Hot Or Not?

What’s the ideal temperature for maximum cleaning efficacy in an ultrasonic cleaner? The  short answer is – it depends.

The effectiveness of an ultrasonic cleaner depends upon its cavitation intensity – the number of imploding bubbles and the force of those bubbles.  The greater the number of bubbles and the forces exerted the better the cavitation intensity which results in better cleaning efficacy.  Give me the maximum number of imploding bubbles with the greatest force then you say?

There are a number of factors that play a role in the production of cavitation intensity – the most important being the forces exerted by the imploding bubbles.  As the temperature of an ultrasonic bath increases there is an increase in the number of bubbles formed; however, with the increase in temperature there is also an increase in vapor pressure and gas that cushion the forces of the imploding bubbles.  Forces generated by the imploding bubbles are dependent upon the amount of vapor and gas inside each bubble.  The less vapor and gas within the bubble at the time of implosion the greater the force.

So should your ultrasonic cleaning bath be hot creating more bubbles, or not for higher bubble implosion forces?  The optimum cavitation intensity is going to occur below 68° Fahrenheit (20° Celsius) so “not” would be the correct answer, but that’s probably not practical for most cleaning applications since the cavitation energy alone will generate temperatures higher than that.  Cavitation intensity, after gradually declining from the 68° Fahrenheitpeak can have upticks at various temperatures due to regassing and degassing of the liquid as the bath temperature warms and cools from use and idle periods.Although cavitation intensity may not be at its maximum potential it’s still possible to reap the extraordinary benefits of ultrasonic cleaning as there are many synergistic effects of combining heat (above 140°F) and acoustic cavitation such as increased solubility and reaction of contaminants.

So generally speaking “hot” would also be a correct answer to the question posed, “what’s the ideal temperature for maximum cleaning efficacy in an ultrasonic cleaner?”  Although there is not a specific temperature that should be used to achieve maximum cavitation if it’s not practical to keep the temperature under 68°F it’s better to get the temperature up around 140°F to realize synergistic benefits and achieve optimum results.  As temperatures rise in the ultrasonic bath it’s possible to fluctuate the liquid depth to improve cavitation intensity.  A liquid depth change of as little as ¼ inch can have an impact on cavitation intensity, but be careful there are minimum liquid levels that should be maintained on units fitted with heater elements.