Chemical and hydrodynamic cleaning of air-cooling unit
What are air-cooling units (ACU) necessary for?
Air-cooling units make it possible to significantly save cooling water, reduce the volume of wastewater, minimize the need to clean the outer surfaces of heat exchangers. Equipments of this type are used as refrigerators and condensers.
Such units have a reduced heat transfer coefficient from the air flow, which, in turn, is compensated by the presence of a large number of fins on the outer surface of the pipes and high speed with which the air flow moves.
Air-cooling units are of various types, but in the production of any of them the standards developed by specialists are observed. Based on accurate calculations and practical experience of application, these standards take into account such parameters as a wide range of surface sizes, degree of finning, type of material used for its production (various steel grades, aluminum alloys, brass, bimetal).
Air-cooling units can be as follows:
- AVG (horizontal)
- AVZ (zigzag)
- AVM (low-flow)
- AVG-V (for viscous products)
- AVG-VV (for products with high viscosity).
One of the pictures below shows a unit of a horizontal type with horizontally arranged bundles of heat exchanging tubes; another photo shows a unit with bundles of tubes arranged in a zigzag manner and in the form of a tent. In the second case (zigzag and tent arrangement), it becomes possible to increase the surface involved in heat transfer for the same area used.
Among the design features of the unit, the possibility is provided for more efficient operation due to the presence of a purified water injection manifold, which automatically switches on in summer when the air temperature rises. In winter, the fan and the motor can simply be turned off, because at low ambient temperatures, cooling and condensation occur by itselves (so-called natural convection).
The intensity of heat removal is also adjustable by changing the inclination of the fan blades, which entails the flow of air through. To this end, air-cooling units are equipped with mechanisms with pneumatic and manual transmission, which allow the blades to be remotely rotated. In addition, louver flaps are installed above the heat exchanger sections, which can also be turned either manually or by means of a pneumatic drive.
In winter, it is possible that a problem arises due to the fact that the product condensed in air-cooling unit can be supercooled. To prevent this from happening, a coil-type air heater with finned tubes is placed under the heat exchanger sections.
What types of contaminants can occur in air-cooling units:
- External contaminantsof the general type. Soil and dust are often accumulated on air-cooling units, its concentration is especially strong on ribbed surfaces.
- This problem is very relevant for ACU, since the surfaces of the units are made of metal that is subject to corrosion. Another problem is the appearance of rust, which adversely affects the performance of the units.
- Deposition of hardness salts. Moisture precipitates and evaporates on the surfaces of the heat exchangers, resulting in salts of hardness being deposited on the outer surfaces of the ACU fins. Such deposits of magnesium and calcium salts are the limescale, which is known to be very dense and requires regular removal.
- Deposits formed inside the heat exchange tubes. Its nature is influenced by the type of coolant. The cooling agent circulating through the tubes gradually settles on the internal surfaces, forming solid deposits, eventually clogging the tubes.
Long operation of ACU leads to the fact that the efficiency of its sections decreases as a result of various contaminants formed in the annular space and on the pipe finning. As a result, the quality of gas cooling is reduced, and the cost of electricity required for the operation of fans increases.
External flushing of ACU removes dirt from both the external surface of the pipes and the space between them. The process is the irrigation of sections with water and detergent composition.
Detergent solutions, special water-based compositions that have high cleaning ability, are biodegradable and do not harm the materials from which the unit structures are made.
First, the cleaning solution is applied to the places requiring cleaning and allowed to stand for some time. Then all surfaces are washed with water.
For flushing the tubes of the unit from the inside, the washing machines are used, which launch special chemical solutions into the in-tube space, where they circulate for some time, removing dirt and deposits.