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Heat Exchanger: What Exactly Is It and How Does It Function?

Many homeowners do not know what a heat exchanger does, but they are pretty familiar with the air conditioning systems that use them. Put simply, a heat exchanger is a device that transfers heat from one medium to another. In HVAC applications, it will transfer the heat from an air stream to the refrigerant in the system.

How Does a Heat Exchanger Work?

Heat exchangers work by transferring the heat from one fluid to another. The fluid enters the system in a gaseous state, becomes liquid when cooled by the refrigerant and exits the heat exchanger in a liquid state. The metal tubes contain the gas that is exposed to the evaporator while the shell transfers heat to or from the refrigerant.

Primary Heat Exchanger

This part contains a tube arrangement that is responsible for contacting the ambient air and transferring heat. This portion of the exchanger contains tubes with an outer refrigerant coil to transfer the heat from outside air to inside air.

Secondary Heat Exchanger

Secondary heat exchangers are generally constructed of stainless steel or coated steel that can endure heat, moisture and acid. They are responsible for transferring heat to or from the liquid refrigerant.

4 Types of Heat Exchangers

There are several types of heat exchangers used in air conditioning and refrigeration systems. The type of system and the number of heat exchangers in it determine which heat exchanger is used.

1. Double Tube Heat Exchangers

Double tube heat exchangers are the most commonly used in residential systems. They have two parallel tubes with fluid flowing through them. There are two tubes so that a differential pressure can be maintained across them. This means there is high pressure on one side and low pressure on the other. An evaporator cools the air or gas on the high-pressure side before it enters the heat exchanger. The refrigerant passes through tubes in the heat exchanger and absorbs heat from the air on the low-pressure side. The refrigerant is then sent to an expansion valve. It enters a low-pressure evaporator where the heat is removed and the refrigerant returns to high pressure for another pass through the heat exchanger. Although this type of heat exchanger is simple and cost-effective to produce, it has one major design flaw. The entire air stream passes through the tubes in the heat exchanger, and the velocity of the air is reduced as it goes through, which can lead to downdrafts and vortex conditions that affect distribution.

2. Shell and Tube Heat Exchangers

The most common type of heat exchanger used in commercial systems is the shell and tube heat exchanger. The best example of this would be the heat exchanger used in the air conditioning unit of your automobile. The “shell” of this type of heat exchanger consists of tubes that the refrigerant flows through. The refrigerant is surrounded by a tube sheet and fins to dissipate heat. The “tube” portion of this type of heat exchanger comprises the tubes that contain the evaporator coil and condenser coil. These also provide a pressure drop to help move the refrigerant through the system. Heat is transferred to the refrigerant in the shell of the heat exchanger from air or gas on one side and from a fluid such as water on the other. The fluid is heated by a heat exchanger connected to a boiler or similar system and can also be heated by solar panels or other energy-producing systems. Handled in this way, the fluid can be used to heat a building in the wintertime and provide cooling during the summer.

3. Plate Heat Exchangers

Plate heat exchangers are used in industrial processes where cooling is critical. This type of heat exchanger uses huge plates that are stacked vertically, with refrigerant flowing between them. The plates are made of thin metal sheets that provide a large surface area for heat transfer. Plate heat exchangers are commonly used in the chemical and petrochemical industry. They also find use in district heating systems where the ability to transfer large amounts of heat is critical to the system’s success.

4. Tube in Tube Heat Exchangers

A tube in tube heat exchanger, also known as a split tube heat exchanger, is the most common type used for air conditioning and refrigeration applications. In this design, the refrigerant flows from one set of tubes around a tube sheet to another set of tubes through a finned tube that contains the evaporator coil. As the refrigerant passes through the finned tube, heat is transferred to and from it as the air passes through the fins. This type of heat exchanger has several advantages over other configurations. Because it uses two sets of tubes, there is no pressure drop across the heat exchanger, which means it can be used at higher pressures. The design of this type of heat exchanger also reduces the potential for vortexes and downdrafts.

What Are the Best Materials for a Heat Exchanger?

The best materials for manufacturing heat exchangers include aluminum, titanium and copper. The use of these metals makes the manufacture of products derived from them cost-effective and the products themselves durable. These heat exchangers can also last for a long time because they do not wear out quickly. Consequently, they an ideal choice for commercial use. Ceramics, composites (based on either metals or ceramics) and even plastics are all possible materials for heat exchangers. The more durable the heat exchanger is and the longer it lasts, the better. These materials are prevalent in commercial applications where heat exchangers are used to heat and cool fluids. If you have an application where you need a custom heat exchanger or need to upgrade the one you have, there are a few things to factor in. You should look at the best materials for heat exchangers and ensure they provide a good balance between ease of manufacture and high performance. You also need to make sure they meet the standards for your application. So, if you need a custom heat exchanger for anything from an air conditioning system to a solar thermal system, you ought to determine the best materials for that particular application. Look at your options carefully and make sure you choose a heat exchanger that meets your specifications and needs. Installing a heat exchanger in your home or building is a great way to save money on heating and cooling costs. Heat exchangers draw heat from the air or ground and transfer it to or from the air inside your home or commercial property. This process can make your building more energy efficient and save you money on heating and cooling costs all year round, but it is most effective in the summertime when you need to cool your home. If you’re located in Lake Forest, CA, or anywhere in the surrounding areas, contact Dynamic Air Services today to learn more about heat exchangers, how they work, and which one is right for you. We perform a complete array of heating, cooling, indoor air quality and ductwork repair, installation and maintenance for both residential and commercial customers.
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