The implementation of a dualistic model for scale up of a tunnel drying of cassava chips

Adeladun Stephen Ajala


Tunnel dryer is a combination of two or more cabinet dryers arranged in a serial order in a tunnel. It has found application in drying of both food and non-food origin but its scale up process has hitherto been based on experimentation and experience without comprehensive scientific background which often leads to the poor performance of those dryers. In this study, theoretical modelling for tunnel drying which could effectively predict the dryer’s performance was developed. The modeling process involved the segmentation of drying parameters into an equipment and material models. Equipment model entails the parameters supplied by the dryer such as air temperature, velocity, humidity profiles and heat transfer to the samples being dried (cassava chips). Material model embraces properties of cassava chips such as drying kinetics and drying equilibrium moisture conditions of the sample.

The results of the scale up values are 4860 kg/cycle, 600kW, 111 kW, 6.075 m3, 150 oC and 12 for dryer batch capacity, heater’s wattage, fan’s wattage, dryer’s volume, allowable temperature and number of trucks respectively.

 The study identified and itemized critical model parameters necessary for effective scale-up of tunnel drying. More so, the effectiveness of the dualistic model for tunnel drying of cassava chips has been demonstrated and methods are outlined for using the model to scale up from bench scale test through pilot plant testing to full scale dryer operation. Incorrect application of these parameters would impede successful scale-up of this dryer.

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