How Ultrasonic Baths Safely Clean Radiator and Air Conditioner Coils and Fins

Periodic automotive radiator flushing helps clean coils but does not remove mineral deposits.  Air conditioner heat exchanger and condenser coils cannot easily be flushed.  Power washing risks damaging delicate fins essential to heat dissipation.  The answer for automotive repair technicians and HVAC professionals is ultrasonic cleaning.  This post describes how ultrasonic baths safely remove contaminants from radiator and air conditioner coils and fins – together termed heat exchangers. 

It presents:

• A definition of heat exchangers as used in this post
• Industry experience in ultrasonic cleaning heat exchanger components
• How ultrasonic energy cleans radiator and air conditioner coils and fins
• Suggestions on selecting ultrasonic cleaners and cleaning formulas

What is a Heat Exchanger?

The term heat exchanger describes a system involving heat transfer.  It covers a lot of ground.  Examples include

• Industrial  heat exchangers in chemical, petroleum and food processing operations
• Radiators in automotive and marine engines to avoid overheating
• Condensers in your home or room air conditioner
• After coolers and charge air conditioners

and similar assemblies.  Our focus is on how ultrasonic baths safely clean radiator and air conditioner coils and fins.  But we’ll start with larger assemblies as examples to illustrate the efficacy of ultrasonic cleaning.

Ultrasonic Cleaning Proven for Industrial Scale Heat Exchangers

Fouled heat exchangers quickly reduce the effectiveness of industrial-scale heat exchangers used in chemical, petroleum and food processing operations.  These can be huge units – 9.5 meters in length and 2 meters in diameter as an example.   The amount of contamination buildup can be significant and difficult to remove.

Power washing using ultra high pressure water jets (such as 30,000 – 40,000 psi) can damage exchanger components, are not always effective and can cause serious injury to personnel if miss-directed.  Moreover, power washer spray force decreases substantially by the time it reaches the end of the tube.

A peer-reviewed article published in Proceedings of International Conference on Heat Exchanger Fouling and Cleaning describes in detail how ultrasonic energy combined with appropriate cleaning chemistry and handling does the job.

How Ultrasonic Energy Cleans Radiator and Air Conditioner Coils and Fins

Cleaning and refurbishing challenges faced by automotive repair and HVAC technicians are on a much smaller scale than those faced when cleaning industrial heat exchangers. 

Yet the method applied is the same and is already employed by technicians performing these activities.

The next sections look at how the technology works and special considerations for radiators and condensers.

How Ultrasonic Cleaning Works

Cleaning is based on what is called ultrasonic cavitation.  This is described as the violent implosion of billions of microscopic vacuum bubbles as they contact automotive radiator and HVAC condensers immersed in a biodegradable cleaning solution formulated to handle specific cleaning tasks.  See below for a recommendation on cleaning solutions.

The solution is contained in an ultrasonic cleaner tank of sufficient dimensions to assure parts being cleaned are completely immersed. 

Tanks are fitted with ultrasonic transducers attached to exterior bottom and sides, the number and placement of which is based on the tank size.  Some large units may be fitted with immersible transducers.

Transducers are powered by a generator that, when activated, causes them to vibrate at ultrasonic frequencies such as 45,000 or 37,000 cycles per second (kHz).  Lower and higher frequencies may also be employed.

This vibration causes the tank to serve as a membrane creating the bubbles that violently implode on the exposed surfaces of components being cleaned in order to blast and carry away contaminants.

While “violent” the implosions are so fast that they do not damage delicate surfaces.  That’s why ultrasonic cleaning is much safer than power washing fins on radiators and condensers.  As proof of this, ultrasonic cleaning is widely used to clean surgical and medical instruments, glassware and similar delicate components.   

 Special Considerations when Cleaning Radiators and Condensers

 As noted above, ultrasonic cavitation works on all surfaces in contact with the ultrasonic cleaning solution.  Cavitation energy can penetrate surfaces such as glass and metal and work on interior surfaces such as radiator and condenser coils.

The inside of coils, where mineral deposits and other build-up may occur, and external fins where dirt can lodge deeply into crevices, are impossible to access by hand cleaning.  Fins can be damaged by high-pressure sprays.

That is why a good practice for thorough ultrasonic cleaning coils is to alternate the cleaning cycle with flushing the internal passages.  Ultrasonic energy will lift off contaminants but it will not carry them out. 

The best approach is to position the unit being cleaned in such a way that the solution flows into the tubes.  Then, clean and flush, clean and flush – always taking steps to insure the cleaning solution enters the tubes – until the flushing water comes out clean.  That helps assure you that mineral deposits and other internal contaminants are removed.

A special note of caution here: If you alternate clean and flush cycles for tube interiors wear protective gloves. 

Do not reach into an operating ultrasonic bath.  It will be hot, and cavitation is not good for your skin.  If the unit being cleaned is in a basket, remove the basket then do the flushing. 

If you suspend components in a large ultrasonic cleaner transfer them to a flush/rinse tank. 

Selecting an Ultrasonic Cleaner for Radiator and Air Conditioner Coils and Fins

Ultrasonic cleaners from Tovatech are available in several sizes and capacities.

Ultrasonic Cleaner Size

As noted above, an important specification point is the size of the items you will be cleaning.  Total immersion is imperative.  Here are points to remember:

• Parts you are cleaning should be placed in a basket unless you plan to suspend them from an overhead support. 
• If you are cleaning using baskets, remember that basket dimensions are slightly smaller than tank dimensions.  Ask your vendor if basket dimensions are not provided.
• Radiator and air conditioner components must not rest on the bottom or contact the sides of the tank.

Ultrasonic Cleaner Location

You’ll need a source of electric power, of course, but for clean and flush cycles you’ll need a source of water and a drain.  Rinse tanks and rinse stations are available to assist you in this.

Ultrasonic Cleaner Features

In addition to on/off switches ultrasonic cleaners are available with several features designed to improve the efficiency and throughput of your cleaning operations.  Here are some examples:

• Timers let you set and forget the cleaning cycle.  Units will shut off at the end, and allow you to attend to other tasks during the cycle.
• Heaters allow you to program the temperature of the cleaning solution as recommended by its manufacturer.  Some units automatically start the ultrasound when the set temperature is reached.
• Sweep automatically provides a slight ± variation in ultrasonic frequency to smooth out the cycles while avoiding areas of too intense and no cavitation.
• Pulse allows you to periodically increase cavitation intensity to remove stubborn contaminants.
• Degas removes trapped air from fresh cleaning solutions that interferes with cavitation.  This can be accomplished by activating the pulse cycle in units so equipped or by running the unit  without a load for a period of time.  Degas is particularly useful in large industrial ultrasonic cleaners to save time.
• Adjustable power lets you tailor the ultrasonic cleaning power to match cleaning requirements.
• Multiple frequencies, as with adjustable power, allow you to set a lower frequency for tough cleaning and higher frequencies for fine cleaning.  

Suggested Ultrasonic Cleaner Models for Radiator and HVAC Service Technicians

Tovatech recommends units with tank dimensions, cleaning solution capacities and features that help you do your job most efficiently. 

Several industrial ultrasonic cleaner options are available.   Examples with many important features are the portable, dual-frequency 25/45 kHz Elma xtra ST ultrasonic cleaners in 7 tank sizes from 8 to 67 gallons. 

The roller mounted Shiraclean units in four tank capacities from 25 to 110 gallons.

If “off the shelf” units described above don’t meet your needs consider a custom ultrasonic cleaner.  Tovatech’s ultrasonic cleaning professionals will guide you through the specification process to develop a unit tailored to your specific requirements.

Ultrasonic Cleaning Formulas for Radiators and Air Conditioner Coils

Many of today’s ultrasonic cleaning formulas are biodegradable and shipped as concentrates for dilution with ordinary tap water.  At the end of their useful life they can be flushed down the drain.  That said, Tovatech advises you to consult with local authorities on proper disposal procedures.

An ultrasonic formulation ideal for removing grease, oils, soot,  wax, combustion residues, and organic contaminants from fins and external tube surfaces is elma tec clean A4 diluted to 1 to 5% with water. 

When removing mineral and other deposits from tube internal surfaces elma tec clean S1, also diluted to 1 to 5% with water, is a good choice.   

These are two of the many examples of cleaning solution formulas available.  For help in selecting ultrasonic cleaning equipment and cleaning solution formulas that best meet your challenges, please contact our scientists for unbiased recommendations.