The propagation velocity of temperature instabilities is directly connected with the displacement of the so-called condensation front. This phenomenon was defined as a displacement of an area with a negligently small thickness that separates condensing vapour in a two-phase mixture from the liquid zone of the subcooled condensate. In the case of a phase change of condensation realized in established conditions, the condensation front displaces in the opposite direction to the vapour incoming to the channel. As a result of hydrodynamic or hydrostatic interactions, the displacement direction of the condensation front depends of whether we deal with the process of the development or decay of the condensation phase change. The present study contains a proposal concerning modeling of the propagation velocity of the condensation front in pipe minichannels for the R134a refrigerant in the conditions of the interactions of hydrodynamic instabilities. The diameters examined of minichannels were D = 0.64; 0.90; 1.40; 1.44; 1.92; 2.30 and 3.30 mm. (C) 2017 Elsevier Ltd. All rights reserved.