Investigation of Flow and Heat Transfer of an Impinging Jet in a Cross-Flow For Cooling of a Heated Cube

2005 ◽  
Vol 128 (2) ◽  
pp. 150-156 ◽  
Author(s):  
D. Rundström ◽  
B. Moshfegh
Keyword(s):  
Heat Transfer ◽  
Channel Flow ◽  
Single Channel ◽  
Velocity Ratio ◽  
Cross Flow ◽  
Impinging Jet ◽  
Steady Increase ◽  
Heated Plate ◽  
Low Velocity ◽  
Mean Values

The current trends toward the greater functionality of electronic devices are resulting in a steady increase in the amount of heat dissipated from electronic components. Forced channel flow is frequently used to remove heat at the walls of the channel where a PCB with a few high heat dissipating components is located. The overall cooling strategy thus must not only match the overall power dissipation load, but also address the requirements of the “hot” components. In order to cool the thermal load with forced channel flow, excessive flow rates will be required. The objective of this study is to investigate if targeted cooling systems, i.e., an impinging jet in combination with a low velocity channel flow, can improve the thermal performance of the system. The steady-state three-dimensional (3-D) model is developed with the Reynolds-Stress-Model (RSM) as a turbulence model. The geometrical case is a channel with a heated cube in the middle of the base plate and two inlets, one horizontal channel flow, and one vertical impinging jet. The numerical model is validated against experimental data obtained from three well-known cases, two cases with an impinging jet on a flat heated plate, and one case with a heated cube in a single channel flow. The effects of the jet Re and jet to-cross-flow velocity ratio are investigated. The airflow pattern around the cube and the surface temperature of the cube as well as the mean values and local distributions of the heat transfer coefficient are presented.

Investigation of Heat Transfer and Pressure Drop of an Impinging Jet in a Cross-Flow for Cooling of a Heated Cube

2008 ◽  
Vol 130 (12) ◽  
Author(s):  
D. Rundström ◽  
B. Moshfegh
Keyword(s):  
Heat Transfer ◽  
Channel Flow ◽  
Pressure Loss ◽  
Cooling System ◽  
Cross Flow ◽  
Impinging Jet ◽  
Heated Wall ◽  
Pressure Drops ◽  
Average Heat ◽  
Loss Coefficients

The objective of this study is to investigate the thermal performance and the cost measured in pressure drops of a targeted cooling system with use of an impinging jet in combination with a low-velocity channel flow on a heated wall-mounted cube. The effects of the Reynolds numbers of the impinging jet and the cross-flow, as well as the distance between the top and bottom plates, are investigated. A steady-state 3D computational fluid dynamics model was developed with use of a Reynolds stress model as turbulence model. The geometrical case is a channel with a heated cube in the middle of the base plate and two inlets, one horizontal channel flow and one vertical impinging jet. The numerical model was validated against experimental data with a similar geometrical setup. The velocity field was measured by particle image velocimetry and the surface temperature was measured by an infrared imaging system. This case results in a very complex flow structure where several flow-related phenomena influence the heat transfer rate and the pressure drops. The average heat transfer coefficients on each side of the cube and the pressure loss coefficients are presented; correlations for the average heat transfer coefficient on the cube and the pressure loss coefficients are created.

Experimental Investigation of Jet Impingement Heat Transfer in Cross-Flow Modified by a V-Shaped Rib

2014 ◽  
Author(s):  
Chenglong Wang ◽  
Lei Wang ◽  
Bengt Sundén
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Velocity Ratio ◽  
Cross Flow ◽  
Jet Impingement ◽  
Impinging Jet ◽  
Heat Transfer Characteristics ◽  
Transfer Characteristics ◽  
Impingement Heat Transfer ◽  
The Cross

Experimental studies are carried out to investigate the jet impingement heat transfer characteristics in cross-flow with and without the presence of a 45 deg V-shaped rib. The local heat transfer coefficients are obtained by a liquid crystal thermography (LCT) technique. The ratio of nozzle-to-surface spacing to jet diameter is 3.56, the jet Reynolds number is kept at 17,000, the cross-flow Reynolds number spans from 32,700 to 65,000, the velocity ratio of jet to cross-flow ranges from 1.5 to 3.0. The impingement heat transfer characteristics in cross-flow are changed from the results without the cross-flow, and they are strongly affected by the velocity ratio. The presence of a V-shaped rib significantly modifies the heat transfer patterns of the impinging jet in cross-flow. Compared to the results without ribs, the heat transfer over the ribbed surface is enhanced for a low velocity ratio but retarded for a high velocity ratio, depending on the interaction between the rib induced flow and the impinging jet.

Effects of alternating elliptical chamber on jet impingement heat transfer in vane leading edge under different cross-flow conditions

2021 ◽  
pp. 1-17
Author(s):  
K. Xiao ◽  
J. He ◽  
Z. Feng
Keyword(s):  
Heat Transfer ◽  
Velocity Ratio ◽  
Cross Flow ◽  
Leading Edge ◽  
Longitudinal Vortices ◽  
Impingement Jet ◽  
Flow And Heat Transfer ◽  
Impingement Heat Transfer ◽  
Cross Flow Velocity ◽  
The Cross

ABSTRACT This paper proposes an alternating elliptical impingement chamber in the leading edge of a gas turbine to restrain the cross flow and enhance the heat transfer, and investigates the detailed flow and heat transfer characteristics. The chamber consists of straight sections and transition sections. Numerical simulations are performed by solving the three-dimensional (3D) steady Reynolds-Averaged Navier–Stokes (RANS) equations with the Shear Stress Transport (SST) k– $\omega$ turbulence model. The influences of alternating the cross section on the impingement flow and heat transfer of the chamber are studied by comparison with a smooth semi-elliptical impingement chamber at a cross-flow Velocity Ratio (VR) of 0.2 and Temperature Ratio (TR) of 1.00 in the primary study. Then, the effects of the cross-flow VR and TR are further investigated. The results reveal that, in the semi-elliptical impingement chamber, the impingement jet is deflected by the cross flow and the heat transfer performance is degraded. However, in the alternating elliptical chamber, the cross flow is transformed to a pair of longitudinal vortices, and the flow direction at the centre of the cross section is parallel to the impingement jet, thus improving the jet penetration ability and enhancing the impingement heat transfer. In addition, the heat transfer in the semi-elliptical chamber degrades rapidly away from the stagnation region, while the longitudinal vortices enhance the heat transfer further, making the heat transfer coefficient distribution more uniform. The Nusselt number decreases with increase of VR and TR for both the semi-elliptical chamber and the alternating elliptical chamber. The alternating elliptical chamber enhances the heat transfer and moves the stagnation point up for all VR and TR, and the heat transfer enhancement is more obvious at high cross-flow velocity ratio.

Experimental and Numerical Impingement Heat Transfer in an Airfoil Leading-Edge Cooling Channel With Cross-Flow

2008 ◽  
Vol 131 (1) ◽  
Author(s):  
M. E. Taslim ◽  
D. Bethka
Keyword(s):  
Heat Transfer ◽  
Mass Flow ◽  
Convective Heat Transfer Coefficient ◽  
Cross Flow ◽  
Internal Heat ◽  
Leading Edge ◽  
Impinging Jet ◽  
Experimental Results ◽  
Transfer Coefficients ◽  
Impingement Heat Transfer

To enhance the internal heat transfer around the airfoil leading-edge area, a combination of rib-roughened cooling channels, film cooling, and impingement cooling is often employed. Experimental data for impingement on various leading-edge geometries are reported by these and other investigators. The effects of strong cross-flows on the leading—edge impingement heat transfer, however, have not been studied to that extent. This investigation dealt with impingement on the leading edge of an airfoil in the presence of cross-flows beyond the cross-flow created by the upstream jets (spent air). Measurements of heat transfer coefficients on the airfoil nose area as well as the pressure and suction side areas are reported. The tests were run for a range of axial to jet mass flow rates (Maxial∕Mjet) ranging from 1.14 to 6.4 and jet Reynolds numbers ranging from 8000 to 48,000. Comparisons are also made between the experimental results of impingement with and without the presence of cross-flow and between representative numerical and measured heat transfer results. It was concluded that (a) the presence of the external cross-flow reduces the impinging jet effectiveness both on the nose and sidewalls; (b) even for an axial to jet mass flow ratio as high as 5, the convective heat transfer coefficient produced by the axial channel flow was less than that of the impinging jet without the presence of the external cross-flow; and (c) the agreement between the numerical and experimental results was reasonable with an average difference ranging from −8% to −20%.

Heat Transfer Characteristics of Non-Uniform Flow Around a Circular Cylinder in a T-Junction Duct

2020 ◽  
Author(s):  
Xiaoyu Wang ◽  
Di Qi ◽  
Tong Li ◽  
Mei Lin ◽  
Hanbing Ke ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Circular Cylinder ◽  
Velocity Ratio ◽  
Correlation Coefficients ◽  
Heat Transfer Characteristics ◽  
Low Velocity ◽  
Stagnation Points ◽  
Transfer Characteristics ◽  
Low Speed Wind Tunnel ◽  
Straight Duct

Abstract Heat transfer characteristics of a circular cylinder in the branch of a T-junction are experimentally investigated in a low-speed wind tunnel with Reynolds number of Rec = 9163. Local and average heat transfer distributions around the circular cylinder are obtained for the cylinder positions from x/Dh=0.5 to 13 and the velocity ratios from 0.117 to 0.614. It is found that the overall heat transfer characteristics in a T-junction duct at high velocity ratio are lower than those at low velocity ratio, and both are higher than those in the straight duct. The local Nusselt number in the T-junction duct is asymmetrical distribution and weakens with increasing velocity ratios and positions of the cylinder. The angles of the front and rear stagnation points in the T-junction duct are the same as those in the straight duct at certain velocity ratio and/or position of the cylinder. However, the angles of the front and rear separation points in the T-junction duct do not match those in the straight duct. Both the heat transfer correlation coefficients and the amplitude ratios increase with increasing positions of the circular cylinder and velocity ratios.

Convective Heat Transfer Enhancement With Micro Pin-Fin Surfaces Cooled by a Piezoelectrically-Driven Translational Agitator

2012 ◽  
Author(s):  
Taiho Yeom ◽  
Terrence W. Simon ◽  
Tao Zhang ◽  
Mark T. North ◽  
Tianhong Cui
Keyword(s):  
Heat Transfer ◽  
Convective Heat Transfer ◽  
Channel Flow ◽  
Convective Heat ◽  
High Frequency ◽  
Single Channel ◽  
Heated Surface ◽  
Large Displacement ◽  
Air Cooling ◽  
Pin Fin

Air cooling of electronic equipment continues to hold many advantages over liquid cooling in terms of simplicity, reliability, cost, etc. Many active and passive air cooling techniques have been developed to meet the thermal challenges of modern, high-power electronics. Active cooling includes such features as piezoelectric flapping fans and synthetic jets that could directly break down and thin the thermal boundary layers on heated surfaces. A microchannel bank of fins, micro pin-fin surfaces, etc. are passive methods for increasing heat transfer area. In the current study, both active and passive methods, piezoelectric translational agitators and micro pin fin arrays, are employed to dramatically enhance convective heat transfer rates. A piezoelectric stack actuator coupled with an oval loop shell displacement amplifier was utilized to generate high-frequency and large-displacement translational agitation over the micro pin fin surface. Two different micro pin-fin surfaces were fabricated using copper and the LIGA process. Heat transfer experiments were performed in a single channel that houses a one-sided, heated surface with attached micro pin fins. The piezoelectric translational agitator oscillates at a high frequency of 596 Hz with a large displacement of up to 1.8 mm. The heat transfer coefficients on the micro pin-fin surface cooled by the agitator and various channel through-flows were compared with those of plain surfaces under the same channel flow rates. A maximum improvement of 222% in the heat transfer rate was achieved when the agitator was operated, the micro pin-fin surface was in place and the channel flow velocity was 11.6 m/sec, compared to that of a non-agitated plain surface case with the same flow rate.

Sign in / Sign up

Export Citation Format

Share Document