What is a plate heat exchanger, and what are its primary components?
A plate heat exchanger is a type of heat exchanger that uses metal plates to transfer heat between two fluids. This has a major advantage over a conventional heat exchanger in that the fluids are exposed to a much larger surface area because the fluids are spread out over the plates..
The major components of plate heat exchangers and their functions include:
Types of Plate Element Patterns
A single plate heat exchanger can contain an outside of 700 plates. As the plate pack compresses, the holes in the plate’s corners produce a constant passage or manifold that allows fluid to flow through the plate pack and exit the device. The space between the thin plates of the heat exchanger makes a tight channel that alternately traverses by cold and hot fluids and offers truly small resistance to heat transfer.
Plate element pattern types include:
Corrugated Pattern
The corrugated pattern is also called the marsh board pattern. It has lower substance contact points between plates and allows for liquids with fiber or sludge contents to flux easily without blockage.
Herringbone Pattern
The “herringbone” pattern was named as the V-shaped press grooves act the bones of a herring.
There are a number of contact points made by piling the V-shaped pressed plates, and then turning them 180° in an interspersing pattern. This ensures the resistance of high pressure, and also the complex flux channels formed by the V- shaped press grooves get high heat transfer performance. Likewise, including the dropped heat transfer resistance due to the thinner plate results in heat transfer performance three to five times more advanced than that of S&T heat exchangers.
How does a plate heat exchanger transfer heat between fluids?
Plate heat exchangers consist of relatively few parts. Because plate heat exchangers are used for transferring heat, they require inlets and outlets where the flowing mediums -or fluids– can enter and leave the heat exchanger. A fluid may be a liquid or a gas. As fluids are often assumed to be liquid only, we will use the term flowing medium to avoid confusion
What are the main advantages of using a plate heat exchanger compared to a shell and tube heat exchanger?
Plate heat exchangers are up to five times more efficient than shell-and-tube designs. Removing and reconfiguring plates allows plate heat exchangers to adapt to specific heat transfer requirements, enhancing their maintenance and efficiency
What are the different types of plate heat exchangers, and in which applications are each type typically used?
Gasketed Plate Heat Exchanger
The gasketed plate heat exchanger employs high-quality gaskets and construction. These gaskets serve the vital role of sealing the plates to prevent leakage. Notably, the plates of this exchanger can be easily removed for maintenance, expansion, or cleaning, leading to significant cost savings.
Brazed Plate Heat Exchanger
Brazed plate heat exchangers find widespread use in refrigeration and various industrial processes. These exchangers excel in erosion resistance due to the brazing of pristine plates. Their compact design and efficient performance make them an economically superior choice.
Welded Plate Heat Exchangers
Welded plate heat exchangers function similarly to gasketed plate heat exchangers, but their plates are welded together. These heat exchangers offer excellent durability and are suitable for handling hot fluids and aggressive substances. However, they lack the mechanical cleaning capability of plate and frame heat exchangers.
Semi-Welded Plate Heat Exchanger
The semi-welded plate heat exchanger combines gasketed and welded plates. It features two plates welded together and another pair of plates sealed with gaskets. This configuration allows one fluid to flow through the welded section and the other through the gasketed section, making it easy to repair and enabling the transfer of different fluids without complications.
Plate and Frame Heat Exchanger
A plate and frame heat exchanger consists of plates arranged to create a frame. The corrugated plates within the frame induce high wall shear stress and turbulence, resulting in excellent stain resistance and efficient heat transfer. These heat exchangers employ gaskets for sealing and guiding fluid flow along the plate edges. They are well-suited for heat exchange between liquids at medium to low pressure and can operate safely at high temperatures and pressures without gaskets.
How is the overall heat transfer coefficient of a plate heat exchanger calculated?
The choice of plate size and quantity is contingent on factors like fluid flow rate, temperature differentials, physical properties, pressure differentials, and desired strength. These exchangers feature plate designs, both symmetrical and asymmetrical, that induce turbulent fluid flow, resulting in enhanced heat transfer coefficients. The contact points between plates contribute to the overall structural integrity of the plate package
What factors should be considered when designing a plate heat exchanger for a specific application?
The different designs of plate heat exchangers include:
Carrying Beam in Plate Heat Exchangers
The upper part that is fixed between the supporting column and the fixed plate where the pressure plates and the exchanger plates are connected.
Fixed Plate in Plate Heat Exchangers
The fixed plate is an abecedarian part of the plate heat exchanger. As the name of this plate represents that it’s a fixed frame plate. Generally, the heat exchanger pipes and the fixed plates are connected together.
Support Column in Plate Heat Exchangers
This is a non-portable part of the plate heat exchanger. The guiding bar and carrying shaft are attached to this part
Pressure Plate in Plate Heat Exchangers
The plate heat exchanger has a mobile pressure plate frame attached with the exchanger carrying shaft. The frame can compress the exchanger’s plates.
Guiding Bar in Plate Heat Exchangers
This part guides the pressure plate and heat exchanger plates over.
Tightening Unit in Plate Heat Exchangers
It’s used to compress the frame corridor of the plate pack. It possesses tensing nuts, tensing washers, and tensing bolts.
Gaskets in Plate Heat Exchangers
The quilting of plates installs between the pressure plate and the fixed frame plate. This plate pack compresses by tensing the screws fastened between the two plates. The gaskets cover the plates to regulate the flux.
How does the arrangement and pattern of plates affect the performance and efficiency of a plate heat exchanger?
Plate exchanger is made by stacking several thin metallic plates together to form flow channels, they exchange only heat between the air streams. The metallic plates can be flat or corrugated and the flow configurations can be parallel flow, counterflow, or crossflow, depending on the requirement
What materials are commonly used in the construction of plate heat exchangers, and how are they selected based on the application?
The most frequently used materials for the plates are stainless steel (AISI 304, 316), titanium and aluminium. The corrugation on the plates forces the fluid on a tortuous path, setting a space between two adjacent plates b, from 1 to 5 millimeters.
How do fouling and scaling affect the performance of a plate heat exchanger, and how can these issues be minimized?
The buildup of fouling also reduces the cross-sectional area of the tubes or flow channels and increases the resistance of the fluid passing over the surface. These side effects combine to increase the pressure drop across the heat exchanger, reducing flow rates and aggravating the problem further
What are the key maintenance practices to ensure the long-term reliability and efficiency of a plate heat exchanger?
Maintenance of a Plate Heat Exchanger
The steps to follow in the general maintenance of a plate heat exchanger are listed below:
Pre-Teardown of a Plate Heat Exchanger
The first step is to disassemble the plate heat exchanger.
Opening procedure:
- Shut down the heat exchanger close the faucets
- Drain the heat exchanger
- Strike pipes from the pressure plate
- Check the sliding shells of the carrying bar
- The outside of the plate assembly must be marked by a slant line
- Measure and note the dimension
- Remove the locking bolts
- Use the tensing bolts to open the heat exchanger. Always use the same tightening confines when you remove and place back the plates in the heat exchanger
Cleaning Heat Exchanger Plates
The plates are designed for both homemade cleaning and cleaning-in- place operations. The user must make sure that the unit has been de-pressurized, locked out, and drained before disassembly. Homemade cleaning is typically fulfilled by washing the plates with a soft non essence encounter, water, and cleaning result. It’s recommended to lay the plate on a flat face during encounter cleaning to avoid the threat of bending the plate. However, care must be taken to remove all debris from the gasket sealing shells when the heat exchanger is reassembled, if the heat exchanger is heavily fouled.
How can gasket materials and designs impact the operation and maintenance of a plate heat exchanger?
Gaskets in Plate Heat Exchangers
The quilting of plates installs between the pressure plate and the fixed frame plate. This plate pack compresses by tensing the screws fastened between the two plates. The gaskets cover the plates to regulate the flux.
Gasket Types in Plate Heat Exchangers
The types of gaskets used in plate heat exchangers include:
Slit-in Gasket (Glue-free type)
The slit-in gasket is especially recommended for those operations where frequent relief of the gasket is demanded. Furthermore, without the cement, cement odor is reduced. The slit-in type gasket is suitable for operations similar to water treatment or food processing.
EPDM Gasket
Generally, EPDM gaskets are recommended for either high temperature or aggressive fluid operations. EPDM gaskets are high quality, unlike rubber gaskets that lose elasticity as time passes.
PTFE Cushion Gaskets (TCG)
PTFE Cushion Gaskets are generally useful in applications where conventional synthetic rubber would be limited due to the cattiness of the fluid being handled. Due to their chemical resistance, PHE can be applied in a wider variety of operations. The TCG gasket does not bear a strong tightening collar during the assembly of the unit due to its elastic core. Therefore, it reduces the pitfalls of plate distortion by over tightening. A TCG gasket can only be useful for one side, if the non corrosive fluid is running on the other side where a conventional gasket can be used.
What are some common troubleshooting techniques for addressing performance issues in plate heat exchangers?
The gaskets are hardened, there are cracks on them, and cold leakage indicates problems.
Possible causes:
- Material failure due to age or high temperature
- Oxidant present in the process stream
- Unsuitable or over-concentrated cleaning liquid
- NBR density to Ozone
Proposed solution:
- Replace gaskets if age is the cause. Check gasket compatibility with the media and upgrade the material if necessary.
- If the CIP (Cleaning-in-Place) is the root cause then review method and cleaning liquid.