Your Buying Guide to Heat Exchangers

Thermal energy storage

You’ve heard of the phrase “heat exchanger.” You may know it refers to a process governed by the Second Law of Thermodynamics. And you may even know a common usage or two. But heat exchangers are known as a central part of many different mechanical objects, including one that is immediately recognizable.

Heat exchangers are used to transfer heat between two or more fluids, between a solid surface and a fluid, or between solid particulates and a fluid, at different temperatures and in thermal contact. The most apparent example is in your HVAC system: The air coils take hot air from the outside atmosphere and cool it down.

When it comes to the design of the heat exchanger, there are at least three worth noting, and they vary depending on the nature and timing of the flow of the liquids.

In cross flow heat exchangers, one fluid flows through the tubes and the second fluid passes around the tubes perpendicularly.

In parallel flow heat exchangers, both the tube side fluid and the shell side fluid flow in the same direction. In this case, the two fluids enter the heat exchanger from the same end with a large temperature difference.

If liquids in a heat exchanger pass each other more than once, the heat exchanger is called a multi-pass heat exchanger. If the liquids pass only once, the heat exchanger is called a single pass heat exchanger.

Heat exchangers have many application and heat exchanger designs can vary. Some general examples of the application of heat exchangers include the air cooled heat exchanger, the brazed plate heat exchanger, and the shell and tube heat exchanger.

A type of heat exchanger often found in the process industries are harpin heat exchangers. Harpin heat exchangers have been referred to as the G-fin, double-pipe, or multitube heat exchanger. Harpin heat exchangers are similar in design to the shell and tube heat exchanger. If you fold a single shell and tube heat exchanger on top of itself, you’ll see the “harpin” appearance.

Technological advancements have made the hairpin heat exchanger worth considering when searching for your next heat exchanger. A great deal has been advanced when it comes to closure of the heat exchanger and other elements, such as the sealing ring, have also been improved.

Before you buy a heat exchanger though, it’s important to consider the mechanisms and laws of physics behind it, so you know closer to what you need and will be looking for.

For instance, for the heat transfer to occur between two liquids, the two liquids must be at different temperatures and must come into thermal contact. Heat can only flow from hotter to cooler liquids. This is the Second Law or Thermodynamics.

Finally, know that at least one heat exchanger has a decades long life span: The shell portion of the shell and tube heat exchanger can last up to 40 years without corrosion or serious damage to the shell.

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