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.