The heat exchanger is a very important component in circuits where there is a heat exchange between a hot fluid and a cold fluid, and that is why regular maintenance allows for a longer useful life and less consistent unit downtime. One of the fundamental parameter for the sizing of a heat exchanger is the fouling factor.

The fluids that pass inside the exchangers, over time, can create deposits on the internal walls, consequently reducing the heat exchange efficiency. Depending on the nature and purity of the fluid, the phenomenon is more or less accentuated; for safety reasons, a safety factor is considered in the design and selection phase of the heat exchanger that allows the oversizing of the heat exchanger. This permit to compensate the phenomenon of deposit on the walls of the exchanger.

The calculation of the safety coefficient depends on a series of factors that are taken into consideration during the design phase:

-          Fluid velocities inside the exchanger;

-          Level of purity of the fluid (presence of particles and suspended solids);

-          Type of fluid;

-          Fluid turbulence.

By their nature, plates heat exchangers have much lower fouling factor values than shell and tubes exchangers, because the motion of the fluids is more turbulent and their speed inside the channels in much higher. The combination of these two characteristics reduces the phenomenon of fouling of the exchange surface.

The fouling phenomenon of the heat exchanger carry on different negative consequences, such as:

-          Increased temperature differences between hot and cold fluid, resulting in increased operating costs;

-          Reduction of heat exchange efficiency, resulting in inefficiencies on the line;

-          Increased pressure drops;

-          Increased risk of exchanger breakage.

Frigosystem always recommends to install protection devices for the exchangers against impurities. It is important that the water that flows inside the heat exchangers is purified from external bodies or is filtered. It is also useful to remember that these systems must be regularly maintained to keep the cleaning and filtering efficiency of the fluid unaltered.

In the case that the heat exchanger is subject to a reduction in performance (and therefore to an increase of internal deposits) it is useful to clean the exchanger inside (in the channels where there is not circulation of refrigerant gas). Cleaning can be done with forced washing with an appropriate descaling chemical solution that is compatible with the construction materials of the exchanger. In order to increase the efficiency of cleaning, the solution must be pumped in the opposite direction to that of normal circuit operation, after leaving the unit off for an adequate time. Subsequently it is useful to clean the circuits after the chemical washing.

Obviously, cleaning must be done by specialized personnel, who must use all safety devices suitable for the case and must pay attention to the component (pressure, movement, hits).