A Beginners Guide To Heat Exchangers

What is a heat exchanger? The term “heat exchangers” means little to many people unless you are in the business of HVAC, process heating or cooling, or other industrial applications. However, whatever your understanding of heat exchangers, one thing is always true.

Maintaining the operating temperatures of office environments or industrial fluids is vital to comfort and manufacturing alike.

Many businesses require specific environmental conditions for the work they do, others need to maintain fluid temperatures for process-based manufacturing and production. This is where heat exchangers come in and their ability to cool or heat rooms or processing systems as required to maintain environmental conditions and operational efficiencies.

Heat transfer equipment can perform several essential functions in both heating and cooling. Sometimes, these systems can capture heat and direct it elsewhere, like outside air to dispose of it, or to other applications needed to increase efficiency and save money. Other heat exchangers keep machinery or chemicals used in processing within safe operating temperatures.

It’s vital for building operations, plant, and facilities managers to understand the different types of heat exchangers available for their needs to help them select the right system for their application. It is equally important to understand how to properly maintain it to ensure maximum lifespan and efficiency.

What is a Heat Exchanger?

Heat exchangers transfer thermal energy from one medium to another (liquid, vapor, or gas).

Two main types of heat exchangers exist:

• Direct heat exchangers: Both mediums come in direct contact with each other in these systems. For example, a cooling tower cools water via direct contact with air.
• Indirect heat exchangers: These systems heat and cool through divided media.

One of the most common scenarios in facilities and processing operations is situations that require heating or cooling. Heat exchangers are commonly used in refrigeration, air conditioning, power plants, chemical processing systems, manufacturing, waste heat recovery units, and food processing applications.

How do Heat Exchangers Work?

Heat exchangers rely on the equalization principle to transfer heat between mediums and fluids. Heat transfer occurs when:

• Heat transfers from a hot to a cold medium.
• A temperature difference exists between mediums.
• Heat lost from the hot medium equals heat gained by the cold medium.

What Types of Heat Exchangers Exist?

Many technologies can remove heat from materials. However, when referring to “Heat Exchangers,” most people equate them to one of two categories.

• Shell-and-tube heat exchangers or;
• Plate-and-frame style heat exchangers.

What is the Difference Between a Shell and Tube Heat Exchanger, and a Plate and Frame Heat Exchanger?

Example of Fluid Flow in a Shell and Tube Heat Exchanger

A shell-and-tube heat exchanger allows two working fluids to exchange heat via thermal contact between tubes housed within a cylindrical shell. The fluid temperatures inside the shell and tube differ; this temperature difference drives temperature exchange.

Some simple examples of shell and tube heat exchangers include boilers, which heat water via tubes that contain combusted materials. Another includes a chiller that uses chilled refrigerant to transfer heat from the water to chill it for use in HVAC or process cooling applications.

On the other hand, a plate-and-frame heat exchanger uses a series of corrugated plates assembled between a frame and pressure plates to retain pressure and transfer heat. Hot fluid flows in one direction through alternating chambers, while cold fluid flows through other alternating chambers. Heat transfer occurs as the hot and cold fluids move through these chambers.

Though both types are readily available, we will center our discussion on plate-and-frame heat exchangers, as they are among the most common heat exchangers in use today.

Example of Fluid Flow in a Plate and Frame Heat Exchanger

Plate-and-frame heat exchangers perform liquid-to-liquid exchange at low to medium pressures. Another option is a gasket-free plate-and-frame heat exchanger, which operates safely at high temperatures and pressures.

Plate-and-frame heat exchangers accomplish heat exchange and resist fouling through a design that comprises corrugated plates on a frame. Fluids travel within the heat exchanger as hot fluid flows down one plate and cold fluid flows up the other plate.

What are the Advantages of Plate Heat Exchangers?

Plate heat exchangers offer key advantages.

• Precise heat transfer. Users can add or compress heat plates to accommodate a specific heating and cooling situation.
• Low capital costs. Plate heat exchangers are inexpensive to add and install and have limited maintenance, cleaning, and operating costs.
• High reliability. Plate heat exchangers experience less fouling, stress, wear, and corrosion.
• These systems consume the least energy and produce the most significant effect.
• Easy to expand. Adjustable plates on existing frames make it easy to expand capacity.

Gasketed plate heat exchangers differ slightly from traditional plate heat exchangers. These systems use gaskets to seal plates together, which keeps cold and hot fluids from mixing and protects against leaks.

Gasketed plate heat exchangers also may use brazing or laser welding as an alternative to traditional gasket seals. This allows technicians to stack plates alternatively to counter current flow. The design lets two fluids flow in opposite directions without mixing while heat transfers from one medium to the other through plates.

Gasketed plate heat exchangers are easy to clean, making them particularly useful in food and pharmaceutical processing or other areas that require high sanitation. It’s a straightforward process to remove plates for cleaning, expansion or replacement.

Next Steps

Heat exchangers play an essential role in cooling or heating rooms or processing systems as required to maintain environmental conditions and operational efficiencies. Once facility managers understand their purpose, they can determine the best ways to apply plated heat exchangers in their facility or processing operation. A Goodway Sales Engineer can help guide you with heat exchanger selection and, once the systems are in place, help you maintain the heat exchangers over their lifespan with Goodway descaling systems and solutions. Click here to see a full line of Goodway descaling products.

The first step is to choose and implement the right heat exchange solution for your needs. Maintaining the heat exchanger over time is critical. Otherwise, it will lose its heat exchange abilities and end up costing most to operate. Part II in this two-part blog series will address how to maintain various types of heat exchangers to maximize their lifespan.