scholarly journals 3-D numerical study of the effect of Reynolds number and baffle angle on heat transfer and pressure drop of turbulent flow of air through rectangular duct of very small height

2016 ◽  
Vol 8 ◽  
pp. 583-585
Author(s):  
Abhijit Paul ◽  
Dipak Sen ◽  
Ajoy Kumar Das
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Pressure Drop ◽  
Turbulent Flow ◽  
Numerical Study ◽  
Rectangular Duct ◽  
Small Height

scholarly journals Numerical study of nanofluids effect on heat transfer and pressure drop of triangular microchannel heat sink

2020 ◽  
Vol 13 (1) ◽  
pp. 173-180
Author(s):  
R Vinoth ◽  
M Parthiban ◽  
Naveen Kumar Nagalli ◽  
S Prakash
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Pressure Drop ◽  
Heat Sink ◽  
Numerical Study ◽  
Microchannel Heat Sink ◽  
Modeling And Analysis ◽  
Chip Cooling ◽  
Large Heat ◽  
Solid Works

The present work deals with study the heat transfer and pressure drop of the triangular microchannel heat sink(MCHS), along different working fluids. The nanofluids such as CuO and Al2O3are used as coolants to enhance the performance of triangular microchannel heat sinks.The modeling and analysis were done with the help of Solid works. The heat transfer performance of the triangular fins were studied with the Reynolds number varying from 96 - 460. Thenumerical result shows that the triangular oblique finned microchannel heat sink has large heat transfer rateof 12.9 % for varying Reynolds number when compared to a straight channel. Similarly, the pressure drop also increases with 38.2% for triangular microchannel flowing nanofluid. Consequently triangular microchannel is enhancing the heat removed in electronics chip cooling

Prediction of Turbulent Flow and Heat Transfer in a Ribbed Rectangular Duct With and Without Rotation

1993 ◽  
Author(s):  
C. Prakash ◽  
R. Zerkle
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Turbulent Flow ◽  
Flow Direction ◽  
Three Dimensional ◽  
Stationary Case ◽  
Rectangular Duct ◽  
Wall Functions ◽  
Flow And Heat Transfer ◽  
Smooth Channel

The present study deals with the numerical prediction of turbulent flow and heat transfer in a 2:1 aspect ratio rectangular duct with ribs on the two shorter sides. The ribs are of square cross–section, staggered and aligned normal (90–deg) to the main flow direction. The ratio of rib height to duct hydraulic diameter equals 0.063, and the ratio of rib spacing to rib height equals 10. The duct may be stationary or rotating. The axis of rotation is normal to the axis of the duct and parallel to the ribbed walls (i.e., the ribbed walls form the leading and the trailing faces). The problem is three–dimensional and fully elliptic; hence, for computational economy, the present analysis deals only with a periodically–fully–developed situation where the calculation domain is limited to the region between two adjacent ribs. Turbulence is modelled with the k–epsilon model in conjunction with wall–functions. However, since the rib height is small, use of wall–functions necessitates that the Reynolds number be kept high. (Attempts to use a two–layer model that permits integration to the wall did not yield satisfactory results and such modelling issues are discussed at length). Computations are made here for Reynolds number in the range (30,000–100,000) and for Rotation number=0 (stationary), 0.06, and 0.12. For the stationary case, the predicted heat transfer agrees well with the experimental correlations. Due to the Coriolis induced secondary flow, rotation is found to enhance heat transfer from the trailing and the side walls, while decreasing heat transfer from the leading face. Relative to the corresponding stationary case, the effect of rotation is found to be less for a ribbed channel as compared to a smooth channel.

Effect of Bend Geometry on Heat Transfer and Pressure Drop in a Two-Pass Coolant Square Channel for a Turbine

2012 ◽  
Vol 135 (2) ◽  
Author(s):  
Krishnendu Saha ◽  
Sumanta Acharya
Keyword(s):  
Heat Transfer ◽  
Pressure Drop ◽  
Turbulent Flow ◽  
Friction Factor ◽  
Thermal Performance ◽  
Numerical Study ◽  
Solution Procedure ◽  
Internal Cooling ◽  
Square Channel ◽  
End Wall

This paper presents a comparative numerical study of turbulent flow inside a two-pass internal cooling channel with different bend geometries. The goal is to find a geometry that reduces the bend related pressure loss and enhances overall heat transfer coefficient. A square channel with a round U-bend is taken as a baseline case and the heat transfer and pressure drop for nine different bend geometries are compared with the baseline. Modifications for the bend geometry are made along the channel divider wall and at the end wall of the 180 deg bend. The bend geometries studied include: (1) a turning vane geometry, (2) an asymmetrical bulb, (3) three different symmetrical bulbs, (4) two different bow shaped geometries at the end wall, (5) a bend with an array of dimples in the bend region, and (6) finally a combination of bow geometry and dimples. The solution procedure is based on a commercial finite volume solver using the Reynolds averaged Navier–Stokes (RANS) equation and a turbulence model. A two equation realizable k-ɛ model with enhanced wall treatment is used to model the turbulent flow. It was found that the bend geometry can have a significant effect on the overall performance of a two-pass channel. The modified bend geometries are compared with the baseline using Nusselt number ratios, friction factor ratios, and thermal performance factors (TPF) as the metrics. All the modified bend geometries show increase in the TPF with the symmetrical bulb configuration showing nearly a 40% reduction in friction factor ratio and a 30% increase in thermal performance. The highest TPF (41% increase over baseline) is observed for the symmetrical bulb combined with a bow along the outer walls and surface dimples.

Numerical Study of Mixed Convection through Horizontal Duct Utilizing Al2O3

2016 ◽  
Vol 819 ◽  
pp. 111-116
Author(s):  
Nur Irmawati Om ◽  
Hussein A. Mohammed
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Rayleigh Number ◽  
Mixed Convection ◽  
Numerical Study ◽  
Dimensionless Temperature ◽  
Rectangular Duct ◽  
Heat Transfer Characteristics ◽  
Flow And Heat Transfer ◽  
Rayleigh Numbers

In the present study, mixed convection in a horizontal rectangular duct using Al2O3 is numerically investigated. The effects of different Rayleigh number, Reynolds number and radiation on flow and heat transfer characteristics were studied in detail. This study covers Rayleigh number in the range of 2 106 ≤ Ra ≤ 2 107 and Reynolds number in the range of 100 ≤ Re ≤ 1100. Results reveal that the Nusselt number increases as Reynolds and Rayleigh numbers increase. It was also found that the dimensionless temperature distribution increases as Rayleigh number increases.

Numerical Prediction of Turbulent Flow and Heat Transfer Enhancement in a Square Passage With Various Truncated Ribs on One Wall

2013 ◽  
Vol 136 (1) ◽  
Author(s):  
Gongnan Xie ◽  
Jian Liu ◽  
Weihong Zhang ◽  
Giulio Lorenzini ◽  
Cesare Biserni
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Turbulent Flow ◽  
Heat Transfer Enhancement ◽  
Pressure Loss ◽  
Numerical Study ◽  
Skew Angle ◽  
Transfer Enhancement ◽  
Reduced Pressure ◽  
Flow And Heat Transfer

Repeated ribs are often employed in the midsection of internal cooling passages of turbine blades to augment the heat transfer by air flowing through the internal ribbed passages. Though the research of flow structure and augmented heat transfer inside various ribbed passages has been well conducted, previous works mostly paid much attention to the influence of rib topology (height-to-pitch, blockage ratio, skew angle, rib shape). The possible problem involved in the usage of ribs (especially with larger blockage ratios) is pressure loss penalty. Thus, in this case, the design of truncated ribs whose length is less than the passage width might fit the specific cooling requirements when pressure loss is critically considered. A numerical study of truncated ribs on turbulent flow and heat transfer inside a passage of a gas turbine blade is performed when the inlet Reynolds number ranges from 8000 to 24,000. Different truncation ratio (truncated-length to passage-width) rib geometries are designed and then the effect of truncation ratio on the pressure drop and heat transfer enhancement is observed under the condition of constant total length. The overall performance characteristics of various truncated rib passages are also compared. It is found that the heated face with a rib that is truncated 12% in length in the center (case A) has the highest heat transfer coefficient, while the heated face with a rib that is truncated 4% at three locations over its length, in the center and two sides (case D), has a reduced pressure loss compared with passages of other designs and provides the lowest friction factors. Although case A shows larger heat transfer augmentation, case D can be promisingly used to augment side-wall heat transfer when the pressure loss is considered and the Reynolds number is relatively large.

Prediction of Turbulent Flow and Heat Transfer in a Ribbed Rectangular Duct With and Without Rotation

1995 ◽  
Vol 117 (2) ◽  
pp. 255-264 ◽  
Author(s):  
C. Prakash ◽  
R. Zerkle
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Turbulent Flow ◽  
Flow Direction ◽  
Three Dimensional ◽  
Stationary Case ◽  
Rectangular Duct ◽  
Wall Functions ◽  
Flow And Heat Transfer ◽  
Smooth Channel

The present study deals with the numerical prediction of turbulent flow and heat transfer in a 2:1 aspect ratio rectangular duct with ribs on the two shorter sides. The ribs are of square cross section, staggered and aligned normal (90 deg) to the main flow direction. The ratio of rib height to duct hydraulic diameter equals 0.063, and the ratio of rib spacing to rib height equals 10. The duct may be stationary or rotating. The axis of rotation is normal to the axis of the duct and parallel to the ribbed walls (i.e., the ribbed walls form the leading and the trailing faces). The problem is three dimensional and fully elliptic; hence, for computational economy, the present analysis deals only with a periodically fully developed situation where the calculation domain is limited to the region between two adjacent ribs. Turbulence is modeled with the k–ε model in conjunction with wall functions. However, since the rib height is small, use of wall functions necessitates that the Reynolds number be kept high. (Attempts to use a two-layer model that permits integration to the wall did not yield satisfactory results and such modeling issues are discussed at length.) Computations are made here for Reynolds number in the range 30,000–100,000 and for Rotation number = 0 (stationary), 0.06, and 0.12. For the stationary case, the predicted heat transfer agrees well with the experimental correlations. Due to the Coriolis-induced secondary flow, rotation is found to enhance heat transfer from the trailing and the side walls, while decreasing heat transfer from the leading face. Relative to the corresponding stationary case, the effect of rotation is found to be less for a ribbed channel as compared to a smooth channel.

Unsteady RANS Simulation of Turbulent Flow and Heat Transfer in a Channel With Periodic Array of Cubic Pin-Fins

2003 ◽  
Author(s):  
A. K. Saha ◽  
Sumanta Acharya
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Turbulent Flow ◽  
Channel Wall ◽  
Numerical Study ◽  
Periodic Array ◽  
Outer Flow ◽  
Flow And Heat Transfer ◽  
Pin Fins ◽  
Unsteady Rans

An unsteady three-dimensional numerical study is performed to explore flow and heat transfer in a periodic array of cubic pin-fins housed inside a narrow channel. Short cubic pin-fins are arranged in an inline pattern with both streamwise and transverse periodicity set to 2.5 times the pin-fin dimension. Calculations are done in the turbulent flow regime for Reynolds numbers in the range of 7090–13280. The unsteady Reynolds-Averaged Navier Stokes (RANS) and energy equations are solved using higher order temporal and spatial discretization schemes. An unsteady k-ε turbulence model is employed to model the unresolved turbulence fluctuations. The unsteady RANS results are able to resolve discrete large scale spatial and temporal fluctuations in the flow. These fluctuations appear to mostly influence the flow in the region between the cubic fins, but are linked to low amplitude oscillations in the outer flow. Three thermal boundary conditions are studied: (1) only channel wall heated (2) only pin-fins heated and (3) both channel wall and pin-fins heated. The overall heat transfer enhancement is about 1.8–2.0 times the heat transfer from a smooth duct flow. The heat transfer from pin-fins is found to be 5–9% higher than that from the top wall at low Reynolds number (7090 and 8900), while it is of comparable magnitude at higher Reynolds number (=13280).

HEAT TRANSFER AND PRESSURE DROP IN TURBULENT FLOW THROUGH A TUBE WITH LONGITUDINAL PERFORATED STAR-SHAPED INSERTS

2011 ◽  
Vol 18 (6) ◽  
pp. 491-502 ◽  
Author(s):  
Andrew Mintu Sarkar ◽  
M. A. Rashid Sarkar ◽  
Mohammad Abdul Majid
Keyword(s):  
Heat Transfer ◽  
Pressure Drop ◽  
Turbulent Flow ◽  
Flow Through
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