Critical Heat Flux In Channels Research Articles

Form factor and its influence on the critical heat flux in channels having different shapes with heat release nonuniformly distributed over the length

The problem of describing and methods for calculating the longitudinal form factor for taking into account the influence of longitudinal nonuniformity of heat release on the critical heat flux are briefly analyzed. An attempt is made to develop the method on the basis of some new physical assumptions. New relations are developed and suggested, the use of which made it possible to describe experimental data on critical heat fluxes in the case of heat release uniformly distributed over the length of tubes and fuel-rod assemblies.

Numerical study on effect of gap width of narrow rectangular channel on critical heat flux enhancement

According to the flow passage characteristic of narrow rectangular channel and liquid film dry-out mechanics of annular flow critical heat flux (CHF), an annular flow CHF analytical model for narrow rectangular channel has been achieved. This model may be used to predict the CHF behavior of boiling two-phase flow in narrow rectangular channel with gap width of not being less than 0.0005 m (the equivalent diameter of this channel is 0.001 m). Through analyzing and calculating, when the inlet dimensionless gap width of narrow rectangular channel is within 30–85, the enhancement of CHF in channel is obvious. At the same time, according to the characteristic of two-phase flow, the new determinant laws of CHF in boiling two-phase flow system have been derived. Through analyzing and calculating, it is substantial that this determinant laws is appropriate. The best dimensionless gap width of heat flux enhancement has been achieved to be 45–75.

A phenomenologically based prediction of the critical heat flux in channels containing an unheated wall

A phenomenologically based prediction of the critical heat flux in channels containing an unheated wall

On the possibilities of increasing the critical heat flux in channels

The physical model of heat transfer crisis is proposed on the basis of studying experimental results obtained on the multipurpose thermohydraulic setup of high parameters and the data available in the literature. The model uses the equation of the critical heat flux density under free motion (pool boiling) obtained on the basis of a single approach to solving two main problems of heat transfer theory—determination of boiling heat transfer intensity and the first critical heat flux density. A brief survey and analysis of studies on enhancing convective single-phase heat transfer and increase in crisis parameters at boiling in channels using additional turbulization over the entire flow section are presented. Special attention is paid to enhancing the heat transfer rate in two-phase flows by means of turbulence promoters affecting only the wall layer.