（electromagnetic heater)The effective heating section length of the heater with a pipe diameter of 89mm is 450mm, and the effective heating area is 89 × 3．14 × 450 = 1257.57 (cm2), then the work done per unit area is 7 / 1.25757 = 5.57 (w / cm2); The effective heating section length of the heater with a pipe diameter of 60mm is 600mm and the effective heating area is 60 × 3．14 × 600 = 1130.40 (cm2), then the work done per unit area is 4.5 / 113.40 = 3.98 (w / cm2). The heating area of the heater with a diameter of 60mm is basically the same as that of the heater with a diameter of 89mm. The heating power of the heater with a diameter of 89mm is about 7KW, which is larger than that of the heater with a diameter of 60mm (4.5kw). Therefore, the total heat exchange of the heater with a diameter of 89mm is large, which is one of the reasons for the rapid scaling of the heating pipe of the heater with a diameter of 89mm.
(electromagnetic heater)The oil inlet and outlet diameters of the heater heating pipe with a pipe diameter of 60mm are the same, while the heater heating pipe with a pipe diameter of 89mm is the oil inlet and outlet of 60mm pipe. There are two problems caused by reducing the diameter at the heating section: ① the flow rate of crude oil decreases after entering the 89mm pipeline and increases relatively when passing through the 60mm pipeline outlet. There are two velocity changes in the heating section, which is conducive to deposition. ② The crude oil attached to the pipe wall is not easy to flow, causing the crude oil attached to the pipe wall to be heated for a long time, resulting in a temperature difference between it and the crude oil in the middle, and the surface tension of the crude oil itself is reduced. The middle part of the heating coil is the high-temperature area of the whole heating section. According to the experimental test, the temperature in the middle part of the coil is 45 ℃ higher than the outlet temperature. It can be seen that reducing the diameter at the heating section is the main reason for the scaling of the heating pipe(electromagnetic heater)
