가정용 보일러의 급탕시설 개선방안에 관한 연구

• Published : 1998.06.01

Abstract

Heat transfer performance improvement by fin and groovs is studied for condensation of R-11 on integral-fin tubes. Eight tubes with trapczodially shaped integral-fins having fin density from 748 to 1654fpm(fin per meter) and 10, 30 grooves are tested. A plain tube having the same diameter as the finned tubes is also used for comparison. R-11 condensates at saturation state of 32 $^{\circ}C$ on the outside tube surface coded by inside water flow. All of test data are taken at steady state. The heat transfer loop is used for testing singe long tubes and cooling is pumped from a storage tank through filters and folwmeters to the horizontal test section where it is heated by steam condensing on the outside of the tubes. The pressure drop across the test section is measured by menas pressure gauge and manometer. The results obtained in this study is as follows : 1. Based on inside diameter and nominal inside area, overall heat transfer coefficients of finned tube are enhanced up to 1.6 ~ 3.7 times that of a plain tube at a constant Reynolds number. 2. Friction factors are up to 1.6 ~ 2.1 times those of plain tubes. 3. The constant pumping power ratio for the low integral-fin tubes increase directly with the effective area to the nominal area ratio, and with the effective area diameter ratio. 4. A tube having a fin density of 1299fpm and 30 grooves has the best heat transfer performance.

References

1. Trans. Inst. Chem. Engrs v.10 Some sidelights on the heat transfer problem Hawes, W.B.
2. Int. J. Heat Mass Transfer v.10 Study on forced convective heat transfer in curved pipes(3rd report. theoretical analysis under the condition of uniform wall temperature and practical formulae) Mork, Y.;Nakayama, W.
3. J. Bas. Engng. v.81 Friction factors for turbulent flow in curved pipes Ito, H.
4. Phil. Mag. v.4 Note on the motion of fluid in a curved pipe Dean, W. R.
5. Ph. D. Thesis, University of Utah. The development of viscous flow within helical coils Austin, L. R.
6. Int. J. Heat Mass Transfer v.6 Heat transfer in tube coils with laminar and turbulent flow Seban, R. A.;McLaughlin, E. F.
7. A.I.Ch.E. v.JI17 Effect of secondary fluid motion on laminar flow heat transfer in helically coiled tubes Dravid, A. N.;Smith, K. A.;Merrill, W.;BRIAN.P. L. T.
8. Int. J. Heat Mass Transfer. v.8 Study on forced convective heat transfer in curved pipes(1st report, laminar region) Mori, Y.;Nakayama, W.
9. Preprint of 1st Japan Heat Transfer Symposium Heat transfer to fully developed laminar flow in a gently curved pipe Maekawa, H.
10. J. Heat Transfer v.90 Heat transfer for laminar flow in a curved pipe Ozisik,M.N.;Topakoglu, H.C.