Alat penukar panas: tipe dan aplikasinya.pdf

Aplikasi perpindahan panas untuk alat penukar panas

1. Heat Exchanger
Hanim Z. Amanah

2. Definition of Heat Exchanger
➢A heat exchanger may be defined as a mechanical device that transfers the heat from hot fluid
to cold fluid, with a maximum rate and with minimum investment as well as minimum running
cost
➢Energy balance: enthalpy lost of hot fluid = Enthalpy gained by cold fluid (Assume negligible
heat losses to surroundings)
Example:
❑Condenser, evaporator
❑Radiators of automobiles
❑Water and air coolers or heaters
❑Condenser and evaporator of
refrigeration system
Application:
❑Chemical, food and manufacturing
industries
❑Electronics
❑Refrigeration and air conditioning

3. Classification of Heat Exchanger
According to Heat transfer mechanism
➢Heater and Cooler (sensible heat changes)
➢Condensers
In condenser, the hot fluid condense (Gas to liquid) at
constant temperature while the temperature of cold fluid
gradually increase from inlet to outlet. The hot fluid reject
latent heat which is absorbed by the cold fluid
➢Evaporator
In evaporator, cold fluid evaporates (Liquid to gas) at constant
temperature while the temperature of hot fluid gradually
decrease from inlet to outlet
Ex: evaporator of refrigeration system →the refrigerant
change its phase at constant temperature by absorbing the
heat from hot fluid (air or water)

4. Classification of Heat Exchanger
According to Transfer Process
➢Direct contact (mixing fluid)
In this type of HE, the two fluids at different temperatures are come and mixed with direct contact
Ex: Cooling tower
➢Indirect contact (no mixing)
In this type of HE, the two fluids at different temperatures exchange heat without direct contact
Ex: tubular heat exchanger, shell and tube heat exchanger

5. Classification of Heat Exchanger
According to Flow arrangement
➢Parallel flow HE/co-current flow HE
The hot and cold fluids flow in the same direction. Both fluids enter the heat exchanger at the
same end and leave at another end.

6. Classification of Heat Exchanger
According to Flow arrangement
➢Counter flow HE/Countercurrent HE
The hot and cold fluids enter the HE at the opposite end and flow in the opposite direction

7. Classification of Heat Exchanger
According to Flow arrangement
➢Cross flow HE
The two fluids flow at a specific angle to each other (usually 90
o
)

8. Classification of Heat Exchanger
According to the Geometry of construction
➢Concentric tube type HE/
tubular or double pipe HE

9. Classification of Heat Exchanger
According to the Geometry of construction
➢Shell and tube type heat exchanger
These are commonly used for heating, cooling, condensation, or
evaporation where large heat transfers are required

10. Classification of Heat Exchanger
According to the Geometry of construction
➢Finned type
When an enhanced heat transfer rate is required, the extended surfaces
are used on one side of the HE

11. Classification of Heat Exchanger
According to the Geometry of construction
➢Compact heat exchanger
The heat transfer surface area per unit volume is very large (> 700 m
2
/m
3
)

12. Overall heat transfer coefficient
➢A heat exchanger typically involves two flowing fluids which are separated by a solid
wall. First, heat is transferred from the hot fluid to the wall by convection, through the
wall by conduction, and from the wall to the cold fluid by convection
➢The thermal resistance network associated with this heat transfer process involves two
convection and one conduction resistance
➢For a double pipe heat exchanger, the heat flux can be calculated using the following
eq.
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13. Overall heat transfer coefficient
➢Total thermal resistance
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➢In the analysis of the heat exchanger, it is convenient to combine all thermal resistance
in the path of heat flow from the hot fluid to the cold one into a single resistance (R)
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14. The Log Mean Temperature Difference Method (LMTD)
➢The temperature difference between the hot and the cold fluids varies
along the heat exchanger
➢It is convenient to have a mean temperature difference (ΔT
m) to be used
for analysis
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