Reference Description of the study Frequency, power, intensity Best and/or interesting result obtained Benzinger et al. [87 ] Microstructured heat exchanger, antifouling investigations 20 kHz, 35 W Pulses of 1 min to break the fouling layer but fouling speed increased Bott and Tianqing [90 ] Ozone + ultrasound to clean heat exchangers, axially propagated ultrasound 20 kHz, 2357.8 kW m−2 2357.8 kW m−2 , 3 × 1 min pulse/day, up to 70% reduction in biofilm thickness Bott [88 ] Control of biofilm formation or biofilm removing in heat exchangers 20 kHz 88% reduction of biofilm growth with 10 treatments/day, 3 × 30 s at 40% amplitude Gondrexon et al. [85 ] Vibrating shell-and-tube heat exchanger, experimental investigation 35 kHz, 80 W Overall heat transfer coefficient increased up to 257% Kurbanov and Melkumov [82 ] Heat exchanger-type for heating and refrigeration 3 and 16 kHz 27% increase in
but other major advantages Li et al. [91 ] Effects of various parameters on antiscale and scale removal. Sedimentary speed and scale inhibition rate analysed 14–20 kHz; 0–250 W Larger acoustic intensity is better for scale removal. 40°C best for antiscale, 50°C for scale removal. Better effect for small distances to the ultrasonic transducer Monnot et al. [83 ] Cooling of chemical reactor (2.9 L), experimental and modelling 800 kHz; 1.6 MHz; 20 kHz; 0–109 W Max
~ 2.04 at 800 kHz, 57.6 W Mott et al. [89 ] Experimental investigation, glass tubes filled with water, standing waves 20–350 kHz, 35–45 W 95.3% of biofilm removed by 2 × 30 s treatment at 20 kHz in 7 cm tubes, 87.5% at 3 × 30 s in 50 cm tubes Tisseau et al. [84 ] Shell and tube heat exchanger, experimental investigation 35 kHz, variable power Overall heat transfer coefficient increase up to 250%