Skip to content
KPI Science News
ISSN 2617-5509 · e‑ISSN 2663-7472 Open Access · CC BY 4.0
Vol. · Issue 3 · 2019 Aug 13, 2019 article

TEMPERATURE FACTOR EFFECT ON THE FLOW STABILITY LOSS IN THE PIPE INITIAL SECTION

GV
Gennadii O. Voropaiev Corresponding Igor Sikorsky Kyiv Polytechnic Institute, Ukraine Ukraine
OB
Oleksandra O. Baskova Institute of Hydromechanics National Academy of Sciences of Ukraine; Igor Sikorsky Kyiv Polytechnic Institute, Ukraine Ukraine
PublishedAug 13, 2019
PDF (Ukrainian)
KPISN 3 VOL · 3
VOL · ISS 3 · 2019 View issue

Abstract

Background. Improving the energy efficiency of heat exchangers is possible by developing the heat exchange surface and changing the flow regime in order to reduce hydraulic losses. The processes of transition from laminar to turbulent regime, exactly as from turbulent to laminar, depend on a large number of factors, including temperature, that affecting the viscosity of the flow and, respectively, the Prandtl number. Another feature of the transitional flow regime is the sharp nature of the change in the heat exchange intensity even with small changes in the Reynolds number, which creates certain difficulties in working with it. Objective. The purpose of the paper is: studying the processes of stability loss and transition to the turbulent regime in the initial section of the pipe with a partially developed surface; determining the influence of the temperature factor on the relationship of hydraulic and thermal flow parameters. Methods. Numerical experiment using direct numerical simulation (DNS) and instruments of the Ansys Fluent software. Results. The threshold values of the temperature gradient at which the flow in a pipe of a given length, for a given Reynolds number loses stability, are determined. The dependences of the temporal and spatial scales of arising disturbances and their growth rates from the combination of the Reynolds number and temperature gradient are determined. The interrelation of wall shear stress values with heat flux values is shown. Dynamic and thermal characteristics of the flow in the area of the corrugated surface were obtained, on the basis of which the threshold values of the temperature gradient at which the partial corrugation is energy efficient are determined. Conclusions. An increase in temperature gradient leads to an earlier generation and intensification of the vortex motion, which causes an increase in convective heat transfer at the fixed Reynolds number. The location of the corrugated insert in relation to the place of the finite perturbations genesis, along with the geometry of the corrugation, significantly changes the dynamic and thermal characteristics of the flow.

Keywords

#Flow in the pipe #Flow stability #Heat transfer intensification #Corrugation #Initial section of the pipe #Temperature gradient #Prandtl number

References

  1. A.G. Laptev et al ., Efficiency of Transport Phenomena in Channels with Chaotic Packing Layer s. SPb, Russia: Kazn', 2016.
  2. A.A. Baskova and G.A. Voropaev, “Structure of the vortex nonisothermal flow at the initial section of the pipe with transition Reynolds numbers”, Gidrodinamika i Akustika , no. 1, pp. 117–131, 2018. doi: 10.15407/jha2018.02.117
  3. R. L. Webb et al ., “Heat transfer and friction in tubes with repeated-rib roughness”, Int. J. Heat Mass Transfer , vol. 14, no. 4, pp. 601–617, 1971. doi: 10.1016/0017-9310(71)90009-3
  4. D.F. Dipprey and R.W. Sabersky, “Heat and momentum transfer in smooth and rough tubes at various Prandtl numbers”, Int. J. Heat Mass Transfer , vol. 6, no. 5, pp. 329–353, 1963. doi: 10.1016/0017-9310(63)90097-8
  5. A.M. Guzmán et al ., “Heat transfer enhancement by flow bifurcations in asymmetric wavy wall channels”, Int. J. Heat Mass Transfer , vol. 52, no. 15-16, pp. 3778–3789, 2009. doi: 10.1016/j.ijheatmasstransfer.2009.02.026
  6. A. Yılmaz, “Optimum length of tubes for heat transfer in turbulent flow at constant wall temperature”, Int. J. Heat Mass Transfer , vol. 51, no. 13-14, pp. 3478–3485, 2008. doi: 10.1016/j.ijheatmasstransfer.2007.10.034
  7. P.G. Vicente et al ., “Experimental investigation on heat transfer and frictional characteristics of spirally corrugated tubes in turbulent flow at different Prandtl numbers”, Int. J. Heat Mass Transfer , vol. 47, no. 4, pp. 671–681, 2004. doi: 10.1016/j.ijheatmasstransfer.2003.08.005
  8. S. Rainieri and G. Pagliarini, “Convective heat transfer to temperature dependent property fluids in the entry region of corrugated tubes”, Int. J. Heat Mass Transfer , vol. 45, no. 22, pp. 4525–4536, 2002. doi: 10.1016/S0017-9310(02)00156-4
  9. S.L. Rivkin and A.A. Aleksandrov, Thermodynamic properties of water and steam , 2nd ed. Moscow, SU: Energoatomizdat, 1984.
  10. M. Gad-el-Hak et al ., “Transition control”, in Instability and Transition , vol. 1, M.Y. Hussaini, R.G. Voigt, eds. New York: Springer, 1990, pp. 319–354. doi: 10.1007/978-1-4612-3430-2_38
§ 06 — Related

Similar articles in this journal

Related peer-reviewed studies published in this journal.
View all issues

Similar Articles

1-10 of 198

You may also start an advanced similarity search for this article.