Shailendra Kumar ¹, R. P. Kandpal ¹, Ramkishore ¹

Affiliations
1 Wood Seasoning Discipline, Forest Products Division, Forest Research Institute, Dehradun-248006, IN

Abstract

The shrinkage pattern of wood provides some important information to monitor the drying stresses. Knowledge of timing, severity and reversal of the drying stresses may help to develop faster kiln drying schedules. Tangential shrinkage at core and shell layers of wood was measured in intact condition and slices were cut from exactly same layers. The slices were allowed to relieve their stresses first and then oven dried. The results indicate that shell layers of the wood are affected by higher magnitude of the drying stresses as compared to core layers. The results also indicate that after the stress reversal in wood, the rate of tangential shrinkage of wood also changes. In 41 days of drying, the stress reversal and shift in rate of intact shrinkage of wood in tangential direction coincided on day 21 of the drying. This work demonstrates that it is possible to determine the timing of the stress reversal by monitoring the rate of the change of wood shrinkage in tangential direction.

Keywords

Drying Schedules, Drying Stresses, Stress Reversal, Wood Shrinkage.

Full Text

     

Shailendra Kumar ¹, Ramkishore ¹, R. P. Kandpal ¹

Affiliations
1 Wood Seasoning Discipline, Forest Products division, Forest research institute, Dehradun-248006, IN

Abstract

A semi-green house type improvised design prototype of solar timber drying kiln was designed and constructed at Forest Research Institute (F.R.I.), Dehradun (30.32° N, 78.03° E). Roof and side walls of the kiln were made of double glass glazing. The inclination angle of south facing roofs of the kiln was divided into two parts in order to provide sufficient heat to solar kiln in winters. Aluminium finning was done in kiln's main flat plate solar collector made of G.I. (Galvanised Iron) sheet for efficient heat removal, which ran parallel to the roof. The air circulating fans were positioned to force air to flow from north to south direction. The design allowed the flowing air interact with Aluminium fins. The east and west walls of the kiln were also provided with inbuilt blackened G.I. sheet flat plate collectors to trap solar energy in early morning and late evening. Empty test runs in month of April, 2014 showed quick temperature rise in kiln especially in morning and evening, and maximum temperature of 98.6° C was achieved inside the kiln at 14:00 hrs. A test wood charge of 1 m³ teak wood of thickness 3.8 cm was dried from 70% to 11% MC (Moisture content) without any significant visible defects in 15 days.

Keywords

Solar Kiln, Solar Collectors, Wood Drying, Solar Radiation.

Full Text