FILM CONDENSATION INSIDE HORIZONTAL PIPES AND MINI CHANNELS

The article provides a brief description of the semi-empirical model of Ananiev, Boyko and Kruzhilin for calculating heat transfer during the condensation of working substances inside smooth horizontal pipes in a turbulent flow regime. Comparisons of heat transfer calculations based on a semi-empirical model with the results of experimental studies during the condensation of refrigerants, hydrocarbons and specialized substances inside pipes from well-known works by different authors are presented, which indicate good agreement between the results of studies and calculations based on the model, taking into account their boundary values. The presented calculations of heat transfer during condensation inside smooth horizontal pipes and minichannels are performed according to the semiempirical formula of Ananiev, Boyko and Kruzhilin, taking into account the influence of steam velocity on heat transfer processes. The calculation results demonstrate good agreement with the experimental data of various authors on the condensation of refrigerants R22, R134a, R125, R32 , R410A, specialized substances R245fa, Novec649, HFE-7000 and natural hydrocarbons R290, R600a, R1270, and DME for turbulent flow areas. For engineering practice, the presented semi-empirical model for calculating heat transfer during condensation of water vapor, refrigerants R22, R134a, R32, R410A, specialized substance HFE-7000, natural hydrocarbons R290, R600a, R1270 for smooth horizontal pipes (din > 3 mm) can be recommended. In this case, it is necessary to take into account the limits of application of the boundary values of the model. Calculation of heat transfer coefficients by semi-empirical correlation shows that it improves the description of the experimental data of many authors of works on the condensation of refrigerants R152a, R290, R134a, and R32 inside round minichannels (3 mm ≥ din > 200 μm) under turbulent and transient flow regimes. Further studies should include the performance of calculations on theoretical and empirical models for calculating heat transfer during condensation inside minichannels in order to create a general method for calculating heat transfer, taking into account the influence of regime flow parameters.