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Withering is the first processing step in the tea processing factory. For efficient tea processing, withering should be as uniform as possible. Uniformity in the trough withering greatly depends on the uniformity of the drying air temperature and velocity distribution along the trough. In literature no study is reported on thermal and velocity profiles of drying air during withering in a trough which would bring about uniformity in the degree of wither. In this backdrop, in the present work a 3D model has been developed using Fluent 6.2 computational fluid dynamics (CFD) package to predict the temperature and velocity distributions of drying air in a withering trough. The results of the model show wide variation in temperature and velocity distributions along the trough length, which contributes non-uniformity in tea leaves withering. The model has been validated within the acceptable limit (within ±1.43%) using the data that were collected from an open tea withering trough installed at Rosekandi tea estate factory, Assam, India. Thus, there is a good agreement between experimental and computational values. Therefore, the present numerical model can be extended incorporating the necessary changes in the trough design so as to obtain a uniform withering of tea leaves. [ABSTRACT FROM AUTHOR]