The Basic Principles of Heat Exchanger Cleaning

Many different designs and applications of compact heat exchangers are used in military, commercial, and business aviation applications as well as ground support equipment. They primarily encompass water, oil, fuel, and air coolers as well as...

Agitation, pulse, vibration, and ultrasonic; are some examples of typical methods that are used to apply energy to enhance a cleaning process. A warning: These multiple path heat exchanger internals are constructed somewhat light and delicate, and even when encased in a hard shell such as for severe-duty and military applications, the internal construction is very similar. Testing done with ultrasonic cleaning has produced many internal destructive results. Also, another issue to always be aware of is the damage that can be caused by overpressurizing.

One method of applying mechanical energy is “Pulsating,” a HECAT patented process, which uses fixed dimensional control of the air and liquid flow paths to produce solid impacting slugs of solvent separated by segments of compressed air. Compressed air is not just used to pressurize the liquid; the stored energy in compressed air is used and applied to push the slugs of solvent deep into the internals (corner and crevices) of a heat exchanger.

The “pulsating” frequency is about 5 to 6 pulses per second and backpressure only enhances and intensifies the “pulsating” scrubbing action. It is one of the few methods proven to defeat the “path of least resistance” rule and effectively scrub down deep into the parallel paths and passageways to effectively clean today’s complex heat exchangers. It is just like applying the energy of your parts washer scrub brush down inside a component, where you cannot reach.

Velocity is a fundamental energy component that is often overlooked, but critical to successful heat exchanger cleaning. The solvent must be introduced with adequate velocity to completely flood the component. Velocity is the necessary energy component needed to carry away weighted debris. Velocity cannot be sustained if the solvent is not introduced with an adequate volume to support it. There must be enough solvent supplied to support the velocity of the flushing process, and there must also be enough solvent supplied to effectively do its job at dissolving the residues. This is why common and inexpensive A/C flushing methods such as pour in-blow out, aerosol cans, and 1-quart flush guns won’t work.

Now that some of the questions of how to clean heat exchangers have been answered, the job should be easier.

Karl Matis is president of HECAT Inc. He can be reached at (800) 380-9501. More in-depth details on the topics of this article can be seen in the HECAT Technical Paper listed on the Article page of the web site,

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