In order to describe the woodchip drying curves and study how the drying factors affect, a series of tests were conducted at different temperatures and velocities.

Drying is the process of removal water from a product. As a thermal process, the performance of any dryer mainly depends on the construction, design parameters as well as the operating conditions: flow rate and heat input [7]. During the tests, the weight of the sample, flow rate and psychrometric parameters: temperature and humidity were measured periodically using the appropriate instrumentation.

Sets of tests were undertaken at different temperatures, between 10°C and 50°C, for different drying velocities. The experimental drying velocities tested on the tray (area 0,25 m2) were up to 0.25 m/s that correspond to an air flow rate of 280 m3/h.

For each test, 3 kg of woodchip at 52% MC were spread over the tray forming a thin layer of 3 cm thickness. The woodchip was stirred to facilitate uniform drying. The sample weight was measured at 2 minutes intervals by a precision scale. Moisture content decreased until it reaches the equilibrium with the ambient. At the end the sample was dried up in an oven at 105°C. The ambient lab conditions were steady during the tests; temperature and relative humidity remained initial levels through the test.

The performance of the dryer was expressed the rate of water content with the product weight in the drying curves. Figure 2 shows the experimental variation of MC with time for selected tests at different drying conditions described in Table 1. As it is expected, MC decreases with increasing drying time describing an exponential curve. Drying time decreases as temperature and flow rate increase.