Heat Transfer Around Sharp 180-deg Turns in Smooth Rectangular Channels

1986 ◽  
Vol 108 (3) ◽  
pp. 500-506 ◽  
Author(s):  
D. E. Metzger ◽  
M. K. Sahm
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Forced Convection ◽  
Cross Section ◽  
Rectangular Cross Section ◽  
Side Wall ◽  
Bottom Wall ◽  
Channel Depth ◽  
Nusselt Numbers ◽  
Rectangular Channels

Measured Nusselt numbers are presented for forced convection within and around sharp 180-deg turns in smooth channels of rectangular cross section. Separately determined top wall, bottom wall, and side wall values are presented individually along with azimuthal averages. The geometry of the channels and connecting turn is characterized by the parameters W*, the ratio of upstream and downstream channel widths; D*, the nondimensional channel depth; and H*, the nondimensional clearance at the tip of the turn. Results from nine combinations of these parameters are presented at several values of channel Reynolds number to illustrate the effect of turn geometry on the heat transfer distributions.

scholarly journals Heat Transfer Around Sharp 180 Degree Turns in Smooth Rectangular Channels

1985 ◽  
Author(s):  
D. E. Metzger ◽  
M. K. Sahm
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Forced Convection ◽  
Cross Section ◽  
Rectangular Cross Section ◽  
Side Wall ◽  
Bottom Wall ◽  
Channel Depth ◽  
Nusselt Numbers ◽  
Rectangular Channels

Measured Nusselt numbers are presented for forced convection within and around sharp 180 degree turns in smooth channels of rectangular cross section. Separately determined top wall, bottom wall, and side wall values are presented individually along with azimuthal averages. The geometry of the channels and connecting turn is characterized by parameters W*, the ratio of upstream and downstream channel widths; D*, the non-dimensional channel depth; and H*, the non-dimensional clearance at the tip of the turn. Results from nine combinations of these parameters are presented at several values of channel Reynolds number to illustrate the effect of turn geometry on the heat transfer distributions.

Influence of the 180° Bend Geometry on the Pressure Loss and Heat Transfer in a High Aspect Ratio Rectangular Smooth Channel

2004 ◽  
Author(s):  
Detlef Pape ◽  
Herve´ Jeanmart ◽  
Jens von Wolfersdorf ◽  
Bernhard Weigand
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Aspect Ratio ◽  
Cross Section ◽  
High Aspect Ratio ◽  
Pressure Loss ◽  
Rectangular Cross Section ◽  
Flow Structures ◽  
Cooling Channel ◽  
Smooth Channel

An experimental and numerical investigation of the pressure loss and the heat transfer in the bend region of a smooth two-pass cooling channel with a 180°-turn has been performed. The channels have a rectangular cross-section with a high aspect ratio of H/W = 4. The heat transfer has been measured using the transient liquid crystal method. For the investigations the Reynolds-number as well as the distance between the tip and the divider wall (tip distance) are varied. While the Reynolds number varies from 50’000 to 200’000 and its influence on the normalized pressure loss and heat transfer is found to be small, the variations of the tip distance from 0.5 up to 3.65 W produce quite different flow structures in the bend. The pressure loss over the bend thus shows a strong dependency on these variations.

Experimental Investigation of Heat Transfer in Microchannels

2003 ◽  
Author(s):  
Poh-Seng Lee ◽  
Suresh V. Garimella
Keyword(s):  
Heat Transfer ◽  
Experimental Investigation ◽  
Reynolds Number ◽  
Copper Substrate ◽  
Deionized Water ◽  
Entrance Length ◽  
Continuum Approach ◽  
Channel Depth ◽  
Rectangular Channels ◽  
Classical Correlations

Heat transport in microchannels is experimentally investigated to explore the validity of classical correlations for conventional-sized rectangular channels in predicting the thermal behavior and the onset of transition in microchannels. The microchannels considered range in width from 194 μm to 534 μm, with the channel depth being nominally five times the width in each case. Ten microchannels were machined into a 2.54 cm by 2.54 cm copper substrate for each test piece. The experiments were conducted with deionized water, with the Reynolds number ranging from approximately 300 to 3500. The results show that the heat transfer in microchannels is satisfactorily predicted with a classical, continuum approach. However, the applicable classical correlations need to be chosen carefully to match the boundary and entrance length conditions imposed in the experiment.

Flow and Heat Transfer in Convectively Cooled Underground Electric Cable Systems: Part 2—Temperature Distributions and Heat Transfer Correlations

1978 ◽  
Vol 100 (1) ◽  
pp. 36-40 ◽  
Author(s):  
R. S. Abdulhadi ◽  
J. C. Chato
Keyword(s):  
Heat Transfer ◽  
Boundary Layer ◽  
Reynolds Number ◽  
Cross Section ◽  
Thermal Boundary Layer ◽  
Electric Cable ◽  
Nusselt Numbers ◽  
Temperature Distributions ◽  
Cable Systems ◽  
Heat Transfer Correlations

Temperature distributions and heat transfer correlations have been obtained experimentally for a wide range of physical, flow and thermal parameters in three models of oil-cooled underground electric cable systems. The results show that in the laminar range, with the oils used, the thermal boundary layer thickness around the heated cables is only of the order of 2–3 mm over the entire length of the test section. Consequently, the best correlation of the heat transfer results is obtained if the Nusselt number, based on the cable diameter, is plotted against Re·Pr0.4, where the Reynolds number is based on the overall hydraulic diameter of the cross section of the flow. For laminar flows, the oil temperatures in the restricted flow channels between three cables or two cables and the pipe wall are about 11°C higher than corresponding bulk temperatures. As the flow becomes turbulent, the thermal boundary layer tends to vanish and the oil temperature becomes uniform over the entire flow cross section. Laminar Nusselt numbers are independent of the skid wire roughness ratio and the flow Reynolds number, but increase with increasing Rayleigh number and axial distance from the inlet, indicating significant natural convection effect. The range of laminar Nusselt numbers was 5–16. Turbulent Nusselt numbers increase with increasing roughness ratios. The Nusselt numbers at Re = 3000 are 30 and 60 for roughness ratios of 0.0216 and 0.0293, respectively.

Enhanced Forced Convection Heat Transfer From a Cylinder Using Permeable Fins

2003 ◽  
Vol 125 (5) ◽  
pp. 804-811 ◽  
Author(s):  
Bassam A/K Abu-Hijleh
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Forced Convection ◽  
Convection Heat Transfer ◽  
Cross Flow ◽  
Horizontal Cylinder ◽  
Convection Heat ◽  
Transfer Rates ◽  
Forced Convection Heat Transfer ◽  
Nusselt Numbers

The problem of cross-flow forced convection heat transfer from a horizontal cylinder with multiple, equally spaced, high conductivity permeable fins on its outer surface was investigated numerically. The heat transfer characteristics of a cylinder with permeable versus solid fins were studied for several combinations of number of fins and fin height over the range of Reynolds number (5–200). Permeable fins provided much higher heat transfer rates compared to the more traditional solid fins for a similar cylinder configuration. The ratio between the permeable to solid Nusselt numbers increased with Reynolds number and fin height but tended to decrease with number of fins. This ratio was as high as 4.35 at Reynolds number of 150 and a single fin with a nondimensional height of 3.0. The use of 1–2 permeable fins resulted in much higher Nusselt number values than when using up to 18 solid fins. Such an arrangement has other benefits such as a considerable reduction in weight and cost.

Heat Transfer Control Around an Obstacle by Using Ribs in the Downstream Region

2014 ◽  
Vol 6 (4) ◽  
Author(s):  
Zahra Ghorbani-Tari ◽  
Lei Wang ◽  
Bengt Sunden
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Cross Section ◽  
Rectangular Cross Section ◽  
Local Heat Transfer ◽  
Local Heat ◽  
Upstream Region ◽  
Downstream Region ◽  
End Wall ◽  
Downstream Area

This paper investigates the effect of the presence of a rib on the local heat transfer around an obstacle using liquid crystal technique. An obstacle with a rectangular cross section is placed in a channel and attached to the end-wall. A rib is positioned in the downstream region of the obstacle. The spacing S between the rib and the obstacle is normalized by the spanwise width of the obstacle and the value is 1.25d. The effects of the rib height e/Dh and Reynolds number are investigated. The e/Dh has the values 0.039 and 0.078. The Reynolds number varies between 35,600 and 55,600. It is shown that the local heat transfer in the upstream region of the obstacle remained unaffected by the presence of the rib. The feature of local heat transfer in the downstream area of the obstacle was substantially modified by the presence of the rib.

Forced-convection freezing heat transfer characteristics in a return bend with a rectangular cross section

1995 ◽  
Vol 30 (4) ◽  
pp. 205-214
Author(s):  
S. Fukusako ◽  
M. Yamada ◽  
A. Horibe ◽  
M. Tago ◽  
Dr. Senior Researcher ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Forced Convection ◽  
Cross Section ◽  
Rectangular Cross Section ◽  
Heat Transfer Characteristics ◽  
Transfer Characteristics
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