Heat Transfer Characteristics from a Row of Impinging Jets  with Small-diameter Circular Orifice Nozzle at Low Reynolds Numbers

An experimental study has been conducted to determine the heat transfer characteristics for low Reynolds number turbulent swirling LPG/Air flames impinging on a flat surface. Effect of variation of Reynolds number (3000–7000), dimensionless separation distance (H/d = 1 to 6) and equivalence ratio (φ = 0.8 to 2) on heat transfer characteristics has been determined at constant swirl number of 4. Further, experiments were also conducted to investigate the effect of swirl number on heat transfer characteristics at Re = 7000, φ = 1.0 and H/d = 5. It has been concluded that the major drawback of flame impingement i.e., non-uniformity in the heating can be resolved by using swirling flames in place of non-swirling flames. With increase in Reynolds number the flame becomes longer and broader. Also, at higher Re the flame becomes noisy and violent because of the enhanced turbulences in the flame. A dip in the temperature was observed at the stagnation point at all Re and this dip was more significant at higher Re. At small separation distances (H/d = 1 and 2) and at large Reynolds numbers (Re = 7000) heating is comparatively more non-uniform because of close proximity of the visible reaction zone to the plate resulting in intense heating in the stagnation region. High average heat fluxes were obtained at low separation distances and at larger Reynolds numbers.

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Effect of Surface Roughness on Heat Transfer and Fluid Flow Characteristics at Low Reynolds Numbers in Small Diameter Tubes

Heat Transfer Engineering ◽

10.1080/01457630304069 ◽

2003 ◽

Vol 24 (3) ◽

pp. 4-16 ◽

Cited By ~ 120

Author(s):

Satish G. Kandlikar ◽

Shailesh Joshi ◽

Shurong Tian

Keyword(s):

Heat Transfer ◽

Surface Roughness ◽

Fluid Flow ◽

Small Diameter ◽

Flow Characteristics ◽

Reynolds Numbers ◽

Low Reynolds Numbers ◽

Low Reynolds ◽

Fluid Flow Characteristics ◽

Effect Of Surface

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Two Dimensional Simulation of Flow and Heat Transfer Characteristics of Turbulent Jets

2010 14th International Heat Transfer Conference, Volume 5 ◽

10.1115/ihtc14-23150 ◽

2010 ◽

Author(s):

Tarek Abdel-Salam

Keyword(s):

Heat Transfer ◽

Reynolds Number ◽

Turbulent Jets ◽

Reynolds Numbers ◽

Impinging Jets ◽

Two Dimensional ◽

Heat Transfer Characteristics ◽

Transfer Characteristics ◽

Flow And Heat Transfer ◽

Dimensional Simulation

In this study, flow and heat transfer characteristics of two-dimensional impinging jets are investigated numerically. 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 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 show that the Reynolds number has significant effect on the heat transfer rate and has no effect on the location of the maximum Nusselt number.

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Heat transfer in a channel with inclined target surface cooled by single array of centered impinging jets

Thermal Science ◽

10.2298/tsci110630010a ◽

2013 ◽

Vol 17 (4) ◽

pp. 1195-1206

Author(s):

Mubarak Al ◽

S.M. Shaahid ◽

Luai Al-Hadhramic

Keyword(s):

Heat Transfer ◽

Target Surface ◽

Reynolds Numbers ◽

Impinging Jets ◽

Heat Transfer Characteristics ◽

Target Plate ◽

Maximum Heat ◽

Transfer Characteristics ◽

Aspect Ratios ◽

Feed Channel

An experimental investigation has been carried out to study the heat transfer characteristics in a channel with heated target plate inclined at an angle cooled by single array of equally spaced centered impinging jets for three different jet Reynolds numbers (Re=9300, 14400 and 18800). Air ejected from an array of orifices impinges on the heated target surface The target plate forms the leading edge of a gas turbine blade cooled by jet impingement technique. The work includes the effect of jet Reynolds numbers and feed channel aspect ratios (H/d = 5, 7, 9 where H=2.5, 3.5, 4.5 cm and d=0.5 cm) on the heat transfer characteristics for a given orifice jet plate configuration with equally spaced centered holes with outflow exiting in both directions (with inclined heated target surface). In general, It has been observed that, H/d=9 gives the maximum heat transfer over the entire length of the target surface as compared to all feed channel aspect ratios. H/d=9 gives 3% more heat transfer from the target surface as compared to H/d=5 (for Re=14400). Also, it has been observed that the magnitude of the averaged local Nusselt number increases with an increase in the jet Reynolds number for all the feed channel aspect ratios studied.

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