Final answer:
Large drop sprinkler heads are designed to combat high challenge fires by breaking through the thermal plumes created by the intense heat of the fire.
Step-by-step explanation:
Large drop sprinkler heads are used to break through the strong thermal plumes of high challenge fires. These fires produce a significant amount of heat, which creates an upward stream of hot gases and smoke known as a thermal plume.
The large water droplets from the sprinkler heads are necessary to penetrate these plumes. This concept is explained by the phenomena where pressure in the nozzle of a fire hose is less than at ground level. This occurs because the water must travel uphill and the speed increases within the nozzle, resulting in a lower pressure despite having high kinetic energy. When the water exits the nozzle and comes into contact with the air, its pressure becomes equal to atmospheric pressure, but it retains the force from the kinetic energy to help combat the fire.