In a new era of sustainability, there’s a growing urgency to save energy and reduce overall environmental impacts. By implementing the use of a plate heat exchanger, energy can be transferred between two fluids at different temperatures. This improves efficiency through heat transfer. The energy already in the system can be transferred before it leaves the system. In this article we tackle the basics of heat exchange and discuss how to maintain a plate heat exchanger.
WHAT IS A HEAT EXCHANGER?
The main functionality of a heat exchanger is to transfer heat between two fluids at different temperatures. Most exchangers consist of a coiled pipe that allows one fluid to passes through a chamber which holds another fluid. The pipes’ walls are metal, or another substance containing a high thermal conductivity to enable the interchange of heat. The chamber in which the pipes are held are made out of plastic or coated with thermal insulation to keep heat from escaping.
Many of the most popular types of heat exchangers used in the mechanical industry consist of shell and tube, air-cooled, plate, and frame.
Many plate heat exchangers are made of corrugated plates on a frame. This creates high turbulence and high wall shear stress, resulting in a high heat transfer and a high fouling resistance.
TYPES OF HEAT EXCHANGERS
There are four main types to consider:
- Gasketed plate heat exchangers – These exchangers use high-quality gaskets and designs to seal plates together and protect against any leaks. You can remove plates easily for cleaning, expansion, or replacing purposes, which helps reduce maintenance costs.
- Brazed plate heat exchangers – Used in many industrial and refrigeration applications, these exchangers can be very efficient and compact. This tends to make them a highly economic choice. If you’re using a stainless steel plate with copper brazing, this dynamic can be highly resistant to corrosion.
- Welded plate heat exchangers – These are very similar to gasketed heat exchangers but the difference is the Welded plates can be attached together. They are very durable and are ideal when it comes to transferring fluids with high temperatures or corrosive materials. Since the plates can be welded together, cleaning the plates isn’t possible compared to cleaning plate heat exchangers.
- Semi-Welded plate heat exchangers – Feature a mix of welded and gasket plates. The two plates are welded together and gasketed to other pairs within the heat exchanger. This results in an easy to service heat exchanger and you’re able to transfer more fluids throughout the system. Semi-Welded heat exchangers are great for transferring expensive materials due to their low risk of fluid loss.
SHELL AND TUBE HEAT EXCHANGER
If you’re looking for an alternative to the options above, consider utilizing a Shell & Tube heat exchanger. Using a Shell & Tube heat exchanger is necessary only when there’s an extreme temperature difference between the two fluids. When using Shell & Tube heat exchangers, technicians will see low-pressure loss. Plate heat exchangers on the other hand, can have high-pressure loss. This is due to a large amount of turbulence created by the narrow flow channels in the system. Shell & Tube exchangers consist of many tubes held within a shell. The heat transfer takes place as one fluid flows through the tubes while another fluid flows over the tubes in the shell.
If you’re using a simple plate heat exchanger, the plates are for liquid-liquid exchange at low to medium pressures. Gasket-free plate heat exchanger on the other hand, tend to operate at high pressures and temperatures. In this case, many professionals seek to use Plate heat exchangers as the most efficient choice for a wide variety of applications.
ADVANTAGES OF A PLATE HEAT EXCHANGER
Once you know what a plate heat exchanger is, it’s time to understand how it can benefit your boiler.
- Provides high value for your overall heat transfer. A flat plate heat exchanger typically has a U value much higher than a shell and tube heat exchanger or a spiral heat exchanger.
- It creates a compact design. Plate heat exchangers have the same thermal capacity as a shell and tube heat exchanger as much as five times its size. This is because of the combination of high-value heat transfer and the general compact configuration of the flat plates.
- Easy maintenance and cleaning. The plate heat exchangers can be taken apart, which allows for easy cleaning and maintenance of the equipment. The exchanger allows the addition or removal of plates to reduce heat transfer capacity.
- Control the temperature. Flat plate heat exchangers work well with small temperature differences among hot and cold fluids.
DISADVANTAGES OF PLATE HEAT EXCHANGERS
Though there are some big advantages to plate heat exchangers, there are also some disadvantages when comparing them to other heat exchangers:
- Leakage. Plate heat exchangers are designed to allow plates and gaskets to be inserted between them. This increases the potential for leakage as gaskets age. Especially when compared to shell and tube or spiral heat exchangers.
- Higher pressure drops. Plate heat exchangers consist of narrow passageways for fluid to flow, which leads to a high heat transfer. This results in a higher pressure drop and a higher cost for pumping than shell and tube heat exchangers.
- Not beneficial for large fluid temperatures. Flat plate heat exchangers don’t work as well as shell and tube exchangers in cases where there’s a large temperature difference between two fluids.
- It doesn’t work well with very high fluid temperatures. The gaskets among plate heat exchangers can restrict temperature limitations.
Maintenance professionals are aware of the perks regular maintenance provides their systems and equipment. By adopting regular maintenance, you ensure your system stays sanitary and operational for better performance efficiency. To guarantee you’re getting the best out of your heat exchanger, follow these steps below:
- Pre-teardown: This includes valving your off unit, draining fluids from the exchanger and disconnecting the pipes. Then checking over the structure of the plate pack, and checking for main leaks and contamination tests throughout the exchanger.
- Teardown: Disassemble the unit and loosen the tie-bolts in the exchanger.
- Cleaning: Remove gaskets if possible, and clean the plates within the system.
- Reassembly: Reassemble the devices mentioned earlier to their exact components. In addition, tighten and configure each plate pack to ensure maximum performance and reliability in the exchanger.
- Verification: Verify each unit is functioning properly.
PLATE HEAT EXCHANGER MAINTENANCE CHECKLIST
We have a made a Plate and Frame Heat Exchanger Maintenance Checklist that dives into each of these steps in great detail. It will provide you with steps you need to take to maintain your plate and frame heat exchanger. Click the button below to keep you system running the way it should.