Heat exchange system suitable for realizing energy conservation through natural cooling in cold region

The invention discloses a heat exchange system suitable for realizing energy conservation through natural cooling in a cold region. The heat exchange system comprises a water return pipeline, a water outlet pipeline, an active refrigeration cycle system, a circulating pump, a three-way valve, a natural cooling coil and a control device. The control device controls the working mode of the heat exchange system by controlling the circulating pump, the active refrigeration circulating system and the three-way valve. And in the active refrigeration control mode, the active refrigeration circulation system is controlled to work, the circulation pump is controlled to start, the port A and the port B of the three-way valve are communicated, and the port A and the port C are closed. In the natural cooling control mode, the circulating pump is controlled to be started, the port A and the port C of the three-way valve are controlled to be communicated, the port A and the port B are controlled to be closed, only the circ