Fully Developed Turbulent Heat
Transfer In Helically Coiled Tubes
Presenter:
Hamed Bonyadi
Instructor:
Prof. Mashayekh
1
Department of Mechanical Engineering
Winter 2024
Contents
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Introduction
Literature Review
Numerical Investigation
Results
Conclusion
1/19
Helically Coiled Tubes
▪ Compact Structure
▪ High Heat Transfer
Coefficient
2/19
Geometrical Parameters of a
Helically Coiled Pipe
D
d: Pipe Diameter
D: Coil Diameter
h: Coil Pitch
γ = d/D: The Curvature Ratio
h
d
3/19
Earlier Observation
Bosinesq
secondary flow develops in the form of two
symmetrical vortices
Williams
maximum flow velocity always occurs towards
the outer wall
Eustice and
White
pressure drop is greater in curved pipes than in
straight ones
Dean
studied analytically the laminar flow in curved
pipes
4/19
Main Features Of Flow In Helical Coil
▪ Secondary flow caused by centrifugal forces
▪ Stabilization effects of turbulent flow
5/19
Literature Review
Ito (1959)
Recri = 20000   0.32
Rogers & Mayhew (1964) Nu = 0.023Re0.85  0.1 Pr 0.4
Zhao (2020)
Nu = 0.013Re0.93  0.177 Pr 0.4
6/19
The Case
7/19
Theory
In fully developed duct flows, the heat transfer coefficient,
i.e. h, is independent of longitudinal position (A.Bejan).
q = mc p (T i −T o )
q
T  Tw −T
o
ln
T i hpS
=
T o mc p
q = hpS T lm
m
s
i
S =
1
h 2 + ( D ) 2
4
8/19
Computation Setup
Computation grid
9/19
Computation Setup
Boundary conditions
Parameter
Constant Wall
Temperature
Inlet Temperature
Inlet Velocity
Value
300 K
330 K
2 m/s
Realizable k - ε turbulence model is used in these
computations. This scheme is ideal for flows
involving rotation (fluent, 2007).
10/19
Computation Setup
Thermophysical properties
Parameter
Value
Density
Specific Heat
Thermal Conductivity
Dynamic Viscosity
990 kg/m3
4180 J/kg.K
0.64 W/m.K
0.000578 Pa.s
Re = 34250
Pr = 3.775
11/19
Results
Velocity Magnitude
Contour
Temperature
Contour
12/19
Results
Outlet
Velocity
Contour
Outlet
Temperature
Contour
13/19
Results
Amount of Turn
90°
180°
270°
360°
450°
540°
630°
720°
810°
900°
990°
1080°
Nusselt Number
233.8874
228.3741
233.0417
239.3035
240.5951
240.5684
240.7813
240.5589
240.4427
240.4393
240.5041
240.7649
Fully developed region achieved utmost at the
end of second turn.
14/19
Results
Comparison with straight pipe
Straight Pipe
Helically Coiled Pipe
Numerically Calculated Nu no.
188
240
Correlation Estimated Nu no.
179
242
15/19
Results
Effect of different curvature ratio
270
260
γ=0.1
240
γ=0.05
230
γ=0.08
γ=0.15
220
γ=0.2
turn
1080°
990°
900°
810°
720°
630°
540°
450°
360°
270°
180°
210
90°
Nu no.
250
16/19
Results
Effect of different pitch
250
245
Nu no.
240
235
230
h=60mm
225
h=40mm
220
h=100mm
215
210
90° 180° 270° 360° 450° 540° 630° 720°
turn
17/19
Conclusion
▪ Helical pipes enhance Nu number at the expense
of much pressure drop
▪ As the γ decrease, the Nu number approaches
that for a straight pipe
▪ The variation of pitch has negligible effect on
the Nu number
18/19
Thank you for your attention!
19/19