How is fuel heated in the Challenger 300/350 aircraft?

Fuel in the Challenger 300/350 aircraft is heated using a system that incorporates the engine oil cooler and a fuel heat exchanger. This process involves directing fuel through a heat exchanger that is connected to the engine's oil system. As the fuel passes through the heat exchanger, it absorbs heat from the engine oil, which has been warmed during the operation of the engines. This method is efficient because it utilizes existing engine systems to manage temperature, helping to prevent fuel from becoming too cold, especially at high altitudes where temperatures can drop significantly. Properly heated fuel is essential for maintaining optimal engine performance and preventing issues such as fuel gelling.

The other options, while they might be relevant in different contexts or aircraft, do not reflect the specific heating method used in the Challenger 300/350. For example, an electric heater is not typically employed for heating fuel in this model, nor is combustion heating, which would not be a practical or safe method for fuel management in aviation. Circulating hot air from the cabin is also not a mechanism used for heating fuel directly in this aircraft design.