Figure 1 - Dirty working plate of the heat exchanger
Heat exchangers operate in harsh conditions, constantly carrying out temperature exchange between mobile working media: liquid or gaseous. Since such processes are effective for the high-energy state of a gas or liquid, their movement in the working space of the devices occurs at increased speeds and/or pressures.
Such conditions provoke contamination of the surfaces of the working parts (see Fig. 1), which reduces efficiency. Therefore, periodic routine maintenance is a mandatory element of the operation of heat exchangers.
Accounting and analysis of factors that reduce the durability of heat exchangers
Types of pollution
The complexity of maintenance is taken into account at the design stage. For liquid working media – water and aqueous solutions – take into account:
- The dimensions of the effective heat exchange surface: the larger they are, the more scale is formed. It depends on the degree of cleanliness of the working media that move inside the device: when using heat exchangers with clean liquids, pollution is less active. Thus, the choice in favor of heat exchangers with the minimum allowable working surface area of the plates removes the polluting effect. For this, they sacrifice reducing the intensity of heat transfer.
- The quality of the energy carrier. The level of contamination depends on the type of working environment. There are two known types of mechanical contamination: fouling and scale. As a result of fouling, solid particles of a liquid or gas with lower kinetic energy settle on heat exchange surfaces (see Fig. 2). Scale is formed when the working medium contains particles released from the liquid under the influence of high temperatures or cavitation processes (see Fig. 3). The intensity of scale formation is more noticeable where the flow of energy carrier it loses speed, for example, due to a sudden change in direction of travel.
- The quality of the filters. Filters are a bottleneck of heat transfer installations because they reduce flow, cause pressure drops, and require increased volumes of energy during pumping. Nevertheless, filters protect the heat exchanger from contamination, and therefore are used in installations with increased durability.
Figure 2 – Appearance of the fouling surface of the plate before (left) and after (right) cleaning
Figure 3 – Deformation of the plate surface under the influence of cavitation
These factors are taken into account for all versions of heat exchangers.
Filtering of work environments
The size of the weighted
