The Local-Conditions Concept of Burn-Out

Thus far, the burn-out phenomenon has been discussed mainly in terms of the important system-describing parameters. This approach is preferable, since the system parameters are, in fact, the independent variables and they must uniquely and unequivocally determine the heat flux required to produce burn-out. It can be argued, however, that burn-out, being a local phenomenon, may be described entirely by local parameters of this there can be no dispute. The problem is to find a description of these local parameters that works. Our 

Barnett (B3) considered the relevance of quality to burn-out and made the important observation that for uniformly heated round tubes, the burn-out 

It can be seen that k in Eq. (10) replaces the system-describing parameters L and Ah in Eq. (1). A direct test of the hypothesis is therefore to plot (j against k for fixed values of P, G, and d, with L and Ah varying. For the hypothesis to be correct, the data points must all lie on a smooth curve. Experience shows, however, that plotting (f against k often produces an undue amount of scatter which may obscure and distort any true relationship existing. This enhanced scatter is caused by the cumulative effect of experimental errors in the various terms in the heat-balance equation from which the quality k is derived. 

The above difficulty is particularly true of burn-out data for water, and Barnett therefore used a different approach for testing Eq. (10). His method was first to change the equation into a form containing only system-describing parameters, which can be done by substitution among the following three expressions  

(14) shows a linear relation between f and k, and implies that Eq. (13) may be written  

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