Plate Heat Exchangers

What Is A Plate Heat Exchanger?

The design of the plate heat exchanger consists of multiple heat transfer plates, consisting of a fixed plate and a loose pressure plate to form a complete unit. Each heat transfer plate has a spacer arrangement and provides two independent channel systems.

In its most basic form, a plate heat exchanger consists of corrugated metal sheets compressed in a frame. Hot and cold media flow on either side of the plate and transfer heat in a complete countercurrent flow arrangement. Each plate is equipped with a dual sealing system that keeps fluid between the channels. The corrugated plates create turbulence in the fluid as it flows through the device, and this turbulence gives the plate heat exchanger an effective heat transfer coefficient.

Plate heat exchanger operation is characterized by high heat transfer efficiency, compact size, flexible design, less construction (due to plate turbulence), and low life cycle costs. Typical heat transfer coefficients for plate heat exchangers may be four to five times higher than for shell and tube designs. The compact heat transfer area in the plate heat exchanger results in an efficient design with space requirements as low as 10% of typical shell and tube designs. Some designs are modular, allowing each part of the plate heat exchanger to be changed as needed. With these designs, users can add or remove boards in the field for new tasks, or even change frame components to accommodate expanded capacity requirements.

The Working Principle Of The Plate Heat Exchanger

Heat Transfer Theory: The laws of physics always allow the driving energy in a system to flow until equilibrium, where the heat dissipates when there is a temperature difference. Heat exchangers follow the principle of equalization. With a plate heat exchanger, heat travels across the surface and separates the hot medium from the cold medium. Thus, heating and cooling fluids and gases use minimal energy levels.

The theory of heat transfer between a medium and a fluid occurs when:

• Heat is always transferred from the hot medium to the cold medium.

• There must always be a temperature difference between the media.

• The heat lost by the hot medium is equal to the heat gained by the cold medium.

Application Of Plate Heat Exchanger

Different types of plate heat exchangers have many potential applications, including pasteurizers, beverage processing, coolers, connectors between boilers and cooling towers, and other process engineering applications. A plate heat exchanger is a modular system that provides excellent heat transfer at a fraction of the size of most conventional designs. Plus, it provides an instant supply of water and most other liquids while maintaining the appropriate setpoint temperature within 1°C or 2°C for your specific application.

In addition, the standard practice for using plate heat exchangers is to use plate heat exchangers as splits in central heating systems to protect expensive equipment such as commercial boilers. Plate heat exchangers are used in these systems to split the central heating system into two circuits, one dedicated to the boiler and the other to the radiator and associated equipment. The general concept behind a central heating system outage is to split the heating into two circuits so that any sediment floating in the old heating system does not damage or shorten the life of an expensive boiler.

Types Of Plate Heat Exchangers

• Gasketed Plate Heat Exchangers: Use high-quality gaskets and designs to seal the plates together and prevent leaks. Plates can be easily removed for cleaning, expansion, or replacement, greatly reducing maintenance costs.

• Brazed Plate Heat Exchanger: This type of heat exchanger is used in many industrial and refrigeration applications. The heat exchanger consists of stainless steel plates brazed with copper, so it has high corrosion resistance. Brazed plate heat exchangers are efficient and compact, making them an excellent economical choice.

• Welded plate heat exchanger: This type of heat exchanger is similar to a gasket plate heat exchanger, but its plates are welded together. This heat exchanger is extremely durable and ideal for conveying fluids with high temperatures or corrosive materials. Since the plates are welded together, mechanical cleaning of the plates is not an option for plate and frame heat exchangers.

• Semi-welded plate heat exchanger: This heat exchanger is a mixture of welded and gasketed plates. They consist of two plates in pairs welded together, which are then sealed to the other pair of plates. Thus one fluid path of the semi-welded plate heat exchanger is welded and the other fluid path is sealed. This results in a semi-welded plate heat exchanger that is easy to service on one side, while the other side can transmit more intense fluids. Semi-welded plate heat exchangers are ideal for transferring expensive materials as they have a very low risk of fluid loss.

Advantages Of Plate Heat Exchangers

• High heat transfer coefficient: For the same fluid, the heat transfer efficiency of the plate heat exchanger is much higher than that of the shell and tube heat exchanger.

• Low Cost: Low capital investment, low installation costs, limited maintenance, and operating costs.

• Compact design: Because the plate heat exchanger has a high heat transfer coefficient, it has the same heat capacity as the shell and tube heat exchanger, and the size is 20% of the shell and tube heat exchanger.

• Easy maintenance and cleaning: Plate heat exchangers can be disassembled individually for easy cleaning and maintenance.

• Easy capacity expansion: Because of the unique design of the plate heat exchanger, it is easy to add or remove plates to expand or reduce their heat transfer capacity.

• Temperature Control: Plate heat exchangers work well with a small temperature difference between the hot and cold fluids.

• High reliability: Low energy consumption in most processes and the ability to reduce dirt, stress, wear, and corrosion.

Disadvantages Of Plate Heat Exchangers

• Potential for leaks: Although the design of plate heat exchangers allows the plates and the gaskets between them to be firmly clamped together, there is still greater potential for leaks compared to shell and tube heat exchangers.

• Higher pressure drop: Narrow passages for fluid flow result in a high overall heat transfer coefficient, but also higher pressure drop, requiring higher pumping costs than shell-and-tube heat exchangers.

Not suitable for large fluid temperature difference: In the case of the large temperature difference between the two fluids, the plate heat exchanger does not work as well as the shell and tube heat exchanger.

Not very effective at very high fluid temperatures: Gaskets impose temperature limitations on the plate heat exchanger.

Pressure-limited use: the general use pressure does not exceed 1.5MPa.

Small flow path: not suitable for gas-to-gas heat exchange or steam condensation.

High incidence of clogging: For situations where there are suspended solids in the fluid, it may clog the pipe.