Heat transfer and performance analysis of phase change thermal control system under variable gravity conditions

The electronic components within spacecraft are undergoing miniaturization and high integration due to advancements in aerospace technology and ongoing human exploration of outer space. As a result, the increased heat flux density can cause equipment temperatures to surpass the limited operating range, leading to thermal failure. Active thermal management is not feasible during spacecraft launch due to resistance friction, making passive thermal management crucial for heat dissipation. Phase change materials (PCMs) are commonly used in spacecraft thermal control devices due to their high latent heat storage (LHS) capacity. However, spacecrafts experience various environmental changes during launch, such as changes in weight and acceleration, complicating the heat transfer phase change problem and influencing the dynamic characteristics of thermal control devices. This study investigates the heat transfer and thermal control performance of phase change thermal control (PCTC) systems under conditions where gravity increases linearly with time. Factors such as melting rate, phase interface, temperature interface, velocity distribution, and thermal control time (ttc) are analyzed. Results show that gravity affects the natural convection impact on PCM melting. The equivalent gravitational acceleration is defined as g(t), and Case A and Case B are defined based on their different functional relationships. Compared to Case B-1 (g(t) = g), the complete melting time (tfull) for Case A-1∼9 (g(t) = kt + g, k = 0.01, 0.02, 0.03, 0.04, 0.05, 0.06, 0.07, 0.08, 0.09) was shortened by 17.56 %–36.92 %, and ttc was reduced by 13.53 %–33.83 %. This paper introduces two forms of thermal failure: temperature exceeding failure (TEF) and latent heat storage failure (LHSF). In Cases A-1∼9, the sensible heat storage temperature (TSHS) rise is 1.75–3.24 times higher than the latent heat storage temperature (TLHS) rise every 400 s. After revising the ttc, the elongation rates of Case A-1 and Case A-9 relative to Case B-1 were the lowest (46.99 %) and the highest (85.34 %), respectively.