Interfacial heat transfer and discharging characteristics of a pillow plate-graphite high-temperature sensible heat storage and heating device

Conventional block-type solid sensible heat storage devices based on tubular indirect heat exchange are constrained by a limited heat transfer area per unit volume, a low storage-medium volume fraction, and complex fabrication and assembly. To overcome these limitations, a pillow plate-graphite high-temperature sensible heat storage and heating device (graphite device) was proposed and constructed, employing block graphite as the storage medium and a pillow plate heat exchanger (PPHE) as the working fluid-side component to form a coupled “storage layer-transition layer-PPHE” heat transfer structure. Discharging experiments were conducted on two transition layer structures combined with two PPHE configurations. The effects of storage layer thickness, working fluid mass flow rate, and segmented flow rate regulation were subsequently investigated. The results show that the equivalent transition layer thermal resistance dominates the heat transfer path, accounting for more than 90% of the total resistance. Relative to the filled transition layer, the cast-in-place transition layer reduced this resistance by approximately 11%, promoting more complete discharging of the storage layer. The flat side of the single-sided inflated PPHE lowered the total thermal resistance by approximately 35% compared with the inflated side, thereby increasing the effective discharging time, average effective discharging power, and effective heat release by 11.21%, 43.71%, and 59.80%, respectively, relative to the double-sided inflated PPHE. Increasing the storage layer thickness extended the effective discharging time and cumulative heat release, whereas a lower flow rate favored sustained effective discharging. The segmented flow rate regulation strategy increased the effective heat release by 14.5%–68.2% under high-initial-flow-rate conditions. These findings provide an experimental basis for the structural optimization and operational regulation of block-type high-temperature sensible heat storage devices.