Principally

Direct-heat-exchange is the main way of water- heating .But it should not exclude the existence and development of the way of Indirect-heat-exchange. Indirect-heat-exchange is based on the theory of the turbulent flow-heating.According to the theory

a series of new heating equipments were made. Two of them are discussed in this thesis. Also it introduces two kinds of heater which have found wide application recently:hemi-fast open water heater and the semi-volume heater.