... )12) Heat preservation: 72h to 80h13) Electric heater: 1.5Kw to 3Kw collector1) Reliable, efficient, twin-glass evacuated ... Diameter of Tubeφ58mmTube Quantity1518202430Manifoldcasing material,Aluminum Alloy,Thickness,1.8mm,Insulating layer,compressed rock woolHeat Pipe pure ... Quantity(set)20102787763574022116916613613040HQ278213209172171Price(USD) Heat pipe solar thermal vacuum tube solar collector