What factors affect the cleaning effectiveness of ultrasonic dishwashers?

The cleaning effectiveness of an ultrasonic dishwasher is not fixed but is influenced by multiple factors, including both the device's parameters and operational conditions during use. The following analysis is conducted from three dimensions: core factors, auxiliary conditions, and interfering factors:

I. Core Technical Parameters (Determined by the Equipment Itself)

Ultrasonic Frequency

Frequency is a key factor influencing cleaning power:

Low-frequency (20-40 kHz): Larger cavitation bubbles with stronger impact force upon rupture, suitable for cleaning stubborn stains such as heavy grease, burnt residues, and metal rust. However, this frequency produces slightly higher vibration noise, which may potentially damage fragile materials (e.g., thin glass, precision ceramics).

High-frequency (40-100 kHz): Smaller, denser cavitation bubbles with milder impact but more uniform coverage, suitable for cleaning delicate tableware (e.g., carved porcelain, stemware, baby bottles), electronic components, etc. Lower noise levels and better material protection.

Single frequency vs. multi-frequency adjustable: High-end models support frequency switching (e.g., 25 kHz + 40 kHz), allowing flexible selection based on stain type for enhanced adaptability.

Power density

Refers to the ultrasonic power per unit area of the cleaning tank (typically 10–50 W/L). If power density is too low, cavitation effects are weak, resulting in insufficient cleaning power; while excessively high power density may cause excessive agitation of the liquid, potentially leading to damage from utensils colliding with each other, as well as increased energy consumption and noise levels.

Reasonable range: Household models typically range from 15-30 W/L, while commercial models (e.g., for restaurants or laboratories) may reach 30-50 W/L due to the need to handle large volumes of contaminants.

Cleaning tank structure and transducer layout

The number and distribution of transducers (ultrasonic vibration sources) directly affect sound field uniformity: improper layout may create “dead zones” (e.g., corners, edges), resulting in poor cleaning performance in those areas.

High-quality models use a “bottom + side” multi-transducer configuration or employ curved tank designs to minimize sound wave reflection interference, ensuring uniform vibration across the entire tank.

II. Operational Conditions During Use (Human-Controlled)

Cleaning Solution Temperature

Temperature affects cleaning performance by influencing “cavitation effect intensity” and “stain solubility”:

Low temperature (20-30°C): Cavitation effect is stable, but oil stain solubility is low, suitable for cleaning protein-based stains (e.g., milk, egg liquid), avoiding high temperatures that cause protein denaturation and coagulation.

Medium temperature (40-60°C): This is the optimal balance between cavitation effect and cleaning power — warm water softens oils without overly inhibiting cavitation bubble formation, suitable for most scenarios such as daily oil stains and tea stains.

High temperature (above 60°C): Although it enhances oil removal capability, the viscosity of the liquid decreases, causing cavitation bubbles to rupture before fully developing, thereby weakening the impact force. Additionally, it may render certain detergents ineffective (e.g., enzyme-based cleaners).

Cleaning solution composition and concentration

Detergent function: Ultrasonic cleaning with plain water alone has limited effectiveness. Adding neutral detergents (such as specialized ultrasonic cleaning agents or dishwashing detergents) enhances cavitation effects by “emulsifying grease + reducing surface tension,” particularly effective for grease-based stains.

Concentration control: Higher is not always better. Excessive detergent can produce excessive foam, obstructing ultrasonic wave propagation and even covering cavitation bubbles, thereby reducing vibration efficiency (a dilution ratio of 1:500 to 1:1000 is generally recommended).

Avoid using strongly corrosive detergents (such as strong alkalis or acids): These may corrode the equipment's transducers and damage the material of the tableware.

Cleaning time

Time and cleanliness follow a “rapid improvement followed by a gradual plateau” relationship:

Light soiling (rice grains, soup residue): 3–5 minutes is sufficient to achieve optimal results; exceeding this time may cause stains to reattach.

Moderate soiling (dried grease, tea stains): 10–15 minutes to ensure cavitation fully breaks down stain adhesion.

Heavy soiling (burnt stains, long-term grease): 20–30 minutes, combined with appropriate temperature and detergent, to avoid incomplete cleaning due to insufficient time.

Dishware placement and immersion status

Must be fully submerged: If any part of the dishware is exposed above the liquid surface, the areas not in contact with the liquid will not be affected by ultrasonic waves, resulting in residual stains.

Avoid overcrowding: Utensils must be spaced apart to ensure liquid circulation and sound wave penetration; otherwise, “shadow zones” may form in stacked areas (e.g., bowls inverted and stacked, cups nested).

Proper orientation: Utensils with openings facing downward (e.g., bowls, cups) must be tilted to prevent air bubbles from forming inside (air blocks ultrasonic wave propagation).

III. Interference and limiting factors (to be avoided)

Initial stain condition

Large residues: Unremoved bones, vegetable leaves, etc., absorb ultrasonic energy, disrupting vibration uniformity and potentially blocking the drain. These should be scraped off beforehand.

Stain aging degree: Fresh grease stains (within 1 hour after meals) are easier to remove than dried stains over 3 days old.