The role of turbulence in determining the heat-transfer characteristics of impinging jets

1965 ◽  
Vol 8 (10) ◽  
pp. 1261-1272 ◽  
Author(s):  
Robert Gardon ◽  
J.Cahit Akfirat
Keyword(s):  
Heat Transfer ◽  
Impinging Jets ◽  
Heat Transfer Characteristics ◽  
Transfer Characteristics

Local and Instantaneous Heat Transfer Characteristics of Arrays of Pulsating Jets

1999 ◽  
Vol 121 (2) ◽  
pp. 341-348 ◽  
Author(s):  
H. S. Sheriff ◽  
D. A. Zumbrunnen
Keyword(s):  
Heat Transfer ◽  
Convective Heat Transfer ◽  
Convective Heat ◽  
Jet Flow ◽  
Impinging Jets ◽  
Industrial Applications ◽  
Heat Transfer Characteristics ◽  
Ensemble Averaging ◽  
Transfer Characteristics ◽  
Pulsating Jets

Recent investigations have revealed that pulsations in an incident jet flow can be an effective technique for modifying convective heat transfer characteristics. While these studies focused on single impinging jets, industrial applications of impinging jets usually involve arrays of jets. To explore the effects of flow pulsations on the heat transfer performance of jet arrays, an experimental investigation has been performed of instantaneous and time-averaged convective heat transfer to a square, in-line array of circular air jets within an unit cell of the array. Hot-film anemometry was used to document the jet flow field. Instantaneous and time-averaged convective heat transfer rates were measured using a heat flux microsensor. An ensemble averaging technique was used to separate the pulsating component of flow velocity and heat transfer from the turbulent components and thereby assess the effect of flow pulsation on turbulence intensity and heat transfer. For the ranges of parameters considered, results indicate convective heat transfer distributions become more uniform in response to pulsations but heat transfer is not enhanced. Improved uniformity can be a useful aspect in many jet applications.

Heat Transfer Characteristics of Baffled Channel Flow

2011 ◽  
Author(s):  
Changwoo Kang ◽  
Kyung-Soo Yang
Keyword(s):  
Heat Transfer ◽  
Channel Flow ◽  
Large Scale ◽  
Heat Removal ◽  
Heat Transfer Characteristics ◽  
Transfer Characteristics ◽  
Flow Heat ◽  
Two Parameters ◽  
Time Periodic

Heat transfer characteristics of baffled channel flow, where thin baffles are mounted on both channel walls periodically in the direction of the main flow, have been numerically investigated in a laminar range. In baffled channel flow, heat transfer characteristics are significantly affected by large-scale vortices generated due to flow separation at the tips of the baffles. In this investigation, a parametric study has been carried out to identify the optimal configuration of the baffles to achieve the most efficient heat removal from the channel walls. Two key parameters are considered, namely baffle interval (L) and Reynolds number (Re). We elucidate the role of the primary instability, a Hopf bifurcation from steady to a time-periodic flow, in the convective heat transfer in baffled channel flow. We also propose a contour diagram (“map”) of averaged Nusselt number on the channel walls as a function of the two parameters. The results shed light on understanding and controlling heat transfer mechanism in a finned heat exchanger, being quite beneficial to its design.

Numerical Study of Flow and Heat Transfer Characteristics of Impinging Jets

2010 ◽  
Author(s):  
Tarek M. Abdel-Salam
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Nusselt Number ◽  
Numerical Study ◽  
Three Dimensional ◽  
Impinging Jets ◽  
Two Dimensional ◽  
Heat Transfer Characteristics ◽  
Transfer Characteristics ◽  
Flow And Heat Transfer

This study presents results for flow and heat transfer characteristics of two-dimensional rectangular impinging jets and three-dimensional circular impinging jets. Flow geometries under consideration are single and multiple impinging jets issued from a plane wall. Both confined and unconfined configurations are simulated. Effects of Reynolds number and the distance between the jets are investigated. Results are obtained with a finite volume computational fluid dynamics (CFD) code. Structured grids are used in all cases of the present study. Turbulence is treated with a two equation k-ε model. Different jet velocities have been examined corresponding to Reynolds numbers of 5,000 to 20,000. Results of the three-dimensional cases show that Reynolds number has no effect on the velocity distribution of the center jet. Results of both two-dimensional and three-dimensional cases show that Reynolds number highly affects the heat transfer and values of the Nusselt number. The maximum Nusselt number was always found at the stagnation point of the center jet.

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.

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