In our discussion of ultrasonic cleaners, we now turn our attention to the effect that temperature has on ultrasonic cleaning. Cavitations produced in a liquid by high frequency – or ultrasonic – sound waves result in streams of liquids essentially “power washing” objects on a microscopic level. What role does temperature play in the process?
As temperature increases, the number of cavitation bubbles at first increase before falling off. At the liquid’s boiling point, cavitation produced by ultrasonic sound waves introduced into the liquid stops completely.
In addition to a decrease in the number of bubbles, the size and energy of the streams they produce decrease as well. This can be demonstrated by a foil test, where a piece of foil is placed in industrial ultrasonic cleaners. The size and distribution of the holes produced in the foil reveal the characteristics of the cavitation taking place.
At higher temperatures, the holes in the foil are smaller and more evenly distributed. While the force of the cleaning stream is reduced, the overall coverage is increased. Finding the right temperature of operation may involve balancing these characteristics.
A figure of 60 degrees Celsius for a water bath is typically used. Generally, a figure of 65% of the boiling point of the liquid is used. The choice of temperature is often determined by the detergent used in the solution, if any. The detergents often have an optimum temperature, which takes precedence over the optimum temperature for agitation. If an acid is being used as a cleaning fluid, temperatures need to be kept as low as possible to prevent the acid damaging the stainless steel tank used in ultrasonic cleaning.
Next, we examine the effect of frequency on ultrasonic cleaning. The final installment looks at the need and advantages of varying the frequency.
If you would like to learn more about ultrasonic cleaners, feel free to contact one of our ultrasonic cleaning experts toll free at (888) 420-4445 or visit our website at http://www.Omegasonics.com?sm=bl.