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Numerical Heat Transfer, Part A: Applications
An International Journal of Computation and Methodology
Volume 70, 2016 - Issue 9
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Original Articles

Numerical prediction on turbine blade internal tip cooling with pin-fin and dimple/protrusion structures

, , &
Pages 1021-1040 | Received 14 Apr 2016, Accepted 23 Jun 2016, Published online: 20 Sep 2016
 

ABSTRACT

Effective cooling techniques are required urgently because of high thermal loads on the blade tip region. The 180° turning bend is recognized to perform well in heat transfer on a blade tip. The thermal fluid-solid coupling models of the internal tip region with pin-fin-dimples/protrusions are established in the present paper. The local flow characteristics near the 180° turning bend, average Nu/Nu0, and the friction loss on the impingement surfaces are obtained. The local flow field near the tip surface is influenced by the 180° turning bend, where the fluid impingement, cross-flow convection and deflection of the secondary flow exist. The average Nu of dimple/protrusion structures is increased by 3.2%-31.5% comparing to that of a smooth case. After arranging pin-fin-dimple/protrusion, the average Nu is increased to 31.2%-127.3%, much higher than dimple/protrusion structures. Furthermore, the arrangement of pin-fin-dimple/protrusion brings no significant increase in the friction, which indicates an efficient heat transfer structure with little resistance.

Nomenclature

Dh ==

hydraulic diameter

Dp ==

pin-fin diameter

D ==

dimple/protrusion diameter

f ==

friction factor

H ==

inlet height of the channel

k ==

turbulent kinetic energy

L1 ==

length of the channel

L2 ==

width of the channel

L3 ==

clearance width of the turning bend

Nu ==

Nusselt number

Nu/Nu0 ==

heat transfer enhancement factor

Ph ==

longitudinal spacing of dimple/protrusion

Pw ==

lateral spacing of dimple/protrusion

q″ ==

surface heat flux

Re ==

Reynolds number

T ==

temperature

W ==

inlet width of the channel

y+ ==

nondimensional grid spacing at the wall

δ ==

dimple/protrusion depth

Δp ==

pressure drop

ε ==

rate of energy dissipation

λ ==

fluid thermal conductivity

μ ==

fluid dynamic viscosity

ρ ==

fluid density

ω ==

specific dissipation rate

Subscripts=
f ==

fluid

w ==

wall

Nomenclature

Dh ==

hydraulic diameter

Dp ==

pin-fin diameter

D ==

dimple/protrusion diameter

f ==

friction factor

H ==

inlet height of the channel

k ==

turbulent kinetic energy

L1 ==

length of the channel

L2 ==

width of the channel

L3 ==

clearance width of the turning bend

Nu ==

Nusselt number

Nu/Nu0 ==

heat transfer enhancement factor

Ph ==

longitudinal spacing of dimple/protrusion

Pw ==

lateral spacing of dimple/protrusion

q″ ==

surface heat flux

Re ==

Reynolds number

T ==

temperature

W ==

inlet width of the channel

y+ ==

nondimensional grid spacing at the wall

δ ==

dimple/protrusion depth

Δp ==

pressure drop

ε ==

rate of energy dissipation

λ ==

fluid thermal conductivity

μ ==

fluid dynamic viscosity

ρ ==

fluid density

ω ==

specific dissipation rate

Subscripts=
f ==

fluid

w ==

wall

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