Transient Operational Characteristics of a Dual Compensation Chamber Loop Heat Pipe Without the Bayonet for Avionics Cooling

Abstract The removal of bayonet structures reduces the manufacturing complexity of loop heat pipes. This study investigates the transient characteristics of a newly designed dual compensation chamber loop heat pipe (DCCLHP) without a bayonet in high acceleration fields and analyzes instability phenomena. This work was conducted under four typical installation orientations, accelerations of 3–15 g, heat loads of 20–450 W, and heat sink temperatures of 15–25 ℃. Results demonstrate that the absence of the bayonet does not significantly degrade DCCLHP performance. Even at the unfavorable Orientation I, the system successfully starts up at 15 g and 20 W while maintaining stable operation at 6 g and 450 W. The acceleration direction significantly influences operational characteristics. Although favorable for liquid return, excessive acceleration may amplify the temperature difference between the two compensation chambers, thereby elevating the evaporator temperature. Notably, the DCCLHP may maintain satisfactory performance under high heat loads at the unfavorable Orientation IV. Additionally, several instability phenomena are observed. Vapor–liquid redistribution may induce evaporator temperature rise in a period of time, and the acceleration magnitude alters the minimum heat load, triggering this redistribution. Temperature oscillations occur only under specific conditions, with higher accelerations causing oscillatory behaviors. Temperature overshoot manifests mainly under lower heat loads and orientations favorable for liquid return, while increasing acceleration magnitude tends to weaken the overshoot. These findings provide critical data support and technical insights for the simplified design of DCCLHPs and their practical applications in aircraft.