... : heat transfer;2, the fin-tube type: DR (extrusion type), L (winding type), high frequency welding;3, fin tube materials: 1, base ... so on. 2, Fin: aluminum (extruded type or wound type), steel (wound type, high frequency welding), copper (winding type).4, finned tube ... specifications: 1, base tube: OD16, OD19, OD1 ", OD38; 2, fin: OD34, OD44, ...