Heat exchanger types
We are in the process of finding out about heat exchangers. Heat exchangers transfer heat between two or more fluids—liquids, vapors, or gases—of different temperatures. Depending on the type of heat exchanger used, the heat transfer process can be gas-to-gas, liquid-to-gas, or liquid-to-liquid. It may occur through a solid separator, which prevents mixing of the fluids, or through direct fluid contact.
Other design characteristics—such as construction materials, components, heat transfer mechanisms, and flow configurations—also help classify and categorize the types of heat exchangers available.
Let’s start by talking about two heat exchanger parts:
1. Tube Plate Heat Exchanger –
This heat exchanger uses tube sheets to hold steel tubes. Hot or cold fluids transfer heat as they flow through or around the tubes. This type dominates both small and large applications. Examples include heat pumps, car radiators, gas heaters, air conditioners, and other heat exchanger units.
2. Plate Heat Exchanger –
A heat exchanger with plates as the heat transfer device is known as a plate heat exchanger. They consist of stainless steel or aluminum plates with corrugated grooves on one side where heat travels to or from fluids with internal tubes for fluid flow between each pair of adjacent plates. These are often used in small-scale applications such as refrigeration systems.
Let’s now look at the various types of heat exchangers—gas-to-gas, liquid-to-gas, liquid-to-liquid—and how they work:
3. Gas-to-Gas heat exchangers –
heat exchangers that transfer heat between two gases are known as gas heat exchangers. These heat exchangers can be vertical or horizontal and can be cylindrical or triangular in shape.
4. Liquid-to-Gas heat exchangers –
this type of heat exchanger transfers heat from a liquid to a gas by allowing the liquid to flow through tubes and the gases on either side of them, separated by a solid wall surface such as metal plates or tube sheets.
5. Liquid-to-Liquid heat exchangers –
This type of heat exchanger is especially important because we commonly find it in air conditioners, cooling systems, heat pumps, and heaters.
6. Plate and Shell heat exchanger –
This uses a large number of metal plates placed closely together with some free space left between them to allow the fluid to flow through them. The heat is transferred through the plates which are either welded or bolted together.
In the case of plate heat exchangers, the two fluids—hot and cold—flow on either side of each plate resulting in heat transfer from one side to another whereas in shell and tube heat exchangers, both fluids flow around a common enclosed volume called a shell.
In addition, there are several other types of heat exchangers based on how they work:
7. Coil heat exchanger –
a coil heat exchanger is a type of heat exchanger that uses heat transfer fluid flowing through a closed-loop tubing system contained inside or outside heat exchangers.
8. Coil and shell heat exchanger –
This heat exchanger encloses a coil heat exchanger within a larger heat-conducting metal shell, which holds the cooling medium—such as water or oil—and additional heat-dissipating hardware like fans to further cool the exterior walls.
9. Air-to-air heat exchangers –
these are used mainly for ventilation at homes, commercial buildings, and industrial plants.
10. Plate fin heat exchanger –
this heat exchanger uses two sets of metal plates with corrugated fins between them to increase the heat transfer surface. This heat exchanger is commonly found in car radiator systems where the coolant enters at one end and heat is transferred through successive plates towards the other end while heat dissipates out of the system through heat sinks (fin type heat exchangers) attached to one side of each plate.
Other types – there are several other types of heat exchangers including spherical-tube heat exchangers (STHX), plate-fin/tube bundle heat exchangers, interleaved fin-and-tube arrangements, etc., depending on how they work and their application fields. In addition, there is also a type called an induced draft heat exchanger, which is used for explosively hazardous environments.
These heat exchangers transfer heat using fluids inside corrugated tubes attached to plates, rather than solid metal plates or internal tubing. They are mainly used for heating in solar heaters and geysers. In these systems, heated water flows up through the corrugated tubes, while colder surrounding air enters from the other side at lower levels. This arrangement can result in less efficient heat transfer.
11. Stacked plate heat exchangers –
Manufacturers stack smaller heat exchangers together, each containing different heat-transfer fluids on either side of a common wall, to increase surface area for better heat transfer. Adding fins between or around the plates further enhances efficiency.
12. Tubular heat exchangers –
Heat exchangers transfer heat by passing fluids through tubes inside a housing, with cool fluid entering from the bottom and hot fluid exiting at the top for efficient heat transfer.
13. Other types –
Other heat exchangers include shell-and-tube heat exchangers, finned-tube bundles, and spiral-fin heat exchangers. Each type has specific applications in various industries, depending on how it handles different fluids to perform its functions effectively.
Keeping this basic information about heat exchanges in mind will help you understand more about them in depth further when we go into heat exchanger types and their applications in various industries.