# Study of the Critical Heat Flux in Small Diameter Channels

11/19/2020 2020 - #04 Thermal physics and thermal hydraulics

https://doi.org/10.26583/npe.2020.4.06

### UDC: 621.039.517

The article describes experimental studies of hydrodynamics and heat transfer in a forced water flow in small-diameter channels at low pressures. The relevance of the studies is associated with a steady trend of interest in small heat exchangers. Small-diameter channels are actively used in components of compact heat exchangers for modern engineering and technical developments.

The main difficulty in studying heat transfer processes in small-diameter channels is the creation of methods for calculating the coefficients of hydraulic resistance and heat transfer in a two-phase flow. The influence of the channel size on the heat transfer and hydrodynamics of a two-phase flow is one of the defining parameters, since the existing internal scales (vapor bubble size, liquid droplet diameter, film thickness) can become comparable to the channel diameter, which can lead to different flow regimes. Obviously, in single-phase flows, there is no reason to expect a change in the laws of momentum and energy transfer with a decrease in the channel size, as long as the continuum approximation remains valid.

The authors analyzed the experiments of domestic scientists on the study of the distribution of thermal-hydraulic parameters in small cross-section tubes in the entire range of variation of flow parameters in the channel up to critical heat flux conditions, when the wall temperature rises sharply with a slowly increasing heat load. In addition, a comparison was made of the experimental data obtained by domestic and foreign authors on the critical heat flux.

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experimental facility working area heat supply and removal critical heat flux boiling point results of experimental studies