Heat exchanger

The utility model provides a heat exchanger with a plurality of heat exchange layers; a plurality of heat exchange modules are arranged one each heat exchange layer; the heat exchange modules comprise heat exchange pipe bundles; a module connection pipe is connected between adjacent heat exchange modules in the same heat exchange layer; the heat exchanger also comprises bypass connection pipes which are connected between a main water inlet header and a main water outlet header of the heat exchanger and are provided with interfaces; the interfaces are connected with the module connection pipes; the pipe sections, corresponding to all heat exchange modules, of the bypass connection pipes are provided with bypass on-off valves. When one certain heat exchange module leaks water, only the leaking module needs to be cut off without cutting off the whole of each heat exchange layer and influencing normal heat exchange of other modules, the problem of uneven heat exchange caused by the traditional manner is overcome, and the loss of a heat exchange area is reduced as much as possible.