Visualized experimental study on steady-state performance of a loop heat pipe under elevated acceleration fields

In this article, an experimental investigation was carried out to explore the steady-state operational behavior of a newly designed nickel-water dual compensation chamber loop heat pipe (DCCLHP) under elevated acceleration fields. Glass windows were fabricated and embedded on a condenser and two compensation chambers (CCs) for the purpose of visual observation of vapor and liquid distribution. The steady-state operational behaviors and any new phenomena were discussed. The heat load from 30 W to 110 W and the acceleration magnitude from 1 g to 13 g as well as four different acceleration directions were taken into account. Experimental results indicate that: (i) as the heat load increases, the steady-state operational temperature of the DCCLHP increases, while thermal resistance may increase or decrease, also depending on both the acceleration direction and magnitude. (ii) The thermal resistance at both direction A and D is significantly larger than that at both direction B and C. The minimum thermal resistance with 0.78 K/W at 11 g with 70 W and operational temperature with 72.7 °C at 3 g with 30 W are achieved at direction C. (iii) as the acceleration magnitude increases, both operational temperature and thermal resistance tend to decrease for both direction B and C, whereas an opposite tendency is observed for both direction A and D. (iv) both the vapor column and liquid column alternatively distribute in the condenser channel that could increase or decrease the loop pressure drop. Inclined vapor–liquid interface and different liquid amount in both CCs are formed at different accelerations. Stratified flow or annular flow could lead to the film condensation heat transfer in the condensation channel.