A plate heat exchanger is a type of heat exchanger that uses metal plates to transfer heat between two fluids. This has a significant advantage over other heat exchangers in that the fluids are exposed to a much larger surface area, which results in improved heat transfer. Additionally, plate heat exchangers are faster in reacting to temperature changes, making them ideal for use in industrial heat exchange applications.
Plate heat exchangers are also known as gasketed plate heat exchangers or PHEs. They are a heat exchanger that uses metal plates to transfer heat between two fluids. In a heat exchanger application, the fluid can be either a liquid or a gas, and the gaskets between the plates prevent them from mixing.
Read our post about Heat exchanger applications in refrigeration.
Plate heat exchangers are also known as –
- gasketed plate heat exchangers
- plate and frame heat exchanger
Application of plate-type heat exchanger
Gasketed plate heat exchangers or plate coolers are most commonly used in refrigeration, air conditioning, and heating applications. However, they are also used in the chemical, petrochemical, pharmaceutical, power generation, and food processing industries.
Gasketed plate heat exchangers are also quite compact and relatively easy to install, making them popular for many industrial applications and heat exchanger applications.
The gasketed plate & frame heat exchanger (PHE) was created by Dr Richard Seligman in 1923 and revolutionised the way fluids are heated and cooled. In 1910, Richard Seligman started the Aluminium Plant & Vessel Company Limited as a fabrication business that supplied welded tanks to the brewing and vegetable oil industries.
What is a gasketed plate heat exchanger used for?
Gasketed plate heat exchangers (GPHEs) are specific heat exchanger that works effectively with medium and low-pressure liquids.
Plate heat exchangers are commonly utilised for heat recovery applications. This can result in significant energy savings, so they are often found in district heating/cooling systems, commercial HVAC units, and industrial processes requiring high-efficiency levels.
Another everyday use is distillation, where liquids are separated, recondensed, and distilled again. PHEs work well because they can handle cold and hot liquids, making them suitable for distillation processes.
Plate heat exchangers are used in many applications, including steam generation, process heating and cooling, district heating/cooling systems, environmental control units for food preparation, commercial HVAC units, and many other industrial processes.
How do plate heat exchangers work?
In a plate and frame heat exchanger, two streams of liquids are separated by a series of plates. The fluid is passed along one side of the plates, and the cold fluid is passed along the opposite side.
As the liquids pass through the plates, heat is transferred from the hot fluid to the cold fluid – this heats the cold stream, while the heat in the hot fluid is dissipated. This allows a large amount of work with a minimal temperature difference, ultimately reducing energy consumption.
PHEs are an excellent example of how basic engineering can improve industrial processes.
Design of plate and frame heat exchangers
The plate design of a plate heat exchanger gives it its name. An acceptable gap separates two sets of fluid-carrying plates. As a result, the hot and cold streams pass through the plates in opposite directions, transferring heat from one stream to the other via the plates.
Metal is pressed into one-piece plates in a plate and frame heat exchanger. Stainless steel is a popular choice among plates because of its capacity to endure high temperatures, strength, and corrosion resistance.
The plates are usually separated by rubber sealing gaskets installed in a ring around the outside of the plates.
The plates are pressed to form troughs perpendicular to the direction of liquid flow through the heat exchanger’s channels.
The troughs link together with the neighbouring plates, forming the channel with 1.3 to 1.5 mm gaps between them.
The plates are compressed together in a solid frame to form parallel flow channels, alternating hot and cool fluids.
The plates’ large area allows for the quickest transmission of heat.
PLATE HEAT EXCHANGER DIAGRAM
Plate heat exchangers or plate and frame heat exchangers consist of a series of metal plates, usually made of stainless steel, which are separated by gaskets. The gaskets are made of an elastomeric material, such as rubber or silicone, and are designed to prevent the two fluids from mixing.
How many plates are there in a plate heat exchanger?
The number of plates in a single exchanger ranges from just ten to several hundred, reaching surface exchange areas up to thousands of square meters.
What are plate heat exchangers made from?
Plate heat exchangers are generally made from aluminium, stainless steel or titanium. The plates are designed to withstand varying temperatures and high-pressure differentials without warping or buckling.
They are typically created out of plates with cells or passages through which the fluid flows. Thin spacers or gaskets then separate the plates to keep the fluid flowing between the two sides.
What are the benefits of a plate heat exchanger?
There are several key benefits of using plate heat exchangers;
- Gasketed plate heat exchangers are easier to maintain, repair, and service.
- They have a small footprint that requires little to no maintenance space.
- Plate heat exchangers have an increased surface area than tube-based exchangers, meaning more heat is transferred in a shorter period.
- The corrugated plates create turbulence in the liquids as they flow through the unit. This turbulence gives an effective heat transfer coefficient.
- PHEs can be used in many applications, from power plants to chemical processing and high-purity applications like pharmaceuticals.
What are the disadvantages of a plate heat exchanger?
One disadvantage is that it cannot be used in applications with large pressure differentials.
- Gaskets are a potential problem if they are crushed excessively, as they can warp and result in system leaking.
- Gaskets are more sensitive to temperature changes than the plates; thus, a high fluid temperature may not be used for fear of damaging the gasket material.
- The small plate pathways drastically decrease the pressure of the flow rates, necessitating extra pump power.
- In a plate exchanger, two fluids with a significant temperature gap will not exchange energy as effectively as they would in a shell and tube exchanger.
- They lose heat to the ambient air, lowering their efficiency.
How do I know my plate heat exchanger is working efficiently?
When your heat exchanger isn’t producing the proper temperature for heating or cooling, it’s time to clean it.
The incorrect temperatures are caused by plate surface fouling, which reduces temperature transmission.
You may also observe a more significant pressure drop because contamination restricts the channel passage and increases fluid velocity.
The best way to know if your plate heat exchanger is efficient is to monitor the time it takes for the fluid entering the unit to reach a specific temperature. The temperature difference between the entrance and exit will indicate how effective your plate heat exchanger is at heat transfer from one fluid stream into another.
Signs that your heat exchanger is not functioning properly
Poor performance is the most common issue with plate heat exchangers. If you notice that yours is performing erratically, with poor heat transfer or less effectively than usual, this could be due to many factors.
Poor performance is usually attributed to;
- An error in the plating
- An accumulation of dust, dirt or debris within the unit (this is known as fouling)
- A buildup of mineral deposits on the plates (known as scaling)
- Something impeding the flow of liquid
- A faulty installation.
Try running a standard CIP cycle to clear out the excess matter in the exchanger. If the debris does not clear, you may need to clean the unit manually.
If you notice liquid deposits outside the GPHE, prompt intervention is needed. A leak indicates that the gaskets have been damaged, although it can also signify improper assembly.
The plates can move side to side, up and down during tightening unless adequately aligned at the top and bottom. This causes the gaskets to become misaligned, resulting in leakage.
If the liquids inside the unit begin to mix, the plates leak. The likely explanation is that the unit has been damaged, and one of the plates has become perforated.
A simple pressure test should be all you need to confirm this. You need to fill the unit with water but only pressurise one side. If there is a perforated plate, the side which has not been pressurised will start to overflow.
If a plate is found to be perforated, you will need to disassemble the unit and inspect the plates with a crevice detection liquid.
Can a PHE be serviced and repaired?
Like any other object or piece of equipment, a heat exchanger requires regular upkeep to function correctly. Fortunately, PHEs are more straightforward to maintain than other exchangers, and problems are easier to spot and rectify.
Even if the PHE appears to be in good working order, planned maintenance is recommended regularly.
When a PHE’s efficiency is allowed to drop due to fouling, it will eventually become inefficient. Deposits accumulate in the grooves of a plate as it becomes filthy, reducing heat transfer capacity.
The performance of a plate deteriorates with each level of deposit buildup, necessitating early detection to avoid prolonged outages and high remedial costs.
Types of plate heat exchangers
Semi-welded plate heat exchangers
Plate heat exchangers are a type of device used to transfer heat between different liquids. They work by having two plates with fluid passages between them, and the flowing liquids exchange the heat.
There are several different types of plate heat exchangers, including semi-welded ones. This means that they are welded together in every other channel, which allows them to handle applications where one of the liquids is aggressive.
Fully-welded plate heat exchangers
In a fully-welded plate heat exchanger, the two plates are welded on every channel and should be used if both liquids are aggressive or temperatures exceed the gasket limitation.
Welded plate heat exchangers: These heat exchangers are mainly used in the oil, gas & chemical industries. An advantage of these heat exchangers is that they are highly durable and ideal for transferring corrosive liquids or reaching high heat temperatures.
What are the different types of heat exchangers?
There are different types available, including:
- Shell and Tube – This is the oldest type of heat exchanger and is still widely used today. The tubes pass through a shell, transferring heat by either convection or conduction between them.
- Plate – These types of exchangers use plates with fluid passages between them.
- Brazed plate – These are also known as fin-and-tube heat exchangers. They have fins attached to the plates and tubes joined by brazing. The fluids pass over the fins and through tubes to transfer their heat.
Plate type heat exchanger manufacturers
Just a small selection of plate type heat exchanger manufacturers;
I hope this article has provided some insight into plate heat exchangers and how they work.