Spiral changing solar vacuum heat collecting pipe and vacuum heat collecting system

The invention provides a spiral changing solar vacuum heat collecting pipe and a vacuum heat collecting system. The spiral changing solar vacuum heat collecting pipe comprises an outer pipe body and an inner pipe body. The inner pipe body is sleeved with the outer pipe body. A vacuum cavity is formed between the outer pipe body and the inner pipe body. A heat exchanging pipe is arranged in the inner pipe body. A part between the inner pipe body and the heat exchanging pipe is filled with a phase change material. The first end of the inner pipe body and the first end of the outer pipe body are both sealed. The second end of the inner pipe body and the second end of the outer pipe body are connected through a sealing connecting piece. The heat exchanging pipe is a spiral flexible coil pipe. The screw pitch of the spiral flexible coil pipe is decreased continuously form the second ends to the first ends. A flexible pip bundle of a screw pitch changing structure and the phase change material are combined together, because of the advantages of screw pitch changing, space arrangement, small weight and the like of the spiral flexible pipe bundle, the spiral flexible pipe bundle has good response to the phase change material, large disturbance can be generated, the heat exchanging efficiency is improved, vibration with multi-stage frequencies is excited, and energy distribution is uniform.