Effect of rotational operation and heat pipe bending on the thermal storage performance of a rotating latent heat storage unit

Phase change materials (PCMs) suffer from low thermal conductivity and progressive liquid-layer thermal resistance buildup during static melting. This study experimentally investigates the effects of intermittent rotation and micro heat pipe array (MHPA) bending on melting in a rotating latent heat storage (LHS) unit. A dedicated test platform evaluates transient thermal resistance, melting fraction evolution, and total melting time under varied rotation intervals, rotation angles, and MHPA bend angles. Active rotation promotes periodic solid-liquid interface reconstruction and suppresses thermal resistance accumulation in the heated region. Compared with the stationary case, a 2-min interval combined with 90° rotation reduces the maximum evaporator temperature by 17.7% and shortens the total melting time (all PCM measurement points continuously above 40 °C) by 13.8%. Enlarging the rotation angle from 45° to 90° further lowers the evaporator temperature by 4.7% and melting time by 1.6%. The MHPA bend angle acts non-monotonically: a 5° bend minimizes apparent thermal resistance by 22.3% relative to the straight configuration, yet prolongs total melting time by 16.2% because excessive heat extraction along the heat pipe weakens the thermal driving force into the PCM. A multi-objective operating strategy thus emerges: for rapid thermal response, adopt a 2-min interval, 90° rotation, and a bend angle ≤5°; for maximal storage efficiency, a 3-min interval with a 7° bend is preferable. This work elucidates the coupled mechanisms of active rotation and MHPA bending on PCM melting and offers design guidance for high-performance active thermal storage systems.