In this chapter flow patterns, heat transfer and pressure drops characterizing two-phase flows in flooded evaporators (bundle boiling) are presented and discussed. First, the particularities of bundle boiling with regards to pool boiling are introduced. Flow patterns and respective measurement techniques and experimental results are presented. Bundle boiling heat transfer and different bundle effects are then discussed before introducing plain and enhanced tubes bundle boiling heat transfer correlations. Dryout mechanisms are then discussed, followed by pressure drops in bundle boiling. The objective of this chapter is to capture the most important phenomena related with heat transfer and pressure drops in flooded evaporators. In particular, the models presented here will allow one to correctly size and optimize the design of this type of two-phase heat exchanger.