scholarly journals The Effect of Baffle Configuration on Heat Transfer and Pressure Drop Characteristics of Jet Impingement System with Cross-Flow

2021 ◽  
Vol 86 (2) ◽  
pp. 15-27
Author(s):  
Sabu Kurian ◽  
Tide P Sunny ◽  
Biju N
Keyword(s):  
Heat Transfer ◽  
Pressure Drop ◽  
Cross Flow ◽  
Jet Impingement ◽  
Hydraulic Performance ◽  
Performance Parameter ◽  
Numerical Predictions ◽  
Parametric Studies ◽  
Cross Flow Velocity ◽  
Plate Distance

Use of baffles in jet impingement systems in presence of initial cross-flow disturbs boundary layer that results in rise in heat transfer. Two configurations of baffle assisted impingement systems were considered and a comparative study on heat transfer and pressure drop is carried out based on operating parameters such as baffle clearance, blow ratio and h/D ratio using commercially available CFD package. Numerical predictions showed that both heat transfer and pressure drop in segmented configuration were higher than louvered configuration for all blow ratio employed in this study. Parametric studies showed that, thermo-hydraulic performance parameter is higher only for louvered configurations at low blow ratio. When cross-flow velocity is comparable with jet velocity, segmented baffles resulted in relatively higher thermo-hydraulic performance because of its higher heat transfer rate relative to the incurring pressure drop. An increase in clearance proportionally increases performance parameter. However, as jet to plate distance increases, thermo hydraulic performance declines significantly.

Heat Transfer Enhancement of Impinging Row Jets in Cross-Flow with Mounting Baffles on Surface

2014 ◽  
Vol 931-932 ◽  
pp. 1218-1222
Author(s):  
Rattanakorn Pansang ◽  
Makatar Wae-Hayee ◽  
Passakorn Vessakosol ◽  
Chayut Nuntadusit
Keyword(s):  
Heat Transfer ◽  
Cross Flow ◽  
Jet Impingement ◽  
Transfer Characteristic ◽  
Impinging Jets ◽  
Upstream Region ◽  
Orifice Diameter ◽  
Thermochromic Liquid Crystal ◽  
Cross Flow Velocity ◽  
Jet Velocity

The aim of this research is to enhance heat transfer on a surface of row of impinging jets in cross-flow by mounting some baffles on the surface. A row of 4 jets with inline arrangement discharging from round orifices impinged normally on inner surface of wind tunnel with simulated cross-flow. The orifice diameter (D) was 13.2 mm. The jet-to-surface distance and jet-to-jet distance were fixed at H=2D and S=3D, respectively. Four couples of baffles with V-shaped arrangement at attack angle, θ=30o, were mounted on surface in upstream or downstream of impinging jets and the location of baffles attachment is L=1.5D apart from the jet impingement region. The velocity ratios (Jet velocity/cross-flow velocity) were varied from VR=3, 5 and 7 while the jet velocity was kept constant corresponding to Re=13,400. The experimental investigation was carried out for heat transfer characteristic by using Thermochromic Liquid Crystal sheet, and heat transfer coefficient distributions were evaluated using an image processing method. The results show that the impinging jets with mounting the baffles in the upstream region of jet impingement region can enhance the heat transfer rate throughout VR.

General Characterization of Jet Impingement Array Heat Sinks With Interspersed Fluid Extraction Ports for Uniform High-Flux Cooling

2017 ◽  
Vol 139 (8) ◽  
Author(s):  
Alexander S. Rattner
Keyword(s):  
Heat Transfer ◽  
Pressure Drop ◽  
Fluid Transport ◽  
Cross Flow ◽  
Jet Impingement ◽  
Heat Sinks ◽  
Fluid Extraction ◽  
Pressure Drops ◽  
Technical Potential ◽  
Gap Height

In conventional jet impingement array heat sinks, all the spent coolant is extracted from component edges, resulting in cross-flow interference and nonuniform heat transfer. Jet impingement arrays with interspersed fluid extraction ports can reduce cross-flow, improving heat transfer uniformity and reducing pumping loads. While this configuration offers technical advantages, limited pressure drop and heat transfer data are available. In this investigation, simulations are performed for laminar single-phase jet impingement arrays with interspersed fluid extraction ports over varying flow rates (Rej = 20–500), fluid transport properties (Pr = 1–100), and geometries (jet pitch to diameter ratios of 1.8–7.1 and jet diameter to gap height ratios of 0.1–4.0). The simulation approach is validated for isolated jet impingement, and grid sensitivity studies are performed to quantify numerical uncertainty. Over 1000 randomized cases are evaluated to develop new correlations for Nusselt number and pressure-drop k-factors. Conjugate heat transfer studies are performed to compare heat sinks (5 × 5 mm heated, 500 W m−2 heat flux) employing jet arrays with interspersed fluid extraction ports, microchannels, and jet arrays with edge fluid extraction. The design with jet arrays with interspersed fluid extraction ports yields lower average temperatures, improved temperature uniformity, and modest pressure drops. This study provides new data for jet impingement thermal management and highlights the technical potential of configurations with interspersed fluid extraction ports.

scholarly journals Numerical Study of Thermal-Hydraulic Performance of a New Spiral Z-Type PCHE for Supercritical CO2 Brayton Cycle

Energies ◽  
2021 ◽  
Vol 14 (15) ◽  
pp. 4417
Author(s):  
Tingting Xu ◽  
Hongxia Zhao ◽  
Miao Wang ◽  
Jianhui Qi
Keyword(s):  
Heat Transfer ◽  
Pressure Drop ◽  
Pressure Loss ◽  
Numerical Study ◽  
Hydraulic Performance ◽  
Optimal Structure ◽  
Original Structure ◽  
Brayton Cycle ◽  
Compact Structure ◽  
Spiral Angle

Printed circuit heat exchangers (PCHEs) have the characteristics of high temperature and high pressure resistance, as well as compact structure, so they are widely used in the supercritical carbon dioxide (S-CO2) Brayton cycle. In order to fully study the heat transfer process of the Z-type PCHE, a numerical model of traditional Z-type PCHE was established and the accuracy of the model was verified. On this basis, a new type of spiral PCHE (S-ZPCHE) is proposed in this paper. The segmental design method was used to compare the pressure changes under 5 different spiral angles, and it was found that increasing the spiral angle θ of the spiral structure will reduce the pressure drop of the fluid. The effects of different spiral angles on the thermal-hydraulic performance of S-ZPCHE were compared. The results show that the pressure loss of fluid is greatly reduced, while the heat transfer performance is slightly reduced, and it was concluded that the spiral angle of 20° is optimal. The local fluid flow states of the original structure and the optimal structure were compared to analyze the reason for the pressure drop reduction effect of the optimal structure. Finally, the performance of the optimal structure was analyzed under variable working conditions. The results show that the effect of reducing pressure loss of the new S-ZPCHE is more obvious in the low Reynolds number region.

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.

The Effectiveness of the Unit Cell Method in Numerically Modeling and Designing Liquid Cooled Heatsinks

2019 ◽  
Vol 11 (6) ◽  
Author(s):  
Ali C. Kheirabadi ◽  
Dominic Groulx
Keyword(s):  
Heat Transfer ◽  
Wall Temperature ◽  
Parametric Design ◽  
Unit Cell ◽  
Liquid Cooling ◽  
Cell Method ◽  
Numerical Predictions ◽  
Finite Element Package ◽  
Parametric Studies ◽  
Relative Differences

This study compares two numerical strategies for modeling flow and heat transfer through mini- and microchannel heatsinks, the unit cell approximation, and the full 3D model, with the objective of validating the former approach. Conjugate heat transfer and laminar flow through a 2 × 2 cm2 copper–water heatsink are modeled using the finite element package COMSOL Multiphysics 5.0. Parametric studies showed that as the heatsink channels’ widths were reduced, and the total number of channels increased, temperature and pressure predictions from both models converged to similar values. Relative differences as low as 5.4% and 1.6% were attained at a channel width of 0.25 mm for maximum wall temperature and channel pressure drop, respectively. Due to its computational efficiency and tendency to conservatively overpredict temperatures relative to the full 3D method, the unit cell approximation is recommended for parametric design of heatsinks with channels’ widths smaller than 0.5 mm, although this condition only holds for the given heatsink design. The unit cell method is then used to design an optimal heatsink for server liquid cooling applications. The heatsink has been fabricated and tested experimentally, and its thermal performance is compared with numerical predictions. The unit cell method underestimated the maximum wall temperature relative to experimental results by 3.0–14.5% as the flowrate rose from 0.3 to 1.5 gal/min (1.1–5.7 l/min).

3D Computational Analysis of Thermal and Hydraulic Performance of Louvered Fin Heat Exchanger With Variable Louver Angle and Louver Pitch

2016 ◽  
Author(s):  
Abdulkerim Okbaz ◽  
Ali Pınarbaşı ◽  
Ali Bahadır Olcay
Keyword(s):  
Heat Transfer ◽  
Heat Exchanger ◽  
Pressure Drop ◽  
Flow Characteristics ◽  
Hydraulic Performance ◽  
Double Row ◽  
Louvered Fin ◽  
Goodness Factor ◽  
Fluid Flow Characteristics ◽  
Louvered Fins

In the present study, 3-D numerical simulations on heat and fluid flow characteristics of double-row multi-louvered fins heat exchanger are carried out. The heat transfer improvement and the corresponding pressure drop amounts were investigated depending on louver angles in the range of 20° ≤θ≤ 30°, louver pitches of Lp = 2,7mm, 3,5mm and 3,8mm and frontal velocities of Uin between 1.22 m/s and 3 m/s. The results are reported in terms of Colburn j-factor, Fanning friction factor f and area goodness factor j/f based on louver angle, louver pitch and Reynolds number. To understand local behavior of flow around louvered fins and heat exchanger tubes, flow visualization results of velocity vectors and stream-lines with temperature counters are presented. It is investigated that increasing louver angle enhances convective heat transfer while hydraulic performance decreases due to increased pressure drop. The flow noticeably behaves louver directed for all louver angles The flow can easily travel between different fins. This case study has been done to design and manufacture an industrial louver fin heat exchanger.

Heat transfer and pressure drop in single rows of tubes in cross-flow

1992 ◽  
Vol 15 (4) ◽  
pp. 219-223 ◽  
Author(s):  
Michael Beziel ◽  
Karl Stephan
Keyword(s):  
Heat Transfer ◽  
Pressure Drop ◽  
Cross Flow
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