What is the purpose of a heat exchanger in an HVAC system?

The primary function of a heat exchanger in an HVAC system is to transfer heat between two or more fluids without allowing them to mix. This mechanism is crucial for the efficient operation of heating and cooling systems. In a heat exchanger, one fluid absorbs heat from another without the two fluids ever coming into direct contact. This enables systems to maintain the required temperatures for both the heated and cooled spaces while efficiently using energy.

In heating applications, for example, a heat exchanger allows warm air or water to heat up cooler air or water indoors without contaminants mixing. This is essential for maintaining air quality and system efficiency. In cooling applications, it helps dissipate the heat absorbed from the indoor air into the outside environment, again without mixing the refrigerant with the ambient air.

The other options do not accurately depict the primary function of a heat exchanger. Mixing different types of fluids or simply cooling fluids isn't the main focus of a heat exchanger. Additionally, increasing the pressure of the refrigerant is typically accomplished in other components of an HVAC system, such as the compressor, and is not a function of the heat exchanger itself.