TEMPERATURE FACTOR EFFECT ON THE FLOW STABILITY LOSS IN THE PIPE INITIAL SECTION
DOI:
https://doi.org/10.20535/kpi-sn.2019.3.175745Keywords:
Flow in the pipe, Flow stability, Heat transfer intensification, Corrugation, Initial section of the pipe, Temperature gradient, Prandtl numberAbstract
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.References
A.G. Laptev et al., Efficiency of Transport Phenomena in Channels with Chaotic Packing Layers. SPb, Russia: Kazn', 2016.
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
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
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
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
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
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
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
S.L. Rivkin and A.A. Aleksandrov, Thermodynamic properties of water and steam, 2nd ed. Moscow, SU: Energoatomizdat, 1984.
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
Downloads
Published
Issue
Section
License
Copyright (c) 2019 The Author(s)
This work is licensed under a Creative Commons Attribution 4.0 International License.
Authors who publish with this journal agree to the following terms:
- Authors retain copyright and grant the journal right of first publication with the work simultaneously licensed under CC BY 4.0 that allows others to share the work with an acknowledgement of the work's authorship and initial publication in this journal.
- Authors are able to enter into separate, additional contractual arrangements for the non-exclusive distribution of the journal's published version of the work (e.g., post it to an institutional repository or publish it in a book), with an acknowledgement of its initial publication in this journal.
- Authors are permitted and encouraged to post their work online (e.g., in institutional repositories or on their website) prior to and during the submission process, as it can lead to productive exchanges, as well as earlier and greater citation of published work
