Thermal and Aerodynamic Researches of Staggered Bundles for Choice of an Effective Spacing of Round-Finned Tubes

The results of an experimental study of local modeling of convective heat transfer and aerodynamic resistance of staggered six-row bundles of bimetallic tubes with spiral knurled aluminum fins under transverse air flow in the range of its velocity alteration in a compressed bundle section of 1.9−11.0 m/s are presented. The velocity range covers the possible modes of operation of industrial air coolers (AVO). The fins with a diameter of approximately 57 mm are rolled on a steel supporting tube with an outer diameter of 25 mm. Tube finning ratio j = 19.26. Such tubes are widely used in the heat exchange sections of AVO of natural gas, in particular, at “Gribanovskii Engineering Plant” JSC (Russia). To measure the reduced heat transfer coefficients, an electric calorimeter had been developed by the authors with a power input of 600−1300 W. The temperature of the wall surface at the base of the fins did not exceed the range of 77–92 °C. The transverse tube spacing in bundles S₁was 64.0 or 68.0 mm, while the longitudinal spacing S₂ was 54.4 or 50.0 mm. The heat transfer of each transverse row of six-row bundles was measured, as well as the average heat transfer and aerodynamic drag, which are summarized by the similarity equation of a power type. The heat transfer rate of the last transverse row in the direction of air movement is 0–5 % lower than the heat transfer rate of the stabilized rows, and here new features of heat transfer variations in the insufficiently studied area of spacing changes S₁ and S₂ have been found. The thermal contact resistance (TCR) was measured in the range of the average temperature of the contact surfaces tк = (79–95) ^оС, and no dependence of the value of TCR on tк for the specified interval was found. The numerical average value of TCR was R_к = 2,13 × 10^–4 m²×K/W, which is typical for reliable mechanical connection of the finned aluminum shell with the supporting steel tube made of carbon steel. The results of variant thermal and aerodynamic calculations with the use of the obtained data established the technical and economic feasibility of placing tubes at the vertices of an isosceles triangle with spacing S₁ = 68–69 mm and S₂ = 55 mm with failure to use the location of the tubes along an equilateral triangle with S₁ = S₂' = 64 mm (where S₂' – is diagonal spacing). With Q = idem and other conditions being equal, the number of tubes on AVO decreases by 5.7 % with a decrease in power consumption to 4.0 %.

1. Shmerkovich V. M. (1971) Air Cooling Apparatuses Implementation in Design of Refineries and Petrochemical Plants. ?oscow, CRIITERpetrochem. 112 (in Russian).

2. Kiselev B. D., Gun R. B., L'vova A. I., Bondarenko B. I. (1983) Album of Technological Schemes of Oil and Gas Processing. Moscow, Khimiya Publ. 128 (in Russian).

3. Mil'man O. O., Federov V. A., Lavrov V. I., Demochkin V. A., Gerasimov A. V., Serezhkin N. I., Khochkin I. A. (1998) Air Condensers for Steam Turbine Units of Low and Medium Power. Teploenergetika = Thermal Engineering, (1), 35?39 (in Russian).

4. Kuntysh V. B., Kuznetsov N. M. (1992) Thermal and Aerodynamic Calculations of Finned Air-Cooling Heat Exchangers. Saint-Petersburg, Energoatomizdat Publ. 280 (in Russian).

5. Malanichev V. A., Miatov O. L., Tipailov A. M. (2004) Development and Modernization of Ventilator Units of Air Cooling Apparatuses. Khimicheskaya tekhnika [Chemical Engineering], (2), 12?27 (in Russian).

6. Bessonnyi A. N., Dreitser G. A., Kuntysh V. B. (1996) Fundamentals of Calculation and Design of Air Cooling Heat Exchangers. Saint-Petersburg, Nedra Publ. 512 (in Russian).

7. Legkii V. M., Tupitsyn Yu. K., Pis'mennyi E. N. (1978) Effect of Step Ratio on Heat Transfer and Aerodynamic Resistance of the Staggered Transversally Washed Bundles of Spirally Finned Tubes. Teploobmen v energeticheskikh ustanovkakh : sbornik [Heat Exchange in Power Plants: collection]. Kiyv, Naukova dumka Publ., 78?82 (in Russian).

8. Yudin V. F. (1982) Heat Exchange of Transversely Finned Tubes. Leningrad, Mashinostroenie Publ. 189 (in Russian).

9. Zhukauskas A. A. (1982) Convective Transfer in Heat Exchangers. Moscow, Nauka Publ. 472 (in Russian).

10. Pis'mennyi E. N. (2004) Heat Transfer and Aerodynamics of Packages of Transversely Finned Tubes. Kiyv, Al'terpress Publ. 244 (in Russian).

11. Wierman C. (1976) Correlation Ease the Selection of Finned Tubes. Oil and Gas, 74 (36), 94?100.

12. Piir A. E. (1999) Research and Development of Energy-and-Material-Saving Designs of Air Heaters. Arkhangelsk. 40 (in Russian).

13. Kuntysh V. B., Dudarev V. V., Sukhotsky A. B., Volodin V. I. (2014) Results of Investigations on Thermal Characteristics of Air Heater Bundle Made of Bimetallic Finned Tubes. Energetika. Izvestiya Vysshikh Uchebnykh Zavedenii i Energeticheskikh Ob’edenenii SNG = Energetika. Proceedings of the CIS Higher Educational Institutions and Power Engineering Associations, (1), 48–56 (in Russian).

14. Lapin A., Schurig W. F. (1959) Heat Transfer Coefficcient for Finned Exchangers. Industrial & Engineering Chemistry, 51 (8), 941-944. https://doi.org/10.1021/ie50596a038

15. Zozulya N. V. (1965) The Study of Heat Transfer Through the Rows of the Staggered Bundles of Aluminum Spirally and Knurlly Finned Tubes. Khimicheskaya promyshlennost' Ukrainy [Chemical Engineering of the Ukraine], (5), 29?31 (in Russian).

16. Kuntysh V. B., Iokhvedov F. M. (1977) Experimental Study of Local Heat Transfer Coefficients of Spirally Finned Tubes Arranged in Transversely Flown Finned Bundles. Izvestiya vysshikh uchebnykh zavedenii Ministerstva vysshego i srednego spetsial'nogo obrazovaniya SSSR. Energetika [Journal of Higher Educational Institutions of the Ministry of Higher and Secondary Special Education of the USSR. Energetics], (1), 105?110 (in Russian).

17. Kuntysh V. B., Iokhvedov F. M. (1979) Influence of the Number of Rows and Arrangement of a Cross-Flown Ribbed Bundle on the Local Heat Transfer of the Last Rows. Izvestiya vysshikh uchebnykh zavedenii Ministerstva vysshego i srednego spetsial'nogo obrazovaniya SSSR. Energetika [Journal of Higher Educational Institutions of the Ministry of Higher and Secondary Special Education of the USSR. Energetics], (3), 58?59 (in Russian).

18. Kuntysh V. B., Piir A. E., Fedotova L.M. (1980) The Study of Contact Thermal Resistance of Bimetallic Finned Tubes of Air Cooling Apparatuses. Izvestiya vysshikh uchebnykh zavedenii «Lesnoi zhurnal» = Bulletin of Higher Educational Institutions. Forestry Journal, (5). 121?126 (in Russian).

19. Rudenko A. I., Nishchik A. P. (2009) The Study of Contact Thermal Resistance in Bimetal Spirally and Knurlly Finned Tubes. Promyshlennaya teplotekhnika = Industrial Heat Engineering, 31 (5), 15?19 (in Russian).

20. State standard R 51364–99. Air Coolers. General Technical Requirements. Moscow, Standards Publishing, 2000. 66 (in Russian).

21. Kuntysh V. B., Bessonnyi A. N., Dreitser G. A., Egorov I. F. (2000) Examples of Calculations of Non-Standardized Efficient Heat Exchangers. Saint-Petersburg, Nedra Publ. 300 (in Russian).