The Technique of Modeling Forced-Convection Burn-Out

A variety of possible sets of important properties are chosen for testing, such as those shown in Table VII. Two properties among the sets listed will be unfamiliar. These are p = dOJdP and y = -d(pjJpy)JdP, where 9S is the saturation temperature corresponding to the pressure P. 

The family of uniformly heated round tubes has the simplest heat flux distribution and test-section geometry for which burn-out may occur, and it was selected for the preliminary investigation to test the different sets of important properties. Now, for a uniformly heated tube, the burn-out flux for a given fluid can be represented by the equation 

however, at any given pressure there is for all substances a unique value of the density ratio pjpy evaluated at the saturation temperature, Eq. (36) may be rewritten as 

This allows the pressure, which has significance only when the fluid experiencing it is named, to be replaced by a dimensionless group of properties which has significance for all fluids. Thus, the first requirement in constructing a model of a system is that the inlet pressures should be selected so that the density ratio of the two phases in the model is the same as that in the system 

Possible Sets or Scaling Laws for Forced Convection Burn-Out and the Implied Scaling Factors for Water and Freon-12 

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