during this booklet the writer offers chosen demanding situations of thermal-hydraulics modeling of two-phase flows in minichannels with switch of section. those surround the typical modeling of movement boiling and stream condensation utilizing an analogous expression. ways to version those respective instances convey, notwithstanding, that experimental info exhibit assorted effects to these acquired by means of tools of calculation of warmth move coefficient for respective instances. partly that may be dedicated to the truth that there are non-adiabatic results found in either sorts of part swap phenomena which alter the strain drop because of friction, liable for applicable modelling. The amendment of interface shear stresses among circulation boiling and circulation condensation in case of annular circulate constitution can be thought of via incorporation of the so known as blowing parameter, which differentiates among those modes of warmth move. nevertheless, in case of bubbly flows, the new release of bubbles additionally modifies the friction strain drop by way of the impression of warmth flux. provided also are the result of a unusual M-shape distribution of warmth move coefficient particular to circulate boiling in minichannels. ultimately, a few cognizance is dedicated to mathematical modeling of dryout phenomena. A 5 equation version permitting choice of the dryout place is gifted, the place the mass stability equations for liquid movie, droplets and gasoline are supplemented by means of momentum equations for liquid movie and two-phase core.