Publikacje

Abstract:

The main aim of this work was to provide heat transfer calculations of flow boiling in
mini‐channels with an application for the Trefftz functions. The test section comprised five parallel
mini‐channels with a depth of 1 mm, with a common heated wall. For the estimation of the tem‐
perature uncertainty, during the experiment the temperature measurement was performed with
the use of K‐type thermoelements and an infrared camera in two mini‐channels simultaneously.
According to the Guide to the Expression of Uncertainty in Measurement, the Monte Carlo method is a
practical alternative to the GUM uncertainty framework. Since the uncertainty components are not
approximately the same magnitude, the Monte Carlo method was indicated to estimate the uncer‐
tainty of the surface temperature measurement. The results obtained from this simulation method
were compared with the results of the computation related to the uncertainty propagation method.
The results of both methods of temperature measurement were found to be consistent. The results
of the statistical analysis were used to describe heat transfer calculations. The heat transfer inves‐
tigations concerning the subcooled boiling region were performed during the other experiment.
The local heat transfer coefficients on the contact surface between the working fluid and the heated
wall were calculated from the Robin boundary condition. The mathematical model described by
the heat equation in the mini‐channel wall and by the Fourier‐Kirchhoff equation in a flowing fluid
leads to an inverse heat transfer problem. This problem was solved using the FEM with the
Trefftz‐type basis functions. The estimation of temperature uncertainty measurements due to the
Monte Carlo method was included in the final results of the heat transfer coefficient.

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Heat Transfer Calculations during Flow in Mini‐Channels with Estimation of Temperature Uncertainty Measurements