CORRUGATED TUBE HEAT EXCHANGER ( FOOD / PHARMA / CHEMICAL)
The development of Corrugated Tubes is perhaps the most exciting advance in heat transfer technology. It has long been accepted that if you agitate a hot liquid it cools faster since the shaking produces turbulence that enhances the heat transfer from the liquid to the air. HRS has developed heat transfer enhancing corrugated tubes to achieve a similar result by creating turbulence in the media without using any mechanical shaking. A new style of corrugated tube is boosting heat transfer multifold at low Reynolds number with minimum increase in pressure loss.
Corrugated Tube Heat Exchangers are shell and tube heat exchangers, which use corrugated tubes instead of plain (smooth) tubes.
Corrugated Tubes - Development
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- Corrugated Tubes take the best features of both the plain tube and the plate heat exchanger.
- Plain tubes offer the best geometry to withstand pressure but the worst for heat transfer due to rapid build-up of boundary layer.
- Plates in a plate heat exchanger induce local turbulence to increase heat transfer coefficient but is limiting in terms of operating pressures and temperatures due to elastomer gaskets. Also, the relatively narrow gap limits its use to fluids without large fibres and particulates.
Technology:
Corrugated tube is produced by indenting a plain tube with a spiral pattern. This imparts different flow regimes - spiral in the core and eddy's at the periphery.
The helical flow contributes to the situation that the fluid particles are alternatively in the vicinity of the tube wall and then in the main flow. Between the helical impressions, around the circumference of the tube, secondary flow, typically in the form of eddies occur.
The flow regime ensures that the rate of decrease in boundary layer resistance exceeds the rate of increase in pressure loss. In other words high heat transfer coefficients with minimum increase in pressure drop.
Hydrodynamic Thermal Boundary Layer
Increase in heat transfer coefficient brings the temperature of the tube wall closer to the temperature of the bulk fluid on the tube.
The roughness elements need to have a minimum height so as to influence the flow ( Fig. A ) and thus the heat transfer ( Fig. B ). To ensure that the heat transfer is improved by roughness elements, the flow must be influenced within the heat conduction layer.
Advantages:
Corrugated tube shell and tube heat exchangers have many benefits and advantages over comparable smooth tube versions:
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Compact tubular heat exchanger; in some cases less than half the size of a traditional plain tube heat exchanger.
- Long running times due to turbulent flow
- Very low maintenance costs, minimum spares requirement.
- Lower heat transfer areas. Heat transfer coefficients of up to 2½ times higher can be generated. Due to the higher coefficients achieved, the heat exchanger size can be reduced by as much as half.
- Fouling caused due to 'burn on' freezing or chemical changes is minimised due to the turbulence created by eddies at the periphery or the tube wall.
- High response to CIP, which is increased because of the increased turbulence generated by the corrugated tube at traditional circulation velocities. In-situ cleaning is improved because of the increased turbulence generated by the corrugated tube, which in lower viscosity fluids minimises the tendency for deposition fouling to occur.
- Wide choice of MOC. Heat exchangers can be made in SS 304 / L, 316 / L, CuNi, Hastelloy, Alloy 20, Duplex, Titanium, etc.
- Uniform thermal processing. Increasing the tube side heat transfer coefficient brings the temperature of the tube wall closer to the temperature of the bulk fluid, minimising fouling.
- More flexibility in annular space sizing. There is no significant obstruction to the flow area of the tube so that they can be used for fluids with a high solid or fiber content with no fear of blockage.
- Monotube 'DT' series can handle large particles up to 50 mm size
Corrugated Tube Types:
Corrugated tube is produced by indenting a plain tube with a spiral pattern. No tube wall thinning takes place & no strength is lost. A smooth indented inner profile ensures easy cleaning. Turbulence is created at low fluid velocities to enhance the heat transfer in the tube. Fouling on the tube surface is minimised. A wide range of diameters & styles are available.
There are three types of corrugated tubes - Soft, Hard and Dimpled.
For an optimum design in terms of area, pressure drop, fouling etc., for a particular type of application the corrugations type is based on the following factors:
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Corrugation depth
- Corrugation pitch
- Corrugation angle
- Number of starts
By choosing the depth, angle and width of the indentation carefully, the rate of decrease in boundary layer resistance can exceed the rate of increase in pressure loss to provide the optimum design in terms of area, pressure drop, fouling, etc., for the particular application.
Models:
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K SERIES - MULTITUBE
The K SERIES heat exchanger is a multitube shell and corrugated tube unit with mechanical design tailored for industrial use. The product normally flows through the tubes and the service flu
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MI SERIES - MULTITUBE
The MI Series heat exchanger is a multitube corrugated shell and corrugated tube unit and has been designed for the food processing and pharmaceutical industries. The product normally flows
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DT SERIES - MONOTUBE
The DT Series heat exchanger is a tube in tube heat exchanger, manufactured from concentric corrugated tubes. The Product normally flows through the inner tube and the service fluid through
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AS SERIES - TRIPLETUBE
The AS Series ANNULAR SPACE heat exchangers are made from three concentric tubes, which give three annular spaces. The product fluid channel is surrounded on both sides by the service fluid
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Comparison:
Comparison Of Corrugated Tube Heat Exchanger With Shell & Tube And Plate Heat Exchangers
PARAMETERS |
Corrugated Tube
Heat Exchanger |
Shell & Tube
Heat Exchanger |
Plate
Heat Exchanger |
Heat Transfer Coefficient |
High |
Low |
High |
High Pressure applications |
Yes |
Yes |
No |
High Temperature applications |
Yes |
Yes |
No |
Temperature Distribution |
Uniform |
Non Uniform |
Uniform |
Two Phase Application |
Excellent |
Good |
Poor |
Aseptic Processing applications |
Yes |
Yes |
No |
Product Burn-out |
No |
Yes |
Yes |
Dead Areas / spots |
No |
No |
Yes |
Products with Solid Particles |
Yes |
Yes |
No |
Products with High Viscosity |
Yes |
Limited |
No |
Product Hold-up / losses |
Low |
High |
Low |
Leakage Risk |
Low |
Low |
High |
Overall Size |
Low |
High |
Low |
Response to Cleaning in Place ( CIP ) |
High |
Medium |
Low |
Extension of Units / Modules |
Yes |
No |
Limited |
Ease of Inspection |
High |
Medium |
Low |
Maintenance Cost / Spares Cost |
Low |
Medium |
High |