Heating Performance of a Heating Unit Using Hydrodynamic Cavitation

Abstract

This study examined the factors affecting the bubble generation of a motor driven bubblegenerator to develop a heating unit using hydrodynamic cavitation. This study also investigated theheat production and thermal efficiency by changing operating conditions. Bubble generation usingthe 25 ℓ-capacity motor is driven bubble generator was confirmed visually in various experimentalconditions: three levels of motor powers(1, 3, 5 HP), two levels of revolutions(1800, 3200 rpm),and two levels of internal pressures of the bubble generator(the atmospheric pressure, pressurizedair). After constructing the heating unit, heat production, and thermal efficiency were measured inthe following experimental conditions: two levels of motor powers(3, 5 HP) and three levels ofwater quantities(102, 152, 230 kg). And then specifically temperature increasing rate and specificconsumed energy required for the heating unit design were calculated. Bubbles were generatedstably at 1,800 rpm and pressure from 0~0.8 bar. When heating water around 30℃, specifictemperature increasing rate was maximized at 0.247℃/min and 0.002422℃/min-kg. Thermalefficiencies were 121% with only motor driving power as input energy and 98% with both motorsdriving power and water circulating pump driving power as input energy. This showed that theheating unit using hydrodynamic cavitation had higher thermal efficiency than the existingcombustion boiler. Maximum specific consumed energy was 0.0270 KJ/min-kg-℃. This studyconfirmed that water can be heated with the heat caused by the explosion of the bubbles generatedby hydrodynamic cavitation. And the results of this study could be utilized for commercial usebecause it showed much higher thermal efficiency than the existing combustion boiler.