How does a heat exchanger work?

We benefit from their presence on a daily basis without even realising it. From heating systems to the radiators in our cars and also refrigerators, heat exchangers are everywhere. But how do they actually work?

Contrary to what its name might suggest, a heat exchanger does not actually "exchange" heat. In reality, a heat exchanger transfers heat between 2 fluids of different temperatures (liquids or gases), without these fluids mixing.

It should also be noted that heat exchangers have multipurpose functionality. Their primary use is not limited to heating a fluid. In fact, depending on the system in which it is integrated, a heat exchanger can also be used to cool a fluid, as in air-conditioning units or refrigerators.

How it works

How a shell-and-tube heat exchanger works.

1. Fluid separation

A heat exchanger is designed with 2 separate circuits, separated by a conductive wall. This separation enables 2 fluids to circulate without mixing, while enabling the transfer of heat between them. Different fluids can be used depending on the type of heat exchanger. This can be water, a heat transmission liquid, air, oil or steam.

2. Thermal circulation and exchange

The hot fluid circulates in one circuit, while the cold fluid circulates in the other. The temperature difference between these two fluids creates a thermal gradient. Heat moves naturally from the hot fluid to the cold fluid through the separating wall, in accordance with the laws of thermodynamics.

3. Transfer optimisation

The efficiency of a heat exchanger is maximised through its design. This includes the choice of conductive materials (copper, stainless steel, aluminium and steel are often used), the flow configuration (counter-current, co-current or cross-flow), and maximising the exchange surface.

Heat exchanger types

There are several types of heat exchanger, each suited to specific needs. The most common types are plate, tubular and finned heat exchangers Each type offers advantages in terms of efficiency, compactness and ease of maintenance.

Plate heat exchanger

Composed of thin stacked plates, it offers a large heat exchange surface and excellent thermal efficiency. It is often found in heat pumps for example.

Tubular heat exchanger

This type of exchanger uses fins to increase the exchange surface. The cooling fluid is usually ambient air, as in vehicle radiators or computers.

Finned heat exchanger

This type of exchanger uses fins to increase the exchange surface. The cooling fluid is usually ambient air, as in vehicle radiators or computers.

Other heat exchangers

there are many other types of heat exchanger, such as spiral heat exchangers for industry, serpentine heat exchangers for hot water tanks, or rotary heat exchangers for heat recovery in ventilation systems.

From homes to industry

Heat exchangers are essential components in many applications, from domestic comfort to the optimisation of industrial processes.

• In the field of heating, they can be used to heat air or produce domestic hot water by recovering the heat generated by heating systems.
• They are essential for the operation of refrigeration systems, air-conditioning units and heat pumps.
• In the automotive sector, heat exchangers are essential for engine operation, cooling both the coolant and oil.
• Power plants also rely on these systems to efficiently convert thermal energy into electricity.
• Industry uses heat exchangers to optimise production processes and improve energy efficiency. They recover heat that would otherwise be lost, contributing to significant energy savings.

A key technology for a sustainable future

The importance of heat exchangers will only increase in the future, particularly in the context of the energy transition and the quest for greater energy efficiency.

Innovations in this field will continue to play a key role in the development of sustainable and environmentally-friendly technologies.