Experiments on thermal characteristics of a natural circulation loop with latent heat energy storage under cyclic pulsed heat load

An experimental investigation has been made of thermal characteristics of a rectangular, annular single-phase natural circulation loop with the inner tube filled with a solid-liquid phase change material (PCM) under cyclic pulsating heat load. A rectangular, annular loop of 150 cm in height and 75 cm in width was constructed with an annular gap of 0.6 cm, within which water was filled. The inner tube of the annular loop was filled with a PCM (n-Eicosene) or air. Under the cyclic pulsating heat load, temperature field within the water-filled annular loop with PCM- or air-filled inner tube was found to evolve into a steady periodic variation for the range of parameters considered. The water temperature and/or its fluctuating amplitude along the heated or cooled sections of the loop with the PCM-filled inner tube were found to be markedly lower than those measured in the loop with the air-filled inner tube under the identical conditions. On the other hand, along the insulated sections of the loop a somewhat minute difference in temporal variations of the water temperatures exists between the loops with PCM- and air-filled inner tube. In addition, at the outer wall along the cooled section, a time-periodic variation of temperature was detected in synchronizing with the pulsating heat load. Parametric effects of varying amplitude and time-period of the pulsating heat input, as well as of varying the inlet coolant temperature of the cooling jacket were investigated.