## 3 Results and Discussion
### Performance of the Header and Flow Characteristics in the Orifices  
The variation of \(\eta\) under different \(\dot{m}_{\text{in}}\) is depicted in Figure 4. It can be observed that with the increasing of \(\dot{m}_{\text{in}}\), \(\eta\) increases firstly to the maximum value of 51.94% at \(\dot{m}_{\text{in}}\) = 12 g/s and then decreases. When \(\dot{m}_{\text{in}}\) is larger than 15 g/s, the degradation of \(\eta\) becomes severer. It becomes 29.99% at \(\dot{m}_{\text{in}}\) = 21 g/s. This will be discussed in the following section. The pressure difference (\(\Delta P\)) crossing the orifice-baffle, which is one of the main driving forces for the liquid drainage [16], increases with the increasing of \(\dot{m}_{\text{in}}\). This is because more liquid flows towards the right side of the orifice-baffle, leading to an increase in the height of the liquid film above the orifice-baffle. Thereafter, the static pressure above the orifice-baffle increases. To obtain a deep understanding of the flow characteristic and discover the causes of deteriorated vapor-liquid separation performance, the mass flow rates of the liquid drainage and vapor leakage through the orifices, i.e., \(\dot{m}_{\text{L,O}}\) and \(\dot{m}_{\text{V,O}}\), are analyzed, as shown in Figure 5. As mentioned above, there exists a strong liquid impact at the right  
Figure 4: Vapor-liquid separation efficiency and the pressure difference across the orifice-baffle. side of the baffle, \(O_{2}\), being the furthest away from the liquid impact, has a higher \(\dot{m}_{\text{L,O}}\) than \(O_{1}\) and \(O_{3}\). Different from \(\eta\) that is peaked at \(\dot{m}_{\text{in}}=12\) g/s, the peak of \(\dot{m}_{\text{L,O}}=3.75\) g/s appears at \(\dot{m}_{\text{in}}=15\) g/s. This is explained as: compared to \(\dot{m}_{\text{in}}=12\) g/s, \(\dot{m}_{\text{in}}=15\) g/s has a higher \(\dot{m}_{\text{L,O}}\) because of a larger driving force, but its \(F_{\text{L}}\) is much smaller owing to the more liquid within \(\dot{m}_{\text{in}}\), leading to a lower \(\eta\) given that \(F_{\text{V}}\) in these two cases are negligible (see Figure 5b). \(\dot{m}_{\text{L,O}}\) maintains at around 3.30 g/s when \(\dot{m}_{\text{in}}\) is 18 g/s and 21 g/s. Meanwhile, \(\dot{m}_{\text{V,O}}\) weakens the vapor-liquid separation performance, derived from Equations (11) and (12). As seen in Figure 5b, \(\dot{m}_{\text{V,O}}\) has an opposite trend to \(\dot{m}_{\text{L,O}}\). It decreases at first when \(\dot{m}_{\text{in}}\) is smaller than 15 g/s and then increases to 0.15 g/s at \(\dot{m}_{\text{in}}=21\) g/s. The vapor only leakage about 0.02 g/s and 0.01 g/s as \(\dot{m}_{\text{in}}\) equals to 12 g/s and 15 g/s, respectively. This is due to the liquid film above the orifice-baffle in these two cases being able to resist the impact of the liquid flow from the wall, in which the orifices are rarely affected by the fluid impact and only a small amount of vapor leakage. Conversely, much vapor leakage out from the orifice under the other three \(\dot{m}_{\text{in}}\) because of the unstable liquid film above the orifice-baffle. Moreover, the vapor is escaped out from \(O_{2}\) is less than that from \(O_{1}\) and \(O_{3}\) owing to its farthest distance away from the liquid impact. Figure 6 displays the distributions of vector and density at the central section of the orifices. Clearly, the flow characteristics in \(O_{2}\) are significantly different from those in \(O_{1}\) and \(O_{3}\). When \(\dot{m}_{\text{in}}\) is between 9-15 g/s, the vapor velocity in \(O_{2}\) is normally lower than 1.5 m/s and it mostly exists near the wall of the orifice. As \(\dot{m}_{\text{in}}\) increases, the vapor with high velocity begins to appear in \(O_{2}\), which indicates more vapor leakage. This phenomenon is mainly due to the induced stronger liquid impact on the orifice-baffle at higher \(\dot{m}_{\text{in}}\).