Posted on 30 April 2016 at 3:00 PM by Vienerg
This blog Heat Exchanger is a device in which heat is transferred from one fluid to another.
Here the heat is transferred between two moving fluids at different temperature.
The Exchanger can heat a liquid to a desired temperature or cool a product for final storage.
Exchangers are widely used in process plants to maintain a process heat balance.
They are used as coolers, exchangers, condensers, re-boilers, vaporizers and heating coils in the chemical and process plant.
Classification based on direction of motion of two fluids:
Parallel flow heat exchanger:
If the two fluids move in the same direction, it is a parallel flow heat exchanger.
Counter flow heat exchanger:
If the fluids flow in opposite direction then it is a counter flow heat exchanger.
Types of heat exchanger according to their construction:
- Shell and Tube
- Plate Exchanger
- Spiral heat Exchanger
- Double pipe Exchanger
Air Cooler Exchanger
Types of heat exchanger based on functions:
- Sub Coolers
- Waste heat boilers
- Steam Generators
SHELL AND TUBE EXCHANGER – FLUID ALLOCATION:
Fewer Costly alloy Components are needed if the corrosive fluid is inside the tube corrosive fluid cannot be sent in the Shellside, since the shell fluid will affect both shell and tubes.
Setting the fouling fluid inside that tube allows good velocity control. Increased velocities reduce fouling. Straight tubes allows mechanical cleaning without removing the tube bundle.
Temperature & Pressure:
For high temperature or Pressure Services requires special or expensive alloy components that are needed when the hot fluid is placed inside the tubes.
Setting the fluid with the lower flow rate on the shell side generally results in a more economical design. The Turbulence which exists on the shell side at much lower velocities than within the tube.
The shell and tube exchanger circulates a hot liquid around the tubes that contain a cooler liquid.
The hot liquid circulator in an enclosed area called the shell. Tube containing the cooler liquid that is looped through the shell.
While the cooler liquid in the tubes cools the warm liquid in the shell, the hot liquid in and shell warms the cooler liquid in the tubes.
Spiral and Plate Exchanger:
For spiral and plate exchanger be sure to provide piping clearance to allow the covers to open and the plates to be removed.
You can locate controls on the ends of the exchanger, however be sure to keep them clear of the cover plate swing area.
Air Cooler Exchager:
On air fan coolers do not route piping over tube banks or fans keep the piping clear of the access area for motor repair.
Air cooled exchangers are generally of two basic types, forced draft or induced draft.
Each type may have recirculation, several bundles, several fans, variable (automatic or manual) fan pinch, variable louvers or steam coils.
Symbols may be modified to represent the type of air-cooled exchanger used .
Preferable position of spiral and plate exchanger:
It is preferable to position the spiral and plate exchangers in single instead of series and parallel for easy operation, maintenance, escape route.
Location of condensate pot for a steam operated exchanger:
To keep the elevation of the condensate pot as possible with respect to the heat exchanger, should be located at grade level in horizontal position if plant operation permits.
Reason for clear space maintained for air coolers:
As per the air drawing capability of the air cooler and to ensure the performance of the air cooler.