Compared with the conventional single head tube, the heat dissipation area is expanded by 2 to 3 times, that is, the surface power load allowed by the heat sink element is 1 to 2 times that of the conventional single head tube. Under the same power conditions, compared with the conventional tube, the heating element has the advantages of small volume, fast heating, uniform heating, good heat dissipation performance, high thermal efficiency, long service life and low cost.