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Numerical Heat Transfer, Part A: Applications
An International Journal of Computation and Methodology
Volume 69, 2016 - Issue 6
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Original Articles

Numerical investigation on heat transfer of supercritical water in a roughened tube

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Pages 558-573 | Received 04 May 2015, Accepted 22 Jun 2015, Published online: 04 Jan 2016
 

ABSTRACT

The turbulent mixed convection heat transfer of supercritical water flowing in a vertical tube roughened by V-shaped grooves has been numerically investigated in this paper. The turbulent supercritical water flow characteristics within different grooves are obtained using a validated low-Reynolds number κ-ε turbulence model. The effects of groove angle, groove depth, groove pitch-to-depth ratio, and thermophysical properties on turbulent flow and heat transfer of supercritical water are discussed. The results show that a groove angle γ = 120° presents the best heat transfer performance among the three groove angles. The lower groove depth and higher groove pitch-to-depth ratio suppress the enhancement of heat transfer. Heat transfer performance is significantly decreased due to the strong buoyancy force at Tb = 650.6 K, and heat transfer deterioration occurs in the roughened tube with γ = 120°, e = 0.5 mm, and p/e = 8 in the present simulation. The results also show that the rapid variation in the supercritical water property in the region near the pseudo-critical temperature results in a significant enhancement of heat transfer performance.

Nomenclature

A=

cross section area

=

buoyancy parameter

c=

specific heat

D=

tube diameter

e=

groove depth

g=

acceleration of gravity

Gκ=

buoyancy production

Gr=

Grashof number

h=

heat transfer coefficient

m=

mass flux

p=

groove pitch

Pκ=

shear stress production

Pr=

Prandtl number

q=

heat flux

r=

radial distance

Re=

Reynolds number

T=

temperature

u=

velocity components in x-direction

v=

velocity components in r-direction

y=

distance from inner wall surface

y+=

non-dimensional distance from wall

x=

axial distance

β=

volumetric coefficient of expansion

ε=

turbulent energy dissipation

γ=

groove angle

κ=

turbulent kinetic energy

λ=

thermal conductivity

μ=

dynamic viscosity

ν=

kinematic viscosity

σκ=

diffusion Prandtl number for κ

σϵ=

diffusion Prandtl number for ε

ρ=

density of fluid

Subscripts=
b=

evaluated at bulk

e=

effective

p=

pressure

pc=

pseudo-critical

s=

evaluated in smooth tube

t=

turbulent

wi=

evaluated at interior wall

w=

evaluated at wall

Nomenclature

A=

cross section area

=

buoyancy parameter

c=

specific heat

D=

tube diameter

e=

groove depth

g=

acceleration of gravity

Gκ=

buoyancy production

Gr=

Grashof number

h=

heat transfer coefficient

m=

mass flux

p=

groove pitch

Pκ=

shear stress production

Pr=

Prandtl number

q=

heat flux

r=

radial distance

Re=

Reynolds number

T=

temperature

u=

velocity components in x-direction

v=

velocity components in r-direction

y=

distance from inner wall surface

y+=

non-dimensional distance from wall

x=

axial distance

β=

volumetric coefficient of expansion

ε=

turbulent energy dissipation

γ=

groove angle

κ=

turbulent kinetic energy

λ=

thermal conductivity

μ=

dynamic viscosity

ν=

kinematic viscosity

σκ=

diffusion Prandtl number for κ

σϵ=

diffusion Prandtl number for ε

ρ=

density of fluid

Subscripts=
b=

evaluated at bulk

e=

effective

p=

pressure

pc=

pseudo-critical

s=

evaluated in smooth tube

t=

turbulent

wi=

evaluated at interior wall

w=

evaluated at wall

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