Temperature distribution in lumber during impingement drying

Summary Techniques are described for measuring the surface temperature of drying lumber with a radiation thermometer and for measuring interior temperatures at various depths with 30-gauge (0.25 mm) thermocouples. Experimental results with 52 mm thick yellow poplar boards dried above 100°C with impinging jets of hot air over a range of temperatures are presented showing surface and interior temperatures and moisture content as functions of drying time. Surface temperatures rose rapidly to within 10 to 30° of dry-bulb temperature, and interior temperature at the center of the boards remained near 100°C until the boards dropped below 10 percent moisture content.Use of trade names does not constitute endorsement of the products by the USDA Forest Service.