Multiple Flow Patterns and Heat Transfer in Confined Jet Impingement

2002 ◽  
Author(s):  
X. Li ◽  
J. L. Gaddis ◽  
T. Wang
Keyword(s):  
Heat Transfer ◽  
Flow Field ◽  
Boundary Conditions ◽  
Jet Impingement ◽  
Flow Patterns ◽  
Computational Results ◽  
Initial Flow ◽  
Flow Parameters ◽  
Visualization Experiment ◽  
Exit Boundary

The flow field of a 2-D laminar confined impinging slot jet is investigated. Numerical results indicate that there exist two different solutions in some range of geometric and flow parameters. The two steady flow patterns are obtained under identical boundary conditions but only with different initial flow fields. Three different exit boundary conditions are investigated to eliminate artificial effects. The different flow patterns are observed to significantly affect the heat transfer. A flow visualization experiment is carried out to verify the computational results and both flow patterns are observed. The bifurcation mechanism is interpreted and discussed.

Influences of Small Jet-to-Wall Spacings on Heat Transfer Characteristics and Flow-Field Entrainment Effects of Microscale Jets

2021 ◽  
Vol 143 (3) ◽  
Author(s):  
Prabhakar Subrahmanyam ◽  
B. K. Gnanavel
Keyword(s):  
Heat Transfer ◽  
Flow Field ◽  
Jet Impingement ◽  
Impinging Jets ◽  
Heat Transfer Characteristics ◽  
Transfer Coefficients ◽  
Inlet System ◽  
Potential Core ◽  
Transfer Characteristics ◽  
The Impact

Abstract Detailed heat transfer distributions of multiple microscaled tapered jets orthogonally impinging on the surface of a high-power density silicon wall is presented. The tapered jets issued from two different impingement setup are studied—(a) single circular nozzle and (b) dual circular nozzles. Jets are issued from the inlet(s) at four different Reynolds numbers {Re = 8000, 12,000, 16,000, 20,000}. The spacing between the tapered nozzle jets and the bare die silicon wall (z/d) is adjusted to be 4, 8, 12, and 16 jet nozzle diameters away from impinging influence. The impact of varying the nozzle to the silicon wall (z/d) standoff spacing up to 16 nozzle jet diameters and its effects on flow fields on the surface of the silicon, specifically the entrainment pattern on the silicon surface, is presented. Heat transfer characteristics of impinging jets on the hot silicon wall is investigated by means of large eddy simulations (LES) at a Reynolds of 20,000 on each of the four z/d spacing and compared against its equivalent Reynolds-averaged Navier–Stokes (RANS) cases. Highest heat transfer coefficients are obtained for the dual inlet system. A demarcation boundary region connecting all the microvortices between impinging jets is prominently visible at smaller z/d spacing—the region where the target silicon wall is within the sphere of influence of the potential core of the jet. This research focuses on the underlying physics of multiple tapered nozzles jet impingement issued from single and dual nozzles and its impact on turbulence, heat transfer distributions, entrainment, and other pertinent flow-field characteristics.

Natural Convection of Nanofluid in a Triangle Cavity with Different Angular Positions

2020 ◽  
Vol 12 (3) ◽  
pp. 325-329
Author(s):  
Mohsen Rostami ◽  
Mohammad Saleh Abadi
Keyword(s):  
Heat Transfer ◽  
Numerical Simulation ◽  
Natural Convection ◽  
Flow Field ◽  
Boundary Conditions ◽  
Angular Position ◽  
Numerical Results ◽  
Heat Transfer Characteristics ◽  
Current Structure ◽  
Flow And Heat Transfer

The effects of the angular position on the flow and heat transfer of the nanofluid in a triangular cavity is investigated numerically. A triangular cavity is chosen with the same boundary conditions as the published results are available. The comparison between the current numerical results with the available data is made to show the accuracy of the numerical simulation. The current structure of triangular cavity is rotated to investigate the effects of various angular positions on the flow and heat transfer characteristics of nanofluid. For this purpose, the equations of continuity, momentum and energy are solved numerically. The results show that the hot fluid is more freely penetrated into the domain by increasing of the angular position. The velocity of fluid in the flow field becomes maximum for the angle of 120 . Also, the creation of vortices in the flow field depends on the value of angular position.

Heat Transfer and Fluid Flow of a Single Jet Impingement in Cross-Flow Modified by a Vortex Generator Pair

2016 ◽  
Author(s):  
Chenglong Wang ◽  
Lei Luo ◽  
Lei Wang ◽  
Bengt Sundén
Keyword(s):  
Heat Transfer ◽  
Flow Field ◽  
Gas Turbines ◽  
Cross Flow ◽  
Vortex Generator ◽  
Jet Impingement ◽  
Transfer Coefficients ◽  
Stagnation Region ◽  
Target Wall ◽  
The Cross

Jet impingement cooling is widely used in modern gas turbines. In the present study, both heat transfer and flow field measurements of jet impingement in cross-flow are carried out with and without a vortex generator pair (VGP). The jet and cross-flow Reynolds numbers are fixed at 15,000 and 48,000, respectively. The local heat transfer coefficients are obtained by a liquid crystal thermography (LCT) technique. Results show that the jet impingement heat transfer on the target wall is remarkably enhanced by the VGP as compared to the baseline case. The stagnation region moves upstream with improved heat transfer when the VGP is present. The flow field is measured by particle image velocimetry (PIV). The cross-flow is shown to deflect the impinging jet but the VGP reduces the streamwise momentum of the cross-flow and drives the crossflow away from the issuing jet. This leads to stronger jet impingement and thus heat transfer enhancement on the target wall.

Simulation of Micro-Scale Jet Impingement Heat Transfer

2000 ◽  
Author(s):  
Paul A. Boeschoten ◽  
Deborah V. Pence ◽  
James A. Liburdy
Keyword(s):  
Heat Transfer ◽  
Nusselt Number ◽  
Mach Number ◽  
Boundary Conditions ◽  
Slip Velocity ◽  
Slip Flow ◽  
Local Maximum ◽  
Jet Impingement ◽  
Micro Scale ◽  
Flow Boundary

Abstract The heat transfer performance of a micro-scale, axisymmetric, confined jet impinging on a flat surface at high Mach numbers (0.2 to 0.6) and low Reynolds numbers (419 to 1310) was computationally studied. The flow is characterized by Knudsen numbers, based on the jet radius, large enough (0.0013) to warrant slip-flow boundary conditions at the impinging surface. The effects of Mach number, compressibility, and slip-flow on heat transfer results are presented, along with the local Nusselt number distributions, and velocity and temperature fields near the impingement surface. Results for uniform wall heat flux show that the wall temperature decreases with increasing Mach number, with a local minimum at r/D = 0.7. The slip velocity also increases with Mach number with peak values also near r/D = 0.7. The resulting Nusselt number increases with increasing Mach number, and a local maximum in the Nusselt number is observed at r/D = 0.6, not at the centerline. In general, compressibility improves heat transfer due to increased fluid density near the impinging surface. Also, inclusion of slip-velocity increases the rate of heat transfer. However, the accompanying temperature-jump condition at the wall is found to reduce the local heat transfer rate. The net effect of the slip-flow boundary conditions applied in this study was an overall reduction in heat transfer.

Flow Field Effects on Heat Transfer in Confined Jet Impingement

1997 ◽  
Vol 119 (3) ◽  
pp. 630-632 ◽  
Author(s):  
J. A. Fitzgerald ◽  
S. V. Garimella
Keyword(s):  
Heat Transfer ◽  
Flow Field ◽  
Jet Impingement ◽  
Field Effects
Sign in / Sign up

Export Citation Format

Share Document