Research on Flow and Heat Transfer Characteristics of Multiple Impinging Jets on a Moving Conveyor Belt

2020 ◽  
Author(s):  
Rui Liu ◽  
Yu Sun ◽  
Jun Ni
Keyword(s):  
Heat Transfer ◽  
Wind Velocity ◽  
Fluid Dynamic ◽  
Simple Algorithm ◽  
Conveyor Belt ◽  
Impinging Jets ◽  
Freezing Rate ◽  
Heat Transfer Characteristics ◽  
Transfer Characteristics ◽  
Confined Domains

Abstract Turbulent impinging jets at three different jet nozzle forms were numerically analyzed using the SIMPLE algorithm and k-epsilon turbulent model to investigate the flow field and heat transfer characteristics. The food placed upon a moving conveyor belt cooled by series of impinging jets under a specific condition. Three semi-confined domains with different jet nozzles were established, thereby with slot, rectangular, and funnel-shaped nozzles, respectively. Based on computational fluid dynamic (CFD) calculations, distributions of the temperature and wind velocity at four critical cross-sections of domains were compared. The results reveal that the freezing rate of foods mainly relates to temperature and wind velocity. For three semi-confined domains, the impinging jet with slot nozzles produces higher exit wind velocity, lower center temperature, and a better mass flow uniformity than others, which could better improve the heat transfer performance, and could increase the freezing rate of foods.

Experimental heat transfer characteristics of a liquid in Couette motion and with Taylor vortices

1961 ◽  
Vol 261 (1305) ◽  
pp. 215-226 ◽  
Keyword(s):  
Heat Transfer ◽  
Reverse Flow ◽  
Fluid Dynamic ◽  
Fluid Motion ◽  
Heat Transfer Characteristics ◽  
Radial Temperature ◽  
Transfer Characteristics ◽  
Experimental Heat ◽  
Concentric Cylinders ◽  
Primary Fluid

The heat transfer characteristics of water in rotational motion between horizontal concentric cylinders has been studied. Primary fluid motion due to rotation of the inner cylinders alone, and due to rotation of inner cylinder with reverse flow caused by a divider, has been considered experimentally for two ratios of annulus width to inner cylinder radius. The results for two geometries and two primary fluid dynamic conditions are correlated by a parameter related to the generalized stability parameter. Radial temperature profiles are given and are shown to be effective in indicating secondary flow patterns.

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.

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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