Understanding the Role of Heat Exchangers in Heating Systems

Heat Exchangers are often overlooked in our everyday lives, but they play a vital role in the operation of heating systems. Whether it is your furnace, car radiator, or refrigerator, all of these are heat exchangers.

A heat exchanger transfers thermal energy between two streams without the fluids mixing directly with each other. They are also commonly used in industrial processes and appliances.

What is a Heat Exchanger?

A heat exchanger is a device that transfers thermal energy between two fluids, which can be either liquids or gases. Heat is transferred through conduction, convection or radiation.

In the case of your home furnace, it transfers heat from combustion gases to a mix of warm and cold air that makes it comfortable for your family. Heat exchangers also protect your house from carbon monoxide poisoning by separating flue gases from the air you breathe.

Plate-and-frame heat exchangers are comprised of flat metal plates that create broad, parallel channels that hot and cold fluids flow through. The plates may be separated by gaskets or welded together in a pattern that promotes high flow turbulence, which allows for greater heat transfer efficiency.

The plates can be designed in many configurations, including counterflow, crossflow or U-shaped. For maximum heat transfer efficiency, a multi-pass design is sometimes used, where fluids enter the exchanger in opposite directions and exit it at different ends for multiple “passes” within the exchanger.

What Is a Plate Heat Exchanger?

A plate heat exchanger transfers thermal energy between two fluids without the fluids mixing together. It does so by separating the cold and hot fluids into separate circuits. It is used for heating and cooling, as well as condensation.

Often, they are made of stainless steel and have rubber sealing gaskets cemented into a section around the edge of each plate. The troughs on the plates increase turbulence and therefore help with heat transfer. They also have an extremely large surface area, which allows for fast flow rates.

Each plate is stamped with various metal patterns that aid the thermal conduction. They are then stacked together in a frame and gasketed in the corners to prevent the hot medium from flowing into spaces between adjacent plates.

The plates are usually brazed or welded together, making them more durable and suitable for higher pressure systems (although over tightening of the bolts can damage the corrugations and squeeze out the gaskets). They are often used for corrosive or toxic flowing media that cannot be handled with traditional shell and tube heat exchangers.

What Is a Tube Heat Exchanger?

A tube heat exchanger has a bundle of tubes that contain the substance that must be heated or cooled. The service fluid, typically water, ice water, or glycol, runs around the tubes. Heat is transferred from the tube to the product fluid through counter current flow or cross-flow depending on the design.

These are robust devices that can be built with many custom features to suit specific applications. They may be corrugated or smooth and can have either a fixed shell or floating head. They also require strict cleanliness of the product feed to prevent fouling.

This is one of the most common types of heat exchangers used in homes and other small buildings. It is efficient and works well in a wide range of temperatures, making it an excellent choice for air conditioning systems. It is crucial to make sure the vents are open so air can circulate properly and not block the heat exchanger.

What Is a Fin Heat Exchanger?

A fin heat exchanger is a series of tubes that have been added with fins to increase the surface area and accelerate the flow of air or other gas. The airflow in a fin heat exchanger is usually crossflow, but it can also be counterflow or parallel flow.

The fins of a plate-fin heat exchanger are designed with several factors in mind, including tube diameter and flow rate. It’s important to consider these factors in order to ensure proper heat transfer between fluids and minimize pressure loss and the formation of dead zones.

There are many different types of finned tube heat exchangers, and the best one for you depends on your particular requirements. Some examples include a low-, medium- or high-fin count, enhanced or formed dimpled surfaces, and varying lengths. These variations can help you achieve a specific heat transfer capability that will match your needs.