A Numerical Study of the Flow and Heat Transfer Characteristics of Outward Convex Corrugated Tubes With Twisted-Tape Insert

2015 ◽  
Vol 138 (2) ◽  
Author(s):  
Longbin Yang ◽  
Huaizhi Han ◽  
Yanjun Li ◽  
Xiaoming Li
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Performance ◽  
Swirling Flow ◽  
Numerical Study ◽  
Twisted Tape ◽  
Transfer Performance ◽  
Heat Transfer Characteristics ◽  
Corrugated Tube ◽  
Flow And Heat Transfer ◽  
Flow Heat

This work presents a mathematical model for simulating the swirling flow in an outward convex corrugated tube with twisted-tape insert (CT). The synergistic effect on the flow, heat transfer, and friction loss behaviors between the surface-based and fluid-based enhancements is numerically investigated. Renormalized group (RNG) k-ε turbulence model applied in our paper is verified by comparing with experimental results investigated by Manglik and Bergles. Comparisons of the CT and smooth tube with twisted-tape insert (ST) plots are confirmed to investigate the performance differences between them. When comparing the performance of the CT against the ST, the maximum ratio of Nusselt number (Nuc/Nus), ratio of friction factor (f/fs), and overall heat transfer performance (η) values realized in the CT are 1.36, 1.53, and 1.15 times higher, respectively, than the maximum values for those same variables in the ST.

A Numerical Study of the Flow and Heat Transfer in the Pin Fin-Dimple Channels With Various Dimple Depths

2012 ◽  
Vol 134 (7) ◽  
Author(s):  
Yu Rao ◽  
Yamin Xu ◽  
Chaoyi Wan
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Convective Heat Transfer ◽  
Heat Transfer Performance ◽  
Numerical Study ◽  
Transfer Performance ◽  
Number Range ◽  
Flow Friction ◽  
Pin Fin ◽  
Flow And Heat Transfer

A numerical study was conducted to investigate the effects of dimple depth on the flow and heat transfer characteristics in a pin fin-dimple channel, where dimples are located spanwisely between the pin fins. The study aimed at promoting the understanding of the underlying convective heat transfer mechanisms in the pin fin-dimple channels and improving the cooling design for the gas turbine components. The flow structure, friction factor, and heat transfer performance of the pin fin-dimple channels with various dimple depths have been obtained and compared with each other for the Reynolds number range of 8200–80,800. The study showed that, compared to the pin fin channel, the pin fin-dimple channels have further improved convective heat transfer performance, and the pin fin-dimple channel with deeper dimples shows relatively higher Nusselt number values. The study still showed a dimple depth-dependent flow friction performance for the pin fin-dimple channels compared to the pin fin channel, and the pin fin-dimple channel with shallower dimples shows relatively lower friction factors over the studied Reynolds number range. Furthermore, the computations showed the detailed characteristics in the distribution of the velocity and turbulence level in the flow, which revealed the underlying mechanisms for the heat transfer enhancement and flow friction reduction phenomenon in the pin fin-dimple channels.

Numerical Investigation of Impingement Heat Transfer on Concave- and Convex-Dimpled Plate With Different Dimple Arrangements

2016 ◽  
Author(s):  
Feng Zhang ◽  
Xinjun Wang ◽  
Jun Li ◽  
Rui Tan ◽  
Dongliang Wei
Keyword(s):  
Heat Transfer ◽  
Flat Plate ◽  
Pressure Loss ◽  
Heat Transfer Performance ◽  
Numerical Study ◽  
Transfer Performance ◽  
Heat Transfer Characteristics ◽  
Number Range ◽  
Impingement Cooling ◽  
Transfer Characteristics

The present numerical study is conducted to investigate the flow and heat transfer characteristics for impingement cooling on concave or convex dimpled plate with four different dimple arrangements. The investigation of the impingement cooling on the flat plate is also conducted to serve as a contrast and these results are compared with experimental measurements to verify the computational method. Dimples studied here are placed, relative to impingement holes, in either spanwise shifted, in staggered, in in-line, or in streamwise shifted arrangements. The flow structure, pressure loss and heat transfer characteristics of the concave and convex dimpled plate of four different dimple arrangements have been obtained and compared with flat plate for the Reynolds number range of 15000 to 35000. The results show that compared with flat plate, the added concave or convex dimples only causes a negligible increase in the pressure loss, and the pressure loss is insensitive to concave or convex dimple arrangement patterns. In addition, compared with flat plate, both spanwise shifted and staggered concave dimple arrangements show better heat transfer performance, while in-line concave dimple arrangement show worse results. Besides that, the heat transfer performance for streamwise shifted concave dimple arrangement is the worst. Furthermore, compared with flat plate, all convex dimple arrangements studied here show better heat transfer performance.

Numerical Modeling of Turbulent Flow and Heat Transfer Within a Bayonet Tube

2007 ◽  
Author(s):  
Feng Sun ◽  
G.-X. Wang
Keyword(s):  
Heat Transfer ◽  
Turbulent Flow ◽  
Heat Transfer Performance ◽  
Numerical Study ◽  
Experimental Result ◽  
Working Fluid ◽  
Transfer Performance ◽  
Flow And Heat Transfer ◽  
Air Jet ◽  
The Impact

This paper presents a numerical study of turbulent flow and heat transfer in a bayonet tube under steady state. First, various turbulent models and wall treatment methods have been tested and validated against the experimental result from a turbulent air jet. The proper combination of turbulent model and wall treatment is then recommended for the turbulent flow within a bayonet tube. The study focuses on the heat transfer performance at the interface of working fluid and the outer tube wall under different Reynolds numbers. Various geometry parameters are considered in this work and the impact of geometry on the heat transfer performance is investigated. Results indicate that the heat transfer at the bottom of the bayonet tube is enhanced compared with that at the straight part. At low Re (< 8000), the maximum Nu occurs at the stagnation point, while the position of the maximum Nu moves away from the stagnant point as Re exceeds 8000. The results are believed to be helpful for the optimized design of a bayonet tube with fully turbulent flows.

scholarly journals Numerical Study on the Effect of Tube Rows on the Heat Transfer Characteristic of Dimpled Fin

2014 ◽  
Vol 6 ◽  
pp. 637052 ◽  
Author(s):  
Xuehong Wu ◽  
Lihua Feng ◽  
Dandan Liu ◽  
Hao Meng ◽  
Yanli Lu
Keyword(s):  
Heat Transfer ◽  
Heat Exchanger ◽  
Heat Transfer Characteristic ◽  
Average Nusselt Number ◽  
Heat Transfer Performance ◽  
Numerical Study ◽  
Transfer Characteristic ◽  
Transfer Performance ◽  
Heat Transfer Characteristics ◽  
Tube Heat Exchanger

The dimpled fin has excellent heat transfer performance and has attracted a lot of attention to apply on the fin and tube heat exchanger. A study presents to investigate the effects of number of tube rows on the air-side heat transfer characteristics of dimpled fin for velocity ranging from 1 to 3 m/s. The Q/Δ P and Q/((Δ P × V)) are used to evaluate the heat transfer performance of the heat exchanger. The results show that the dimpled arrangement can change the mainstream direction, increase the disturbance, and enhance the heat transfer. With the increase of the number of tube rows, the average Nusselt number decreases and Q/Δ P and Q/((Δ P × V)) increase gradually. Compared with the multipipe tube rows, the performance of two-row tube is better.

scholarly journals Numerical study on the flow and heat transfer of water-based Al2O3 forced pulsating nanofluids based on self-excited oscillation chamber structure

2021 ◽  
pp. 167-167
Author(s):  
Hong Yuan ◽  
Zhao Wang ◽  
Quan Gao ◽  
Ting Fu
Keyword(s):  
Heat Transfer ◽  
Nusselt Number ◽  
Local Nusselt Number ◽  
Performance Index ◽  
Heat Transfer Performance ◽  
Transfer Performance ◽  
Heat Transfer Characteristics ◽  
Transfer Characteristics ◽  
Flow And Heat Transfer ◽  
Excited Oscillation

In this study, the flow and heat transfer characteristics of the forced pulsating Al2O3/water nanofluid were numerically studied. The pulsating excitation of the nanofluid is provided by the Helmhertz self-excited oscillating cavity. The large eddy simulation method is used to solve the equation, and the local Nusselt number and heat transfer performance index are used to analyze the heat transfer characteristics of the nanofluid in the self-excited oscillation heat exchange tube. In addition, the effect of different downstream tube diameters on heat transfer enhancement is discussed. The research results show that the existence of the countercurrent vortex can increase the disturbance of the near-wall fluid, thereby improving the mixing degree of the near-wall fluid and the central mainstream. As the countercurrent vortex migrates downstream, pulse enhanced heat transfer is realized. Furthermore, it was also found that when the downstream tube diameter d2=1.8d1, the periodic effect of the local Nusselt number of the wall is the best and the heat transfer performance index has the most stable pulsation effect within a pulsation cycle. But when d2=2.0d1, the change curve of heat transfer performance index in a pulsating period is the highest, the maximum value is 3.95.

scholarly journals Numerical study on the influencing mechanism of twisted ratio in outward convex corrugated tubes with a twisted tape insert

2018 ◽  
Vol 22 (Suppl. 2) ◽  
pp. 577-584
Author(s):  
Huaizhi Han ◽  
Longbin Yang ◽  
Yiran Hu ◽  
Ruitian Yu ◽  
Qun Zhang
Keyword(s):  
Heat Transfer ◽  
Thermal Performance ◽  
Numerical Study ◽  
Twisted Tape ◽  
High Twist ◽  
Numerical Investigations ◽  
Corrugated Tube ◽  
Influencing Mechanism ◽  
Flow And Heat Transfer ◽  
Twist Ratio

Numerical investigations were conducted on flow and heat transfer in an outward convex corrugated tube with various structural twisted tape inserts. The study investigated the influence of twisted ratio on thermodynamic regulation and mechanism in the corrugated tube. The results indicate that Nusselt number in the corrugated tube (Nuc) exceeds those in the corrugated tube and smooth tube by 120-136% and 171-317%, respectively. Meanwhile, the friction factor increases by 148-153% and 476-514%, respectively. The best overall thermal performance (h = 1.97) is obtained with a high twist ratio (y/w = 5). However, the highest thermal performance (Nuc/Nus = 4.78) is obtained with the lowest twist ratio (y/w = 1.25).

Effect of droplet characteristics and rotation speed on the flow and heat transfer characteristics of mist/air cooling in a rotating ribbed two-pass rectangular channel

2016 ◽  
Vol 231 (2) ◽  
pp. 119-132 ◽  
Author(s):  
Xinjun Wang ◽  
Feng Zhang ◽  
Daren Zheng ◽  
Jun Li
Keyword(s):  
Heat Transfer ◽  
Nusselt Number ◽  
Heat Transfer Performance ◽  
Rotation Speed ◽  
Rectangular Channel ◽  
Air Cooling ◽  
Transfer Performance ◽  
Heat Transfer Characteristics ◽  
Transfer Characteristics ◽  
Flow And Heat Transfer

The flow and heat transfer characteristics of mist/air cooling in the rotating ribbed two-pass rectangular channel are numerically investigated using the CFD software ANSYS-CFX. In this article, a comparison in heat transfer performance between the mist/air cooling and the air-only cooling is performed. Additionally, the effect of the initial mist diameter, temperature, velocity and the channel rotation speed on the mist/air cooling performance is analysed. The results show that the droplet flow distance and Nusselt number of the mist/air cooling increase as the initial mist temperature decreases. In addition, as the initial mist diameter decreases, the diameter of mist on the whole channel decreases, resulting in the higher heat transfer, whilst the mist concentration also decreases, leading to the lower heat transfer. Therefore, there is an optimal initial mist diameter which makes the heat transfer performance best. Nevertheless, the droplet movement and heat transfer performance of mist/air cooling are nearly insensitive to the initial mist velocity. It is also noted that the Coriolis force increases with the channel rotation speed, causing the flow deflection becomes more obvious. Consequently, as the channel rotation speed increases, in the first passage the averaged Nusselt number on the trailing wall increases, and that on the leading wall decreases, while the trend in the second passage is reversed.

Sign in / Sign up

Export Citation Format

Share Document