The disclosure relates to a heat exchanger. The heat exchanger includes a shell and heat exchange tube bundles located in the shell, the shell has an inlet and an outlet, and a refrigerant flows in through the inlet, exchanges heat with a fluid in the heat exchange tube bundles, and then flows out from the outlet, and the outlet is provided with an extension section that extends into an interior of the shell and has a receiving portion configured to receive at least a part of a liquid in the refrigerant flowing toward the outlet after heat exchange. The disclosure is easy to manufacture, install and maintain, and has a low cost. By optimizing the structure of an outlet pipeline of the heat exchanger, the influence of liquid carryover can be effectively controlled, and the overall performance, safety and reliability of the system can be enhanced.