Abstract: Fluid distribution in the inlet chamber of tube - shell heat exchanger plays a very important role for the heat transfer efficiency and the leaks of tube and tube sheet joint. In this paper，the distribution of flow field and pressure field in the inlet chamber were simulated with computational fluid dynamics（CFD）for different chamber diameter and different number of tube passes under different inlet flow. The simulation results clearly showed fluid flow field and pressure distribution，it is useful for finding out the reasons of the joint leaks of tube and tube sheet，also the reasons of low heat transfer intensities in different regions. The ways to improve the flow field and pressure field distribution of chamber were put forward，they have important theory and application value for engineering practice.

Key words: shell and tube heat exchanger, inlet chamber, numerical simulation, flow field distribution, pressure distribution