Selection of cross-seasonal heat collection/storage media for wood solar drying

Abstract

In order to break through the limitations of wood solar drying and its application in the tropics, the core part of a wood solar drying system (collection/storage media) should be adapted to the seasonal characteristics of the high latitudes (Harbin, China). Therefore, formulating a scheme for selecting cross-seasonal heat collection/storage media for use in a wood solar drying system is of great significance. In this study, three common industrial media were tested for heat collection and heat storage in different environmental conditions. The poplar drying process was taken as an example, and the minimum temperature of the medium required for heat collection was calculated. The cross-seasonal heat collecting/storage medium scheme was developed for drying poplar. The results show that an aqueous ethylene glycol solution (W-EG) was the optimal heat collection medium. W-EG collected 109.3% more heat than heat transfer oil (THO), and the thermal efficiency (η) was 91.1% greater than η for THO when the ambient temperature was –10 °C. When the ambient temperature ranged from 5 °C to 35 °C, water (W) was the best heat collecting medium; the heat collection and thermal efficiency were significantly higher than those provided by W-EG and THO, and the heat dissipation capacity of THO was better than W-EG. Therefore, in late autumn, winter, and early spring, W-EG is the optimal heat collecting/storage medium. In late spring, early autumn, and summer, W is the optimal heat collecting medium, and W-EG was the optimal heat storage medium.