Fluid Flow and Heat Transfer in Microchannels With Rectangular Cross Section

2003 ◽  
Author(s):  
Jung-Yeul Jung ◽  
Ho-Young Kwak
Keyword(s):  
Heat Transfer ◽  
Friction Factor ◽  
Cross Section ◽  
Rectangular Cross Section ◽  
Transfer Coefficients ◽  
Forced Convective Heat Transfer ◽  
Heat Transfer Coefficients ◽  
Flow And Heat Transfer ◽  
Convective Heat Transfer Coefficients ◽  
Factor Constant

Forced convective heat transfer coefficients and friction factor for flow of water and FC-72 in microchannels with a rectangular cross section were measured. An integrated microsystem consisting of five microchannels on one side and a localized heater and seven polysilicon temperature sensors along the selected channels on the other side was fabricated by using a double side polished silicon wafer. For the microchannels tested, the friction factor constant C = f ReDh obtained are values between 35.7 and 81.9, which are close to the theoretical value of 57.0. The measured Nusselt number in the laminar regime tested could be correlated by a correlation, Nu = A ReDh1.37 Pr1/3 where A is the value between 0.000 454 and 0.000 646.

Study on Forced Convective Heat Transfer of FC-72 in Vertical Small Tubes

2020 ◽  
Vol 12 (6) ◽  
Author(s):  
Yantao Li ◽  
Yulong Ji ◽  
Katsuya Fukuda ◽  
Qiusheng Liu
Keyword(s):  
Heat Transfer ◽  
Experimental Data ◽  
Convective Heat Transfer ◽  
Convective Heat ◽  
Convection Heat Transfer ◽  
Bulk Liquid ◽  
Transfer Coefficients ◽  
Forced Convective Heat Transfer ◽  
Heat Transfer Coefficients ◽  
Convective Heat Transfer Coefficients

Abstract This paper presents an experimental investigation of the forced convective heat transfer of FC-72 in vertical tubes at various velocities, inlet temperatures, and tube sizes. Exponentially escalating heat inputs were supplied to the small tubes with inner diameters of 1, 1.8, and 2.8 mm and effective heated lengths between 30.1 and 50.2 mm. The exponential periods of heat input range from 6.4 to 15.5 s. The experimental data suggest that the convective heat transfer coefficients increase with an increase in flow velocity and µ/µw (refers to the viscosity evaluated at the bulk liquid temperature over the liquid viscosity estimated at the tube inner surface temperature). When tube diameter and the ratio of effective heated length to inner diameter decrease, the convective heat transfer coefficients increase as well. The experimental data were nondimensionalized to explore the effect of Reynolds number (Re) on forced convection heat transfer coefficient. It was found that the Nusselt numbers (Nu) are influenced by the Re for d = 2.8 mm in the same pattern as the conventional correlations. However, the dependences of Nu on Re for d = 1 and 1.8 mm show different trends. It means that the conventional heat transfer correlations are inadequate to predict the forced convective heat transfer in minichannels. The experimental data for tubes with diameters of 1, 1.8, and 2.8 mm were well correlated separately. And, the data agree with the proposed correlations within ±15%.

scholarly journals Boiling of a refrigerant of low GWP on the surface with copper microchannels

2018 ◽  
Vol 70 ◽  
pp. 02007
Author(s):  
Robert Kaniowski ◽  
Robert Pastuszko
Keyword(s):  
Heat Transfer ◽  
Cross Section ◽  
Atmospheric Pressure ◽  
Rectangular Cross Section ◽  
Heating Surface ◽  
Heat Transfer Process ◽  
Geometrical Parameters ◽  
Variable Depth ◽  
Transfer Coefficients ◽  
Heat Transfer Coefficients

The boiling curves and heat transfer coefficients between the heating surface and fluid were investigated in the paper. Copper samples with horizontal microchannels of rectangular cross-section, variable depth and width were the objects of the study. The following geometrical parameters have been used: microchannel width 0.2; 0.3 and 0.4 mm, depth between 0.2 and 0.5 mm (change every 0.1 mm). Boiling refrigerant was Novec-649 (GWP = 1), and the experiment was performed at atmospheric pressure. Geometrical parameters impact, within a given range of heat flux 3 – 130 kW/m2, on the heat transfer process was determined.

Vibration Effects on Convective Heat Transfer in Enclosures

1970 ◽  
Vol 92 (3) ◽  
pp. 429-437 ◽  
Author(s):  
R. E. Forbes ◽  
C. T. Carley ◽  
C. J. Bell
Keyword(s):  
Heat Transfer ◽  
Convective Heat Transfer ◽  
Convective Heat ◽  
Rectangular Cross Section ◽  
Correlation Equation ◽  
Transfer Coefficients ◽  
Response Characteristics ◽  
Heat Transfer Coefficients ◽  
Different Temperatures ◽  
Convective Heat Transfer Coefficients

The effect of mechanical vibrations on natural convective heat transfer in an enclosure of rectangular cross-section was investigated experimentally. The enclosure was comprised of two vertical and opposed surfaces which were maintained at different temperatures, surrounded by four other adiabatic surfaces. Vibration stresses were applied to this heat transfer cell by mounting it vertically on the armature of an electrodynamic vibrator. Frequencies from 0 to 4000 Hertz and accelerations from 0 to 110 g’s were utilized in the investigation. The results show that vibration of a thermally active enclosure can have a significant effect on its heat transfer characteristics especially near the resonant natural frequency of the column of fluid contained within the enclosure. Increases in convective heat transfer coefficients of as much as 50 percent were obtained during this investigation. A correlation equation was developed by utilizing the dynamic response characteristics of the fluid column when considered as a seismic mass.

Impact of Ceramic Matrix Composite Topology on Friction Factor and Heat Transfer

2021 ◽  
Author(s):  
Trevor M. Cory ◽  
Ryan D. Edelson ◽  
Karen A. Thole ◽  
Tyler Vincent ◽  
San Quach ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Convective Heat Transfer ◽  
Friction Factor ◽  
Convective Heat ◽  
Pressure Loss ◽  
Surface Topology ◽  
Transfer Coefficients ◽  
Pressure Losses ◽  
Heat Transfer Coefficients ◽  
Convective Heat Transfer Coefficients

Abstract Ceramic matrix composites (CMCs) are of interest for hot section components of gas turbine engines due to their low weight and favorable thermal properties. To implement this advanced composite in a gas turbine engine, characterizing the influence of CMC’s surface topology on heat transfer and cooling performance is critical. However, very few published studies have reported the flow and heat transfer effects caused by this unique surface topology. This study is an experimental and computational investigation to evaluate the effect of weave orientations, relevant to CMC surfaces, on the resulting pressure loss and convective heat transfer within an internal channel. The weave pattern was additively manufactured as the walls of a scaled-up coupon containing a single channel. For each of the three weave orientations, bulk pressure losses and convective heat transfer coefficients were measured over a range of Reynolds numbers. Scaling the pressure losses in terms of a friction factor and convective heat transfer coefficients in terms of a Nusselt number showed the importance of choosing the appropriate definition of the hydraulic diameter, which was particularly important for the friction factor. A coupon having one wall with the weave surface increased pressure loss and heat transfer compared to a smooth wall with the largest increases occurring when the CMC weave strands were perpendicular to the flow. Friction factor augmentations were much higher than heat transfer augmentations. When adding the weave to a second channel wall, pressure loss and heat transfer were further increased. Orienting the CMC strands perpendicular to the flow consistently showed the largest augmentations in heat transfer over a smooth channel, but at a much higher pressure loss penalty than that seen with the CMC strands parallel to the flow.

Impact of Ceramic Matrix Composite Topology on Friction Factor and Heat Transfer

2021 ◽  
Vol 144 (3) ◽  
Author(s):  
Trevor M. Cory ◽  
Ryan D. Edelson ◽  
Karen A. Thole ◽  
Tyler Vincent ◽  
San Quach ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Convective Heat Transfer ◽  
Friction Factor ◽  
Convective Heat ◽  
Pressure Loss ◽  
Surface Topology ◽  
Transfer Coefficients ◽  
Pressure Losses ◽  
Heat Transfer Coefficients ◽  
Convective Heat Transfer Coefficients

Abstract Ceramic matrix composites (CMCs) are of interest for hot section components of gas turbine engines due to their low weight and favorable thermal properties. To implement this advanced composite in a gas turbine engine, characterizing the influence of CMC’s surface topology on heat transfer and cooling performance is critical. However, very few published studies have reported the flow and heat transfer effects caused by this unique surface topology. This study is an experimental and computational investigation to evaluate the effect of weave orientations, relevant to CMC surfaces, on the resulting pressure loss and convective heat transfer within an internal channel. The weave pattern was additively manufactured as the walls of a scaled-up coupon containing a single channel. For each of the three weave orientations, bulk pressure losses and convective heat transfer coefficients were measured over a range of Reynolds numbers. Scaling the pressure losses in terms of a friction factor and convective heat transfer coefficients in terms of a Nusselt number showed the importance of choosing the appropriate definition of the hydraulic diameter, which was particularly important for the friction factor. A coupon having one wall with the weave surface increased pressure loss and heat transfer compared to a smooth wall with the largest increases occurring when the CMC weave strands were perpendicular to the flow. Friction factor augmentations were much higher than heat transfer augmentations. When adding the weave to a second channel wall, pressure loss and heat transfer were further increased. Orienting the CMC strands perpendicular to the flow consistently showed the largest augmentations in heat transfer over a smooth channel, but at a much higher pressure loss penalty than that seen with the CMC strands parallel to the flow.

Heat Transfer From the Heated Convex Wall of a Return Bend With Rectangular Cross Section

1983 ◽  
Vol 105 (1) ◽  
pp. 64-69 ◽  
Author(s):  
N. Seki ◽  
S. Fukusako ◽  
M. Yoneta
Keyword(s):  
Heat Transfer ◽  
Cross Section ◽  
Rectangular Cross Section ◽  
Local Heat Transfer ◽  
Local Heat ◽  
Turbulent Heat Transfer ◽  
Transfer Coefficients ◽  
Heat Transfer Coefficients ◽  
Convex Wall ◽  
The Mean

An experimental investigation has been performed to clarify the turbulent heat transfer characteristics along the heated convex wall of a return bend which has a rectangular cross section with large aspect ratio for various heights of the duct. The experiments are carried out under the condition that the convex wall is heated at constant heat flux while the concave wall is insulated. Water is used as the working fluid with duct heights of 15, 40, 60 and 80 mm, Reynolds numbers of 8 × 103 to 8 × 104, and Prandtl numbers ranging from 6.5 to 8.5. The mean and the local heat transfer coefficients are always smaller than those for the straight parallel plates and straight ducts. Both the local and the mean heat transfer coefficients decrease as the duct height increases. Near the outlet region of the return bend the local heat transfer coefficient increases in the flow direction as the height decreases. Behavior is just the opposite at the inlet. Correlation equations for the mean and the local Nusselt numbers are determined in the range of parameters covered.

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