What is a Heat Exchanger?

A heat exchanger is a piece of equipment designed to efficiently transfer heat from one source to another. The heat exchanger may exist in two different states: direct contact or separated by a solid wall. You will find a heat exchanger in many devices including a space heater, air conditioner, chemical and power plants, petroleum refineries, natural gas processing plants, petrochemical plants, sewage treatment centers and refrigerators. A car's engine is probably the most common example of a heat exchanger, represented by the radiator. The heat source in a car is the engine, and the cooling fluid is the water inside the radiator. This water transfers the heat from the hot engine through the radiator. Read on to learn more about the heat exchanger and its uses.

The Purpose of a Heat Exchanger

A heat exchanger is installed within the equipment used for heating and cooling. Once the unit is hot, the heat is transferred to the heat exchanger, which then heats another liquid that produces the heat. A forced air heating system is a good example of a heat exchanger in action. An even better example is a home radiator. The heat is produced from a water heater and is transferred through a heat exchanger and sent to the radiator. As a result, the radiator becomes hot and warms the room.

Flow Arrangement of the Heat Exchanger

There are 3 primary arrangements in how the heat exchanger handles the flow of liquid.

  1. Counter flow - The most efficient way to handle the flow of liquid. The two liquids enter the heat exchanger at the same time from opposite sides. This flow arrangement transfers the most heat.
  2. Parallel flow - Has the two liquids entering the heat exchanger from the same end. The liquids run next to each other and the heat transfer over as they move to the other end.
  3. Cross flow - Moves the liquids perpendicular to each other.

Heat Exchanger Designs

A heat exchanger can be found in 4 main designs: plate, regenerative, intermediate fluid or solid and shell and tube. The shell and tube design is the typical heat exchanger you'll find. The shell and tube design features tubes with multiple fins. One fluid goes through a tube while another fluid flows over the tube.

A plate heat exchanger has a fluid running over baffles which cause the fluids to separate. The plate heat exchanger is more efficient than shell and tube. A regenerative heat exchanger uses heat from a specific process to heat the fluid. The intermediate heat exchanger uses a fluid or solid within itself to hold heat and then transfer it to the other side to be released.