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Numerical Heat Transfer, Part A: Applications
An International Journal of Computation and Methodology
Volume 69, 2016 - Issue 10
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Original articles

Numerical investigation of heat transfer using a novel punched vortex generator

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Pages 1150-1168 | Received 28 Jul 2015, Accepted 08 Oct 2015, Published online: 23 Mar 2016
 

ABSTRACT

Novel types of double delta winglets (DDWTs) and double delta winglet with holes (DDWTHs) have been developed. The influence of parameters, including the angle of DDWTs and the distance between DDWTs, on thermal enhancement and flow resistance characteristics in a rectangular channel is examined. The results reveal that the larger angle and increasing distance could make an active role in turbulent heat transfer enhancement, and slight influence on laminar flow. According to the field profile, the cross-flow and encircling flow are generated by DDWTs, which increases the mixing efficiency and reduces the thermal boundary layer thickness as well. Vortex generators, such as delta wings, rectangular wings, DDWTs, and DDWTHs, are compared. The delta wings and rectangular wings perform better heat transfer enhancement and higher resistance, while the DDWTs and DDWTHs have better overall heat transfer performance, especially for large Reynolds numbers.

Nomenclature

A=

heat transfer surface area (m−2)

a=

distance from the channel inlet (m)

Ap=

sum area of heat elements

cp=

specific heat (J/(kg · K))

de=

hydraulic diameter (m)

f=

friction factor

g=

distance between DDWTs

H=

height of the channel (m)

hv=

convective heat transfer coefficient (W/(m2 · K))

j=

Colburn factor

L=

length of the channel (m)

l=

wing length (m)

m=

mass flow rate (kg/s)

Nu=

Nusselt number

Pr=

Prandtl number

Q=

heat transfer rate (W)

Re=

Reynolds number

S=

distance from the channel bottom (m)

T=

temperature (°C)

u=

average velocity (m/s)

W=

width of the channel (m)

Δp=

pressure drop (Pa)

α=

angle between the two combined delta wings (°)

v=

kinematic viscosity (N/m2)

ρ=

fluid density (kg/m3)

λ=

thermal conductivity of the plate (W/(m · K))

μ=

dynamic viscosity (kg/(m · s))

Subscripts=
air=

air side

gas=

gas side

i=

heat element

in=

inlet

out=

outlet

w=

wall surface

Nomenclature

A=

heat transfer surface area (m−2)

a=

distance from the channel inlet (m)

Ap=

sum area of heat elements

cp=

specific heat (J/(kg · K))

de=

hydraulic diameter (m)

f=

friction factor

g=

distance between DDWTs

H=

height of the channel (m)

hv=

convective heat transfer coefficient (W/(m2 · K))

j=

Colburn factor

L=

length of the channel (m)

l=

wing length (m)

m=

mass flow rate (kg/s)

Nu=

Nusselt number

Pr=

Prandtl number

Q=

heat transfer rate (W)

Re=

Reynolds number

S=

distance from the channel bottom (m)

T=

temperature (°C)

u=

average velocity (m/s)

W=

width of the channel (m)

Δp=

pressure drop (Pa)

α=

angle between the two combined delta wings (°)

v=

kinematic viscosity (N/m2)

ρ=

fluid density (kg/m3)

λ=

thermal conductivity of the plate (W/(m · K))

μ=

dynamic viscosity (kg/(m · s))

Subscripts=
air=

air side

gas=

gas side

i=

heat element

in=

inlet

out=

outlet

w=

wall surface

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