Heat exchanger, exhaust gas recirculation system and internal combustion engine

The heat exchanger (10) has a heat exchanger block (11) that performs heat exchange between work fluid (AF) such as exhaust gas or air and cooling fluid (KF) such as coolant. Working fluid filters are provided between the working fluid connecting lines (14.1,14.2). The working fluid connecting lines are connected to the heat exchanger block. Pick-up flange (18) is provided in each connecting line and is provided with a diffuser. An independent claim is included for exhaust gas recirculation system.