## 3 Results and Discussion
### Dynamic Response Characteristics of the Heat Pipe Systems
For example, it cost nearly 450 s for TSHP-1 to return to the stable status after the surface temperature of T1 was up to 94 \({}^{\circ}\)C. It could be seen that the pressure of the evaporation section was high enough to prevent the working liquid in the heat pipe from reflowing back. Additionally, the liquid slug might be formed in the condensation section. However, the liquid slug could be pushed back to the evaporation section with heat load B input of 10 W, even though it took a long time in this process. That was why nearly 450 s was the cost for TSHP-1 to recover to the stable status, which was approximately three times longer than that of status when the surface temperature of T1 was 75 \({}^{\circ}\)C. More detailed explanations about the pressure distribution of the heat pipe during different statuses can be found in Section 3.1. Figure 8 demonstrates the surface temperature distribution of TSHP-1 versus heat load A and heat load B. As shown in Figure 8a, the surface temperature distribution of TSHP-1 with different heat load A from 45 W to 80 W under a certain heat load B input of 12 W was demonstrated in detail. It could be seen that the surface temperature along TSHP-1 from the evaporation section to the condensation section (from T1 to T6) showed a small difference before it dried out, except for the heat load B section (from T7 to T9). TSHP-1 would have good temperature uniformity performance with heat load A input less than 75 W under a certain heat load B input of 12 W. Because the heat pipe was under the stable status. However, the surface temperature of T7 to T9 was quite different from each other. The surface temperature increased successively from T7 to T9 due to the rapidly increasing steam pressure during the heat load B section. Moreover, the surface temperature of T1 and T9 would suddenly increase when TSHP-1 came to the threshold critical power under a certain heat load B of 12 W. It was worth noting that the surface temperature of the whole heat pipe slightly increased before TSHP-1 came to the threshold critical power. The surface temperature distribution of TSHP-1 with different heat load B from 0 to 12 W under a certain heat load A input of 45 W was shown in Figure 8b. The surface temperature along TSHP from the evaporation section to the condensation section (from T1 to T6) showed a small difference for TSHP-1 under the stable status during the whole testing process, except for the heat load B section (from T7 to T9). The surface temperature still increased successively from T7 to T9 due to the rapidly increasing steam pressure during the heat load B section. Firstly, the surface temperature of T7 was higher than that of T9 without heat load B input, and then the surface temperature of T9 increased slowly versus heat load B. Finally, it exceeded that of T7. In summary, the main section of TSHP-1 (from T1 to T6) had good temperature uniformity performance when it was less than the threshold critical power. The addition of heat load B for TSHP-1 could cover a larger power range than that of a heat pipe with the same dimension. Moreover, the necking section of TSHP  
Figure 7: The recovery characteristics of TSHP-1 with heat load B input of 10 W after the surface temperature of T1 increased to **(a)** 75 \({}^{\circ}\)C and **(b)** 94 \({}^{\circ}\)C caused by heat load A input up to 65 W.  
also played an important role in the steam pressure distribution adjustment. Therefore, different heat loads B could obtain the different threshold critical power of TSHP-1, and it also meant that low threshold critical power heat pipe could normally work under an overpower status with heat load B input. It also meant that TSHP-1 with heat load B was especially suitable for overclocking work situations. The thermal resistance of TSHP-1 versus heat load A and heat load B was demonstrated in Figure 8c,d.