Experimental Determination of the Global Mass Transfer Coefficients of the Tropical Woods in order to Deduce the Drying Curves at the Lower Temperature
Résumé
We determine the global mass transfer coefficients of five tropical woods (obeche, iroko, lotofa, sapele and frake) coming from Cameroon. In this effect, drying kinetics using a solar dryer and a conventional dryer are utilized. In addition, comparison is doing between the values obtained and these coming from Chileans tropical woods and temperate. Thus, when the drying kinetics are between 0.25 to 1.5m/s, dry temperature equal to 33.5°C and wet temperature equal to 25°C, global mass transfer coefficients are between 2x10-5 and 4x10-5 kg/(m 2 .s), for the conventional dryer. These values are conform to these obtained on the Chilean tropical woods and less than these obtained on the temperate woods. In the case of an indirect solar dryer functioning between October and November 2004 at Yaoundé, this coefficient is lower because the wood thickness is almost 24mm in the case of conventional drying and 50mm in the case of solar drying. It is coherent to use the correlation established with the temperate wood and given below where the parameters ao, bo, co and p should be specific on the tropical woods: 1 K = a exp c T e + b exp c T V exp − 1 − X − X
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