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Subject: Agricultural Process Engineering × Author: Nayak, Sujata × End date: 2009 × Start date: 2003 × Type: Thesis ×
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    ThesisItemOpen Access
    Simulation and optimization of a solar dryer
    (CCSHAU, 2005) Nayak, Sujata; Garg, M.K.
    On clear days or cloudless skies, the predicted solar radiation by ASHRAE method was about 20 per cent higher than the observed value. Thus for prediction of solar radiation at Hisar a clearness number of 0.8 was taken for estimation of solar radiation. There was a close agreement between the observed and predicted values of solar radiation for different seasons at Hisar when the clearness number was taken as 0.8. During summer maximum solar radiation was predicted when the south facing collector was tilted at 10-15°C from horizontal and during winter the maximum solar radiation was observed at about 50° tilt from horizontal. However, it becomes difficult for the users to modify the tilt according to seasons. Thus for maximum solar radiation collection, a collector tilt of 30°C (latitude of place) was taken for the design of solar collector.. A computer based mathematical model was developed for a solar dryer for predicting solar radiation, drying air temperature, product temperature in trays, moisture removal rate and drying efficiency. The developed model was used for studying the performance of solar dryer and was tested for its validation. No significant difference was obtained between the observed and predicted values. On the basis of design data, a natural convection solar dryer was got fabricated for drying of fruits and vegetables. The capacity of dryer was about 20 kg and the collector area was 2 m2. Average collector outlet temperature during no-load testing was comparatively higher than that of collector temperature during load testing and there was little variation of collector temperature between the predicted and observed values. From the experimental studies, it was observed that the cauliflower dried in 14 hrs (2 days) from initial moisture content of 82.02 per cent (wb) to final moisture content of 10.26 per cent (wb). It was seen that for drying of less quantity of product natural circulated air is sufficient and for drying of large amount of product, external source like blower or fan is required. Therefore, the developed mathematical model can be used to predict the dryer performance at different places by changing the input data only.