Numerical Study of Flow and Heat Transfer for Circular Jet Impingement on the Bottom of a Cylindrical Cavity

1993 ◽  
Vol 115 (3) ◽  
pp. 292-297 ◽  
Author(s):  
S. Gavali ◽  
K. Karki ◽  
S. Patankar ◽  
K. Miura
Keyword(s):  
Heat Transfer ◽  
Nozzle Exit ◽  
Numerical Study ◽  
Jet Impingement ◽  
Local Heat Transfer ◽  
Local Heat ◽  
Separation Distance ◽  
Laminar Jet ◽  
Flow And Heat Transfer ◽  
Impingement Surface

A numerical study is presented for an axisymmetric laminar jet impingement on a confined disk, with the spent fluid being collected through an annual channel that is concentric with the nozzle. In this study, parametric variations were made of the dimensionless separation distance between the nozzle exit and the impingement surface, of the ratio of the diameter of the impingement surface to the nozzle diameter, and of the Reynolds number. The flow field is characterized by two recirculation zones, one adjacent to the nozzle exit and the other near the confining wall. The local heat transfer distribution on the impingement surface exhibits an off-axis maximum and a local minimum near the confining wall. The nozzle separation distance has an effect on surface heat transfer only for configurations with closet confinement. The thermal boundary condition on the impingement surface is found to have little effect on the total heat transfer.

scholarly journals Computational Fluid Dynamics Analysis of Impingement Heat Transfer in an Inline Array of Multiple Jets

2021 ◽  
Vol 2021 ◽  
pp. 1-10
Author(s):  
Parampreet Singh ◽  
Neel Kanth Grover ◽  
Vivek Agarwal ◽  
Shubham Sharma ◽  
Jujhar Singh ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Numerical Study ◽  
Jet Impingement ◽  
Local Heat Transfer ◽  
Local Heat ◽  
Separation Distance ◽  
Experimental Results ◽  
Impingement Heat Transfer ◽  
Computational Fluid Dynamics Analysis ◽  
The Impact

Amid all convective heat transfer augmentation methods employing single phase, jet impingement heat transfer delivers significantly higher coefficient of local heat transfer. The arrangement leading to nine jets in square array has been used to cool a plate maintained at constant heat flux. Numerical study has been carried out using RANS-based turbulence modeling in commercial CFD Fluent software. The turbulent models used for the study are three different “k-ε” models (STD, RNG, and realizable) and SST “k-ω” model. The numerical simulation output is equated with the experimental results to find out the most accurate turbulence model. The impact of variation of Reynolds number, inter-jet spacing, and separation distance has been considered for the geometry considered. These parameters affect the coefficient of heat transfer, temperature, and turbulent kinetic energy related to flow. The local “h” values have been noticed to decline with the rise in separation distance “H/D.” The SST “k-ω” model has been noticed to be in maximum agreement with the experimental results. The average value of heat transfer coefficient “h” reduces from 210 to 193 W/m2K with increase in “H/D” from 6 to 10 at “Re” = 9000 and S/D of 3. As per numerical results, inter-jet spacing “S/D” of 3 has been determined to be the most optimum value.

Effect of Film Extraction on Impingement Heat Transfer Characteristics of Jet Arrays on Spherical-Dimpled Surfaces

2015 ◽  
Author(s):  
Xing Yang ◽  
Zhao Liu ◽  
Zhenping Feng
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Film Cooling ◽  
Coupling Effect ◽  
Jet Impingement ◽  
Local Heat Transfer ◽  
Target Surface ◽  
Local Heat ◽  
Separation Distance ◽  
Plate Spacing

Detailed heat transfer distributions are numerically investigated on a multiple jet impingement target surface with staggered arrays of spherical dimples where coolant can be extracted through film holes for external film cooling. The three dimensional Reynolds-averaged Navier-Stokes analysis with SST k-ω turbulence model is conducted at jet Reynolds number from 15,000 to 35,000. The separation distance between the jet plate and the target surface varies from 3 to 5 jet diameters and two jet-induced crossflow schemes are included to be referred as large and small crossflow at one and two opposite exit openings correspondingly. Flow and heat transfer results for the dimpled target plate with three suction ratios of 2.5%, 5.0% and 12.0% are compared with those on dimpled surfaces without film holes. The results indicate the presence of film holes could alter the local heat transfer distributions, especially near the channel outlets where the crossflow level is the highest. The heat transfer enhancements by applying film holes to the dimpled surfaces is improved to different degrees at various suction ratios, and the enhancements depend on the coupling effect of impingement and channel flow, which is relevant to jet Reynolds number, jet-to-plate spacing and crossflow scheme.

Simulation of Laminar Slot Jets Impinging on a Moving Surface

2002 ◽  
Vol 124 (6) ◽  
pp. 1049-1055 ◽  
Author(s):  
Himadri Chattopadhyay ◽  
Sujoy K. Saha
Keyword(s):  
Heat Transfer ◽  
Nozzle Exit ◽  
Momentum Flux ◽  
Local Heat Transfer ◽  
Local Heat ◽  
Surface Velocity ◽  
Exit Angle ◽  
Total Heat Transfer ◽  
Moving Surface ◽  
Flow And Heat Transfer

Laminar flow and heat transfer on a moving surface due to a bank of impinging slot jets have been numerically investigated. Two types of jet, namely axial and knife-jet with an exit angle of 60 deg were considered. The surface velocity up to two times the jet velocity at the nozzle exit was imposed on the impinging surface. It has been observed that while with increasing velocity of the impinging surface, the total heat transfer reduces; the distribution pattern becomes more uniform. For the same amount of mass and momentum flux at the nozzle exit, heat transfer from the axial jet is considerably higher than that from the vectored jets at all surface velocities considered. It was found that the local heat transfer over the surface for the case of the axial jet and the knife-jet scales with Re0.5 and Re0.55, respectively.

Effect of Slot Jet Temperature on Impingement Heat Transfer Over a Heated Circular Cylinder

2018 ◽  
Vol 141 (2) ◽  
Author(s):  
Sharad Pachpute ◽  
B. Premachandran
Keyword(s):  
Heat Transfer ◽  
Circular Cylinder ◽  
Ambient Temperature ◽  
Stagnation Point ◽  
Nozzle Exit ◽  
Jet Impingement ◽  
Local Heat Transfer ◽  
Local Heat ◽  
Rear Side ◽  
Impingement Heat Transfer

In this paper, heat transfer and effectiveness of a turbulent slot jet impinging over a heated circular cylinder have been investigated numerically by varying the ratio of jet temperature to the ambient temperature, Θj = Tj/Tamp, from 0.7 to 1.2. In all cases, the ambient temperature (Tamb) is assumed to be constant (300 K). The Reynolds number defined based on the average nozzle exit velocity, the diameter of the cylindrical target (D), and properties at the nozzle exit temperature, ReD=ρVD/μ is varied from 6000 to 20,000. The ratio of cylinder diameter to the slot width, D/S = 5.5, 8.5, and 17 are considered and the nondimensional distance from the nozzle exit to the cylinder, H/S is varied in the range of 2 ≤ H/S ≤ 12. The v′2¯−f turbulence model was used for numerical simulations. Numerical results reveal that the local Nusselt number is found to be higher at the stagnation point in the case of cold jet impingement at Θj = 0.7. The local heat transfer at the rear side of the cylinder is 8–18% less as compared to that of Θj = 1.0 for ReD = 6000. The local effectiveness calculated over a circular cylinder strongly depends on H/S and D/S. Based on the parametric study, a correlation has been provided for the local effectiveness at the stagnation point.

scholarly journals Analysis of laminar flow and heat transfer in an interrupted microchannel heat sink with different shaped ribs

2019 ◽  
Vol 140 (3) ◽  
pp. 1259-1266 ◽  
Author(s):  
Wei Wang ◽  
Yongji Li ◽  
Yaning Zhang ◽  
Bingxi Li ◽  
Bengt Sundén
Keyword(s):  
Heat Transfer ◽  
Laminar Flow ◽  
Heat Sink ◽  
Numerical Study ◽  
Local Heat Transfer ◽  
Local Heat ◽  
Windward Side ◽  
Microchannel Heat Sink ◽  
Flow And Heat Transfer ◽  
Friction Performance

AbstractA numerical study was conducted to investigate the mechanism of laminar flow and heat transfer enhancement in an interrupted microchannel heat sink (IMCHS) with different shaped ribs at Reynolds number ranging from 100 to 900. The global flow features, heat transfer and friction for IMCHS with no ribs, rectangle ribs, triangle ribs and trapezoid ribs are detailed compared. The results show that the local heat transfer and friction performance of IMCHS with ribs show significant increase at the windward side of the ribs. Additionally, the smaller the chamfer of ribs, the larger average heat transfer and friction performance. For IMCHS with rectangle ribs, the maximum increment of Nu and f can reach to 1.81 and 2.59, respectively. Concerning the overall heat transfer performance (PEC), the trapezoid ribs show the best behavior with PEC = 1.65–1.38 at Re = 100–900.

Effect of Angle and Separation Distance on Heat Transfer on an Inclined Surface Subject to Airflow

2003 ◽  
Author(s):  
Srinivasan C. Rasipuram ◽  
Karim J. Nasr
Keyword(s):  
Heat Transfer ◽  
Fluid Velocity ◽  
Jet Impingement ◽  
Local Heat Transfer ◽  
Local Heat ◽  
Impinging Jets ◽  
Separation Distance ◽  
Convective Heating ◽  
Air Jets ◽  
Inclined Surface

Impinging jets may be used to achieve enhanced local heat transfer for convective heating, cooling, or drying. The issuing jet may contact the surface normally or obliquely. Factors such as jet attachment, surface angle, jet angle, separation distance between jet orifice and surface of impingement, and trajectory influence heat transfer dramatically. This study addresses the thermal problem of jet impingement on an inclined surface. This investigation is motivated by the practical application of air jets issuing out of a defroster’s nozzles and impinging on the inclined windshield surface of a vehicle. Effect of incoming fluid velocity, angle that the inclined surface makes with the horizontal plane and angle of impinging jet on heat transfer will be examined. The results are correlated in terms of governing dimensionless parameters. The end-result will be a numerically-based correlation that is capable of predicting heat transfer on an inclined surface subject to impinging airflow.

Laminar Heat Transfer in a Channel With Two Right-Angled Bends

1984 ◽  
Vol 106 (3) ◽  
pp. 591-596 ◽  
Author(s):  
R. S. Amano
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Stokes Equations ◽  
Numerical Study ◽  
Local Heat Transfer ◽  
Local Heat ◽  
Navier Stokes ◽  
Navier Stokes Equations ◽  
Flow And Heat Transfer ◽  
Long Channel

A numerical study is reported on the flow and heat transfer in the channel with two right-angled bends. The modified hybrid scheme was employed to solve the steady full Navier-Stokes equations with the energy equation. The computations were performed for different step heights created in a long channel. The local heat transfer rate along the channel wall predicted by employing the present numerical model showed good agreement with the experimental data. The behavior of the flow and the heat transfer were investigated for the range of Reynolds number between 200 and 2000 and for step height ratios H/W = 1, 2, and 3. Finally, the correlation of the average Nusselt number in such channels as a function of Reynolds number is postulated.

AN EXPERIMENTAL AND NUMERICAL STUDY OF HEAT TRANSFER IN A SIMULATED COLLECTOR FOR A SOLAR DRYER

1993 ◽  
Vol 17 (2) ◽  
pp. 145-160
Author(s):  
P.H. Oosthuizen ◽  
A. Sheriff
Keyword(s):  
Heat Transfer ◽  
Numerical Study ◽  
Local Heat Transfer ◽  
Lower Surface ◽  
Local Heat ◽  
Electrical Heating ◽  
Temperature Profiles ◽  
Measured Temperature ◽  
Transfer Rates ◽  
Thermocouple Probe

Indirect passive solar crop dryers have the potential to considerably reduce the losses that presently occur during drying of some crops in many parts of the “developing” world. The performance so far achieved with such dryers has, however, not proved to be very satisfactory. If this performance is to be improved it is necessary to have an accurate computer model of such dryers to assist in their design. An important element is any dryer model is an accurate equation for the convective heat transfer in the collector. To assist in the development of such an equation, an experimental and numerical study of the collector heat transfer has been undertaken. In the experimental study, the collector was simulated by a 1m long by 1m wide channel with a gap of 4 cm between the upper and lower surfaces. The lower surface of the channel consisted of an aluminium plate with an electrical heating element, simulating the solar heating, bonded to its lower surface. Air was blown through this channel at a measured rate and the temperature profiles at various points along the channel were measured using a shielded thermocouple probe. Local heat transfer rates were then determined from these measured temperature profiles. In the numerical study, the parabolic forms of the governing equations were solved by a forward-marching finite difference procedure.

Numerical Prediction of Flow and Heat Transfer in a Parallel Plate Channel With Staggered Fins

1987 ◽  
Vol 109 (1) ◽  
pp. 25-30 ◽  
Author(s):  
K. M. Kelkar ◽  
S. V. Patankar
Keyword(s):  
Heat Transfer ◽  
Local Heat Transfer ◽  
Periodic Variation ◽  
Local Heat ◽  
Temperature Fields ◽  
Parallel Plates ◽  
Constant Property ◽  
Cross Sectional ◽  
Flow And Heat Transfer ◽  
Order Of Magnitude

Fluid flow and heat transfer in two-dimensional finned passages were analyzed for constant property laminar flow. The passage is formed by two parallel plates to which fins are attached in a staggered fashion. Both the plates are maintained at a constant temperature. Streamwise periodic variation of the cross-sectional area causes the flow and temperature fields to repeat periodically after a certain developing length. Computations were performed for different values of the Reynolds number, the Prandtl number, geometric parameters, and the fin-conductance parameter. The fins were found to cause the flow to deflect significantly and impinge upon the opposite wall so as to increase the heat transfer significantly. However, the associated increase in pressure drop was an order of magnitude higher than the increase in heat transfer. Streamline patterns and local heat transfer results are presented in addition to the overall results.

scholarly journals Natural Convection From Isothermal Horizontal Cylinders

2009 ◽  
Author(s):  
Ian M. O. Gorman ◽  
Darina B. Murray ◽  
Gerard Byrne ◽  
Tim Persoons
Keyword(s):  
Heat Transfer ◽  
Natural Convection ◽  
Local Heat Transfer ◽  
Local Heat ◽  
Separation Distance ◽  
Thermal Plume ◽  
Number Range ◽  
Vertically Aligned ◽  
Isothermal Cylinders ◽  
Horizontal Cylinders

The research described here is concerned with natural convection from isothermal cylinders, with a particular focus on the interaction between a pair of vertically aligned cylinders. Prime attention was focused on how the local heat transfer characteristics of the upper cylinder are affected due to buoyancy induced fluid flow from the lower cylinder. Tests were performed using internally heated copper cylinders with an outside diameter 30mm and a vertical separation distance between the cylinders ranging from two to three cylinder diameters. Plume interaction between the heated cylinders was investigated within a Rayleigh number range of 2×106 to 6×106. Spectral analysis of the associated heat transfer interaction is presented showing that interaction between the cylinders causes oscillation of the thermal plume. The effect of this oscillation is considered as a possible enhancement mechanism of the heat transfer performance of the upper cylinder.

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