Mist/Steam Heat Transfer in Confined Slot Jet Impingement

2000 ◽  
Vol 123 (1) ◽  
pp. 161-167 ◽  
Author(s):  
X. Li ◽  
J. L. Gaddis ◽  
T. Wang
Keyword(s):  
Heat Transfer ◽  
Stagnation Point ◽  
Jet Impingement ◽  
Target Surface ◽  
Future Generation ◽  
Reynolds Numbers ◽  
Heat Fluxes ◽  
Stagnation Region ◽  
Blade Cooling ◽  
Confined Channel

Internal mist/steam blade cooling technology has been considered for the future generation of Advanced Turbine Systems (ATS). Fine water droplets of about 5 μm were carried by steam through a single slot jet onto a heated target surface in a confined channel. Experiments covered Reynolds numbers from 7500 to 25,000 and heat fluxes from 3 to 21 kW/m2. The experimental results indicate that the cooling is enhanced significantly near the stagnation point by the mist, decreasing to a negligible level at a distance of six jet widths from the stagnation region. Up to 200 percent heat transfer enhancement at the stagnation point was achieved by injecting only ∼1.5 percent of mist. The investigation has focused on the effects of wall temperature, mist concentration, and Reynolds number.

Mist/Steam Heat Transfer in Confined Slot Jet Impingement

2000 ◽  
Author(s):  
X. Li ◽  
J. L. Gaddis ◽  
T. Wang
Keyword(s):  
Heat Transfer ◽  
Stagnation Point ◽  
Jet Impingement ◽  
Target Surface ◽  
Future Generation ◽  
Reynolds Numbers ◽  
Heat Fluxes ◽  
Stagnation Region ◽  
Blade Cooling ◽  
Confined Channel

Internal mist/steam blade cooling technology has been considered for the future generation of Advanced Turbine Systems (ATS). Fine water droplets about 5 μm were carried by steam through a single slot jet onto a heated target surface in a confined channel. Experiments covered Reynolds numbers from 7500 to 25000 and heat fluxes from 3 to 21 kW/m2. The experimental results indicate that the cooling is enhanced significantly near the stagnation point by the mist, decreasing to a negligible level at a distance of 6 jet widths from the stagnation region. Up to 200% heat transfer enhancement at the stagnation point was achieved by injecting only ∼1.5% of mist. The investigation has focused on the effects of wall temperature, mist concentration, and Reynolds number.

Mist/Steam Heat Transfer With Jet Impingement Onto a Concave Surface

2003 ◽  
Vol 125 (3) ◽  
pp. 438-446 ◽  
Author(s):  
Xianchang Li ◽  
J. Leo Gaddis ◽  
Ting Wang
Keyword(s):  
Stagnation Point ◽  
Heated Surface ◽  
Leading Edge ◽  
Jet Impingement ◽  
Future Generation ◽  
Heat Fluxes ◽  
Concave Surface ◽  
Surface Cooling ◽  
Cooling Enhancement ◽  
Confined Channel

Internal mist/steam blade cooling technology is proposed for the future generation of Advanced Turbine Systems (ATS). Fine water droplets about 5 μm were carried by steam through a slot jet onto a concave heated surface in a confined channel to simulate inner surface cooling at the leading edge of a turbine blade. Experiments covered Reynolds numbers from 7500 to 22,000 and heat fluxes from 3 to 21 kW/m2. Results indicate that the cooling is enhanced significantly near the stagnation point by the mist, decreasing downstream. Unlike impingement onto a flat target where the enhancement vanished at six jet diameters downstream, the cooling enhancement over a concave surface prevails at all points downstream. Similar to the results of the flat surface, the cooling enhancement declines at higher heat fluxes. Up to 200 % cooling enhancement at the stagnation point was achieved by injecting approximately 0.5 % of mist.

Combined Effects of Jet Plate Thickness and Fillet Radius on Leading Edge Jet Impingement With Round and Racetrack Shaped Jets

2015 ◽  
Author(s):  
Weston V. Harmon ◽  
Lesley M. Wright ◽  
Daniel C. Crites ◽  
Mark C. Morris ◽  
Ardeshir Riahi
Keyword(s):  
Heat Transfer ◽  
Turbine Blades ◽  
Plate Thickness ◽  
Leading Edge ◽  
Jet Impingement ◽  
Target Surface ◽  
Reynolds Numbers ◽  
Stagnation Region ◽  
Vena Contracta ◽  
Nusselt Numbers

The effect of jet plate thickness is considered as regionally averaged Nusselt numbers are measured on a concave surface, which models the leading edge of modern gas turbine blades. The performance of both round and racetrack shaped orifices for leading edge impingement is considered. Regionally averaged heat transfer coefficient distributions are obtained in a steady state experiment using heated aluminum plates. From this traditional heat transfer technique, the heat transfer afforded by jet plates of varying thickness is quantified. The thickness of the jet plate is varied from 1.33 to 4.0 diameters (for both the round and racetrack shaped jets). To model the modern, cast airfoil, the effect of an inlet and outlet radius on the jet orifice is also investigated. For all cases, the jet – to – target surface spacing (z/djet) is 4, the jet – to – jet spacing (s/djet) is 8, and the target surface diameter – to jet diameter (D/djet) is 5.33. Target surface Nusselt numbers are obtained for three separate Reynolds numbers. For the round orifices, jet Reynolds numbers of 14,000, 28,100, and 42,100 are used while the corresponding Reynolds numbers for the racetrack shaped jets are 11,800, 23,600, and 35,400. Although the Reynolds number is reduced for the racetrack shaped jets, the mass flow through each jet remains constant (from the round to the racetrack jets). The Nusselt numbers measured in the stagnation region of the target surface are relatively insensitive to the jet plate thickness. For all cases considered, the flow is not developed as it exits the orifice, so the flow structures of the jets ensuing from each of the plates are similar. When the inlet of the jet is rounded, the vena contracta effect within the orifice is minimized, and a more symmetrical jet develops within the orifice. For a fixed flow rate, the racetrack shaped jets provide enhanced heat transfer compared to the round jets for all geometries considered.

Mist/Steam Heat Transfer With Jet Impingement Onto a Concave Surface

2002 ◽  
Author(s):  
Xianchang Li ◽  
J. Leo Gaddis ◽  
Ting Wang
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Enhancement ◽  
Stagnation Point ◽  
Flat Surface ◽  
Leading Edge ◽  
Jet Impingement ◽  
Heat Fluxes ◽  
General Level ◽  
Transfer Enhancement ◽  
Surface Cooling

Internal mist/steam blade cooling technology has been considered for the future generation of Advanced Turbine Systems (ATS). Fine water droplets about 5 μm were carried by steam through a single slot jet onto a concave heated target surface in a confined channel to simulate inner surface cooling at the leading edge of a turbine blade. Experiments covered Reynolds numbers from 7,500 to 22,000 and heat fluxes from 3 to 21 kW/m2. The general level of heat transfer coefficient is, within experimental uncertainty, the same as the flat surface at comparable conditions. The experimental results indicate that the cooling is enhanced significantly near the stagnation point by the mist, decreasing downstream. Unlike impingement onto a flat plate the enhancement continues at all points downstream. Similar to the results of the flat surface, the heat transfer enhancement declines at higher heat fluxes. Up to 200% heat transfer enhancement at the stagnation point was achieved by injecting approximately 0.5% of mist.

Liquid Jet Impingement Without and With Heat Transfer

2009 ◽  
Author(s):  
F. A. Jafar ◽  
G. R. Thorpe ◽  
O¨. F. Turan
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Jet Impingement ◽  
Target Surface ◽  
Reynolds Numbers ◽  
Liquid Jet ◽  
Substantial Impact ◽  
Plate Spacing ◽  
Numerical Predictions ◽  
Surface Configuration

Equipment used to cool horticultural produce often involves three-phase porous media. The flow field and heat transfer processes that occur in such equipment are generally quantified by means of empirical relationships amongst dimensionless groups. This work represents a first step towards the goal of harnessing the power of computational fluid dynamics (CFD) to better understand the heat transfer process that occur in beds of irrigated horticultural produce. The primary objective of the present study is to use numerical predictions towards reducing energy and cooling water requirement in cooling horticultural produce. In this paper, flow and heat transfer predictions are presented of a single slot liquid jet on flat and curved surfaces using a CFD code (FLUENT) for 2-D configurations. The effects of Reynolds number, nozzle to plate spacing, nozzle width and target surface configuration have been studied. Reynolds numbers of 250, 500, 700, 1800 and 1900 are studied where the liquid medium is water. Here, the Reynolds number is defined in terms of the hydraulic nozzle diameter, inlet jet velocity and fluid kinematic viscosity. The results show that Reynolds numbers, nozzle to plate spacing and nozzle width have a significant effect on the flow filed and heat transfer characteristics; whereas the target surface configuration at stagnation area has no substantial impact. The use of a numerical tool has enabled detailed investigation of these characteristics, which have not been available in the literature previously.

Impingement Heat Transfer Enhancement on a Cylindrical, Leading Edge Model With Varying Jet Temperatures

2012 ◽  
Author(s):  
Evan L. Martin ◽  
Lesley M. Wright ◽  
Daniel C. Crites
Keyword(s):  
Heat Transfer ◽  
Experimental Technique ◽  
Leading Edge ◽  
Jet Impingement ◽  
Target Surface ◽  
Large Temperature ◽  
Transfer Coefficients ◽  
Stagnation Region ◽  
Heat Transfer Coefficients ◽  
Impingement Heat Transfer

Stagnation region heat transfer coefficients are obtained from jet impingement onto a concave surface in this experimental investigation. A single row of round jets impinge on the cylindrical target surface to replicate leading edge cooling in a gas turbine airfoil. A modified, transient lumped capacitance experimental technique was developed (and validated) to obtain stagnation region Nusselt numbers with jet-to-target surface temperature differences ranging from 60°F (33.3°C) to 400°F (222.2°C). In addition to varying jet temperatures, the jet Reynolds number (5000–20000), jet-to-jet spacing (s/d = 2–8), jet-to-target surface spacing (ℓ/d = 2–8), and impingement surface diameter-to-jet diameter (D/d = 3.6, 5.5) were independently varied. This parametric investigation has served to develop and validate a new experimental technique which can be used for investigations involving large temperature differences between the surface and fluid. Furthermore, the study has broadened the range of existing correlations currently used to predict heat transfer coefficients for leading edge, jet impingement.

Heat Transfer Characteristics of an Oblique Jet Impingement Configuration in a Passage With Ribbed Surfaces

2011 ◽  
Vol 134 (3) ◽  
Author(s):  
Florian Hoefler ◽  
Simon Schueren ◽  
Jens von Wolfersdorf ◽  
Shailendra Naik
Keyword(s):  
Heat Transfer ◽  
Jet Impingement ◽  
Reynolds Numbers ◽  
Impinging Jets ◽  
Turbine Blade Cooling ◽  
Blade Cooling ◽  
Spatially Resolved ◽  
Nusselt Numbers ◽  
Heat Capacity Measurements ◽  
Transient Liquid Crystal Technique

Heat transfer measurements of a confined impingement cooling configuration with ribs on the target surfaces are presented. The assembly consists of four nonperpendicular walls of which one holds two rows of staggered inclined jets, each impinging on a different adjacent wall. The ribs are aligned with the inclined jet axes, have the same pitch, and are staggered to the impinging jets. The flow exhausts through two staggered rows of holes opposing the impingement wall. The passage geometry is related to a modern gas turbine blade cooling configuration. A transient liquid crystal technique was used to take spatially resolved surface heat transfer measurements for the ground area between the ribs. A comparison with the smooth baseline configuration reveals local differences and a generally reduced heat transfer for the rib-roughened case. Furthermore, lumped heat capacity measurements of the ribs yielded area averaged heat transfer information for the ribs. From the combination of ground and rib heat transfer measurements, it is concluded that the overall performance of the ribbed configuration depends on the Reynolds number. Of the five investigated jet Reynolds numbers from 10,000 to 75,000, only for the highest Re the averaged Nusselt numbers increase slightly compared with the smooth baseline configuration.

Impingement Heat Transfer Enhancement on a Cylindrical, Leading Edge Model With Varying Jet Temperatures

2013 ◽  
Vol 135 (3) ◽  
Author(s):  
Evan L. Martin ◽  
Lesley M. Wright ◽  
Daniel C. Crites
Keyword(s):  
Heat Transfer ◽  
Experimental Technique ◽  
Leading Edge ◽  
Jet Impingement ◽  
Target Surface ◽  
Large Temperature ◽  
Transfer Coefficients ◽  
Stagnation Region ◽  
Heat Transfer Coefficients ◽  
Impingement Heat Transfer

Stagnation region heat transfer coefficients are obtained from jet impingement onto a concave surface in this experimental investigation. A single row of round jets impinge on the cylindrical target surface to replicate leading edge cooling in a gas turbine airfoil. A modified, transient lumped capacitance experimental technique was developed (and validated) to obtain stagnation region Nusselt numbers with jet-to-target surface temperature differences ranging from 60 °F (33.3 °C) to 400 °F (222.2 °C). In addition to varying jet temperatures, the jet Reynolds number (5000–20,000), jet-to-jet spacing (s/d = 2–8), jet-to-target surface spacing (ℓ/d = 2–8), and impingement surface diameter-to-jet diameter (D/d = 3.6, 5.5) were independently varied. This parametric investigation has served to develop and validate a new experimental technique, which can be used for investigations involving large temperature differences between the surface and fluid. Furthermore, the study has broadened the range of existing correlations currently used to predict heat transfer coefficients for leading edge jet impingement.

Jet Impingement Heat Transfer Enhancement by U-Shaped Crossflow Diverters

2019 ◽  
Vol 12 (4) ◽  
Author(s):  
Srivatsan Madhavan ◽  
Kishore Ranganath Ramakrishnan ◽  
Prashant Singh ◽  
Srinath Ekkad
Keyword(s):  
Heat Transfer ◽  
Heat Dissipation ◽  
Jet Impingement ◽  
Target Surface ◽  
Reynolds Numbers ◽  
Pumping Power ◽  
Transfer Coefficients ◽  
Heat Transfer Coefficients ◽  
Impingement Heat Transfer ◽  
Baseline Case

Abstract Array-jet impingement is typically used in gas turbine blade near-wall cooling, where high rates of heat dissipation is required. The accumulated crossflow mass flux results in significant reduction in jet effectiveness in the downstream rows, leading to reduced cooling performance. In this paper, a jet impingement system equipped with U-shaped ribs (hereafter referred as “diverter”) was used for diverting the crossflow away from the jets emanating from the nozzle plate. To this end, a baseline configuration of array-jet impingement onto smooth target surface is considered, where the normalized jet-to-jet spacing (x/dj = y/dj) was 6 and the normalized jet-to-target spacing (z/dj) was 2. Crossflow diverters with thickness t of 1.5875 mm and height h of 2dj (= z) were installed at a distance of 2dj from the respective jet centers. Detailed heat transfer coefficients have been calculated through transient liquid crystal experiments carried out over Reynolds numbers ranging from 3500 to 12,000. It has been observed that crossflow diverters protect the downstream jets from upstream jet deflection, thereby maximizing their stagnation cooling potential. An average of 15–30% enhancement in Nusselt number is obtained over the flow range tested. This benefit in heat transfer came at a cost of increased pumping power to maintain similar flow rate in the system. At a given pumping power, crossflow diverters yielded an enhancement of 9–15% in heat transfer compared with the baseline case.

Heat Transfer Characteristics of an Oblique Jet Impingement Configuration in a Passage With Ribbed Surfaces

2010 ◽  
Author(s):  
Florian Hoefler ◽  
Simon Schueren ◽  
Jens von Wolfersdorf ◽  
Shailendra Naik
Keyword(s):  
Heat Transfer ◽  
Jet Impingement ◽  
Reynolds Numbers ◽  
Impinging Jets ◽  
Turbine Blade Cooling ◽  
Blade Cooling ◽  
Spatially Resolved ◽  
Nusselt Numbers ◽  
Heat Capacity Measurements ◽  
Transient Liquid Crystal Technique

Heat transfer measurements of a confined impingement cooling configuration with ribs on the target surfaces are presented. The assembly consists of four non-perpendicular walls of which one holds two rows of staggered inclined jets, each impinging on a different adjacent wall. The ribs are aligned with the inclined jet axes, have the same pitch and are staggered to the impinging jets. The flow exhausts through two staggered rows of holes opposing the impingement wall. The passage geometry is related to a modern gas turbine blade cooling configuration. A transient liquid crystal technique was used to take spatially resolved surface heat transfer measurements for the ground area between the ribs. A comparison with the smooth baseline configuration reveals local differences and a generally reduced heat transfer for the rib-roughened case. Furthermore, lumped heat capacity measurements of the ribs yielded area averaged heat transfer information for the ribs. From the combination of ground and rib heat transfer measurements it is concluded that the overall performance of the ribbed configuration depends on the Reynolds number. Of the five investigated jet Reynolds numbers from 10,000 up to 75,000, only for the highest Re the averaged Nusselt numbers increase slightly compared to the smooth baseline configuration.

Sign in / Sign up

Export Citation Format

Share Document