The effects of transient heat flux on the tube in contact with the natural convection, on enthalpy and entropy generation, for developed laminar flow of fluid with high Prandtl number

Document Type : Research Article


Department of chemical Engineering, University of Sistan and Baluchestan, Zahedan, Iran


Heat flux is passed through the tube wall with natural convection in a tube wall of developed laminar flow. Tubes are used to find the best case with the minimum enthalpy and entropy generation. Process of heat flux pass is simulated with natural convection in several cases through the wall. By varying heat flux along the tube kept in touch with natural convection, temperature, entropy generation and enthalpy of each case change. Tubes are studied distribution of temperature, entropy generation and enthalpy along the radius and distribution of entropy generation and enthalpy along the cylinder axis, via different diagrams. Entering heat flux to the tube wall, temperature, entropy generation and enthalpy of the fluid increase significantly along the radius. The contact of heat flux to the tube wall in the direction of fluid movement, entropy generation decreases in the flow direction. Heat flux is applied to the tube wall, in parts of the tube being a heat flux, enthalpy increases in the direction of the tube wall. Enthalpy is reduced in the tube wall in parts that are associated with the natural convection. The novelty of the work is heat flux and natural convection on the pipe in various fluids and air in electric coil on the tube as heat flux and diesel furnace, solar water heaters, refrigerant tube etc. Material is not a special. Material is the fluid with high Prandtl number by number of 13400. Method of the paper is design and simulation by ansys software 15.0.7.


[1] B. Niezgoda-┼╗elasko, and J. ┼╗elasko, Refrigerant boiling at low heat flux in vertical tubes with heat transfer enhancing fittings. Int. J. Refrig., 54 (2015) 151-169.
[2] C. Chen, et al., Experimental study on critical heat flux characteristics of R134a flow boiling in horizontal helically-coiled tubes. Int. J. Therm. Sci., 50 (2011) 169-177.
[3] A. Olekhnovitch, J. Sun, and A. Teyssedou, A complex but accurate correlation for predicting critical heat flux in a round tube for low and medium pressures under circumferentially non-uniform heating conditions. Int. J. Heat. Mass. Transf., 51 (2008) 2041-2054.
[4] Z. Li, A new constant heat flux model for vertical U-tube ground heat exchangers. Energ. Buildings., 45 (2012) 311-
[5] K. Ezato, et al., Critical heat flux experiments using a screw tube under DEMO divertor-relevant cooling conditions. Fusion. Eng. Des., 83 (2008) 1097-1101.
[6] Z. Liu, L. Liao, and T. Zhang, Critical heat flux of countercurrent boiling in an inclined small tube with closed bottom. Int. Commun. Heat. Mass. Transf., 35 (2008) 995-1000.
[7] J. Pan, et al., Critical heat flux prediction model for low quality flow boiling of water in vertical circular tube. Int. J. Heat. Mass. Transf., 99 (2016) 243-251.
[8] W. Fuqiang, et al., Effects of glass cover on heat flux distribution for tube receiver with parabolic trough collector system. Energ. Convers. Manage., 90 (2015) 47-52.
[9] H. Shariatmadar, et al., Experimental and numerical study on heat transfer characteristics of various geometrical arrangement of impinging jet arrays. Int. J. Therm. Sci., 102 (2016) 26-38.
[10] D. W. Zhao, et al., Experimental research on transient critical heat flux in vertical tube under oscillatory flow condition. Int. J. Multiph. Flow., 37 (2011) 1235-1244.
[11] H. Y. Gu, M. Zhao, and X. Cheng, Experimental studies on heat transfer to supercritical water in circular tubes at high heat fluxes. Exp. Therm. Fluid. Sci., 65 (2015) 22-32.
[12] H. A. Mohammed, and Y. K. Salman, Free convective heat transfer from a constant heat flux vertical circular tube with different entrance restrictions length. Energ. Convers. Manage., 48 (2007) 2233-2243.
[13] K. Hata, Y. Shirai, and S. Masuzaki, Heat transfer and critical heat flux of subcooled water flow boiling in a HORIZONTAL circular tube. Exp. Therm. Fluid. Sci., 44 (2013) 844-857.
[14] D. de Faoite, et al., Inverse estimate of heat flux on a plasma discharge tube to steady-state conditions using thermocouple data and a radiation boundary condition. Int. J. Heat. Mass. Transf., 77 (2014) 564-576.
[15] C. B. Tibiriçá, G. Ribatski, and J.R. Thome, Saturated flow boiling heat transfer and critical heat flux in small horizontal flattened tubes. International Journal of Heat and Mass Transfer, 2012. 55 (25–26): p. 7873-7883.
[16] J. Yan, et al., Subcooled flow boiling heat transfer of water in a circular tube under high heat fluxes and high mass fluxes. Fusion. Eng. Des., 100 (2015) 406-418.
[17] M. Lin, Q. W. Wang, and Z. X. Guo, A simple method for predicting bulk temperature from tube wall temperature with uniform outside wall heat flux. Int. Commun. Heat. Mass. Transf., 39 (2012) 582-586.
[18] J. Cai, Applying support vector machine to predict the critical heat flux in concentric-tube open thermosiphon. Ann. Nucl. Energ., 43 (2012) 114-122.
[19] X. Shen, et al., Convective heat transfer of molten salt in circular tube with nonuniform heat flux. Exp. Therm. Fluid. Sci., 55 (2014) 6-11.
[20] J. Yan, et al., Critical heat flux of highly subcooled water flow boiling in circular tubes with and without internal twisted tapes under high mass fluxes. Int. J. Heat. Mass.
Transf., 95 (2016) 606-619.
[21] V. Bianco, O. Manca, and S. Nardini, Entropy generation analysis of turbulent convection flow of Al2O3–water nanofluid in a circular tube subjected to constant wall heat flux. Energ. Convers. Manage., 77 (2014) 306-314.
[22] M. Mohseni, and M. Bazargan, Entropy generation in turbulent mixed convection heat transfer to highly variable property pipe flow of supercritical fluids. Energ. Convers. Manage., 87 (2014) 552-558.
[23] C. Chang, X. Li, and Q.Q. Zhang, Experimental and
Numerical Study of the Heat Transfer Characteristics in Solar Thermal Absorber Tubes with Circumferentially Non-uniform Heat Flux. Energ. Procedia., 49 (2014) 305-313.
[24] C. Marugán-Cruz, et al., Heat transfer and thermal stresses in a circular tube with a non-uniform heat flux. Int. J. Heat. Mass. Transfer., 96 (2016) 256-266.
[25] J. A. Esfahani, and P.B. Shahabi, Effect of non-uniform heating on entropy generation for the laminar developing pipe flow of a high Prandtl number fluid. Energ. Convers. Manage., 51 (2010) 2087-2097.
[26] N. Minocha, et al., 3D CFD simulations to study the effect of inclination of condenser tube on natural convection and thermal stratification in a passive decay heat removal system. Nucl. Eng. Des., 305 (2016) 582-603.
[27] P. V. Trevizoli, and J.R. Barbosa Jr, Entropy Generation Minimization analysis of oscillating-flow regenerators. Int. J. Heat. Mass. Transf., 87 (2015) 347-358.
[28] H. Feng, et al., Constructal entropy generation rate minimization for X-shaped vascular networks. Int. J. Therm. Sci.,92 (2015) 129-137.
[29] W. Shao, Z. Cui, and L. Cheng, Multi-objective optimization design of air distribution of grate cooler by entropy generation minimization and genetic algorithm. Appl. Therm. Eng., 108 (2016) 76-83.
[30] B. F. Pussoli, et al., Optimization of peripheral finned-tube evaporators using entropy generation minimization. Int. J. Heat. Mass. Transf., 55 (2012) 7838-7846.
[31] H. Ye, and K.-S. Lee, Refrigerant circuitry design of fin-and-tube condenser based on entropy generation minimization. Int. J. Refrig., 35 (2012) 1430-1438.
[32] G. C. Li, and S.-A. Yang, Entropy generation minimization of free convection film condensation on an elliptical cylinder. Int. J. Therm. Sci., 46 (2007) 407-412.
[33] A. Bejan, The Method of Entropy Generation Minimization, in Energy and the Environment, A. Bejan, P. Vadász, and D.G. Kröger, Editors. 1999, Springer Netherlands: Dordrecht. p. 11-22.
[34] T. H. Ko, Thermodynamic analysis of optimal mass flow rate for fully developed laminar forced convection in a helical coiled tube based on minimal entropy generation principle. Energ. Convers. Manage., 47 (2006) 3094-3104.
[35] B. K. Jha, and M.O. Oni, Natural convection flow in a vertical tube inspired by time-periodic heating. Alex. Eng. J., 55 (2016) 3145-3151.
[36] M. Farzaneh-Gord, H. Ameri, and A. Arabkoohsar, Tube-in-tube helical heat exchangers performance optimization by entropy generation minimization approach. Appl. Therm. Eng.,108 (2016) 1279-1287.
[37] J. Abolfazli Esfahani, and M. Modirkhazeni, Entropy generation of forced convection film condensation on a horizontal elliptical tube. Comptes. Rendus. Mécanique., 340 (2012) 543-551.
[38] D. Huang, et al., A brief review on convection heat transfer of fluids at supercritical pressures in tubes and the recent progress. Appl. Energ., 162 (2016) 494-505.
[39] N. S. Akbar, Entropy generation and energy conversion rate for the peristaltic flow in a tube with magnetic field. Energ., 82 (2015) 23-30.
[40] T. Wang, Z. Huang, and G. Xi, Entropy generation for mixed convection in a square cavity containing a rotating circular cylinder using a local radial basis function method. Int. J. Heat. Mass. Transf., 106 (2017) 1063-1073.
[41] G. Zhang, et al., Entropy generation of supercritical water in a vertical tube with concentrated incident solar heat flux on one side. Int. J. Heat. Mass. Transf., 108 (2017) 172-180.
[42] S. M. Elsherbiny, M. A. Teamah, and A.R. Moussa,
Experimental mixed convection heat transfer from an isothermal horizontal square cylinder. Exp. Therm. Fluid. Sci., 82 (2017) 459-471.
[43] J. H. Heo, and B.-J. Chung, Influence of helical tube dimensions on open channel natural convection heat transfer. Int. J. Heat. Mass. Transf., 55 (2012) 2829-2834.
[44] H. T. Chen, et al., Numerical and experimental study of natural convection heat transfer characteristics for vertical plate fin and tube heat exchangers with various tube diameters. Int. J. Heat. Mass. Transf., 100 (2016) 320-331.
[45] J. C. Kurnia, et al., Numerical investigation of heat transfer and entropy generation of laminar flow in helical tubes with various cross sections. Appl. Therm. Eng., 102 (2016) 849-860.
[46] L. M. Jiji, Heat Convection, New York, 2006.
[47] F. P. Incropera, D. P. Dewitt, Introduction to Heat Transfer, fourth ed (2002).
[48] R. kakulvand, Effect of non-uniform temperature distribution on entropy generation and enthalpy for the laminar developing pipe flow of a high Prandtl number fluid. Chem. Rev. Lett., 2 (2019) 98-106.
[49] E. Babanehad, A. Beheshti, The Possibility of Selective Sensing of the Straight-Chain Alcohols (Including Methanol to n-Pentanol) Using the C20 Fullerene and C18NB Nano Cage, Chem. Rev. Lett., 1 (2018) 82-88.
[50] B. kakulvand, Review of drag coefficients on gas – liquid tower: the drag coefficient independent and dependent on bubble diameter in bubble column experiment, Chem. Rev. Lett., 2 (2019) 48-58.
[51] R. kakulvand, The effects of transient radiant flow on pipe in contact with natural convection, for developed laminar flow of fluid with high Prandtl number, on enthalpy and entropy generation, Chem. Rev. Lett., 2 (2019) 130-137.
Volume 2, Issue 4
November 2019
Pages 165-175
  • Receive Date: 25 August 2019
  • Revise Date: 27 December 2019
  • Accept Date: 31 December 2019
  • First Publish Date: 31 December 2019