A case study of the control system for mixing fine bubbles in water in a pressure-controlled water tank

Abstract

In normal air, oxygen is approximately 20%. Considering dissolved ox-ygen (DO), plays a crucial role in industrial processes and environmental applications, including wastewater treatment, aquaculture, and chemical processing. Oxygen transfer efficiency is a key factor in enhancing aeration system performance while minimizing energy consumption. This study analyzes the efficiency of a fine bubble aeration process using a Venturi bubble generator in a pressure-controlled water tank. The objective is to evaluate the effects of water and air flow rates on DO retention, energy efficiency, and mass transfer influenced by fluid turbulence. The experiment was conducted under nine different water and air flow rate conditions: 50 LPM/40 CCM, 50 LPM/80 CCM, 50 LPM/100 CCM, 30 LPM/40 CCM, 30 LPM/80 CCM, 30 LPM/100 CCM, 20 LPM/40 CCM, 20 LPM/80 CCM, and 20 LPM/100 CCM. DO degradation was analyzed under both open-air conditions at room temperature and closed-air conditions with controlled air pressure. The results indicate that maintaining an air pressure of 1 bar reduces the DO depletion rate by approximately 6.52% compared to open-air conditions. In terms of energy consump-tion, the 50 LPM/40 CCM configuration demonstrated a 35% lower energy consump-tion (0.91 kWh) than the 20 LPM/100 CCM configuration (1.39 kWh). Additionally, the study examined the relationship between turbulence intensity and bubble size distribution. The findings revealed that an increase in the Reynolds number is associated with a reduction in bubble size, enhancing gas-liquid mass transfer efficiency. The average bubble diameter to Venturi throat diameter ratio (DBave/Dth) decreased with increasing turbulence, highlighting the importance of flow control in aeration systems. The results demonstrate that fine bubble aeration with pressure control significantly improves oxygen dissolution efficiency while reducing energy consumption, with bubble sizes ranging from approximately 630 microns at 50 LPM/40 CCM to 300 microns at 20 LPM/40 CCM.?????????????????????????????????????????????????? 20% ?????????????????????????? (DO) ????????????????????????????????????????????????????????????????? ???? ??????????????? ????????????????????? ??????????????????? ??????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????? ????????????????????????????????????????????????????????? ????????????????????????????????????????????????????????????????????????????? DO ???????????????????????? ?????????????????????????????????????????????????????????? ????????????????????????????????????????????????????? 9 ?????? ?????? 50 LPM/40 CCM, 50 LPM/80 CCM, 50 LPM/100 CCM, 30 LPM/40 CCM, 30 LPM/80 CCM, 30 LPM/100 CCM, 20 LPM/40 CCM, 20 LPM/80 CCM ??? 20 LPM/100 CCM ?????????????????????????????? DO ???????????????????????????????????????????????????????????????????????? ?????????????????????????????????????? 1 ???????????????????????????? DO ????????? 6.52% ??????????????????????????? ???????????????????????? ????????????????? 50 LPM ???????? 40 CCM ????????????????? 35% (0.91 kWh) ?????????????????????????????? 20 LPM ???????? 100 CCM (1.39 kWh) ????????? ???????????????????????????????????????????????????????????????????????????????? ??????????????????????????????????????????????????????????????? ??????????????????????????????????????????????????????????? ??????????????????????????????????????????????????????????????????? (DBave/Dth) ??????????????????????????????????? ???????????????????????????????????????????????????????? ??????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????? ?????????????????????????????????? ????????????????????????????????????????????? 630 ???????????????????? 50 LPM/40 CCM ??? 300 ???????????????????? 20 LPM/40 CCM