Two identical boilers were lowered into two vessels containing equal volumes of water. One is at the bottom of the vessel

Two identical boilers were lowered into two vessels containing equal volumes of water. One is at the bottom of the vessel, the other is at the top. In which vessel will the water heat up faster? Why?

The faster the water will heat up in the vessel where the boiler is lowered to the bottom. Convection of heated water masses and their mixing will occur, warm masses will rise, cold masses will descend and heat up. A boiler near the surface will also heat the water, but there will be no convection, and cold masses of water from the bottom will not rise and heat up quickly, heating will take much longer.