# Impact of Mesh Resolution and Temperature Effects in Jet Ejector CFD Calculations
## 3 Results
### Analysis for Temperature Changes Using Refined Mesh  
This case depicts the three temperatures variations, according to the \(\zeta\) coefficient introduced in Table 4 and calculated using the _refined_ mesh. As defined in Table 4, in this  
Figure 8: Mach number scenes comparison. On top: Mach number scenes views at consecutive A and B points from Figure 7. On bottom: Mach number differences between both cases. study three temperature levels will be compared at the ejector inlets: the T case where the reference temperatures at the inlets are imposed (T\({}_{\rm p}\) = 380 K, T\({}_{\rm s}\) = 313 K); the T' case where these temperatures are imposed multiplied by a factor of 1.1, and the T\" case where the temperatures are multiplied by 1.2. Figure 9 shows the comparison of the line \(\pi_{\rm sp}\) = 0.26 for the three temperature levels. By increasing the inlet temperatures at both inlets proportionally, the dimensionless values that determine the ejector operation do not vary and result in a similar line of behavior on the ejector map. As can be seen in the graph below, the three lines coincide in the critical zone, as well as in the critical point and in the subcritical zone. In all three cases, the same oscillating behaviors of the subcritical zone and the variability of its negative slope are observed. This repeatability in the results, reproducing the intricate wavy shape of the ejector behavior in the subcritical zone, gives a clear demonstration of the precision of the _refined_ mesh. In order to compare, in detail, the obtained results at the three different regions (critical, subcritical, and backflow) at one temperature, points C, D, and E of Figure 9 have been marked for a more detailed analysis. Figure 10 shows the Mach number distribution in the ejector for the three chosen points, C, D, and E, for the T temperature. In this figure, to facilitate the visualization of the flow under supersonic conditions, only the areas where the Mach number is greater than one have been represented on the color scale. As can be seen, the shockwave distribution follows the expected trend. Moreover, all cases with different temperatures revealed the same tendency when they change from the critical, to the subcritical, to the backflow zones. In Figure 10, the top snap shows the Mach number scene for the critical conditions (point C). We can see that the flow is double chocked because in the mixing zone, where the primary and secondary flows mix, the supersonic behavior of the flow occupies the entire cross-section, blocking the pass of both flows. At the outlet of the primary nozzle, the first oblique shock wave appears producing a Mach disk in the axis zone of the ejector. It is then followed by a chain of diamond oblique shockwaves, continuing toward the mixing chamber. Later, the amplitude of the waves diminishes, to eventually disappear around the  
Figure 9: The lines of \(\pi_{\rm sp}\) = 0.26 for the temperatures according to Table 4 using the _refined_ mesh. entrance of the diffuser. The figure also shows the first part of the jet where the walls of the duct affect its shape and produce the aforementioned blockage of the entire cross-section of the ejector. The second scene (point D) in the middle, represents the subcritical conditions. In this case, we can see that only the primary flow is choked, and the secondary flow has a passage close to the walls in subsonic conditions. In this case, the jet length is lower than the previous case and the waves disappear around the middle of the mixing zone. The bottom snap (point E) represents the backflow condition's Mach number scene. In this case, the chain of oblique shockwaves is very short and ends in the first part of the mixing zone. This smaller jet produces an increase in the secondary flow section pass and causes the return of the flow near the ejector wall due to the pressure difference between the ejector outlet and the secondary inlet.