## THERMAL SCIENCE

International Scientific Journal

### Thermal Science - Online First

online first only
### Study on the disturbance effect of pulsating flow and heat transfer in self-excited oscillation shear layer

**ABSTRACT**

The fluid movement motion has an important influence on the evolution of the pulsating flow in the hot runner. Using the Large Eddy Simulation numerical method, the instantaneous velocity, wall shear stress, boundary layer thickness and Nu number of hot runner section under different structural parameters at an inlet pressure of 5000 Pa were studied. The research results showed that the backflow vortex can be formed in the hot runner, and the fluid at the axis center of hot runner can form a pulsating flow under the squeezing action of the backflow vortex. The pulsating flow had a strong disturbance effect on the fluid around the axis center and accelerated the heat exchange between the fluid around the axis center and the wall. The disturbance effect of pulsating flow gradually strengthened with the flow of the main flow to the downstream. When d2/d1 was 1-1.8, the wall shear stress first increased and then decreased, and the wall heat transfer efficiency first increased and then decreased. The maximum wall shear stress was 36.4Pa. When L/D was 0.45-0.65, the boundary layer thickness first decreased and then increased, and the heat transfer efficiency first increased and then decreased. The minimum boundary layer thickness was 0.392mm and the maximum Nu number was 138. When d2/d1=1.4 and L/D=0.55, the maximum comprehensive evaluation factor reached 1.241, and the heat transfer efficiency was increased by 24.1%.

**KEYWORDS**

PAPER SUBMITTED: 2021-06-11

PAPER REVISED: 2021-09-23

PAPER ACCEPTED: 2021-11-16

PUBLISHED ONLINE: 2022-01-02

- Kline, S. J., et al., The Structure of Turbulent Boundary Layers, Journal of Fluid Mechanics, 30 (2006), 4, pp. 741-773
- Rafiee, S. E., Rahimi, M., Three-dimensional Simulation of Fluid Flow and Energy Separation Inside a Vortex Tube, Journal of Thermophysics and Heat Transfer, 28 (2014), 1, pp. 87-99
- Colucci, D.W., Viskanta, R., Effect of nozzle geometry on local convective heat transfer to a confined impinging air jet, Experimental Thermal and Fluid Science, 13 (1996), 1, pp. 71-80
- Chiriac,V. A., Ortega, A., A Numerical Study of the Unsteady Flow and Heat Transfer in a Transitional Confined Slot Jet Impinging on an Isothermal Surface, International Journal of Heat and Mass Transfer, 45 (2002), 6, pp.1237-1248
- Liu, L.K., et al., Transient Convective Heat Transfer of Air Jet Impinging onto a Confined Ceramic-Based MCM, Journal of Electronic Packaging, 126 (2004), 1, pp.159-172
- Wang, J. S., et al., Heat Transfer Enhancement Mechanism of Semi Elliptical Vortex Generator, Chinese Journal of Mechanical Engineering, 42 (2006), 5, pp. 160-164 (in Chinese)
- Ye, Q. L., et al., Experimental Study on Heat Transfer Enhancement and Pressure Drop Characteristics of Inclined Semi Elliptical Cylindrical Vortex Generator, Chinese Journal of Mechanical Engineering, 46 (2010), 16, pp. 162-169 (in Chinese)
- Liu, J. C., et al., Structure Improvement and Fluid Flow Performance Analysis of Plate Fin Heat Exchanger, Chinese Journal of Mechanical Engineering, 50 (2014), 18, pp. 167-176 (in Chinese)
- Wang, J. S., et al., Flow and Heat Transfer Characteristics of Bluff Body Turbulence in Turbulent Boundary Layer, Chinese Journal of Mechanical Engineering, 51 (2015), 24, pp. 168-176 (in Chinese)
- Fan, A., et al., A Numerical Study on Thermo-hydraulic Characteristics of Turbulent Flow in a Circular Tube Fitted with Conical Strip Inserts, Applied Thermal Engineering, 31 (2011), 15, pp. 2819-2828
- Promvonge, P., Eiamsa-Ard, S., Heat Transfer Enhancement in a Tube with Combined Conical-nozzle Inserts and Swirl Generator, Energy Conversion and Management, 47 (2006), 18, pp. 2867-2882
- Skullong, S., et al., Thermal Behaviors in a Round Tube Equipped with Quadruple Perforated-delta-winglet Pairs, Applied Thermal Engineering, 115 (2017), pp. 229-243
- Hu, G. Q., et al., Study on Heat Transfer in Self-excited Oscillation with Backflow Vortex Disturbance Effect, Journal of Thermophysics and Heat Transfer, 5 (2021), pp. 1-11
- Biswas, G., Chattopadhyay, H., Sinha, A., Augmentation of Heat Transfer by Creation of Streamwise Longitudinal Vortices Using Vortex Generators, Heat Transfer Engineering, 33 (2012), 4, pp. 406-424
- Deshmukh, P. W., Vedula, R. P., Heat Transfer and Friction Factor Characteristics of Turbulent Flow Through a Circular Tube Fitted with Vortex Generator Inserts, International Journal of Heat and Mass Transfer, 79 (2014), pp. 551-560
- Skullong, S., et al., Thermal Performance of Turbulent Flow in a Solar Air Heater Channel with Rib-groove Turbulators, International Communications in Heat and Mass Transfer, 50 (2014), pp. 34-43
- Liang, G., et al., Numerical Study of Heat Transfer and Flow Behavior in a Circular Tube Fitted with Varying Arrays of Winglet Vortex Generators, International Journal of Thermal Sciences, 134 (2018), pp. 54-65
- Zhang, C. C., et al., Numerical Investigation of Heat Transfer and Pressure Drop in Helically Coiled Tube with Spherical Corrugation, International Journal of Heat and Mass Transfer, 113 (2017), pp. 332-341
- Yu, J. C., Li, Z. X., Numerical Analysis of Convective Heat Transfer Enhancement by Laminar Pulse Flow in Circular Tubes with Annular Inner Fins, Journal Tsing University, 45 (2005), 8, pp. 1091-1094 (in Chinese)
- Kurtulmus, N., Sahin, B., Experimental Investigation of Pulsating Flow Structures and Heat Transfer Characteristics in Sinusoidal Channels, International Journal of Mechanical Sciences, 167 (2020), 105268
- Khosravi-Bizhaem, H., Abbassi, A., Ravan A. Z., Heat Transfer Enhancement and Pressure Drop by Pulsating Flow Through Helically Coiled Tube: An Experimental Study, Applied Thermal Engineering, 160 (2019), 114012
- Jin, D. X., Lee, Y. P., Lee, D. Y., Effects of the Pulsating Flow Agitation on the Heat Transfer in a Triangular Grooved Channel, International Journal of Heat and Mass Transfer, 50 (2007), 15, pp. 3062-3071
- Yoshikawa, H., et al., Effects of Pulsation on Separated Flow and Heat Transfer in Enlarged Channel, Journal of Thermal Sciences, 20 (2011), 1, pp. 70-75
- Lee, J., Lee, S. J., The Efect of Nozzle Configuration on Stagnation Region Heat Transfer Enhancement of Axisymmetric Jet Impingement, International Journal of Heat and Mass Transfer, 43 (2000), 18, pp. 3497-3509
- Zheng, D., Wang, X., Yuan, Q., The Effect of Pulsating Parameters on the Spatiotemporal Variation of Flow and Heat Transfer Characteristics in a Ribbed Channel of a Gas Turbine Blade with the Pulsating Inlet Flow, International Journal of Heat and Mass Transfer, 153 (2020), 119609
- Yang, B., et al., Numerical Investigation on Flow and Heat Transfer of Pulsating Flow in Various Ribbed Channels, Applied Thermal Engineering, 145 (2018), pp. 576-589
- Akdag, U., Akcay, S., Demiral, D., Heat Transfer in a Triangular Wavy Channel with CuO/Water Nanofluids Under Pulsating Flow, Thermal Science, 23 (2017), 1, pp. 191-205
- Pan, Z. M., Application and Test of Pipeline Booster in Natural Gas Pipeline, Ph. D. thesis, Chongqin University, Chongqin, China, 2009
- Cheng, Z., et al., Multi-objective optimization of self-excited oscillation heat exchange tube based on multiple concepts, Applied Thermal Engineering, 197 (2021), 117414
- Wang, J. S., et al., Flow and Heat Transfer Characteristics of Bluff Body Turbulence in Turbulent Boundary Layer, Chinese Journal of Mechanical Engineering, 51 (2015), 24, pp. 168-176 (in Chinese)
- Felten, F., et al., Numerical modelling of electromagnetically-driven turbulent flows using LES methods, Applied Mathematical Modelling, 28 (2004), 1, pp. 15-27
- Breuer, M., Pourquie, M., First experiences with LES of flows past bluff bodies, in: W. Rodi, G. Bergeles (Ed.), Proc. 3rd Int. Symp. on Engineering Turbulence Modelling and Measurements, Heraklion-Crete, Greece, 27-29 May 1996, Elsevier, Amsterdam, 1996, pp. 177-186
- Davletshin, I. A., et al., Convective Heat Transfer in the Channel Entrance with a Square Leading Edge Under Forced Flow Pulsations, International Journal of Heat and Mass Transfer, 129 (2019), pp. 74-85