What does a fuel heat exchanger do?

A fuel heat exchanger plays a crucial role in regulating the temperature of fuel before it is injected into the engine. It is essential for preventing icing, which can occur when the fuel is too cold, particularly in high-altitude operations where temperatures can drop significantly. When fuel flows through the heat exchanger, it can absorb heat from the engine or another warm medium, ensuring that it remains at a temperature that promotes optimal combustion and prevents the formation of ice crystals. This function is vital for maintaining the efficiency and reliability of the aircraft's fuel system, especially in varying environmental conditions.

The other options do not accurately describe the primary function of a fuel heat exchanger. Increasing the volume of fuel before injection, making fuel lighter, and filtering impurities pertain to different aspects of fuel management systems but are not the primary focus of a heat exchanger. A fuel heat exchanger's main purpose is to maintain appropriate fuel temperatures to ensure smooth engine operation and prevent icing issues.