Fuel cell circulating water system for underwater closed cabin and operation process

The fuel cell circulating water system comprises a pressure-resistant shell, a conformal heat exchange water tank, a metal hose, an electromagnetic valve, a spiral heat exchange tube group, a temperature control three-way valve, an inner rib, a fuel cell stack, a circulating water tank, long-time continuous electronic equipment, a circulating water pump, an outer rib, a cylindrical vacuum heat insulation plate, a light shell and the like. The spiral heat exchange tube sets are arranged between the inner ribs, the space between the inner ribs and the space, which is not easy to use, of the arc section of the pressure-resistant shell are fully utilized, seawater is prevented from being introduced into the cabin to cool the system through a cabin wall heat transfer mode, equipment and pipelines of a seawater system in a traditional cooling mode are omitted, and the cooling efficiency is improved. The auxiliary machine power consumption of the system is effectively reduced, the seawater pipeline is prevented from