Forced convection boiling,

While dimensional analysis is often a useful tool for dealing with a problem, it has not yet been successful for studying this phenomenon, mainly because the fluid properties of importance in forced-convection boiling have not been identified. Burn-out correlations based on dimensional analysis have appeared, e.g., Griffith (G5), Reynolds (R2), Zenkevitch (Zl), Ivashkevich (12), Tong et al. (T6), but the fluid properties used in these cases have been chosen on the basis of various assumptions without any demonstration that the properties used were the correct ones. They have, in fact, been shown in recent work by Barnett (B5), (to be considered later) to be either incorrect or incomplete. 

Jens and Leppert (J4), and, more recently, Barnett (B2), have emphasized the need to distinguish between a temperature-controlled surface and a heat-flux-controlled surface when referring to boiling phenomena. Failure to observe the distinction has caused some confusion in the literature, particularly as further complications arise from differences that exist between pool boiling and forced-convection boiling. 

From here on, unless otherwise stated, we shall be considering only forced-convection boiling with a heat-flux-controlled surface. 

The conclusion to be drawn from the above examples and many others is that softness in a boiling system, preceding the boiling channel inlet, may cause flow oscillations of low frequency. It is probably the pressure perturbations arising from the explosive nature of nucleate boiling that initiates the oscillation, and the reduced burn-out flux which follows probably corresponds to the trough of the flow oscillation, as a reduction in flow rate always drops the burn-out flux in forced-convection boiling. 

B2. Barnett, P. G., The scaling of forced convection boiling heat transfer, AEEW-R.134 (1963). 

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