An Analysis of Heat Exchange Crisis in the Capillary Porous System for Cooling Parts of Heat and Power Units

A model of dynamics of the vapor bubbles that emerge on solid surfaces of porous structures and the steam generating wall (bottom layer) is presented in this work. The model was filmed and photographed by a high-speed camera SKS-1М. The discharge of high heat flows (up to 2·106 W/m2) was maintained by the joint action of capillary and mass forces with the help of intensifiers. An analytical model was developed based on the theory of thermoelasticity. The limit state of the porous coating with poor thermal conductivity and the metal bottom layer was determined. Heat flows were calculated from the spontaneous birth of the vapour nucleus (10–8) to the material destruction (10²–10³ s), thus the interval from the process of relaxation to the maximum process (destruction) was described. The size of the pullout particles determined in the model at the moment of porous coating destruction showed good congruence with the experimental data obtained at the optic stand. The destruction of coating under the compression forces occurs much earlier than the tension forces. It is probable that the destruction will happen under the impact of the compression and shear forces. The intervals of the heat flow when such destruction takes place are different for quartz and granite coating. Each thickness of the pullout particles under the impact of compression forces has its limit values of the heat flows, which are located within the mentioned intervals. As the specific heat flow in the heated layer increases and, therefore, the heating time decreases, the impact of the compression stresses increases as well. Despite the high resistance to compression, destruction from the compressive heat tension occurs in more favorable conditions immediately, and in diminutive volumes. Experimental testing units, test conditions, the outcome of the heat exchange crisis, the limit state of the surface and the calculation of critical heat flows are presented. The capillary porous system that works under the joint action of capillary and mass forces is studied. The system has advantages compared to pool boiling, thin-film evaporators and heat pipes.

References

[1] Polyaev V.M., Genbach A.N., Genbach A.A. Methods of Monitoring Energy Processes, Experimental Thermal and Fluid Science, International of Thermodynamics. Experimental Heat Transfer and Fluid Mechanics. 7th International Conference on Thermal Equipment, Renewable Energy and Rural Development, New York, USA, Avenue of the Americas, 1995, vol. 10, pp. 273–286.

[2] Polyaev V.M., Genbach A.A. Heat Transfer in a Porous System in the Presence of Both Capillary and Gravity Forces. Thermal Engineering, 1993, vol. 40, iss. 7, pp. 551–554.

[3] Polyayev V.M., Genbach A.N., Genbach A.A. Limiting surface conditions under thermal influence. High Temperature, 1991, vol. 29, iss. 5, pp. 923–934 (in Russ.).

[4] Polyaev V.M., Genbach A.A. Control of Heat Transfer in a Porous Cooling System. Proceedings, 2nd World Conference on Experimental Heat Transfer, Fluid Mechanics and Thermodynamics, Dubrovnik, Yugoslavia, 1991, pp. 639–644.

[5] Polyayev V.M., Genbach A.N., Minashkin D.V. Processes in a porous elliptical heat exchanger. Proceedings of Higher Educational Institutions. Маchine Building, 1991, no. 4–6, pp. 73–77 (in Russ.).

[6] Genbach A.A., Bondartsev D.Yu. Experimental method of investigation of heat transfer crisis in capillary-porous structures for elements of boiler-turbine equipment. Tyazheloye mashinostroyeniye, 2018, no. 3, pp. 32−38 (in Russ.).

[7] Genbach A.A., Bondartsev D.Yu. Experimental method of investigation of the heat transfer crisis in a capillary-porous cooling system. News of the National Academy of Sciences of the Republic of Kazakhstan, Series of Geology and Technical Sciences, 2018, vol. 2(428), pp. 81–88.

[8] Genbach A.A., Bondartsev D.Yu. Fracture of capillary-porous coatings in case of intensive heat-and-mass transfer. Russian metallurgy, 2018, no. 10, pp. 40–46 (in Russ.).

[9] Genbach A.A., Bondartsev D.Yu., Iliev I.K. Limit thermal fluxes and thermal stresses in porous coatings of a heat-energy installation. Thermal Science, 2019, vol. 23, iss. 2, pp. 849−860, doi: 10.2298/TSCI171016139G

[10] Genbach A.A., Islamov F.A. Limit thermal fluxes and thermal stresses in porous coatings of a heat-energy installation. Transactions of Academenergo, 2018, no. 1, pp. 73–80 (in Russ.).

[11] Polyaev V.M., Genbach A.A. Control of Heat Transfer in Porous Structures. Proceedings, Russian Academy of Sciences, Power Engineering and Transport, 1992, vol. 38, iss. 6, pp. 105–110 (in Russ.).

[12] Jamialahmadi M., Müller-Steinhagen H., Abdollahi H., Shariati A. Experimental and Theoretical Studies on Subcooled Flow Boiling of Pure Liquids and Multicomponent Mixtures. International Journal of Heat and Mass Transfer, 2008, vol. 51, iss. 9–10, pp. 2482–2493, doi: 10.1016/j.ijheatmasstransfer.2007.07.052

[13] Ose Y., Kunugi T. Numerical Study on Subcooled Pool Boiling. ASME/JSME 2011 8th Thermal Engineering Joint Conference, 2011, vol. 2, pp. 125–129.

[14] Krepper E., Končar B., Egorov Y. CFD Modeling Subcooled Boiling-Concept, Validation and Application to Fuel Assembly Design. Nuclear Engineering and Design, 2007, vol. 237, iss. 7, pp. 716–731, doi: 10.1016/j.nucengdes.2006.10.023

[15] Ovsyanik A.V. Modelirovaniye protsessov teploobmena v kipyashchikh zhidko-styakh [Mo-delling of Processes of Heat Exchange at Boiling Liquids]. Gomel, GSTU im. P.O. Sukhogo publ., 2012. 284 p.

[16] Alekseik O.S., Kravets V.Yu. Physical Model of Boiling on Porous Structure in the Limited Space. Eastern-European Journal of Enterprise Technologies, 2013, 64, 4/8, pp. 26–31.

[17] Polyaev V.M., Genbach A.A. Analysis of the laws of friction and heat transfer in a porous structure. Herald of the Bauman Moscow State Technical University. Series Mechanical Engineering, 1991, no. 4, pp. 86–96 (in Russ.).

[18] Polyayev V.M., Genbach A.A., Bocharova I.N. Effect of pressure on heat transfer intensity in a porous system. Proceedings of Higher Educational Institutions. Маchine Building, 1992, no. 4–6, pp. 68 –72 (in Russ.).

[19] Polyaev V.M., Genbach A.A. The field of application of porous systems. Energetika. Proceedings of CIS higher education institutions and power engineering associations, 1991, no. 12, pp. 97–101 (in Russ.).

[20] Genbach A.A., Bondartsev D.Yu., Iliev I.K. Investigation of a high-forced cooling system for the elements of heat power installations. Journal of machine Engineering, 2018, vol. 18, iss. 2, pp. 106–117, doi: 10.5604/01.3001.0012.0937

[21] Genbach A.A., Bondartsev D.Yu., Iliev I.K. Modelling of capillary coatings and heat exchange surfaces of elements of thermal power plants. Bulgarian Chemical Communications, 2018, vol. 50, special iss. G, pp. 133–139.

[22] Polyayev V.M., Mayorov V.A., Vasil’yev L.L. Gidrodinamika i teploobmen v poristykh elementakh konstruktsiy letatel’nykh apparatakh [Hydrodynamics and heat transfer in porous structural elements of aircraft]. Moscow, Mashinostroyeniye publ., 1998. 168 p.

[23] Kovalev S.A., Solov’yev S.L. Ispareniye i kondensatsiya v teplovykh trubakh [Evaporation and condensation in heat pipes]. Moscow, Nauka publ., 1989. 112 p.

[24] Kupetz M., Jeni Heiew E., Hiss F. Modernization and extension of steam turbine power plants in Eastern Europe and Russia. Teploenergetika, 2014, no. 6, pp. 35–43 (in Russ.), doi: 10.1134/S0040363614060058

[25] Grin’ E.A. Possibilities of fracture mechanics in relation to the problems of strength, resource and justification of safe operation of thermal mechanical power equipment. Teploenergetika, 2013, no. 1, pp. 25–32 (in Russ.).