Freezer Aluminum Roll Bond Evaporator as Freezer Parts

One-way type evaporator
The main characteristic of this big kind of evaporator is: the solution in the evaporator only passes the heating chamber once, does not make the circulation flow that becomes the concentrated liquid discharge. Solution through the heating chamber, in the wall of the tube was membrane flow, so customarily also known as liquid film evaporator. According to the material in the evaporator in the flow direction of different, one-way type evaporator and divided into the following kinds.

1. Rise membrane type evaporator its heating room by many vertical long tube composition. Commonly used heating tube diameter of 25 ~ 50mm, tube length and tube diameter ratio of about 100 ~ 150. material liquid by preheating from the bottom of the evaporator introduction, in the heating tube is heated by boiling and rapid vaporization, the steam generated in the heating tube in the high-speed rise, generally operating at atmospheric pressure suitable for the export of the steam speed of 20 ~ 50m / s, decompression when operating at a speed of steam up to 100 to 160m / s or greater. Solution is driven by the rising steam, along the wall of the tube into a film rising and continue to evaporate, steam, liquid mixture in the separator 2 separation, the completion of the liquid discharged from the bottom of the separator, the secondary steam is exported at the top. It should be noted that, if the evaporation of water from the material liquid is not much, it is difficult to achieve the above requirements of the steam speed, that is, the rising film evaporator is not suitable for the evaporation of the thicker solution; It is very viscous, easy to crystallize or easy to scale the material is not applicable.

2. Decreasing film type evaporator decreasing film type evaporator and rising film type evaporator difference is that, the material liquid is added from the top of the evaporator, under the action of gravity along the wall of the tube into a film falling, and in the process of evaporation and thickening, at the bottom of the concentrated solution. Because of the membrane mechanism is different from the ascending membrane evaporator, so the descending membrane evaporator can evaporate the higher concentration, viscosity (for example, in the range of 0.05 ~ 0.45Ns/m2), heat-sensitive material. But because of the liquid film in the tube distribution is not easy to be uniform, heat transfer coefficient is smaller than the ascending film type evaporator, still does not apply to easy to crystallize or easy to scale the material.

Because the solution in the one-way type evaporator in the membrane flow, thus convection heat transfer coefficient is greatly improved, make the solution can in the heating room once through no longer circulate to achieve the required concentration, so than the cycle type evaporator has more advantages. The solution does not circulate to bring the benefit has:
(1) The residence time of the solution in the evaporator is very short, so it is especially suitable for the evaporation of heat-sensitive materials;
(2) the concentration of the whole solution, not as circulating type is always close to the concentration of the completion of the liquid, and thus the effective temperature difference of this evaporator is larger. Its main disadvantage is: the fluctuation of the feed load is quite sensitive, when the design or operation is not suitable when it is not easy to film, at this time, the convection heat transfer coefficient will be significantly reduced.

The scraper type evaporator evaporator shell with heating steam jacket, which is equipped with rotatable blade that scraper. The scraper has the fixed type and the rotor type two kinds, the former and the shell inner wall clearance for 0.5 ~ 1.5mm, the latter and the wall clearance with the rotor rotor and change. The material liquid is added from the upper part of the evaporator along the tangential direction (also added to the coaxial dumping disk with the scraper). Due to gravity, centrifugal force and rotating scraper scraping with the role of the solution in the inner wall of the formation of spinning film, and in the process of being evaporated and concentrated, the completion of the liquid discharged at the bottom. This kind of evaporator is a kind of one-way type evaporator which utilizes applied power to form film, and its outstanding advantage is that it is very adaptable to the material, and the residence time is short, generally several seconds or tens of seconds, so it can be adapted to the high viscosity (such as quebracho extracts, honey, etc.) and easy to crystallize, scaling, and heat-sensitive material. However, its structure is complex, power consumption, each square meter of heat transfer surface needs about 1.5 ~ 3kW. in addition, its handling capacity is very small and high manufacturing and installation requirements.

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