NUMERICAL STUDY ON HEAT TRANSFER ENHANCEMENT AND FLOW STRUCTURE IN A TUBE WITH CENTRAL SLANT DEFLECTOR

2018 ◽  
Author(s):  
Jinyi Lv ◽  
Peng Liu ◽  
Zhichun Liu ◽  
Wei Liu
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Enhancement ◽  
Flow Structure ◽  
Numerical Study ◽  
Transfer Enhancement

Optimization and Development for Fin-and-Tube Heat Exchangers With Vortex Generators

2010 ◽  
Author(s):  
Ya-Ling He ◽  
Pan Chu ◽  
Wen-Quan Tao
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Enhancement ◽  
Flow Structure ◽  
Heat Exchangers ◽  
Pressure Loss ◽  
Numerical Study ◽  
Moderate Pressure ◽  
Computational Domain ◽  
Transfer Enhancement ◽  
Local Flow

In this paper, heat transfer enhancement and pressure loss penalty for fin-and-tube heat exchangers with rectangular winglet pairs (RWPs) were numerically investigated in a relatively low Reynolds number flow. The purpose of this study was to explore the fundamental mechanism between the local flow structure and the heat transfer augmentation. The RWPs were placed with a special orientation for the purpose of enhancement of heat transfer. The numerical study involved three-dimensional flow and conjugate heat transfer in the computational domain, which was set up to model the entire flow channel in the air flow direction. The effects of attack-angle of RWPs, row-number of RWPs and placement of RWPs on the heat transfer characteristics and flow structure were examined in detail. It was observed that the longitudinal vortices caused by RWPs and the impingement of RWPs-directed flow on the downstream tube were important reasons of heat transfer enhancement for fin-and-tube heat exchangers with RWPs. It was interesting to find that the pressure loss penalty of the fin-and-tube heat exchangers with RWPs could be reduced by altering the placement of the same number of RWPs from inline array to staggered array and simultaneously maintain the heat transfer enhancement level. The results showed that the rectangular winglet pairs (RWPs) can significantly improve the heat transfer performance of the fin-and-tube heat exchangers with a moderate pressure loss penalty.

Experimental and Numerical Study of Heat Transfer and Flow Friction in Channels With Dimples of Different Shapes

2015 ◽  
Vol 137 (3) ◽  
Author(s):  
Yu Rao ◽  
Yan Feng ◽  
Bo Li ◽  
Bernhard Weigand
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Enhancement ◽  
Flow Structure ◽  
Channel Flow ◽  
Numerical Study ◽  
Rectangular Channel ◽  
Transfer Enhancement ◽  
Number Range ◽  
Flow Friction ◽  
Different Shapes

An experimental and numerical study was conducted to investigate the effects of dimple shapes on the heat transfer and flow friction of a turbulent flow over dimpled surfaces with different dimple shapes: spherical, teardrop, elliptical, and inclined elliptical. These dimples all have the same depth. The heat transfer, friction factor, and flow structure characteristics in the cooling channels with dimples of different shapes have been obtained and compared with each other for a Reynolds number range of 8500–60,000. The study showed that the dimple shape can have distinctive effects on the heat transfer and flow structure in the dimpled channels. The teardrop dimples show the highest heat transfer, which is about 18% higher than the conventional spherical dimples; and the elliptical dimples have the lowest heat transfer, which is about 10% lower than the spherical dimples; and however the inclined elliptical dimples have comparable heat transfer and pressure loss performance with the spherical dimples. The experiments still showed the realistic heat transfer enhancement capabilities of the dimpled channels relative to a smooth rectangular channel flow under the same flow and thermal boundary conditions, even after considering the thermal entrance effects in the channel flow and the enlarged heat transfer (wetted) area due to the dimpled surface. The three-dimensional numerical computations showed different vortex flow structures and detailed heat transfer characteristics of the dimples with different shapes, which revealed the influential mechanisms of differently shaped dimples on the convective heat transfer enhancement.

A numerical study of the effect on flow structure and heat transfer of a rectangular winglet pair in a plate fin heat exchanger

2009 ◽  
Vol 223 (9) ◽  
pp. 2109-2115 ◽  
Author(s):  
M Gupta ◽  
K S Kasana ◽  
R Vasudevan
Keyword(s):  
Heat Transfer ◽  
Heat Exchanger ◽  
Heat Transfer Enhancement ◽  
Flow Structure ◽  
Numerical Study ◽  
Vortex Generator ◽  
Working Fluid ◽  
Pair Type ◽  
Transfer Enhancement ◽  
Navier Stokes Equation

Longitudinal vortices have a great capability of disrupting the growth of boundary layers and bring about the heat transfer enhancement between the fluid and its neighbouring surface. The potential of a winglet pair type vortex generator for the heat transfer enhancement in a plate fin heat exchanger, with triangular fins as inserts, is numerically evaluated in this article. The rectangular winglet pair is mounted on the triangular fins. The numerical computations are performed by solving an unsteady, three-dimensional Navier—Stokes equation, and an energy equation by using the modified MAC method. Air is taken as the working fluid. This study shows the flow structure and the performance of the winglet pair in improving the heat transfer. The computations are performed at Re=200 and placing the winglet at an angle of attack, β=20°. The results show that the heat transfer is increased by 13 per cent, even at the exit, with the winglet pair. The heat transfer enhancement with a winglet pair for different Re=200—500 and Pr=0.71 and for varying heights of the winglet pair is also predicted.

Three-Dimensional Numerical Study of Flow and Heat Transfer Enhancement Using Vortex Generators in Fin-and-Tube Heat Exchangers

2009 ◽  
Vol 131 (9) ◽  
Author(s):  
P. Chu ◽  
Y. L. He ◽  
W. Q. Tao
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Enhancement ◽  
Flow Structure ◽  
Heat Exchangers ◽  
Numerical Study ◽  
Three Dimensional ◽  
Performance Comparison ◽  
Transfer Enhancement ◽  
Local Flow ◽  
Overall Performance

In this paper, a three-dimensional numerical investigation was performed for heat transfer characteristics and flow structure of full scale fin-and-tube heat exchangers with rectangular winglet pair (RWP). For the Reynolds number ranging from 500 to 880, the baseline configuration (without RWP) is compared with three enhanced configurations (with RWP): inline-1RWP case, inline-3RWP case, and inline-7RWP case. It was found that the air-side heat transfer coefficient improved by 28.1–43.9%, 71.3–87.6%, and 98.9–131% for the three enhanced configurations, with an associated pressure drop penalty increase of 11.3–25.1%, 54.4–72%, and 88.8–121.4%, respectively. An overall performance comparison was conducted by using the London area goodness factor. It is revealed that among the three enhanced configurations, the inline-1RWP case obtains the best overall performance, and the inline-3RWP case is better than the inline-7RWP case. The numerical results were also analyzed on the basis of the field synergy principle to provide fundamental understanding of the relation between local flow structure and heat transfer augmentation. It was confirmed that the reduction in the average intersection angle between the velocity vector and the temperature gradient was one of the essential factors influencing heat transfer enhancement. The analysis also provides guidelines for where the enhancement technique is highly needed.

Sign in / Sign up

Export Citation Format

Share Document