In a jacket-water heated submerged tube evaporator, what is the primary factor that determines the rate of scale build-up on the submerged tube bundle?

Correct Answer: Option B — The jacket water inlet temperature to the submerged tube bundle.

Scale formation on submerged tubes is primarily driven by the temperature of the heating medium. Higher jacket water temperatures accelerate the precipitation of calcium carbonate and magnesium hydroxide from the seawater onto the tube surfaces. Controlling this temperature is the most effective operational method to minimize rapid scaling.