Imagine a world where industries can efficiently transfer heat between fluids without consuming excessive energy or space. What is a plate heat exchanger? It’s a device that has made this possible, revolutionising various sectors, from HVAC systems to food and beverage processing. Their compact design and high efficiency have led to widespread adoption, making them essential components in modern heat transfer systems. In this blog post, we will explore the inner workings of a plate heat exchanger, diving into its components, types, applications, advantages, and maintenance and troubleshooting.
Understanding How Plate Heat Exchangers Work
A plate heat exchanger (PHE) is a marvel of engineering designed to transfer heat between two fluids of disparate temperatures without mixing them. As one of the most widely used types of heat exchangers, its primary purpose is to facilitate heat transfer, which is essential in various industrial applications.
For clarity, plate heat exchangers are also known as;
- Plate-to-plate heat exchanger
- Plate-type heat exchanger
- Plate and frame heat exchanger
- Plate exchanger
- PHE heat exchanger
- Gasketed plate heat exchanger
- Gasket plate heat exchanger
- Plate frame heat exchanger
Shell and tube heat exchangers, air-cooled, plate, and frame heat exchangers are among the most popular types used in the mechanical industry. They are trusted for their high performance and long life. However, plate heat exchangers are highly regarded due to their compactness, efficiency, ease of servicing, and minimal maintenance requirements.
Plate Heat Exchanger Diagram
As the plate heat exchanger diagram below shows, plate heat exchangers are composed of a series of plates with gaskets to form an air-tight seal sandwiched between two frame ends held together by frame bars. The number of plates in a plate heat exchanger varies depending on the application.
Components of a Plate Heat Exchanger
A plate heat exchanger is composed of several components, including inlets, outlets, gaskets, heat exchanger plates, a carry bar, clamping bolts, a guide bar, and two covers. The end plates seal the plate heat exchanger, while the nuts and tightening bolts compress the frame corridor of the plate pack. The plate heat exchanger plates separate the flowing mediums and prevent them from mixing, ensuring the efficient transfer of heat between the fluids.
If you notice consistent issues with your plate heat exchanger, it might be time to evaluate the condition of your current components and invest in durable replacement plates for a more reliable solution.
Types of Plate Heat Exchangers
When it comes to plate heat exchangers, there is a variety to choose from, including plate, brazed, and welded plates, semi-welded, and plate and frame.
A plate heat exchanger is a type of heat exchanger that uses metal plates to transfer heat between two fluids. The fluids are exposed to a large surface area because the fluids are spread out over the entire heat transfer surface promoting efficient heat transfer.
The plates are fitted with gaskets that seal the channels and direct the fluids into alternate channels. The plate pack is assembled between a frame plate and a pressure plate, and it is compressed by tightening bolts fitted between these plates. The gasket controls the flow of the fluids and prevents them from mixing, making it possible to handle different pressure levels.
Pros of Gasketed Plate Heat Exchangers:
- Efficiency: Due to the large surface area, these heat exchangers are very efficient at transferring heat, which leads to energy savings.
- Compact Size: The design allows for a high heat transfer area in a small footprint, which can be beneficial in areas where space is limited.
- Flexible Design: The number of plates can be added or removed to increase or decrease the heat transfer area, providing high flexibility.
- Ease of Maintenance: The bolted design allows easy disassembly to clean, maintain, or replace heat exchanger plates and gaskets.
Cons of Gasketed Plate Heat Exchangers:
- Gasket Failure: Over time, gaskets may fail, causing leakage and contamination between the two fluids. The gaskets are subject to wear and tear and must be periodically replaced with a full regasketing service.
- Limited Pressure and Temperature: They can’t handle extremely high temperatures or pressure as compared to shell and tube heat exchangers.
- Fouling: The small gap between plates may cause fouling when dealing with fluids containing particles or when the fluid causes scaling. This can lead to a decrease in performance over time.
- Not Suitable for Viscous Fluids: These heat exchangers are less effective when used with highly viscous fluids, as these can cause pressure drops and reduced efficiency.
- Complex Design: While the flexibility of the design is a benefit, it also means these heat exchangers are more complex to design and assemble than some other types.
Brazed plate heat exchangers, on the other hand, are characterised by their compact design and excellent erosion resistance.
Plate and frame heat exchangers consist of corrugated plates in a frame and are used to transfer heat between liquid and liquid at medium to low pressure.
Semi-welded plate heat exchangers combine the features of both gasketed and welded plate heat exchangers, allowing one fluid to flow through the welded part and the other fluid flow through the gasket. The corrugated pattern in these exchangers facilitates lower points of contact, allowing for the unobstructed passage of liquids containing fibres or sludge.
Working Principles of Plate Heat Exchangers
How does a plate heat exchanger work? Plate heat exchangers work on the principle of thermodynamics, wherein two liquids flow on either side of a thin corrugated metal plate, facilitating heat transfer between the two. The design of these exchangers provides efficient heat transfer, as the large surface area of pressure plates enables more effective heat exchange through partial plates.
This design of plate exchangers also allows for a compact size, making them ideal for applications where space is limited. Additionally, plate heat exchangers are relatively inexpensive and easy to maintain, making them a popular choice for many industries.
Counter-current flow is the most efficient flow type for plate heat exchangers, as it allows for the exchange of heat content between fluids at different temperatures without mixing. The hot and cold mediums flow in alternating patterns, exchanging heat without mixing, making them more efficient than parallel flow heat exchangers.
In counter-current flow, the hot and cold mediums are in direct contact with each other, allowing for the most effective heat transfer. The primary benefit of counter-current flow heat transfer plates is their efficiency, making them the most effective means of transferring heat in a frame heat exchanger.
Corrugated plates are a crucial component in plate heat exchangers, as they create rectangular channels for fluid flow and heat exchange, with gaskets containing one type of liquid per plate. The plates are arranged to generate turbulence in the fluids as they pass through the unit, thereby providing an effective heat transfer coefficient.
Using corrugated plates in a frame heat exchanger produces high turbulence and wall shear stress, resulting in turbulent flow, elevated heat transfer and high fouling resistance. This design contributes to the overall efficiency and effectiveness of plate heat exchangers in various applications.
If you suspect your plate heat exchanger is blocked, check out our guide on troubleshooting a blocked gasketed heat exchanger.
Plate Heat Exchanger Applications
Plate heat exchangers are utilised in a wide range of industries, including HVAC, refrigeration, chemical processing, power generation, and food and beverage processing. They are also employed in oil refineries for water circulation cooling and waste heat recovery.
These versatile devices have demonstrated their value across various sectors, making them indispensable in today’s world.
In HVAC systems, plate heat exchangers play a vital role in transferring heat between air and water. Their efficient heat transfer capabilities make them an ideal choice over tube heat exchangers for HVAC and plumbing applications, where they are widely employed for the transfer of heat from one fluid to another.
The use of plate heat exchangers in HVAC systems has greatly improved the energy efficiency and overall performance of these systems. Companies such as SWEP specialise in brazed plate heat exchangers, with their equipment found in many types of heat recovery systems.
Food and Beverage Processing
Plate heat exchangers are extensively used in food and beverage processing for various purposes, such as pasteurisation of beverages, pasteurisation of cream and milk, and purification of other products. Their energy-efficient, reliable, and versatile nature makes them an ideal choice for the food and beverage industry, where they are employed for the transfer of heat from one fluid to another and have significantly improved the safety and quality of food and beverage products in the industry.
8 Common Applications for Plate Heat Exchangers
Plate heat exchangers are used in a variety of industries and applications. Some of the most common plate heat exchanger applications include:
- Food and beverage production – plate heat exchangers are often used in food and beverage production to pasteurize milk or make beer and wine.
- Cooling towers – plate heat exchangers can be used in cooling towers to transfer heat from the water to the air.
- Desalination plants – plate heat exchangers are used in desalination plants to pre-heat seawater before it enters the reverse osmosis process.
- Power generation plants – plate heat exchangers are used in power generation plants to condense steam from the turbine exhaust.
- Air conditioning systems (HVAC) – plate heat exchangers can be used in HVAC systems to transfer heat between the air and a fluid, such as water or oil.
- Refrigeration systems – plate heat exchangers can be used in refrigeration systems to transfer heat between the refrigerant and the air or water.
- Chemical processing – plate heat exchangers are often used in chemical processing to heat or cool chemicals.
- Shipping – Ships, including cargo and cruise vessels, use plate heat exchangers for thermoregulation. These marine heat exchangers primarily cool the engines through ‘central cooling’ and provide fresh water to cool onboard utilities.
Advantages and Disadvantages of Plate Heat Exchangers
Like any technology, plate heat exchangers come with their own set of advantages and disadvantages. Understanding these pros and cons can help users make informed decisions about their application and maintenance.
The high efficiency of plate heat exchangers can be attributed to their large surface area, which enables more effective heat transfer. Additionally, their robust construction, comprising multiple plates sealed together with gaskets, makes them resistant to high temperatures and pressures.
Furthermore, their design allows for easy access to the plates for cleaning and inspection, and the gaskets can be conveniently replaced when necessary. These advantages make them a popular choice in various industries.
Despite their many advantages, plate heat exchangers also have some drawbacks. One of the main disadvantages is the notable pressure drop and the higher heat transfer resistance of the sealing material.
Additionally, fouling can cause a decrease in heat transfer effectiveness and increase maintenance costs. It is essential to consider these disadvantages when selecting a plate heat exchanger for a specific application.
Maintenance and Troubleshooting of Plate Heat Exchangers
Regular maintenance is crucial for prolonging the lifespan of a plate heat exchanger and ensuring its optimal functioning. Proper maintenance involves cleaning and inspecting the plates, as well as replacing gaskets when necessary to avoid blockages and other issues.
Providing free space around the plate heat exchanger during servicing is also essential for proper maintenance.
At WCR UK we support many industries including food and beverage and marine and shipping.
Cleaning and Inspecting Plates
To clean the plates of a plate heat exchanger, either circulating appropriate chemicals through the unit or by removing heat plates and dismantling them for mechanical cleaning or dye penetrant testing can be employed. The plates should be cleaned with a soft non-abrasive cloth, water, and a cleaning agent and placed on a flat surface during cleaning to avoid bending the plate.
After cleaning, plates should be visually inspected and examined using a light to check for cracks and perforations.
Gasket replacement is a critical aspect of maintaining a plate heat exchanger, as it ensures that the two fluids do not mix and that the plate heat exchanger functions optimally. The process involves removing the used gasket and replacing it with a new one.
Timely replacement ensures the longevity and proper functioning of plate heat exchangers in various applications.
In summary, plate heat exchangers have revolutionised heat transfer in various industries thanks to their compact design, high efficiency, and ease of maintenance. With a range of types available, including gasketed, brazed, welded, semi-welded, and plate and frame, these devices have proven their versatility and usefulness in numerous applications. Despite some disadvantages, such as pressure drops and sealing material heat resistance, plate heat exchangers remain an essential component of modern heat transfer systems.
As technology continues to advance and industries strive for more sustainable and efficient solutions, plate heat exchangers stand out as a vital tool in meeting these goals. By understanding their components, working principles, applications, advantages, and maintenance, users can optimise their performance and contribute to a more energy-efficient and environmentally friendly future.
Frequently Asked Questions
What does a plate heat exchanger do?
A plate heat exchanger facilitates the efficient transfer of thermal energy between two mediums, allowing one to cool down and the other to heat up. Through this exchange process it enables effective use of energy, as hot and cold fluids are kept separately yet effectively connected.
In short, a plate heat exchanger helps in transferring heat energy from one medium to another.
Why are plate-type heat exchangers more efficient?
The plate-type heat exchanger is more efficient than a shell and tube design because it provides a larger surface area to exchange heat, resulting in greater efficiency. This increased surface area allows for better heat transfer area and of energy, making the plate-type exchanger more effective at transferring heat.
Consequently, it is the most popular choice amongst heat exchangers.
What is the difference between plate and coil heat exchanger?
The main difference between a gasketed plate heat exchanger and a coil heat exchanger is that a plate heat exchanger is much more powerful and efficient at generating hot water than a coil-type heat exchanger. Plate heat exchangers have larger surface areas and are capable of generating significantly higher output in terms of power, water flow rate, and pressure.
In contrast, a coil heat exchanger requires more time to warm up before it can achieve the desired output.
How does a heat exchanger work?
Heat exchangers are devices used to efficiently transfer thermal energy between two or more substances of different temperatures. They utilise metal shells and tubes which contain a hot fluid, which passes its heat to the cold fluid passing through the other side, thereby the temperature difference and transferring the heat energy between the two.
This process of heat transfer effectively cools the hotter substance while heating up the colder one.
How does a plate heat exchanger work?
A plate heat exchanger utilises a series of plates to transfer heat energy between two fluids. The hot medium passes through each plate, with the heat from the medium being transferred to the cold medium as it passes alongside it.
This efficient process requires minimal energy and maximises heat transfer, making it a reliable and cost-effective option for heating and cooling applications.