VERTICAL HEAT EXCHANGER

PROBLEM TO BE SOLVED: To perform an efficient removal of gas generated in a vertical heat exchanger and an effective removal of accumulated sludge. SOLUTION: There are provided a vertical heat exchanger and a method for using the heat exchanger, wherein at least a part of one end of a bent pipe is constituted of an upper pipe plate (an upper cover part in a spiral type heat exchanger); the other end is connected to a fluid passing pipe just near the bent pipe where the same fluid as that in the bent pipe flows outside a heat exchanger, and/or at least a part of a drain pipe is constituted of a lower pipe plate (a lower cover part in a spiral type heat exchanger); and the other end is connected to a fluid passing pipe just near the bent pipe where the same fluid as that in the bent pipe flows outside a heat exchanger.