What is the primary purpose of the preheating coil used in hot air balloons?

The primary purpose of the preheating coil in hot air balloons is to vaporize the fuel, which leads to more efficient burner operation. When the fuel is vaporized before it enters the combustion chamber, it can mix more thoroughly with air, resulting in a more efficient and stable flame. This is crucial for maintaining the effective heating of the air inside the balloon's envelope, enabling controlled ascent and descent.

In hot air balloons, the burner typically uses liquid fuel, which needs to be vaporized to ensure proper combustion. By employing a preheating coil, the liquid fuel warms up before reaching the burner, thereby reducing any chances of incomplete combustion that could result from using cold fuel. This process increases the overall efficiency of the burner and contributes to better performance and safety of the hot air balloon during flight.