Experimental study of Spatial Inclined Air Impingement Jet on a Target Plate

- 1 -

Experimental study of Spatial Inclined Air Impingement Jet on a Target Plate

Asst. Prof. Dr.Adnan A. Abdurasuol Dr. Muna S. Kassim

Al-Mustansyria University/Mech. Eng. Dept. Al-Mustansyria University/Mech. Eng. Dept.

Iraq/Baghdad /[email protected] Iraq/Baghdad /[email protected]

B.Sc. Thamer KH. Ali

Al-MmustansyriaUniversity/Mech. Eng. Dept.

Iraq/Baghdad /[email protected]

Abstract

Present work studies the inclined impingement of air with relatively small jet diameter on a uniformly

heated plate fixed at the upper side of the test section placed in a long narrow duct simulating the internal

cooling of a gas turbine blade. Thermocouples are fitted at the plate surface at certain points designed to

cover the stagnation point of impingement of air and the zone beyond it. Experimental tests cover two

duct sizes of H=20mm and 30mm, with duct size to jet diameter ratio of H/d=4 and 6 respectively.

Experimental results show that temperature distribution and local and average heat transfer coefficients

on the plate is varied with different parameters tested. As jet velocities increases, rate of heated plate

cooling increases. As jet impingement angle increases local and average heat transfer coefficient

decreases. Comparison of the results at different skew angles of 45° and 60° relative to =0° with

keeping constant show that increasing Re Number, always heat transfer coefficient ratio

[(hav) =45°,60°/(hav) =0°] will decreases the values for the ratio (maximum decrease 5%). Average heat

transfer coefficient for the bigger duct size to that of smaller duct size tested decreases with increasing

Re number ( 6 % maximum decrease ) .

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Latin Symbol

Cross-section area of the jet

impingement, m2

A

Surface area of the plate, m2 AS

Diameter of jet pipe [mm] d

Gravitational acceleration (m/s2) g

Local heat transfer coefficient W/m2.K h

Average heat transfer coefficient

[W/m2.K]

hav

Stagnation heat transfer coefficient

[W/m2.K]

hst

Height of duct (m). H

Current (amp). I

Thermal conductivity (W/m.K) K

Local Nusselt number Nu

Average Nusselt numbe Nuav

Stagnation Nusselt number Nust

Power (Watt) P

Wall heat flux (W/m2) q"

Heat energy W Q

Radial distance from the jet centerline

impingement plane intersection.

r

Reynold Number Re

Surface temperature [°C] TS

Ambient temperature [°C ] T∞

Velocity of jet [m/s] VJ

Cartesian coordinate x,y,z

Distance between jet and target plate

[m]

Z

Greek Symbol

Skew angle(°) θ

Dynamic viscosity (N.sec/m2) μ

Kinematics viscosity (m2/sec) v

Fluid density (kg/m3) ρ

Density of air (kg/m3)

Airρ

Pitch angle(°)

Subscribe

jet J

Average value av

Stagnation state st

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1-Introduction Jet impingement cooling is a forced convection

technique which is common in industrial cooling or

drying and has been the subject of numerous

investigations in thermal control of gas turbine

blades, annealing of metals and nonmetals, tempering

of glass, cooling of pistons in internal combustion

engines, and drying of various materials. Obliquely

impinging air jets have many applications in heat

transfer due to their ability to produce high localized

and area averaged heat transfer coefficients. The

main variables for jet impingement heat transfer are

the angle of impingement, the Reynolds number, the

distance of the nozzle above the impingement surface

being cooled, the angle of the jet number of jets and

the presence of cross flow. In terms of geometry,

there are two cases: a planar case with the jet issuing

from a slot, and an axisymmetric case with a round

nozzle. The dynamics of both cases are different:

round jets exhibit formation of axisymmetric vortex

rings, which are stretched during their convection

along the wall. In plane jets, the vortices are formed

as filaments parallel to the slot. The flow field in an

impinging jet can be divided into three characteristic

regions : the jet zone, the stagnation zone, and the

wall jet zone. See Figure (1)

J.F. Foss and S.J. Kleis, [1] studied the mean flow

characteristics for the oblique impingement of an

axisymmetric jet. This study was motivated by the

(under the wing, externally blown flap) configuration

for stool air craft; its objectives were to identify the

characteristics of this flow field and to dominant

mechanisms responsible for them. If the propulsion

jet interacts with the airfoil surface prior to its

impingement upon the extended flap, then the proper

design of the gap should allow the streamwise

vorticity, which is created by the interaction, to be

passed to the suction side of the flap. Stevens and B.

W. Webb, [2] studied the effect of inclination on

local heat transfer under an axisymmetric, free liquid

jet it is found that the point of maximum heat transfer

along the x–axis (the line of intersection of the jet

inclination plane with the impingement surface) is

shifted upstream (with respect to the jet flow) as a

function of jet inclination with a maximum observed

shift of 0.5 nozzle diameter. Lamyaa A. EL–Gabry

and Deborah A. Kaminski, [3] studied the

experimental investigation of local heat transfer

distribution on smooth and roughened surfaces under

an array of angled impinging jets. Measurements of

the local heat transfer distribution on smooth and

roughened surfaces under an array of angled

impinging jets are presented. Tadhg S. O’Donovan

and Darina B. Murray, [4] studied the fluctuating

fluid flow and heat transfer of an obliquely impinging

air jet. Heat transfer to an obliquely impinging air jet

is investigated experimentally. Distributions of the

mean and the fluctuating component of the surface

heat transfer are reported for a jet Reynolds number

of 10000, nozzle to impingement surface distance,

H/D, from 2 to 8 and angle of impingement, α, from

30 t0 90 degree (normal impingement ).

As noticed in the previous literature little of work is

done of the case of jet impingement with spatial

variation of pitch angle and skew angle.

The purpose of present work is to verify cooling rate

of a target plate subjected to an inclined jet

impingement from a small pipe diameter local

temperature on the plate is measured from which

local and averaged heat transfer coefficient are

calculated.

2- Experimental Rig

The aim of the present work is to construct a rig

in which a direct impingement flow of air through a

pipe to the bottom face of a uniformly heated plate is

modeled. The air strikes the plate at the certain point

(same stagnation point for all angles (X=105mm,

Z=60mm)) of its bottom face. The air jet maximum

velocity is to be limited to a value of ~ 30 m/sec as

restricted by the accuracy of temperature

measurements in ref. [34] due to the temperature rise

in the stagnation zone. Local temperature

distributions on the plate face are to be measured and

local heat transfer coefficients are to be calculated at

variable jet velocities impinging from a 5mm pipe

diameter. A test section is to be designed in which the

plate is fitted in it and air impinges on it. The

apparatus shown in Figure (2) works in an open–

loop airflow circuit which takes air from building and

discharges it to the surrounding atmosphere. Blower

is used for air impingement at which a 5mm pipe is

fitted at its end for air impingement on the target

plate. The experimental facility consists of the

following items:

1. The test section.: The test section is rectangular

in shape 50cm in length and a 15cm wide, its height

can be varied in accordance with test being done.

Two heights are used 20mm and 30mm in the

experimental section of this work. It is manufactured

from Plexiglas sheet 8mm in thickness. Plexiglas is

chosen due to transparency and low thermal

conductivity. Figure (3) shows a schematic diagram

for test section.

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2. The impinging blower and pipe system: This

system is used to inject a jet of air from a pipe of

diameter 5mm fitted at the lower face of the duct into

the upper side of the test section at which the heated

plate is fixed. The injection system is shown in the

Figure (4) as a schematic diagram. The injection

system consists of the following parts :

a) A blower of 22.17 m3/min blowing capacity

used to supply air flow for inclined

impingement on the heated plate.

b) A P.V.C pipe 4inch in diameter and 1.5

meter in length.

c) Plenum duct for minimizing turbulence

intensity at pipe inlet The straightener length

is chosen as 100 mm so as its length/

diameter ratio as 20 fixed at blower outlet

and in the inlet of the p.v.c. pipe.

d) Two control valves are placed in the a short

pipe (0.5 inch in diameter ) fitted at the PVC

pipe outlet , one to control air flow and velocity

in the injection pipe and the other as a second

control of flow by passing the air to the

surrounding.

e) Injection pipe. In which air is injected from

circular pipe into the boundary layer developing

along the top wall of the test section. Diameter of

the injection pipe is 5 mm .

The compound angle was inclined at different angles

with respect to the test surface when projected into

the stream wise /normal plane, and different angles

with respect to the test surface when projected into

the span wise /normal plane.

The employed compound angles are θ={0, 45,

60}deg. and =30, 45, 60, 75, 90.Where θ is the

angle of the injection pipe with respect to the test

surface as projected into the stream wise / normal

plane. is the angle of the injection pipe with

respect to the test surface as projected into the span

wise normal plane.

3. The target plate : The plate is manufactured so as

to be heated with constant heat flux, fixed at the top

wall of the test section, to be subjected to a jet of air

of varying velocity from the pipe fitted at the lower

wall. The heated plate is made of Duralumin Alloy

(0.6% Mn, 4.4% Cu, 1.5% Mg and 93.5% Aluminum

with a high thermal conductivity (177 W/m.K)). Its

dimension is 150mm wide, 200mm length and 3mm

in thickness. The back side of the plate is wrapped

with a heater wire 3.5 ohm/m resistance. The heater

wire is distributed on the plate as in Figure (6) to

ensure uniform heating of the plate and wire heater is

chosen to satisfy the requirements in accordance with

the power input by the power supply. A certain zone

of the heated plate is drilled with 96 holes distributed

as eight horizontal rows and twelve vertical columns.

This zone is chosen and designed to cover the

impingement region during different tests to be

carried out for heat coefficients measurements in

inclined impingement of air on the heated plate.

Each of the holes is equipped with a thermocouple

junction type K (Chromel Alumel). The

thermocouple wire is 0.2mm in diameter and welded

by spark welding forming a tip junction less than

0.5mm diameter. The thermocouple wire is of length

of 1meter each, its tip is inserted into the desired hole

in the plate face holes. The thermocouple junction is

spherical in shape and is inserted through the plate

hole, fitted in position in the plate by forcing the

cylindrical portion of the formed hole (the cylindrical

part is formed due to high ductility of the Aluminum

alloy) onto the thermocouple junction Figure (5).

The outer portion of the plate is filled with

polyurethane foam (thermal conductivity 0.06

W/m.K) [37] to reduce the heat loss by conduction to

the back side of plate assembly of the plate and also

through the thermocouple wires. Two thermocouple

junctions of the same type are installed in the outer

face of the plate; first one is fixed at the middle

section of the back layer of the insulation material

used for estimating the conduction losses through the

insulation (polyurethane) layer. A second

thermocouple is fixed at the Plexiglas section nearer

to the plate edge, used for measuring conduction

loses through the Plexiglas plate used for test section

construction.

3- Calculations Procedure:

The following procedure has been followed to

perform the calculations operation:

a- Jet Air Velocity: The air jet velocity is measured by a Pitot tube

calculated by using the following equation

Airρ

Airρ

H2Oρ

H2OΔHg2

JV

….(1)

Where, ∆HH2O, ρ and g were pressure drop of water

(mm), density of air or water and gravitational

acceleration, respectively.

Air impingement velocity is measured using a Pitot

tube of diameter 1mm fixed near the pipe exit.

Velocity distribution at pipe exit is formed to be

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uniformly distributed due to small size of pipe

diameter.

b-Input Electrical power : Qinput=IV* Watt ……………………(2)

c-Heat Transfer by Convection Qconv.:

The net heat transferred by convection from

the plate face is calculated as:

Qconv = Qinput -Qrad -Qcond -Qleads W ………….(3)

where )T4

T4S

(S

Aσrad

Q

W ………..(4)

= emissivity of plate face

= Stevan–Boltzman constant = 5.67 x 10-8

W/m2.K

4

TS = mean surface temperature of plate face °K

T∞ = ambient temperature °K

For polyurethane foam layer

L

)faceupper

Tfacelower

(T

SA

fpK

condQ

.( 5)

Where Kp.f = conductivity of polyurethane foam layer

taken as 0.06 W/m.K

AS : cross sectional area of plate = (15*20) cm2

Tlower face-Tupper face: temperature difference

between the lower plate face and the upper plate face

at

L: thickness of polyurethane layer from lower face to

the upper face

Qleads : the heat lost to the thermocouple leads

terminals which is calculated using:

Qleads=n* Qlead watt ……….(6)

n : number of thermocouples

Qlead : heat conducted through one thermocouple

calculate

lethermocoupL

TS

T

lethermocoupA

lethermocoupK

leadQ

……(7)

where Kthermocouple, Athermocouple, Lthermocouple are

conductivity, cross sectional area and length of

thermocouple wire.

d--Heat flux by convection Qconv: The heat flux on each of cube five faces is

assumed constant and

equal to:

SA

conv.Q

conv.q W/m

2 …………..(8)

AS = surface area of the plate

=0.2*0.15=0.03m2

The local heat transfer coefficient on each point

of lower face of the plate is calculated by:

fT

sT

conv.q

h

………….. (9)

Ts : local surface temperature C°

Tf: is taken as a film temperature where

2

)Ts

T

fT

……. (10)

T∞ : is the ambient temperature °C.

Air temperature at blower exit is noticed to be

0..2°C higher than ambient temperature due to

compression effect through the blower. For the case

of impingement and cross flow T is taken as the mean

value of ambient temperature and impingement air

temperature i.e. the bulk mean temperature is used in

this case.

The values of (Ts - T∞ ) are in the range 10- 30 °C to

reduce the conduction and radiation losses.

The heat transfer coefficient of plate face is

calculated by integrating the local heat transfer on

each point of the plate and dividing by the face area

as:

sA

96i

1i

h.dA

avh

W/m

2.K ………. (11)

The local heat transfer coefficients is calculated for

the portion of the heated target plate at which the

thermocouple junctions are fitted.

hav : The average heat transfer coefficient.

dA : the infinitesimal area of one node of the

plate.

The Nusselt number is calculated on the basis of

average heat transfer coefficient

for a plate face, hav, using the formula:

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airK

h.d

Nu ………………..(12)

Kair : the thermal conductivity of air

d: diameter of the pipe of jet (d).

e-Error analysis : Error analysis using

method Kline & Melintock method mentioned in

reference [17] is used in this work .The

measured quantities and the errors estimated for each

of them are as follows:

Temperature, T , max error 0.2 °C

Voltage , V, max error 0.005 Volt

Current, I, max error 0.01 Amp.

Manometer head, max error 0.5 mm H2O

The result for above mentioned method in calculating

the min -max percentage errors is as follows:

Heat transfer coefficient , h ( W/m2.C ) 0.8%-1.6%

Jet velocity , Vj ( m / sec ) , 0.84%-4.5%

Nusselt number , Nu , 0.5%- 1.26 %

Reynolds number , Re , 0.5%- 1.32%

4-Results and Discussion The following is the results of the present

work for two case of duct sizes 20mm and 30mm ,

H/d= 4 and 6 respectively. In each duct size the

inclined jet impinges the target plate at different

angles of pitch and skew . Pipe diameter is 5mm for

H=20mm and H=30mm the following is a description

for the local, average, stagnation and Nu number

distribution on the heated target plate. Examples of

local heat transfer coefficients contours and its

average values for a skew angle θ=45° with variable

a pitch angle are shown in Figures (7) and (8) for

=30° and =45° respectively .A comparison

between the two Figures show that as increases

the local and average heat transfer coefficients

decreases.

Figure (9) and Figure (10) show local heat

transfer coefficients contours for θ=60° and for

=45° and 60° respectively. The same behavior is

noticed. Figure (11) shows the local Nusselt

distribution at the stagnation point and the

neighboring points in radial direction for the case of

skew angle θ =45° and variation in the pitch

angle =30°, 45°, 60°, 75° and 90°.

The figure declares that increases the angle

reduces the average heat transfer coefficients on the

plate represented by the Nusselt number values. The

same trend of decreasing results of Nu number is

noticed for θ =60° in Figure (12) and θ =0° in Figure

(13).

Figure (14) , Figure (15) and Figure (16) show

the average Nusselt number on the target plate

variation with pitch angle for a skew angle θ=45°

and 60° and 0° respectively. Higher average Nusselt

number is noticed relative to air impingement angle.

The Figure shows as increases the average

Nusselt number decreases.

Figure (17) and Figure (18) show the average

heat transfer coefficient on the target plate variation

with Reynolds number for a skew angle θ=45° and

60° respectively. Higher average heat transfer

coefficient is noticed relative to Reynolds number.

The Figures show that as Re increases the average

heat transfer coefficient increases.

Figure (19) and Figure (20) show the

stagnation heat transfer coefficient on the target plate

variation with Reynolds number for a skew angle

θ=45° and 60° respectively. Higher stagnation heat

transfer coefficient is noticed relative to Reynolds

number. The Figures show as Re increases the

stagnation heat transfer coefficient increases.

In order to verify the variation in average heat

transfer rates in case of air impingement only with

θ=45° and 60° to Average heat transfer coefficient in

air impingement with (θ=0°). . The hav on the plate

face is calculated for different jet velocities tested and

for different pitch angle .

The general behavior of [hav]θ=45° /[hav] θ=0° ratio

with Re shows a linear decrease in the ratio with

increase Re and the ratio decreases with increase

. This results shown in the Figure (21) and Figure

(22).

Experimental results for inclined impingement

of air on the target plate for duct height H=30mm

show that Nu number and h have the same trend of

behavior as for the impingement of air only with

H=20mm. The Figures from 23 to 25 show the same

behavior for inclined air impingement only

(H=20mm) with higher values of average and

stagnation heat transfer coefficients on the target

plate.

In order to verify the variation in average heat

transfer rates in case of air impingement only with

(H/d=6), H=30mm to average heat transfer

coefficient in air impingement only with (H/d=4),

H=20mm. The average heat transfer coefficient is

calculated for plate using local temperature

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distributions on plate face using equation (11). The

hav on the plate face is calculated for different jet

velocities tested and for different pitch angle .

The general behavior of [hav]H/d=6/[hav]H/d=4 ratio

with Re shows a linear decrease in the ratio with

increase Re and the ratio decreases with increase of

for θ=45°. The results are shown in the Figure

(26).

4- Conclusions The present work uses on inclined jet of air

impingement on a target plate fixed at the upper side

of a test section which represent part of along narrow

duct simulating the cooling passage in a gas turbine

blade. Two cases are studied, one for inclined

impingement with H=20mm and the other case for

H=30mm. The air jet is 5 mm in diameter is

impinged on the heated target plate from a long pipe

(with fully developed flow) having the same

mentioned inner diameter. Different impingement

and skew θ angles are tested. The followings

conclusions are found:

1) A pre test to verify the validity of the heated

plate use shows that temperature distribution on

the plate is uniform in case when the plate

subjected to no impingement.

.

2) In all studied cases the results show that

stagnation point heat transfer coefficient are with

the highest values relative to the other points,

regardless of the angles of impingement used and

the jet velocities (Re number) in the tests.

3) Keeping the skew angle θ within a certain

values of 45°, 60° the results show the average

heat transfer coefficients increases as the pitch

angle is decreased. Increasing jet velocities

represented by Reynolds number shows that as

jet velocity increases, the average heat transfer

coefficient also increased relatively.

4) Stagnation point heat transfer coefficients show

the same behavior as the average values

coefficient mentioned in (4).

5) At certain pitch angle the ratio of average heat

transfer coefficient at tested skew angles θ of

45°, 60° to the average heat transfer coefficient

at skew angle of θ =0° angle, decrease as the

velocity of the impinging jet increases.

6) The same behavior mentioned in (6) is noticed

for the stagnation local heat transfer coefficient.

7) The parameter representing relative heat transfer

coefficient for duct height to jet diameter ratio

(H/d=6) relative to the similar values for

(H/d=4), and at same tested values of θ and

shows that this parameter decreases as the jet

velocities increases. The percentage of

decrement is within very small values ranges

from (2–6%).

5-References

[1] J.F. Foss, and S.J. Kleis, 1976, “Mean flow

characteristics for the oblique impingement

of an axisymmetric jet”, AIAA journal

vol.14,No.6.

[2] J. Stevens and B.W. Webb, 1990, “The effect

of inclination on local heat transfer under

an axisymmetric free liquid jet”, Int. J. Heat

Mass Transfer. Vol. 34, No.4/5, pp. 1227-

1236.1991.

[3] L.M. El-Gabry and D.A. Kaminski,

“Experimental Investigation of Local Heat

Transfer Distribution on Smooth and

Roughened Surfaces under an Array of

Angled Impinging Jets”, Proceedings of Int.

Mech. Eng. Congress and Exposition,

November, 2001.

[4] Tadhg S. O’Donovan and Darina B. Murray,

2008, “Fluctuating fluid flow and heat

transfer of an obliquely impinging air jet”, International Journal of heat and mass transfer

, volume 51, page 6169–6179, 2008.

[5] Kercher D.M. and Tabakoff W. , “Heat

Transfer by a Square Array of Round Air

Jets Impinging Perpendicular to a Flat

Surface Including the Effect of Spent Air”, Trans. ASME, Journal of Engineering for

Power, Vol. 92, PP. 73-82, 1970.

[6] A.K. Mohanty and A.A. Tawfek, “Heat

Transfer Due to a Round Jet. Impinging

Normal to a Flat Surface ”, Jr. Heat Mass

Transfer, Vol.36, No.6, PP.1639-1647, 1993.

[7] D. Lytle and B.W. Webb, “Air Jet

Impingement Heat Transfer at Low Nozzle

Plate Spacings”, Jr. Heat Mass Transfer,

Vol.37, No.12, PP.1687-1697, 1994.

- 8 -

[8] M. Dianat and M. Fairweather and W. P.

Jones, 1996, “Predictions of axisymmetric

and two-dimensional impinging turbulent

jets”, Int. j. Heat and Fluid Flow 17: 530-538,

1996.

[9] J.Y. Sang, C.H. Huang and M.H. Shu,

“Impingement Cooling of Confined

Circular Jet”, Int. Jr. Heat Mass Transfer,

Vol.40, No.6,PP.1355-1364, 1997.

[10] J. Mi, G.J. Nathan and D.S. Nobes, “Mixing

Characteristics of Axisymmetric Free Jets

from a Contoured Nozzle, an Orifice Plate and a Pipe” , Transaction of the ASME,

Vol.123, PP.878-883, 2001.

[11] E.A. Anderson, R.E. Spall, “Experimental

and Numerical Investigation of Two-

Dimensional Parallel Jets” , Jr. Fluid

Engineering, Vol.123, PP.401-406, 2001.

[12] James P. Johnston and Bruce P. Mosier and

Zia U. Khan, “Vortex generating jets;

effects of jet-hole inlet geometry”, International Journal of Heat and Fluid Flow

23 (2002) 744–749.

[13] J.A. Kadhim, “Low Speed Wind Tunnel

Design, Construction, and Calibration”, M.Sc. Thesis, Military Technical College,

1986.

[14] Fluid Flow in Closed Conduits, “British

Standard Methods, Part 1 ”, Pressure

Differential Devices, BS No.1042: Section

1.1, 1981.

[15] F.P. In Cropera and D.P. Dewitt,

“Fundamentals of Heat Transfer”, Fourth

Edition, John Wiley and Sons, 1996.

[16] R.J. Moffat, “What s New in Convective Heat

Transfer ”, Int. Jr.Heat and Fluid Flow,

Vol.19, PP.90-101, 1998.

[17] J.P. Holman, “Heat Transfer” 5th

edition,

McGraw-Hill, 1981.

[18] Goldstien, R.j Sobolik.K.A and Seol.W.S.

,“Effect of entrainment on the heat transfer

to a heated circular air jet impinging on a

flat surface”, ASME journal of heat transfer

vol 112,pp608-611.1990.

Figure (1) Characteristic zones in impinging jets

Figure (5) Thermocouples terminals

Figure(2) Photo picture of test section

plexiglass duct

Secondary selector

Primary selector

Reader

Aluminum plate

- 9 -

Figure (6) Aluminum plate Dimensions in cm

Heater

Thermocouples region

Figure(3) Schematic diagram of test section Figure(4) Schematic diagram for injection system

Figure (5) Thermocouples terminals

- 11 -

- 11 -

Figure (10) h contours θ=60°, =60°, VJ=25 m/sec,

VC=0 m/sec, hav=47.22 W/m2.k, Nuav=9.12, Nust=9.62

0 5 10h

0

1

2

3

4

5

6

7

8

V3

50.3877

49.776

48.0277

45.9199

44.866

43.8121

42.7582

41.7043

40.6504

39.5965

Figure (7) h contours, θ=45°, =30°, VJ=25 m/sec,

VC=0 m/sec , hav=48.54 w/m2.k, Nuav=9.19, Nust=9.64

0 5 10h

0

1

2

3

4

5

6

7

8

V3

49.0607

48

46.4953

43.4362

42.5652

41.6942

40.8233

39.9523

39.0813


VC=0 m/sec , hav=42.74 w/m2.k, Nuav=8.09, Nust=8.47

-6 -4 -2 0 2 4 6

6.0

6.5

7.0

7.5

8.0

8.5

9.0

9.5

10.0

10.5

11.0

Nu

r/d

F(deg)

30

45

60

75

90

Figure (11) Nusselt Number Distributions for θ=45°

and = (30°, 45°, 60°, 75°, 90°), Re =7485

-6 -4 -2 0 2 4 6

6.0

6.5

7.0

7.5

8.0

8.5

9.0

9.5

10.0

10.5

11.0

Nu

r/d

F(deg)

45

60

75

Figure (12) Nusselt Number Distributions for

θ=60°and =(45°,60°,75°), Re=7485

0 5 10h

0

1

2

3

4

5

6

7

8

V3

53.7031

51.8024

50.9347

48.2695

47.2368

46.2041

45.1715

44.1388

43.1061

42.0734

0 5 10h

0

1

2

3

4

5

6

7

8

V3

50.6312

49.6183

48.75

47.3007

46.8285

46.449

44.0419

43.2088

42.3757

41.5426

40.7096

39.8765

39.0434


VC=0 m/sec, hav=51.36w/m2.k, Nuav =9.78, Nust=9.93

Stagnation point

r

- 12 -

Figure (13) Nusselt Number Distributions for

θ=0°and =(45°,60°,75°) Re =7485

30 40 50 60 70 80 90

3

4

5

6

7

8

9

10

11

12

13

14

15

Nuav

F(deg)

Re=2937

Re=4400

Re=5988

Re=7485

Re=9000

Figure (14) Effect of jet inclination angle on the

magnitude of the mean Nusselt number at θ=45°

for different Reynolds number

45 50 55 60 65 70 75

3

4

5

6

7

8

9

10

11

12

13

14

15

Nu

av

F(deg)

Re=2937

Re=4400

Re=5988

Re=7485

Re=9000


magnitude of the averageNusselt number at a

skew angle (SA) of θ=60°

45 50 55 60 65 70 75

3

4

5

6

7

8

9

10

11

12

13

14

15

Nuav

F(deg)

Re=2937

Re=4400

Re=5988

Re=7485

Re=9000


magnitude of the average Nusselt number at a

skew angle (SA) of θ=0°

-6 -4 -2 0 2 4 6

6.0

6.5

7.0

7.5

8.0

8.5

9.0

9.5

10.0

10.5

11.0N

u

r/d

F(deg)

45

60

75

- 13 -

Figure (19) Effect of Reynolds number on the magnitude of

the stagnation heat transfer coefficient at a skew angle (SA)

of θ=45° with different jet inclination angle

2000 3000 4000 5000 6000 7000 8000 9000

30

35

40

45

50

55

60

65

70

hav(w

/m2.k

)

Re

F(deg)

30

45

60

75

90

Figure (17) Effect of Reynolds number on the

magnitude of the average heat transfer coefficient

at a skew angle (SA) of θ=45°

2000 3000 4000 5000 6000 7000 8000 9000

30

35

40

45

50

55

60

65

70

hst(w

/m2.k

)

Re

F(deg)

30

45

60

75

90

2000 3000 4000 5000 6000 7000 8000 9000

30

35

40

45

50

55

60

65

70

hav(w

/m2.k

)

Re

F(deg)

45

60

75

Figure (18) Effect of Reynolds number on the magnitude

of the average heat Transfer Coefficient at a skew angle

(SA) of θ=60° with different PA(pitch angle)

2000 3000 4000 5000 6000 7000 8000 9000

30

35

40

45

50

55

60

65

70

hst(w

/m2.k

)

Re

(F)(deg)

45

60

75

Figure (20) Effect of Reynolds number on the

magnitude of the stagnation heat transfer coefficient

at a skew angle (SA) of θ=60° with different PA(pitch angle)

- 14 -

2000 3000 4000 5000 6000 7000 8000 9000

1.00

1.05

1.10

1.15

1.20

1.25

1.30

1.35

1.40

1.45

1.50

1.55

1.60

[hav]Q

=4

5/

[hav]Q

=0

Re

F

45

60

75

2000 3000 4000 5000 6000 7000 8000 9000

1.00

1.05

1.10

1.15

1.20

1.25

1.30

1.35

1.40

1.45

1.50

1.55

1.60

[ha

v]Q

=6

0/

[ha

v]Q

=0

Re

F(deg)

45

60

75

Figure (21) Average heat transfer coefficient

enhancement at a skew angle (SA) θ=45° relative

to zero angle of a skew angle of impingement

Figure (22) Average heat transfer coefficient

enhancement at a skew angle (SA) θ=60° relative

to zero angle of a skew angle of impingement

2000 3000 4000 5000 6000 7000 8000 9000

3

4

5

6

7

8

9

10

11

12

13

14

15

F(deg)

45

60

75

Nu

av

Re


of the average Nusselt number at a skew angle (SA) of

θ=45° with different PA (pitch angle) H=30mm

2000 3000 4000 5000 6000 7000 8000 9000

3

4

5

6

7

8

9

10

11

12

13

14

15

Re

Nuav

F(deg)

45

60

75


of the average Nusselt number at a skew angle (SA) of

θ=60° with different PA (pitch angle) H=30mm

- 15 -

40 50 60 70 80 90

3

4

5

6

7

8

9

10

11

12

13

14

15

Nu

st

F(deg)

Re=2937

Re=4400

Re=5988

Re=7485

Re=9000

Figure (25) Effect of jet inclination on the magnitude

of the stagnation Nusselt number θ=60° H=30mm

2000 3000 4000 5000 6000 7000 8000 9000

1.015

1.020

1.025

1.030

1.035

1.040

1.045

1.050

1.055

1.060

1.065

1.070

(ha

v) H

/d=

6/(

ha

v) H

/d=

4

Re

F(deg)

45

60

75

Figure (26) The ratio of the average heat transfer coefficient for

Impingement only with H/d=6 relative to average heat transfer

Coefficient for impingement only with H/d=4 for: θ=45° .

Experimental study of Spatial Inclined Air Impingement Jet on a Target Plate

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