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heating tubes. Therefore, the solutions in the central circulating tube and the other
tubes are heated unevenly. Due to the suction effect by the rising steam in the heating
tubes, the solution level in the central tube falls while that in the other tubes rises. This
circulation improves the heat transfer efficiency of the evaporator, thus facilitating
the evaporation process.
In order to facilitate the solution’s circulation in the evaporator, the cross section
area of the central circulating tube is usually 40–100% of the total area of the heating
tubes. The height of the heating tube is 0.6–2 m, and its diameter is 25–75 mm, with
a height-diameter ratio of 20–40.
The advantages of this evaporator are its simple structure, reliable operation,
good heat transfer efficiency, and small cost. The disadvantages, however, are that
it is difficult to clean and overhaul, the speed of the solution circulation is slow
(normally under 0.5 m/s), and the evaporation concentration level is almost identical
to that of the resultant solution with a high viscosity and high boiling point, thus
decreasing the temperature difference during heat transfer and obstructing the heat
transfer efficiency.
The evaporator featuring a central circulating tube is widely used in chemical
industry. It is known as the standard-type evaporator.
Suspending-basket-type evaporator. Its structure is shown in Fig. 6.6. It is named
Fig. 6.6 Suspending-baskettype
evaporator
L. Lin et al.
heating tubes. Therefore, the solutions in the central circulating tube and the other
tubes are heated unevenly. Due to the suction effect by the rising steam in the heating
tubes, the solution level in the central tube falls while that in the other tubes rises. This
circulation improves the heat transfer efficiency of the evaporator, thus facilitating
the evaporation process.
In order to facilitate the solution’s circulation in the evaporator, the cross section
area of the central circulating tube is usually 40–100% of the total area of the heating
tubes. The height of the heating tube is 0.6–2 m, and its diameter is 25–75 mm, with
a height-diameter ratio of 20–40.
The advantages of this evaporator are its simple structure, reliable operation,
good heat transfer efficiency, and small cost. The disadvantages, however, are that
it is difficult to clean and overhaul, the speed of the solution circulation is slow
(normally under 0.5 m/s), and the evaporation concentration level is almost identical
to that of the resultant solution with a high viscosity and high boiling point, thus
decreasing the temperature difference during heat transfer and obstructing the heat
transfer efficiency.
The evaporator featuring a central circulating tube is widely used in chemical
industry. It is known as the standard-type evaporator.
Suspending-basket-type evaporator. Its structure is shown in Fig. 6.6. It is named
Fig. 6.6 Suspending-baskettype
evaporator