Comparative Analysis of Heat Transfer Efficiency in Round and Flat Continuous Diffusers


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Numerical simulation of flow and heat transfer in round and flat continuous diffusers with a smooth surface was performed using a three-parameter differential RANS turbulence model supplemented by a transfer equation for turbulent heat flux. The comparative analysis of local and integral characteristics of flow and heat transfer showed that at the same opening angle in a round diffuser the Nusselt number is higher than in a flat diffuser and this excess increases with increasing opening angle. However, the Reynolds analogy factor for a round diffuser is slightly higher than for a flat diffuser due to the higher value of the friction coefficient in a round diffuser. It is shown that with increasing Reynolds number the Reynolds analogy factor, both current and averaged over the diffuser length, slightly decrease. The Nusselt number averaged over the length also decreases, while the averaged friction coefficient remains practically constant.

RANS turbulent model, round and plane diffuser, Nusselt number, Reynolds number, Reynolds analogy factor.

DOI: http://doi.org/10.33257/PhChGD.26.3.1186


Volume 26, issue 3, 2025 year


Сравнительный анализ эффективности теплообмена в круглом и плоском безотрывных диффузорах

Численное моделирование течения и теплообмена в круглых и плоских безотрывных диффузорах с гладкой поверхностью проведено с использованием трехпараметрической дифференциальной RANS-модели турбулентности, дополненной уравнением переноса для турбулентного потока тепла. Проведенный сравнительный анализ локальных и интегральных характеристик течения и теплообмена показал, что при одинаковом угле раскрытия в круглом диффузоре число Нуссельта выше, чем в плоском диффузоре и это превышение возрастает с увеличением угла раскрытия. Однако коэффициент аналогии Рейнольдса для круглого диффузора при этом ненамного выше, чем для плоского диффузора за счет большего значения коэффициента трения в круглом диффузоре. Показано, что с ростом числа Рейнольдса коэффициент аналогии Рейнольдса, как текущий, так и осредненный по длине диффузора немного уменьшаются. Уменьшается также усредненное по длине число Нуссельта, в то время как коэффициент трения остается практически постоянным.

RANS-модель турбулентности, круглый, плоский диффузор, число Нуссельта, коэффициент трения, коэффициент аналогии Рейнольдса.

DOI: http://doi.org/10.33257/PhChGD.26.3.1186


Volume 26, issue 3, 2025 year



1. Migai V.K., Improving the efficiency of modern heat exchangers, L.: Energiya, 1980. 144 p. [In Russian].
2. Kalinin E.K., Dreitzer G.A., Kopp I.Z., Myakochin A.S., Effective heat transfer surfaces, Moscow: Energoatomizdat, 1998. 408 p. [In Russian].
3. Dzyubenko B.V., Kuzma-Kichta Yu.A., Leontiev A.I., Fedik I.I., Kholopanov L.P., Intensification of heat and mass transfer at macro, micro and nanoscales, Moscow: FSUE Tsniiatominform, 2008. 532 p. [In Russian].
4. Bergles A.E., Recent developments in enhanced heat transfer, Heat Mass Transfer, 2011, vol. 47, no 8, p. 1001–1008. DOI: 10.1007/s00231-01100872-y
5. Leontiev A.I., Kiselev N.A., Burtsev S.A., Strongin M.M., Vinogradov Yu. A. Experimental investigation of heat transfer and drag on surfaces with spherical dimples, Experimental Thermal and Fluid Science, 2016, vol. 79, p. 74–84.
6. Gukhman A. A., Kirpikov V. A., Gutarev V. V., Tsirel'man N. M., Investigation of heat transfer and hydrodynamic drag in the turbulent flow of a gas in the field of a longitudinal pressure gradient of variable sign. I., J. Eng. Phys., 1969, vol. 16, no. 4, pp. 387–395. https://doi.org/10.1007/BF00828512
7. Gukhman A. A., Kirpikov V. A., Gutarev V. V., Tsirel'man N. M. Investigation of the transfer of heat and of hydrodynamic resistance in the turbulent flow of a gas in the field of a longitudinal pressure gradient of variable sign. II, J. Eng. Phys., 1969, vol. 16, no. 6, pp. 669–672. https://doi.org/10.1007/BF00828627
8. Abbasov E. S., Umurzakova M. A., Thermal efficiency of CVS with diffusor-confusor solar receivers, Solar engineering, 2007, no. 1, pp. 37–43.
9. Kharlamov S. N., Alginov R. A, Hydrodynamics and heat transfer in complex pipelines at any confguration of wall, in Proceedings of the 7th International Forum on Strategic Technology (IFOST 2012) Tomsk, 2012, no. 6357683. DOI: 10.1109/IFOST.2012.6357683
10. Reshmin A.I., Teplovodsky S.Kh., Trifonov V.V., Turbulent flow in a circular continuous diffuser at Reynolds numbers less than 2000, Fluid Dynamics, 2011, vol. 46, pp. 278–285. https://doi.org/10.1134/S0015462811020104
11. Luschik V.G., Paveliev A.A., Yakubenko A.E., Three parameter model of shear turbulence, Fluid Dynamics, 1978, vol. 13, pp. 350–360. DOI: 10.1007/BF01050525
12. Isaev S. A., Baranov P. A., Gouvernyuk S. V., Zubin M. A., Numerical and physical modeling of turbulent flow in an expanding channel with a vortex cell. Engineering and Physics Journal, 2002, vol. 75, no. 2, pp. 3–8. DOI: 10.1023/A:1015608715843
13. Zubarev V. M., Numerical modeling of a turbulent incompressible flow with an increasing positive pressure gradient, Engineering and Physics Journal, 2019, vol. 92, no. 3. pp. 654–663. https://doi.org/10.1007/s10891-019-01972-0
14. Luschik V.G., Makarova M.S., Reshmin A.I. Intensification of heat transfer during turbulent flow in flat and round continuous diffusers, Engineering and Physics Journal, 2021, vol. 94, no. 2, pp. 483–495.
15. Luschik V.G., Makarova M.S., Reshmin A.I., Plate heat exchanger with diffuser channels, Physical-Chemical Kinetics in Gas Dynamics, 2023, vol. 24, no. 2 [in Russian]. http://chemphys.edu.ru/issues/2023-24-2/articles/1030/16.
16. Luschik V.G., Reshmin A.I., Egorov K.S., Double pipe heat exchanger with diffusor channels with gas and liquid coolants, Physical-Chemical Kinetics in Gas Dynamics, 2024, vol.25, no. 4, pp. 1–21. [in Russian]. http://chemphys.edu.ru/issues/2024-25-3/articles/1115/
17. Luschik V.G., Reshmin A.I. Promising heat exchangers with diffuser channels, Physical-Chemical Kinetics in Gas Dynamics, 2024, vol.25, no. 6, pp. 1–22. [in Russian]. http://chemphys.edu.ru/issues/2024-25-6/articles/1126/
18. Lushchik V.G., Pavel’ev A. A., and Yakubenko A. E., Three-Parameter Model of Turbulence. Heat Transfer Calculations, Fluid Dynamics, 1986, vol. 21, no. 2, 200–211. DOI:10.1007/BF01050170
19. Luschik V.G., Pavelev A.A., Yakubenko A.E., Turbulent flows. Models and numerical investigation. A review, Fluid Dynamics, 1994, vol. 29, no 4, pp. 440–457.
20. Spravochnik po teplofizicheskim svoistvam gazov i zhidkostei (Handbook on thermophysical properties of gases and liquids. Ed. by Vargaftik N.B), Moscow: Nauka, [in Russian]. 1972. 720 p.