Abstract
The paper discusses the results of flow boiling heat transfer in minichannels obtained on the basis of time-dependent experiments. The main interest of the work was to investigate the occurrence of the accompanying instabilities during the boiling incipience. The essential part of the experimental standwas a test section with two minichannels, each of 1.7 mm depth. The heated element for FC–72flowing along the minichannels was a thin foil. In the tested minichannel, the temperature of the outer surface of the foil was measured due to thermoelements. The onset of flow boiling in minichannels was induced by increasing the heat flux supplied to the heater. The main aims of the investigation were to determine the heat transfer coefficient by means of the FEM with time—dependent Trefftz–type basis functions based on the Hermite interpolation and to recognize dynamic instabilities during boiling incipience. The results were illustrated as: the heat transfer coefficient, the mass flow rate and the inletpressure versustime and as boiling curves.
Highlights
Extensive studies are carried out to understand mechanisms of heat transfer processes during fluid flow along channels of small cross-sections
The method of solving the nonstationary inverse heat transfer problem using the FEM with time-dependent Trefftz-type basis functions obtained on the basis of the Hermite interpolation were discussed in this paper
This method was used in calculations concerning heat transfer coefficient determination on the basis of the timedependent study on flow boiling heat transfer in minichannels
Summary
Extensive studies are carried out to understand mechanisms of heat transfer processes during fluid flow along channels of small cross-sections. These include experimental research and theoretical analysis. Heat transfer coefficient determination belongs to inverse heat transfer problems [12,13,14] They could be solved with the use of numerical methods based on the Trefftz method [1,2,3,15,16,17,18,19,20,21,22,23,24,25,26]. The time-dependent measurements from experiments were used in mathematical method for determining the heat transfer coefficient
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