general description of steam boiler in power plant

1. UNIVERSITY OF SIRT
FACULTY OF ENGINEERING
MECHANICAL ENGINEERING
DEPARTMENT
HEAT TRANSFER IN
STEAM BOILER
B Y S T U D E N T : H A S S A N A . E Z R I G

2. HIGHLIGHTS:
-overview
-Introduction
-Radiation
-Conduction
-Convection
-mathematical representation
-References

3. OVERVIEW:
Boiler is a widely used steam
generating system in
industries and power plants.
A significant portion of the
world energy consumption is
being used in boilers. A
substantial amount of energy
is wasted through high
temperature flue gas or
exhaust of the boiler. A small
improvement on the boiler
efficiency will help to save a
large amount of fossil fuels
and to reduce CO2 emission.

4. INTRODUCTION:
A steam boiler is designed to absorb
the maximum amount of heat
released from the process of
combustion. Heat transfer within
steam boiler accomplished by
three methods: radiation,
convection, and conduction. The
relative percentage of each heat
transfer is dependent on the type
of steam boiler.

5. RADIATION:
Radiation is the process of
continuous interchange of
energy by means of
electromagnetic waves.
Steam boiler tubes absorb
the radiant heat from flame
and radiate a small portion of
the heat back to the furnace.

6. CONDUCTION:
-Conduction within steam boiler is the
transfer of heat from one part of a body
to the other or from one body to another
in physical contact.
-It is the flow of energy that occurs in a
substance without appreciable
movement of molecules due to lattice
vibrations and flow of free electrons.
-Heat flow from flue gases to water/steam
across the metal wall in a steam boiler,
loss of furnace heat to the surrounding
atmosphere through insulation, and heat
loss from hot steam/water pipes through
insulation are all examples of
conduction.

7. CONVECTION:
-Convection is the process of transferring
heat by movement energy through a
material.
-When any fluid in a steam boiler is
heated, its density is decreases and
the fluid becomes lighter. Then the
heavier or cooler fluid will flow and
replace the heated portion of the
fluid. In turn the cooler portion
becomes heated.

8. MATHEMATICAL REPRESENTATION:
Radiation:
𝑞𝑟𝑎𝑑= ℎ𝑟
(𝑇𝑠 - 𝑇𝑠𝑢𝑟 )
ℎ𝑟 is the radiation heat transfer coefficient
ℎ𝑟 =   (𝑇𝑆 +𝑇𝑠𝑢𝑟 ) (𝑇𝑠
2+𝑇𝑠𝑢𝑟
2 ) w/𝑚2. 𝑘
= emissivity rang 0 1
= 5.67 *10−8
w/𝑚2
𝑘4
stefan-boltzman
constant

9. CONDUCTION:
𝑞𝑐𝑜𝑛𝑑 = −𝑘 𝐴𝑐
𝑑𝑇
𝑑𝑥
Watt
K= thermal conductivity
A= cross-section

10. :
CONVECTION
q = h 𝐴𝑠 𝑇𝑠 − 𝑇∞
h= convection heat transfer
coefficient w/𝑚2
. 𝑘
𝐴𝑠 = 𝑠𝑢𝑟𝑓𝑎𝑐𝑒 𝑎𝑟𝑒𝑎 𝑚2

11. REFERENCES:
1-
http://steamofboiler.blogspot.com/2011/02/heat-
transfer-within-steam-boiler.
2-
https://ideas.repec.org/a/eee/rensus/v79y2017ic
p970-983.html
3-
https://faculty.utrgv.edu/constantine.tarawneh/
Heat%20Transfer/HeatTransferBooklet.pdf