Mass Transfer
Batch tray dryers suffers from the disadvantage of

Non-uniform & low production rate
High maintenance cost
High labour cost & low heat economy
All of the listed here

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Mass Transfer
A 25 cm x 25 cm x 1 cm flat sheet weighing 1.2 kg initially was dried from both sides under constant drying rate conditions. It took 1500 seconds for the weight of the sheet to reduce to 1.05 kg. Another 1m x 1m x 1cm flat sheet of the same material is to be dried from one side only.Under the same constant drying rate conditions, the time required for drying (in seconds) from its initial weight of 19.2 kg to 17.6 kg is

1500
1000
2000
2500

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Mass Transfer
Channelling is most severe

In dumped packing of regular units
At very high liquid flow rate
In towers packed randomly with crushed solids
In towers packed with stacked packing

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