Dehydration

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SIMULATION STUDIES ON GAX BASED VAPOUR ABSORPTION REFRIGERATION SYSTEM FOR COMBINED DRYING AND STORAGE APPLICATIONS R Sivakumar, R Saravanan and Alberto Coronas

Extended Abstract
India is the second largest producer of fruits and vegetables in the world. In 2010-11, fruit production stood at 74.877 million tonnes and vegetables production at 146.554 million tonnes. On the other hand 18% of fruits and vegetables from India are going to waste for want of adequate storage facilities. The amount of food wasted is worth Rs 44,000 crore due to poor preserving method. Low wastage is evident in key crops like cauliflower (5%) and even lower for potato & onion. Highest 13-14% wastage is evident in case of tomato and mushroom. Also 20% of food grain that India produces annually is eaten by rodents. Important thing to note is that high inflation in recent years has been evident even in components that enjoy low wastage and high cold storage capacity (potato & onion). Reasons for these cases are 1.India is short by 10 million tonnes of cold storage capacity due to which over 30 percent of agricultural produce goes waste every year. 2. More than 30% of produce from fields is lost to poor pre/post-harvesting facilities and lack of cold chain infrastructure. 3. Only 7% of food in India is processed. With such a monumental wastage in Indian agricultural sector; it would be advisable to rethink seriously into the pre and post harvesting processes. Especially drying and cold storage methods whose are the major energy consumers among the world. Drying is the oldest known method of preserving food. Historically, food was dried in the sun. Dehydrated foods are ideal for backpacking, hiking, and camping because they weigh much less than their non-dried counterparts and do not require refrigeration. Drying food is also a way of preserving seasonal foods for later use. At present many commercial dryers available in market. Fluidized bed dryer shows major advantages like high drying rate, low drying time, high heat and mass transfer, ease of control then other type of dryers. In other case some foods and many other commodities can be preserved by storage at low temperature, which retards the activities of micro organisms. A cold storage unit incorporates a refrigeration system to maintain the desired room environment for the commodities to be stored. A refrigeration system works on two principles: 1. Vapour absorption system (VAS), and

2. Vapour compression system (VCS)
VCS is comparatively cheaper than VAS. There are three types of VCS systems available depending upon the cooling arrangements in the storage rooms i.e., diffuser type, bunker type and fin coil type. VAS, although comparatively costlier, is quite economical in operation and adequately compensates the higher initial investment. Wherever possible such a system should be selected to conserve on energy and operational cost. In present scenario hybrid drying and cold storage systems which gives twin benefit of cold storage and drying with optimum energy consumption are in limelight. This paper concerned with the studies on fluidized bed dryer (FBD) combined GAX based vapour absorption refrigeration systems (VARS). Heat rejected from the condenser is used as heat source for FBD. The desired temperature range for storage of some fruits and vegetables are given below: Desired Storage Environment of Fruits and Vegetables in the cold storage (Ref: TNAU AGRITECH PORTAL)

Commodity| Cold storage Temperature (°C)| Relative Humidity (%)| Commodity| Cold storage Temperature (°C)| Relative Humidity (%)| Apple| -1 - 3| 90 - 98| Cucumber| 7 - 10| 90 - 95|
Apricots| -0.5 - 0| 90 - 95| Brinjal| 0 - 2| 90 - 95| Avocado| 7 - 13| 85 - 90| Grapes| -1 - 1| 85 - 90|
Asparagus| 0 - 2| 95 - 97| Lemons| 4 - 15| 86 - 88|
Beans, green| 4 - 7| 90 - 95| Lettuce| 0 - 1| 95 - 98| Beet root| 0 - 2| 95 - 97| Lime| 3 - 10| 85 - 90|
Broccoli| 0 -...
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