Investigations on the Influence of Flow Migration on Flow and Heat Transfer in Oblique Fin Microchannel Array

2016 ◽  
Vol 138 (10) ◽  
Author(s):  
Nasi Mou ◽  
Yong Jiun Lee ◽  
Poh Seng Lee ◽  
Pawan K. Singh ◽  
Saif A. Khan
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Secondary Flow ◽  
Flow Rate ◽  
Heat Transfer Performance ◽  
Profile Analysis ◽  
Flow Distribution ◽  
Transfer Performance ◽  
Flow And Heat Transfer ◽  
Microchannel Array

In order to scrutinize the coolant mass distribution and its effect to the heat transfer in oblique fin microchannel array, extensive numerical studies are performed on planar oblique fin configuration. Full-domain simulations using common-flow down (CFD) approach are employed to provide better insights into the flow distribution, flow stability, and heat transfer performance at a global level. The flow field and temperature profile analysis shows that nonuniform coolant distribution and coolant migration occur in the oblique fin microchannel, and the heat transfer performance for both edges of the heat sink is affected due to changing secondary flow rate. However, the flow migration does not affect the local coolant velocity and temperature profiles significantly in the middle region (0.2 < Z′ < 0.8). Meanwhile, it is also found that Reynolds number affects the coolant migration, the stability of the fluid flow, and heat transfer performance significantly. Higher Reynolds number increases the percentage of secondary flow rate and, hence, enhances the heat transfer for fin surfaces in secondary channels.

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.

Heat Transfer Performance of Internal Cooling Channel With Single-Row Jet Impingement Array by Varying Flow Rates

2016 ◽  
Vol 9 (1) ◽  
Author(s):  
Sin Chien Siw ◽  
Nicholas Miller ◽  
Maryanne Alvin ◽  
Minking Chyu
Keyword(s):  
Heat Transfer ◽  
Flow Rate ◽  
Heat Transfer Performance ◽  
Flow Distribution ◽  
Jet Impingement ◽  
Target Surface ◽  
Internal Cooling ◽  
Transfer Performance ◽  
Flow Rates ◽  
Optimum Flow Rate

The current detailed experimental study focuses on the optimization of heat transfer performance through jet impingement by varying the coolant flow rate to each individual jet. The test section consists of an array of jets, each jet individually fed and metered separately, that expel coolant into the channel and exit through one end. The diameter D, height-to-diameter H/D, and jet spacing-to-diameter S/D are all held constant at 9.53 mm, 2, and 4, respectively. Upon defining the optimum flow rate for each jet, varying diameter jet plates are designed and tested using a similar test setup with the addition of a plenum. Two test cases are conducted by varying the jet diameter within 10% compared to the benchmark jet diameter, 9.53 mm. The Reynolds number, which is based on hydraulic diameter of the channel and total mass flow rate entering the channel, ranges from approximately 52,000 up to 78,000. The transient liquid crystal technique is employed in this study to determine the local and average heat transfer coefficient distributions on the target plate. Commercially available computational fluid dynamics software, ansys cfx, is used to qualitatively correlate the experimental results and to fully understand the flow field distributions within the channel. The results revealed that varying the jet flow rates, total flow varied by approximately ±5% from that of the baseline case, the heat transfer enhancement on the target surface is enhanced up to approximately 35%. However, when transitioning to the varying diameter jet plate, this significant enhancement is suppressed due to the nature of flow distribution from the plenum, combined with the complicated crossflow effects.

Effects of Baffle Overlap Proportion on Shell-Side Performance of Shell and Tube Heat Exchanger With Helical Baffles

2013 ◽  
Author(s):  
Bin Gao ◽  
Qincheng Bi ◽  
Zesen Nie
Keyword(s):  
Heat Transfer ◽  
Heat Exchanger ◽  
Flow Rate ◽  
Heat Transfer Performance ◽  
Transfer Performance ◽  
Shell Side ◽  
Tube Heat Exchanger ◽  
Flow And Heat Transfer ◽  
Shell And Tube ◽  
Side Flow

Different overlap configurations of discontinuous helical baffles affect the flow pattern of the shell-side fluid directly, and thus there is a significant impact on the flow and heat transfer characteristics of the shell-side fluid. In the present paper, experiments were carried out to study the impact of baffle overlap proportion on the shell-side flow and heat transfer performance of the shell-and-tube heat exchanger with helical baffles (STHEHB). Two different shell-side friction factors, the friction factor per helical pitch (fs,1B) and the friction factor per tube length (fs,1m), were defined based on different reference lengths. The results showed that, since the baffle overlap proportion leads to different helical pitch as well as flow fields in shell side, opposite conclusions are obtained by choosing different reference length. Based on the same Reynolds number, the shell-side Nusselt number of the STHEHB with 10% baffle overlap is higher than that with 50% baffle overlap. The reason is that the larger baffle overlap proportion produces more serious leak flows and weakens the heat transfer in shell side. The comparison of heat transfer coefficient per unit pressure drop versus shell-side flow rate showed that the STHEHB with smaller baffle overlap proportion has better comprehensive heat transfer performance, but the difference between the two decreases gradually with the increase of the flow rate.

scholarly journals Experimental study of developing turbulent flow and heat transfer in ribbed convergent/divergent rectangular ducts

2015 ◽  
Vol 19 (6) ◽  
pp. 2219-2231 ◽  
Author(s):  
Sivakumar Karthikeyan ◽  
Natarajan Elumalai ◽  
Kulasekharan Narasingamurthi
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Flow Rate ◽  
Heat Transfer Performance ◽  
Transfer Performance ◽  
Square Duct ◽  
Convergent Channel ◽  
Maximum Heat ◽  
Maximum Heat Transfer ◽  
Mean Diameter

The article represents an experimental investigation of friction and heat transfer characteristics of divergent / convergent rectangular ducts with an inclination angle of 1? in the y-axis. Measurements were taken for a convergent / divergent rectangular duct of aspect ratio AR at inlet1.25 and outlet in convergent channel 1.35; but in case of divergent duct it can be reversed. The four uniform rib heights, e = 3, 6, 9 and 12 mm the ratio between rib height to hydraulic mean diameter (e/Dm) are 34.8, 69.7, 104.6 and 138.7 a constant rib pitch distance, P = 60 mm has been used. The flow rate in terms of average Reynolds number based on the hydraulic mean diameter (Dm) is 86 mm of the channel was in a range of 20,000 to 50,000. The two ceramic heating strip of 10 mm thickness is used as a heating element have attached on top and bottom surfaces for the test sections. The heat transfer performance of the divergent / convergent ducts for 3, 6, 9 and 12 mm ribs was conducted under identical mass flow rate based on the Reynolds number. In our experiments has totally 8 different ducts were used. In addition, the acceleration / deceleration caused by the cross section area, the divergent duct generally shows enhanced heat transfer behavior for four different rib sizes, while the convergent duct has an appreciable reduction in heat transfer performance. From result point view divergent duct with 3 mm height ribbed square duct gets maximum heat transfer coefficient with minimum friction loss over the other convergent / divergent ducts.

EXPERIMENTAL STUDY ON THERMAL TRANSPORT PHENOMENON OF NANOFLUIDS AS WORKING FLUID IN HEAT EXCHANGER

2014 ◽  
Vol 22 (01) ◽  
pp. 1450005 ◽  
Author(s):  
SHUICHI TORII
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Heat Transfer Performance ◽  
Pure Water ◽  
Horizontal Tube ◽  
Constant Heat Flux ◽  
Working Fluid ◽  
Transfer Performance ◽  
Nanoparticles Concentration ◽  
Transfer Behavior

This paper aims to study the convective heat transfer behavior of aqueous suspensions of nanoparticles flowing through a horizontal tube heated under constant heat flux condition. Consideration is given to the effects of particle concentration and Reynolds number on heat transfer enhancement and the possibility of nanofluids as the working fluid in various heat exchangers. It is found that (i) significant enhancement of heat transfer performance due to suspension of nanoparticles in the circular tube flow is observed in comparison with pure water as the working fluid, (ii) enhancement is intensified with an increase in the Reynolds number and the nanoparticles concentration, and (iii) substantial amplification of heat transfer performance is not attributed purely to the enhancement of thermal conductivity due to suspension of nanoparticles.

Local Heat Transfer Distribution in a Rotating Serpentine Rib-Roughened Flow Passage

1993 ◽  
Vol 115 (3) ◽  
pp. 560-567 ◽  
Author(s):  
N. Zhang ◽  
J. Chiou ◽  
S. Fann ◽  
W.-J. Yang
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Heat Transfer Performance ◽  
Local Heat Transfer ◽  
Local Heat ◽  
Transfer Performance ◽  
Height Ratio ◽  
Nusselt Numbers ◽  
Rayleigh Numbers ◽  
Rib Roughened

Experiments are performed to determine the local heat transfer performance in a rotating serpentine passage with rib-roughened surfaces. The ribs are placed on the trailing and leading walls in a corresponding posited arrangement with an angle of attack of 90 deg. The rib height-to-hydraulic diameter ratio, e/Dh, is 0.0787 and the rib pitch-to-height ratio, s/e, is 11. The throughflow Reynolds number is varied, typically at 23,000, 47,000, and 70,000 in the passage both at rest and in rotation. In the rotation cases, the rotation number is varied from 0.023 to 0.0594. Results for the rib-roughened serpentine passages are compared with those of smooth ones in the literature. Comparison is also made on results for the rib-roughened passages between the stationary and rotating cases. It is disclosed that a significant enhancement is achieved in the heat transfer in both the stationary and rotating cases resulting from an installation of the ribs. Both the rotation and Rayleigh numbers play important roles in the heat transfer performance on both the trailing and leading walls. Although the Reynolds number strongly influences the Nusselt numbers in the rib-roughened passage of both the stationary and rotating cases, Nuo and Nu, respectively, it has little effect on their ratio Nu/Nuo.

A Numerical Investigation Into the Heat Transfer Performance and Particle Dynamics of a Compressible, Highly Mass Loaded, High Reynolds Number, Particle Laden Flow

2021 ◽  
Author(s):  
Kyle Hassan ◽  
Robert F. Kunz ◽  
David Hanson ◽  
Michael Manahan
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Computational Model ◽  
High Reynolds Number ◽  
Heat Transfer Performance ◽  
Particle Dynamics ◽  
Transfer Performance ◽  
Temperature Distributions ◽  
High Reynolds ◽  
Particle Laden Flow

Abstract In this work, we study the heat transfer performance and particle dynamics of a highly mass loaded, compressible, particle-laden flow in a horizontally-oriented pipe using an Eulerian-Eulerian (two-fluid) computational model. An attendant experimental configuration [1] provides the basis for the study. Specifically, a 17 bar co-flow of nitrogen gas and copper powder are modeled with inlet Reynolds numbers of 3×104, 4.5×104, and 6×104 and mass loadings of 0, 0.5, and 1.0. Eight binned particle sizes were modeled to represent the known powder properties. Significant settling of all particle groups are observed leading to asymmetric temperature distributions. Wall and core flow temperature distributions are observed to agree well with measurements. In high Reynolds number cases, the predictions of the multiphase computational model were satisfactorily aligned with the experimental results. Low Reynolds number model predictions were not as consistent with the experimental measurements.

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