Solar Drying of Red Chillies – Using of My Dryer

Solar Drying of Red Chillies – Using of My Dryer

The initial moisture content of the dried fresh red chillies in the next test was 260%, d.b., (equivalent to 72%, w.b.) This is similar to the results reported by Sittiphong et al., (2001). The chillies should then be dried until the level of moisture is about 15 % d. b. Two experiments were performed for the dryer evaluation with drying of red chillies.

The first experiment was carried out during 18–19 September, 2005 with a load of 35 kg of fresh product. This loading is about full capacity of the dryer trays, each with a thin layer of chillies. Drying was started at 18:00 by burning about 60 kg of wood (one time of feeding). Initially, the combustion was quite difficult to take place as the wood-fuels was wet due to its direct exposure to the rain. As a result, during the first 5 hours of burning, the increasing of the tray temperature was relatively slow. Drying was continued for the following day by using the solar energy. This means that, for the first 13 hours of the experiment, the source of heat was from wood burning, and for the remaining period the heat was from both solar energy and wood burning.

The decrease of moisture content during the experiment is shown in Figure 6.20. The products on tray 1 and 2 took about 11 and 13 hours, respectively, to reach a moisture level of 15%. This means the products on the two trays were dried only by burning wood as the source of heat. For the products on tray 3 and 4, during the first 13 hours of drying using back-up heater, the moisture content was reduced to 50 and 125 %, respectively, and therefore, drying had to continue during the following day to reach the wanted level. During the following day the energy for drying was supplied by both solar and by the stored heat in the bricks. With moderate level of solar radiation, it took the whole day for products on tray 3 and 4 to reach a moisture content of 15%.

Another experiment was conducted during March 4 -6, 2006 with drying of about 35 kg of red chillies using only solar energy. During the test, the solar radiation was relatively high with an average daily insolation of 5.8 kWh/m². Diurnal variation of solar radiation, and drying air on each tray during the first day of experiment, is shown in Figure 6.21. Drying occurred mainly during daytime, but, during nighttime, while the products were kept in the dryer, there was still a small decrease of moisture content observed.

The decreasing of moisture content of products on each tray is shown in Figure 6.22. The figure also shows the moisture content changes by sun drying. The products on tray 4 took about one and a half day to reach moisture content of 15%., and continued drying resulted in a final moisture content of 5.4 % by the end of the second day. For the products on tray 1, 2 and 3, the moisture content was about 127, 146, and 98 %, respectively, by the end of the second day.During the third day of drying, the product on tray 4 was interchanged with that on tray 1. This resulted in the moisture content of the product (initially from tray 1) reaching 15% at noon of the third day, and about 1% by the end of the day. For the forth day, tray 4 was re-interchanged again with tray 2.

By interchange trays, all the products were declared dry at noon of the forth day. From these experimental results, the interchanges of trays are recommended for the uniformity of drying and for a uniform drying time, and to avoid over drying of the products. To get uniform drying in the shortest time, the dryness level and solar radiation during the drying days have to be carefully estimated in determination the optimal timing for the trays interchange.

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