Design And Experimental Studies Of A Solar Dryer For Salted Plum

This paper is a part of research project on solar plum drying financially supported by Yunnan Normal University and Science and Technology Bureau of Dali Administrative Zone.Plum product is one of the pillar economic products in Eryuan County of DaLi Region, and preserved plum is the main product of Plum products. Traditionally, the processing and preservation of dried plum relied on directly natural air drying such as exposing them to the sunlight. However, the period of the process is very long such as 40-50 days. In the processing of preserved plum, the drying process of salted-plum is a key procedure, but needs long time traditionally. The drying of salted-plum usually conducts under air temperature in between 40@ and 70@, and this can be efficiently implemented by the use of solar air collectors.Based on the drying characteristics of the salted-plum, a new solar dryer was developed. The dryer is consisted of a green cabinet and air collectors, and the air heated by the device is circulated by fans which is powered by a photovoltaic module with rated power of20W. A series of field examination on such a device for the drying of salted-plum was conducted in Eryuan County of Yunnan from April to May in 2003. The test results of the device indicated that this device is structurally reasonable with small thermal initia (thermal mass), and response time to the sunshine is very short. During the shinning days, the temperature inside the cabinet above 45癈 was found in the most of the daytime. In the overcast days or night, it can work normally by using auxiliary energy such as electricity. Thus, this device can be used in the whole year. Experimental results showed that, by using this device, the dehydration speed is 3.44 times as that by the traditionally direct air drying. Obviously, it can greatly shorten the drying period and improve the product quality resulting from direct exposing to the atmosphere. A technological and economic assessment on this device was also made and presented in this study. Result of the analysis showed that the repayment period of the device was 5.27year, and thus the device developed in this study is significantlyattractive for the production of the salted plum. In the one hand, solar drying can improve the product quality and sanitary conditions and shorten the drying period. In the other hand, the utilization of solar energy for the drying of plum can save fusil energy and preserve the ecological environment of our planet.