| dc.description.abstract | This Doctoral Thesis evaluates ultrasonic degasification as a potential tool for mitigating total dissolved gas (TDG) supersaturation in the river downstream a hydropower plant. The volumetric liquid-gas mass transfer coefficient, kLa, is identified as a benchmark for comparing the efficiency of different parameters influencing liquid-gas mass transfer. Natural degasification in case of TDG supersaturation in a river downstream of a Norwegian hydropower plant is evaluated based on TDG saturation measurements, enabling the calculation of kLa through certain assumptions and simplifications. Laboratory experiments are conducted to explore the degasification of TDG supersaturated water in a controlled environment. A method is developed to increase TDG saturation levels in water for both small- and medium-scale experiments. This water is utilized to test the influence of selected parameters on liquid-gas mass transfer during degasification by technical methods, with a focus on ultrasonic degasification, in both a small-scale batch reactor and a medium-sized degasification test rig. The resulting kLa values are in agreement with literature, and ultrasonic degasification is identified as a highly effective method for increasing liquid-gas mass transfer, both in static and kinematic conditions, hence reducing TDG saturation levels. An empirical model, derived from batch reactor data and adjusted using test rig results, offers possibilities for estimations regarding application in real-world scenarios.
The study contributes to the understanding of important parameters driving liquid-gas mass transfer during degasification of TDG supersaturated, flowing water. In addition, it advances the understanding of the complexities of degasification mechanisms within formerly unknown fields of application. While offering significant insights, remaining questions, and emerging challenges highlight the necessity of further research. Collaborative efforts among academia, industry, and authorities are vital to expand knowledge, implementation, and regulatory frameworks, in order to enhance aquatic environmental protection and advance hydropower as an environmentally friendly technology. Continuing the pursuit of knowledge is encouraged to build upon the foundation this Thesis establishes. | en_US |
