Local-conditions hypothesis

A general statement of the Barnett local-conditions hypothesis ... 

Kirby (K3) has found an interesting hypothesis that works in the net quality region. It is a contraction of Barnett s local-conditions hypothesis [Eq. (10)] and is therefore not strictly applicable at low qualities where slight... 

The Barnett local-conditions hypothesis has been applied to the above example by rewriting the general burn-out correlation for uniformly heated round tubes [Eq. (22)] as follows ... 

Fig. 40. Test of the Barnett local-conditions hypothesis applied to a tube with a skewed-cosine heat-flux profile [from Barnett (B4)]. Fluid water, d = 0.422 in., L — 12 in., P = 2000 psia.

M3. Macbeth, R. V., Burnout analysis. 4. Application of a local conditions hypothesis to world data for uniformly heated round tubes and rectangular channels, AEEW-R.267 (1963). 

Kirby local-conditions hypothesis, 245-246 Krichevsky-Ilinskaya equation, 169-170 Krichevsky-Kasarnovsky equation, 166-169... 

Macbeth, R. V., 1963a, Burnout Analysis Pt. 2, The Basic Burnout Curve, UK Rep. AEEW-R-167 Pt. 3, The Low Velocity Burnout Regime, AEEW-R-222 Pt. 4, Application of Local Conditions Hypothesis to World Data for Uniformly Heated Round Tubes and Rectangular Channels, AEEW-R-267, UK AEEW, Winfrith, England. (5)... 

The reasoning behind the burnout formula (6.56) is known as the local-conditions hypothesis. The burnout heat flux is found to be a function of the values of four variables at the actual point of burnout, i.e.,... 

The fundamental hypothesis of CIT is the existence of a local-equilibrium condition. A series of finite volume cells is considered in a material body, in which local variables such as temperature and entropy are uniform and in equilibrium, but time-dependent. The variables can take different values from cell to cell. The majority of textbooks are written using this formulation (see, e.g., Kestin 1979, which refers to this as the principle of local state). The most important result of CIT under the local-equilibrium hypothesis is that, as a natural result of the Second Law of Thermodynamics in the course of a mechano-thermal process, we have the following entropy inequality ... 

As shown above, the classical description has been undoubtedly useful nevertheless, it has some drawbacks both from the fundamental and practical points of view. It is based on the macro- and/or local- equilibrium hypothesis, which may be too restrictive for a wider class of phenomena where other variables, not found in equilibrium, may influence the thermodynamic equations in the situations taking place when we get out of equilibrium. The concept is consistent with the limiting case of linear and instantaneous relations between fluxes and forces, which, however, becomes unsatisfactory under extreme conditions of high frequencies and fast non-linear changes (explosions). Then the need arises to introduce the second derivatives ( ), such as 0 = 0 (T, T T , P,. ..) and the general thermodynamic potential, 0, is can be no longer assumed via a simple linear relation but takes up a new, non-stationary form 0 = - ST + VP + (d0/Fr)T r ,p+ (state variables become dependent on the temperature derivatives. 

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