Exploratory studies on using thermal energy storage for vacuum wood drying

Vacuum wood drying is a fast and proven method, in which wood is subjected to dry at lower temperature. However, continuous transfer of the heat is not possible through convection under lower pressure. Moreover, energy storage and its transfer to wood layers through conduction can make a system more efficient and eco-friendly. Aluminium crosser/stickers were used to fill a phase change material (PCM) and flow hot water by keeping them in tight contact and placing side by side. Charging and discharging of the PCM were carried out at various water temperatures, and melting duration were recorded. In another experiment, simultaneous charging–discharging along with heating wood layers was conducted to ascertain effectiveness of the system. Molten PCM in aluminium stickers/crossers was stacked along with 50-mm-thick Melia dubia wood in a vessel, and vacuum drying was carried out. The results indicate that to melt PCM, higher water temperature (20 °C above melting point) resulted in quickest melting as compared with lower temperatures. Heat storage in PCM resulted in maintaining sufficiently higher wood core temperature. Under, a lower pressure system, using PCM-filled aluminium stickers long with wood layers resulted in an efficient drying. The study demonstrates feasibility of integrating thermal energy storage with timber vacuum dryers heated by solar water heaters.