ISO 20480-3:2021 pdf – Fine bubble technology — General principles for usage and measurement of fine bubbles — Part 3: Methods for generating fine bubbles.
1 Scope This document describes methods for generating fine bubbles. 2 Normative references The following documents are referred to in the text in the sense that some or all of their content constitutes requirements of this document. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies. ISO 20480-1, Fine bubble technology — General principles for usage and measurement of fine bubbles — Part 1: Terminology ISO 20480-2, Fine bubble technology — General principles for usage and measurement of fine bubbles — Part 2: Categorization of the attributes of fine bubbles 3 Terms and definitions For the purposes of this document, the terms and definitions given in ISO 20480-1 and ISO 20480-2, and the following apply. ISO and IEC maintain terminological databases for the use in standardization at the following addresses: — ISO Online browsing platform: available at https:// www .iso .org/ obp — IEC Electropedia: available at http:// www .electropedia .org/ 3.1 flow path passage that conveys fluid [SOURCE: ISO 5598:2020, 3.2.302] 3.2 cavitation formation and collapse of bubbles in a liquid when the pressure falls to or below the liquid vapour pressure, the collapse releases energy, sometimes with an audible sound and vibration [SOURCE: ISO 16904:2016, 3.7] 3.3 Venturi tube device which consists of a convergent inlet which is conically connected to the cylindrical part called the “throat” and an expanding section called “divergent” with a conical shape [SOURCE: ISO 5167-1:— 1) , 3.2.5]
3.5 impeller spinning disc in a centrifugal pump with protruding vanes, which is used to accelerate the fluid in the pump casing [SOURCE: ISO 13501:2011, 3.1.51] 3.6 solubility maximum mass of a solute that can be dissolved in a unit volume of solution measured under equilibrium conditions [SOURCE: ISO 17327-1:2018, 3.16] 3.7 surfactant surface active substance that reduces the surface tension of the solution [SOURCE: ISO 8124-7:2015, 3.7] 3.8 critical micelle state of maximum concentration of dispersing agent before micelles form [SOURCE: ISO 14887:2000, 3.4] 3.9 ultrasound high frequency (over 20 kHz) sound waves which propagate through fluids and solids [SOURCE: ISO 20998-1:2006, 2.22] 3.10 self-priming suction of fluid into flow path without using a mechanism for feeding pressure 3.11 nozzle structure that accelerates and releases fluid 3.12 porous membrane membrane containing pores (voids) 3.13 non-condensable gas air and/or other gases which is not liquefied under the conditions of a saturated steam [SOURCE: ISO 11139:2018, 3.183] 3.14 electrolysis process in which electric current is used to promote a chemical reaction Note 1 to entry: In the case of water, the separation reaction generating hydrogen and oxygen is a typical example. [SOURCE: ISO/TR 15916:2015, 3.34]
4.5 Pressurized dissolution system (for microbubble generation) The water in a container is sucked in by a pressurizing pump. When the liquid flow passes through a narrower cross section, the gas is sucked from outside into the pipe due to the negative static pressure. The introduced gas is forcefully mixed with the water. The water oversaturated with gas in a pressurized state returns to normal pressure when it passes through the nozzle. As a result, the generation of bubble nuclei is promoted. The bubble nuclei that are discharged into the liquid as the liquid flows from the nozzle grow to numerous fine bubbles through the absorption of oversaturated dissolved gas as a result of mass transfer, see Figure 5. NOTE 1 No recirculation stream is used for the fine bubble generating system. All the volume flow is saturated with air end decompressed (full stream saturation). NOTE 2 The pressurized air is introduced to the pressure side of the pump, usually directly into the saturator (retention tank/surplus gas separation).