Pattern of flow in the evaporation process can be classified into five sections as follow:
- Single phase liquid flow
- Single phase steam flow
|Figure 1: Flow Patterns in Evaporation Process|
Although it is difficult to know the type of flow inside water wall tubes and the changes position of flow type from one to another, method to explain position of certain flow type is much needed. A method to describe transitional of flow type inside water wall tubes is in the form of mapping type of flow. This type of flow is illustrated in graphical form. The coordinate of graphic is the function of gas phase superficial velocity (jg) and liquid phase superficial velocity (jf). The graphic which explain the fluid flow upward in vertical tube has been made by researchers Hewit & Robert in 1969 as figure below.
|Figure 2: Mapping of Flow in Vertical Tube|