# Design and Application of New Aeration Device Based on Recirculating Aquaculture System
## 3 Results
### Test Results of Combined Aeration  
Figure 7 shows the results of nine sets of orthogonal tests. From the figure, it can be seen that the DO (\(C_{t}\)) was positively correlated with the operation time (\(t\)) of the NAD; i.e., it gradually increased with the increase in the operation time of the device.  
In all test groups, when the device was operated for 30 min, the DO in the water tank increased to a much higher value than the initial one. This indicates that the device has a strong oxygenation capacity for RAS pond water. Moreover, the oxygenation curve gradually converged in the late stage of the test, when the oxygen transfer coefficient (\(K_{L}a_{T}\)) gradually decreased; then, the curve rapidly decreased to a specific level and maintained a dynamic equilibrium. This is because the closer the DO level is to the saturation state, the smaller the mass solubility difference is, and the lower the mass transfer coefficient is; higher DO levels in water also facilitate respiration in cultured fish, and aquatic plants and animals.  
Based on the test results in Figure 7a, the average DO increase with the operating parameters of test 7 was 3.14 mg/L. Notably, there was a greater oxygen increase under these operating conditions when compared with Figure 6a. That is, when the operating parameters of the impeller aeration component remained unchanged, activating the microporous aeration component produced a better oxygenation effect, which indicates that operating both components simultaneously is beneficial for the aeration process, ascribing a greater practical application value to the NAD. The same conclusion can be drawn by comparing the other test results in Figures 6 and 7.  
Figure 6: Variations in DO under different operating conditions when the two oxygenation components were operated individually: (**a**) impeller aeration component; and (**b**) microporous aeration component.  
It is worth noting the results of experiments 11 and 15, according to which the mean values of the DO increase (\(R_{s}\)) were 5.50 mg/L and 5.17 mg/L and the DO distribution uniformity values were 96.6% and 98.1%, respectively. Running the device with the oper  
Figure 7: Variations in DO in orthogonal tests with different NAD operating parameters. Results of (**a**) test 7, (**b**) test 8, (**c**) test 9, (**d**) test 10, (**e**) test 11, (**f**) test 12, (**g**) test 13, (**h**) test 14, and (**i**) test 15.  
ating parameters of test 11 (\(n_{1}\) = 1000 r/min and \(n_{2}\)= 2280 r/min) resulted in the highest average DO and oxygenation capacity; therefore, this speed was determined to be the optimal operating parameter for the device. In Figure 7, the power of the comparison RAS oxygenation device in the control group was 2.2 kW, while that of the NAD under the operating parameters of test 11 was 2.83 kW. A comparison of the above data shows that operating the NAD with 28.6% higher power under the optimal operating parameters increased DO and the oxygenation capacity of the device by 122% compared with the comparison RAS oxygenation device. Through a comparative analysis of the test results from each experimental group, it was observed that the combined operation of the two components yielded superior outcomes compared to their separate activation. This finding underscores the synergistic effect achieved by the simultaneous operation of both components, highlighting the importance of integrated approaches in optimizing the aeration efficiency within RAS.