The previous chapter dealt with boiling in a pool of stationary liquid. Flow boiling is different from pool boiling in that the fluid is moving with a velocity caused by natural circulation in a loop or by an external force such as a pump. The basic heat transfer mechanisms in flow boiling are similar to those discussed in pool boiling; however, the fluid velocity enhances heat transfer in flow boiling. The boiling curve, therefore, is shifted to the upper left corner as compared with the case of pool boiling diagrammed in Figure 5.2. Another distinguishing feature of flow boiling is varying flow regions along the tube in the flow direction.

In addition to heat transfer in flow boiling, the pressure drop for two-phase flow will also be discussed in this chapter.