... .0, twine pipe water heater. National patent, ZL 2012 2 0178696.3, high power density PTC heating pipe.National patent, ... ZL 201320630141.2, surround PTC heating tube.National patent, ZL 201520103573. ... assembling; it could be used for heating diesel pipe, diesel filter, oil pipe, compressed air pipe. 4) The surface temperature without water, ...