This model extends `Flow1D2ph` by computing the
distribution of the heat transfer coefficient `gamma` and
making it available through an extended version of the
`wall` connector.

This simplified model can be used for one-phase or two-phase water/steam flow. The heat transfer coefficient is computed according to the following hypotheses:

- If the fluid is subcooled liquid or superheated steam, Dittus-Boelter's correlation [1] is used.
- If the fluid is a two-phase mixture with a steam fraction less
than the (constant) critical value
`xCHF`, boiling heat transfer is assumed with a heat transfer coefficient equal to`gamma_b`. - If the fluid is wet steam with a steam fraction greater than
the (constant) critical value
`xCHF`, the heat transfer coefficient is computed according to Dittus-Boelter's correlation, by considering only the steam fraction of the mixture.

A smoothing algorithm is applied to the nodes which are in the neighbourhood of a transition boundary between non-boiling and boiling conditions, to avoid non-physical sudden changes of the nodal values of the heat transfer coefficient when the transition boundary passes through a node. The computed values of the heat transfer coefficient are thus a continuous function of the nodal enthalpies and pressures, so that it is not necessary to generate events in order to handle discontinuities

**References**

- J. C. Collier:
*Convective Boiling and Condensation*, 2nd ed.,McGraw Hill, 1981, pp. 146.

*24 Mar 2005*by Francesco Casella:

`FFtypes`package and`NoFriction`option added.*16 Dec 2004*by Francesco Casella:

Standard medium definition added.*1 Nov 2004*by Francesco Casella:

Equations revisited.*24 Sep 2004*by Francesco Casella:

Adapted to Modelica.Media.*11 Feb 2004*by Francesco Casella:

Computation of the h.t.c. extended to all the thermodynamic conditions of the fluid.*1 Oct 2003*by Francesco Casella:

First release.

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