What are the Different Types of Heat Exchangers?

A heat exchanger is a device that helps with heat transfer involving two fluids in different compartments. Usually, there’s a temperature gradient between the two fluids. PPS Professional Process Systems heat exchanger systems have numerous applications. These include heating and air conditioning systems, chemical processing systems, evaporators, and many more.

The following are the different types of heat exchangers available:

1)Shell and Tube Heat Exchanger

Contrary to popular beliefs, heat sealers and heat exchangers are two completely different things.

This type of heat exchanger gets its name from the fact that it has several tubes. The shell and tube heat exchanger helps to facilitate heat movement between fluids flowing through different tubes. Usually, the fluids flow through a bundle of tubes encased in a large shell vessel surrounding the entire bundle. The bundle of tubes inside the shell vessel helps process fluids that are more viscous or those containing more particles. The shell and tube heat exchanger is better at doing this than several other types of heat exchangers.

The heat exchanger has undergone significant modifications to its design, mainly because of its many applications. These modifications aim to ensure it meets specific application specifications. Examples of these modified versions include:

i)Annular models: These heat exchangers are typically made of three to four concentric layers of tubes. They apply heat contemporaneously from the outside and inside. This helps to avoid layering.

ii) Monotube heat exchangers: These are also called jacketed tubes or tube-in-tube heat exchangers. They are made of an external shell containing a single tube inside. These designs are more appropriate for heat-treating products that may have a high-fiber content, pulp content, or large particles.

iii) Single Tubesheet Design: Here, the tubes are held in place at one end of the shell by a large, round metal sheet (tube sheet). The tube sheet contains holes where the tubes can be anchored. Tubesheets cap one end of the shell once you put the tubes inside. The capped side of the shell ensures that cooling or heating fluids remain there.

2) Plate and Frame Heat Exchanger

This type of heat exchanger is made up of corrugated plates placed parallel to each other. A gasket is used to separate them. These gaskets help control the flow of cold and hot fluids as they pass across the plate surfaces.

Tightening bolts are used to keep gasketed plates compressed, with a frame plate and pressure plate on either side. Lower and upper guiding bars provide the space between which the pressure plate and gasketed plates suspend.

Hot and cold fluids flow in alternating directions as heat transfer occurs from the warmer conduit to the cooler one. The whole design is simple enough, making it easy to remove or add plates. This makes cleaning easier than in other types of heat exchangers.

The plate and frame heat exchanger is optimal for heating fluids of low or medium viscosity. This is because the plates and their corrugated design create adequate turbulence for fluid movement. Plates that are spaced more widely are better for more viscous fluid, helping to maintain the needed flow requirements.

3) Scraped Surface Heat Exchanger

This kind of exchanger is best for applications that need heat transfer to sticky products and highly thick (viscous) fluids. The scraping blades facilitate this by ensuring the products don’t settle on the internal surfaces.

At the bottom of the scraped surface tube, there is an opening through which the product enters the cylinder. Cooling or heating fluids move in a counter-current pattern in a cylinder enveloping the product channel. Since uniform heat transfer to the product can be a problem, the blades solve it by removing the product from the channel wall.

The scraping blades are designed to meet the different product requirements. Because quality is always essential, the material used for the scraping blade should never compromise quality and consistency. An electric motor powers the scraping blades using a rotor. The rotor is the attachment point for the scraping blades, enabling them to be mounted either vertically or horizontally.

The product and the rotors turn in the same direction as they move through the heat exchanger. This prevents damage to the product. A high polish on the inner surface should be achieved for better heat transfer.

Applications for scraped surface heat exchangers include:

i)Heat-sensitive products like cream cheese, fishmeal, and fruit purees.

ii)Particulate products like beef and poultry meat, rice pudding, and pet foods.

iii) Sticky products like caramel, gelatin, and toothpaste.

iv) Thick pastes like ketchup, mayonnaise, peanut butter, salad dressing, and shampoos.

Ultimately, the different types of heat exchangers are best suited for different products although technical modifications may be needed at times.