heat exchanger (shell and tubes) by sujan kharel
TRANSCRIPT
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TRANSFER OF THERMAL ENERGY BETWEE
TWO OR MORE FLUIDS
between a solid surface and a fluid
between solid particulates and a fluid
Heat exchanger
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Based on transfer process
Indirect Contact – Shell & Tube Heat ExchangersDirect Contact – Cooling Towers
Gas-Liquid exchangers
Liquid-Liquid exchangers
Gas-Gas heat exchangers
Based on phase of fluids
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Based on construction
Tubular Double pipe heat exchanger Shell and tube heat exchangers Spiral heat exchangers
Plate-type Plate and frame heat exchangers Spiral plate heat exchangers
Extended Surface Plate-fin exchanger Tube-fin exchanger
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Based on flow arrangementsParallel flow / Co-current flow
Counter flow
Cross flow
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Types of HEDouble-pipe exchangerShell and tube exchangersPlate and frame exchangersPlate-fin exchangers.Spiral heat exchangers.Air cooled heat exchangersAgitated vessels.Fired heaters.
Shell and Tube Heat exchangerA system with Shell & Tubes used
for heat exchange. A shell (a large pressure vessel)
with a bundle of tubes inside it.
WorkingOne fluid runs through the tubes, and another fluid flows over the tubes (through the shell) to transfer heat between the two fluids.
The set of tubes is called a tube bundle.
See the Animation………
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AdvantagesLess expensive as compared to
Plate type coolers Can be used in systems with
higher operating temperatures and pressures
Pressure drop across a tube cooler is less
Tube leaks are easily located and plugged since pressure test is comparatively easy
Disadvantages
Heat transfer efficiency is less compared to plate type cooler
Cleaning and maintenance is difficult since a tube cooler requires enough clearance at one end to remove the tube nest
Requires more space in comparison to plate coolers
Bafels
Device used to restrain the flow of a fluid or to prevent the spreading of fluid in a particular direction.
Flow-directing panel in some vessels such as shell and tube heat exchangers, chemical reactors, or static mixers.
Use of Baffles In Shell And Tube Heat Exchangers
Why are baffles used?
To support the tube
To direct the fluid stream across the tube
To improve the rate of heat transfer Shell
Tubes
Baffle
Fouling
• Fouling occurs when any type of particles both organic or inorganic plug or plate out on heat transfer surfaces creating a resistance to transfer energy
• There are two types of fouling– Macro-fouling– Micro-fouling
Macro Vs Micro Fouling
• Macro-fouling
– Sand– Silt– Scale– Rust– Mineral deposits
Example- CaCO3
• Micro-fouling– Biological
growth– Algae– Bacteria– Mussels
• Micro-fouling is controlled by water treatment
2.Corrosion of heat exchangers
Another series problem in heat exchangers is corrosion
Severe corrosion can and does occur in tubing and very often with common fluids such as water.
To avoid corrosion►Proper material selection based on full analysis of the operating fluids, velocities and temperatures is a must.
►Protection of the heat exchanger from corrosion [e.g. cathodic protection]
►Treatment of the cooling water used and using inhibitors.
3.Heat exchangers vibration
Vibration of the tubes as a result of the flow of the shell side past them is important phenomena specially when the H.X size and flow quantities of flow are increased
Vibration effects
►Vibration has a bad effect on both tubes and shell
►The joints between the tubes and tube sheet can fail due to vibration causing leakage
►It causes leakage in the joints between shell and tubes
►Increase the shut down time to repair the H.X
How to avoid vibration
Using inlet support baffles
Using double segmental baffles [improve tube support]
Inlet support baffles
Double-segmental baffles