# Analysis and Optimization of Truck Windshield Defroster
## 4 Results and Discussion
### Optimization of the Defrosting Air Duct  
As discussed above, the poor defrosting performance was mainly due to the low air volume flow rate and air velocity at the outlet nozzle CL and CR. To improve this, the first step was to optimize the position of the guide plate in the defrost duct using the pressure loss reduction simulation. Figure 7 shows the geometry of the defrosting duct before and after optimization; in order to show the position change of the defrosting air duct deflector more clearly, Figure 7 is only a cross-sectional view of the central area of the defrosting air duct at the center thickness (outlet center center; CC), where the black line is the position of the guide plate before optimization, the yellow line is the position of guide plate after optimization, the green line is the edge line of the defrosting duct, and the blue line is the auxiliary line for modeling. The position of the deflector was extended to the entrance of the defrosting air duct, which avoided the pressure loss of the original defrosting air duct at the deflector due to the gas shunt. Through continuous optimization, the angle of the deflector was finally adjusted to 48\({}^{\circ}\), which avoided the  
Figure 6: Frost thickness of the windshield surface at 25 min. Figure 7: Original and optimized wind duct geometry. generation of the vortex, making the structure of the deflector play a role in guiding the air flow, and minimizing the pressure loss caused by the vortex. Figure 8 shows the pressure losses of the air flow in the defrosting duct before and after optimization. It shows that the pressure loss of the air flow at the outlets in the optimized defrosting duct was significantly lower than that in the original duct. The average reduction in pressure loss at each outlet nozzle was 21.56%. By comparing the positions of the guide plates in Figure 6, the optimized model could increase the air volume flow rate at the outlets, CL and CR, and hence increased the defrosting performance, as shown in Figure 8. The figure also indicates that the pressure loss at the five outlets was different, as the design was based on the minimum pressure loss method. Figure 9 shows the distribution of frost thickness on the glass surface after defrosting for 25 min in the optimized duct. It shows that 89% of the windshield was defrosted. However, the defrosting effect of the side window glass was still not ideal. After 25 min of defrosting, the defrosting area of the side window was about 80%. This may have been caused by the low air flow rate and velocity distribution of the left hand (LH) and right hand (RH) defrosting air ducts, which requires further optimization of the defrosting air duct. Figure 8: Comparison of pressure loss before and after optimization. Figure 9: \(Cont\). In addition to the optimization of the guide plate in the defrosting duct, Figure 10 shows the further improvement of the defrosting duct by optimizing the outlet structure, which was also based on pressure drop method simulation. By changing the outlet structure of the defrost duct, the injection angle of the jet flow could be changed, affecting the air distribution on the windshield. As shown in Figure 10a,b, the optimized model increased the horizontal angle between the duct and the windshield in the middle of the defrosting duct, and changed the angle and direction of the jet flow, to improve the airflow distribution on the windshield and hence improve the defrosting performance. Figure 11 shows the comparison of the velocity distribution of the frost layer before and after optimization after defrosting for 25 min. In the original duct before optimization, an obvious \"V\" (highlighted area in Figure 10a) shape appeared on the windshield with slow defrosting. This V  
Figure 10: Defrosting duct. (**a**) Original defrosting duct; (**b**) optimized defrosting duct. Figure 9: Frost thickness of windshield surface at 25 min after optimization. (**a**) Front windshield; (**b**) side windshield. shape disappeared in the optimized defrosting duct.