DETERMINING OF PARAMETERS OF HEAT EXCHANGE FOR VAPORIZATION OF THE MIXED REFRIGERANT ON THE HIGH THERMAL CONDUCTIVITY SINTERED POWDER CAPILLARY-POROUS COATINGS

The results of experimental research of heat exchange under the nucleate boiling of refrigerants R404a, R407c and R410a on the tubes with capillary-porous coating are presented. Experimental studies were carried out with the aid of an experimental installation in conditions of a large volume at pressures of saturation pн = 0.9–1.4 MPa and densities of the heat flux q = 5–35 kW/m2. For the first time the criterion equation for the calculation of the intensity of heat transfer during evaporation of ozone safe refrigerants on surfaces with high thermal conductivity sintered capillary-porous coating was obtained. Experimental data are summarized satisfactorily in a wide range of parameters of the porous layer, i.e. the pressure (pн = 0.9–1.4 MPa) and heat loads (q = 5–35 kW/m2). The ratio makes us possible to calculate the heat transfer coefficients within ±20 %. The dependence can be used in engineering calculations of the characteristics of the heat exchangers of the evaporative type. The coefficient of heat transfer during boiling of refrigerants on the investigated surfaces with the sintered capillary-porous coating, 4 times higher than on a smooth one and 1.5 times higher than on the finned surface, that allows us to come to a conclusion about the advantage of porous coatings. Boiling in capillary-porous coating leads to a decrease in weight and size of the installations due to the heat exchange intensification and the size of the tubes smaller as compared to the size of the finned ones.

1. Kichatov B. V. (2000) Modeling of Processes of Hydrodynamics and Heat Transfer in the Interaction of Two-Phase Flows with a Porous Medium. Moscow. 235 (in Russian).

2. Smirnov G. F., Tsoi A. D. (1999) The Heat Transfer During Evaporation in Capillaries and Capillary-Porous Structures. Moscow, MPEI Publ. 439 (in Russian).

3. Ovsyannik A. V. (2004) The Boiling Heat Transfer on the Developed Surfaces. Gomel State Technical University named after P. O. Sukhoi. 371 (in Russian).

4. Ovsyannik A. V. (2012) Modeling of Heat Transfer in Boiling Liquids. Gomel, Gomel State Technical University named after P. O. Sukhoi. 284 (in Russian).

5. Ovsyannik A. V. (?ead) (2015) The Study of Heat and Mass Transfer at Phase Transformations of One-Component and Mixture Ozone-Safe Refrigerants: Research Report (Final). No SR 20141921. Gomel, Gomel State Technical University named after P. O. Sukhoi. 101 (in Russian).

6. Vasil’ev L. L. (head) (2000) Intensification of Heat Transfer at Phase Transitions in Porous Coatings of Heat Sources: Research Report (Final). No SR 19981975. Minsk, A. V. Luikov Heat and Mass Transfer Institute of the National Academy of Sciences of Belarus. 73 (in Russian).

7. Shapovalov A. V. (2005) Heat Transfer in Evaporation in a Porous Structure with a Large Volume and Capillary Fluid Transport to Areas of Steam Generation. Vestn. Gomel'skogo Gos. Tekhn. Un-ta imeni P. O. Sukhogo [Bulletin of Gomel State Technical University named after P. O. Sukhoi], (2), 15–22 (in Russian).

8. Kichatov B. V., Polya?v V. M. (1999) The Boiling of Liquid on Surfaces with Porous Coatings. Teploenergetika = Thermal Engineering, (3), 72–76 (in Russian).

9. Vasil’ev L. L., Zhuravlev A. S., Ovsyannik A. V., Novikov M. N. (2001) Generalization of Experimental Data on Boiling Heat Transfer of Propane on Copper Sintered Capillary-Porous Coating. Vestn. Gomel'skogo Gos. Tekhn. Un-ta imeni P. O. Sukhogo [Bulletin of Gomel State Technical University named after P. O. Sukhoi], (2), 3–13 (in Russian).

10. Novikov M. N. (2001) Intensification of Heat Transfer at Propane Boiling on a Porous Coatings. Minsk. 180 (in Russian).