investigation of radiation heat transfer in fire tube steam boiler...
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Abstract—In this study, radiation heat transfer in fire-tube steam
boiler furnace was conducted and numerical calculations are
performed for all cases with the use of the Fluent CFD code.
Computational simulation was made by using the conservation of
mass, momentum and energy equations. In the present work, the flow
is assumed to be steady, incompressible and turbulent. In this work,
consideration has been made on the numerical simulation of the
combustion of methane gas with air in a burner element, the flow
being turbulent due to temperature and pressure gradients in the
boiler furnace. Moreover, various burner nozzle designs (methane
gas outlet) are investigated such as single nozzle, three nozzles and
five nozzles.
Keywords— radiation heat transfer, CFD, turbulence.
I. INTRODUCTION
N boiler, heating is accomplished by transferring heat from
by burning fuel to water which is in contact with heating
surfaces. Today, initial cost of boiler is very high. So, many
owner want to use long time and to reduce repair time and
cost. The result of this thesis will be used for investigating the
heat transfer of boiler furnace and for designing the new
operation range of a boiler furnace when the fuel properties are
changed. Also, the effects of nozzle are investigated.
Numerical calculations are performed individually for all cases
with the use of the FLUENT CFD code.
II. PROBLEM SET UP AND MODELING
The boiler considered in the present study is 5 tons, natural
gas, fire tube boiler and having one burner. In this study, the
fuel used is methane, which is burned in the combustion
chamber and the flue gases pass through the tubes and
exhausted through the chimney. The boiler is used for
production of superheated steam for process industry. The
overall boiler diameter is 2150mm and length is 3600mm. In
boiler, the combustion chamber diameter and length are
3020mm and 1100mm. The boiler tube is included 82 numbers
and its diameter and length are 76.2 mm and 2150 mm [6].
The overall design of the studied boiler is as shown in fig.1.
The problem is modeled with the following assumptions;
• The flow is steady and incompressible.
• The mixture is an ideal gas.
• Burner element wall is no slip condition.
Kyaw Nandar Lin is with the Mechanical Engineering Department,
Technological University of Yangon, Myanmar (g-mail: manandar.lin@g-
mail.com).
• Turbulent flow
Air inletMethane inlet
Furnace
Boiler diameter =2150mm
Boiler length =3600mm
Furnace diameter =1100mm
Furnace length =3020mm
Tube diameter =76.2mm
Number of tubes =82nos
Boiler
tube
Fig. 1 3D illustration of the boiler
A. Governing equations;
The conservation equations for mass, momentum and
energy in general form are shown below [2].
.( ) 0vt
ρρ
∂+ ∇ =
∂
r
(1)
( ) .( ) .( )v v v p g Ft
ρ ρ τ ρ=∂
+∇ =− ∇ +∇ + +∂
rr r r r
(2)
( ) .( ( )) ( . )E v E p k T h J v Sj jeff eff hjtρ ρ τ
∂+∇ + =∇ ∇ − + +∑
∂
rr r
(3)
τ=
, the stress tensor is given by
2
( ) . .3
Tv v v Iτ µ
== ∇ + ∇ − ∇
r r r
Where I is the unit tensor.
In energy equation E is given as,
2
2
p vE h
ρ= − +
“h” is sensible enthalpy and for incompressible flow it is
given as
ph Y jh j
j ρ= +∑ and
Investigation of Radiation Heat Transfer in Fire
Tube Steam Boiler Furnace
Kyaw Nandar Lin
I
h j = ,T dT
h c jpjT
ref
= ∫
B. Boundary conditions
The flow and thermal variables are defined by the boundary
conditions on the boundaries of the studied model. Pressure
inlet conditions are applied at the inlet in the furnace. Pressure
outlet boundary condition is applied at the furnace outlet and
the walls are treated as constant wall temperature (300○K). The
walls are stationary with no slip conditions applied on the wall
surface. The detailed boundary conditions are summarized
below;
Inlet methane inlet P=2.94P
Air inlet P=101325P
Outlet constant pressure at p= 1bar
Walls no slip condition: u=0, v=0, w=0
Temperature all walls are set at T=300 K
C. Computational domain
In this study, three dimensional burner elements was
designed using Gambit package. In the view of the complex
geometry of the boiler, the simulation is conducted in three
cases.
Case (1): in this stage of study, the computational domain
includes ¼ of furnace because boiler furnace is summary
design. The burner outlet is assumed single nozzles. The
computational domain with boundary conditions is shown in
fig-2.
Symmetry wall
Symmetry wallPressure outletP=1bar
T= 300�K
Methane inlet
Air inlet
Fig. 2 Computational domain for furnace with boundary
conditions (single nozzle)
Case (2): In this stage of study, the computational domain
includes the entire boiler furnace. The burner outlet is assumed
three nozzles. The computational domain with boundary
conditions is shown in fig.3. Also, the computational domain
of the case (3) is includes the entire boiler furnace and burner
outlet is assumed five nozzles [4].
Pressure outlet=1bar
P=1bar
T=300�K
Air inlet
Methane inlet
Fig. 3 Computational domain for furnace with boundary
conditions (three nozzles).
D. Computational method
The fluent modeling is based on the three-dimensional
conservation equation for mass, momentum and energy. The
differential equations are discretised by the finite volume
method and are solved by the SIMPLE algorithm. As a
turbulence model, the k- ε was employed. The fluent code uses
an unstructured non-uniform mesh, on which the conservation
equation for mass, momentum and energy are discretised. No-
slip condition is assumed at the burner walls. The model
constants for the standard k- ε model are C∝=0.09, C ε1 =1.44,
C ε2 =1.92, and wall Prandtl number of 1 [3].
The commercial software package Fluent (version 6.1.22)
from Fluent .Inc is used in this study. Fluent employs a
control-volume -based technique to convert the governing
equations to algebraic equations, which are solved using the
implicit method. In the segregated formulation, the governing
equations are solved sequentially, i.e segregated from one
another. The SIMPLE algorithm is used to couple the pressure
and velocity and solves the pressure-correction implicitly. First
order upwind scheme is used to spatial discretisation of the
convective terms.
Fig. 4 illustrates the model geometry with computational
grid for the study. In this study, grid spacing is assumed 0.03
spacing [4].
Fig. 4 Computational model of the studied boiler
E. Convergence
The solution convergence is obtained by monitoring the
continuity, momentum, energy turbulence and species
equations separately. A convergence criterion of 10-3 is used
for mass conservation, 10-6 is used for energy conservation,
and 10-3 for velocities and turbulence values. The temperature
distribution is determined after a converged solution is
achieved. The energy conservation is made by enforcing the
thermal energy transfer out of the domain equal to that of into
the domain. The net transport of energy at the inlet and outlets
consists of both the convection and diffusion components [3].
III. RESULTS AND DISCUSSION
Fig. 5 Temperature distribution of the furnace (single nozzle)
Fig. 6 Temperature distribution of the furnace (three nozzles)
Fig. 7 Temperature distribution of the furnace (five nozzles)
Fig. 8 Velocity distribution of the furnace (single nozzle)
Fig. 9 Velocity distribution of the furnace (three nozzles)
Fig. 10 Velocity distribution of the furnace (five nozzles)
This study illustrates the analysis of simulation of
combustion and thermal flow behavior inside an industrial
boiler. Fig. 5, 6 and 7 shows the temperature distribution of the
furnace for single nozzle, three nozzles and five nozzles. Fig.
8,9 and 10 shows the velocity distribution of the furnace for
single nozzle, three nozzles and five nozzles.. According to the
results, five nozzles design is better than other two. Mixing
effect of Fuel and air is bests. So, flame Patten and
temperature distribution is good and furnace outlet
temperature is about 1100K. The temperature reaches its
maximum of about 2900 K at the flame front.
IV. CONCLUSION
In this paper, the results of radiation heat transfer at boiler
furnace are presented. The temperature distribution and
velocity distribution graphs are showed. According to the
graph, the temperature reaches its maximum of about 2900K
and furnace outlet temperature 1100K .But more measurement
and research are needed to fully develop the method, the first
results are encouraging. .
ACKNOWLEDGMENT
My gratitude are due to the General Manager of MPF
(Yangon) for giving opportunity to present this paper and his
encouragement, and also Chief Engineer for providing
necessary support and guidance and, Technical Advisor for
giving advices on technical matters and supervision. Likewise,
I am very thankful to Dr. Mi Sandar Mon, Professor and Head
of Mechanical Engineering Department, Yangon
Technological University, for her suggestions and valuable
guidance during the development of this paper.
REFERENCES
[1] M. A. Habib, M. Elshafei,” Computer Simulation of NOx Formation in
Boilers” King Fahd University of Petroleum and Minerals, Dhahran
31261, KSA.
[2] Raja saripalli, Ting wang, Benjamin day,”simulation of combustion and
thermal flow in an industrial boiler,” Proceedings of the Twenty-
Seventh Industrial Energy Technology Conference, New Orleans, LA,
May 10-13, 2005
[3] Fluent 5.5 documentation
[4] GAMBIT toturial guide, September 2004.
[5] Frederick f.ling,”boiler and burner” 2000.
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