |
| ν | = | frequency (Hz) |
| ρ | = | density (kg/m3) |
| σ | = | standard deviation (K) |
| τ | = | time (sec) |
| Ψ | = | amplitude (K) |
Dimensionless numbers
| Nu | = | Nusselt number |
| Ra | = | Rayleigh number |
| Pr | = | Prandtl number |
Subscripts
| av | = | average |
| b | = | boiling |
| bor | = | border |
| j, k | = | indices |
| s | = | saturation |
| 0 | = | initial value |