# Optimization of Airflow Organization in Bidirectional Air Supply Data Centers in China
## 4 Airflow Organization Optimization
### Analysis of the Optimized Data Center Temperature Distribution  
Figure 11 presents the temperature contour plots at the cross-section (z = 1.2 m) under different optimization strategies, while Figure 12 shows the average and maximum inlet air temperatures for each server rack row in both the baseline model and the optimized model. Figure 11: Data center temperature distribution under different optimization strategies. (**a**) Case1; (**b**) Case2; (**c**) Case3; (**d**) Case4; (**e**) Case5; (**f**) Case6; (**g**) Case7. A comparative analysis of Figures 11 and 12 reveals that among the individual optimization strategies, Case1, Case2, and Case3 exhibit non-uniform temperature distributions and significant cold-hot air mixing. Specifically, Case1 demonstrates a distinct temperature boundary on the left side of the cold aisle. Compared to the baseline model, this strategy achieves a 0.35 \({}^{\circ}\)C reduction in average server inlet temperatures for all rack rows except AD and AF. However, the high-temperature area expands at the left end of cold aisle EF, with the maximum inlet temperature reaching 32 \({}^{\circ}\)C for AF rack servers, indicating intensified hot air recirculation in localized zones. In Case2, the bidirectional supply zone shows expanded blue low-temperature areas at this cross-section. However, compared with Scheme A, the average inlet air temperature of servers in this zone increases by 0.15 \({}^{\circ}\)C, indicating that the cold aisle top containment actually reduces the effective cooling capacity available for server cooling. In the unidirectional supply zone, the left side of cold aisle AB is almost entirely covered by high-temperature regions, with the maximum inlet air temperature of servers in row AA reaching 30 \({}^{\circ}\)C. This occurs because the underfloor-supplied cold air bypasses the servers and directly escapes from the cold aisle, causing the temperature in the return air zone to drop to approximately 20 \({}^{\circ}\)C.  
In Case3, an overall expansion of the low-temperature zones within the cold aisles is observed, accompanied by a 0.6 \({}^{\circ}\)C reduction in the average server inlet temperature compared to the baseline configuration. However, intensified local thermal recirculation is identified in cold aisle EF, resulting in elevated maximum inlet temperatures for servers in row AE. Furthermore, both the average and peak inlet temperatures for servers in row AF are found to increase, with the maximum temperature reaching 32 \({}^{\circ}\)C, demonstrating comparable performance to Case1. In Case4, the temperature field shows a distinct left--low/right--high non-uniform distribution pattern. Specifically, the return air temperature on the left side decreases to 21 \({}^{\circ}\)C, reducing the supply-return temperature differential to 2 \({}^{\circ}\)C. The cold air bypasses-induced low-temperature zones in hot aisles are completely eliminated, leading to a significant reduction in average server inlet temperatures. However, localized high-temperature regions persist near the air conditioning units on the right side of rack rows, with maximum inlet temperatures exceeding 26 \({}^{\circ}\)C observed for servers in rows AA, AB, AD, and AF, suggesting potential hotspot risks. Figure 12: Server inlet temperature. (**a**) Average inlet air temperatures for servers; (**b**) maximum inlet air temperatures for servers. In the combined optimization strategies, Case5 demonstrates no significant improvement in aisle temperature distribution, with large uncooled areas persisting at the right end of cold aisle AB in the unidirectional supply zone and cold aisle GH in the bidirectional supply zone. In Case6, the return air temperature on the left side is further reduced, with cold aisles predominantly covered by blue zones, indicating significantly improved temperature uniformity. The average server inlet temperature decreases to 19.6 \({}^{\circ}\)C, although maximum inlet temperatures approaching 24 \({}^{\circ}\)C are still observed for servers in rows AA and AF.