Contents:
In this paper, a new design of a natural convection solar dryer used to dry fruits is presented; taking into account the local climatic conditions prevailed in Jordan during summer season. The dryer will have a capacity of kg of sliced apples and the simulation is based on mass and heat balances.
The special tailored program could be used to calculate drying parameters for similar products under different climatic conditions. The next step will be focused on constructing the solar dryer in order to conduct actual experiments in the field. During the long past history, several thousand years ago, solar energy was used to dry main food products, such as fruit, vegetables, meat and fish, in order to be preserved for later use.
Although new technologies, such as cold storage, brought changed techniques, but still solar drying is used in different parts of the world, including the Middle East Region, due to the increasing demand for healthy and low-cost natural foods. Equally important is the new trend for green economies and sustainable development. Drying of agricultural products, e. Dryers have been developed and used to dry agricultural products in order to improve their shelf life [1].
Most of these dryers use an expensive source of energy such as electricity [2]. Projects of such nature have not been adopted by small farms either because the final design and data collection procedures are frequently inappropriate or the cost has remained inaccessible and the subsequent transfer of technology from a researcher to an end user has been anything but effective [3].
According to sources of the Ministry of Agriculture, the total cultivated area with apple trees and its annual production, in Jordan, is about Dunums i. Apples are popular fruits in the world market because of their unique and attractive flavor, color and nutritional value. During the harvest season there is a large quantity of this fruit and it has a relatively low price.
Drying might be an interesting method in order to keep the price of this fruit in the accessible range and prevent fresh fruit deterioration. There is a spoilage of fruits and vegetables that could be preserved using drying techniques in Jordan. Large quantities of small apples that are not demanded in the market could be used in solar energy drying.
It is therefore, envisaged that the design of a simple solar dryer could contribute greatly to solving this problem. Main factors affecting food dryers are: Drying time is also affected by type of food and its water content, and thickness of slices. Generally speaking very wet foods like mango, pineapple and tomato will take two full days of solar heated drying. Some like apple, coconut, potato, onion etc. Leafy products like herbs take only part of a day. It is important t note that excessive heat should be avoided in order to produce a high-quality product, since high heat rates may cause product degradation.
Drying time can be shortened either by raising the product temperature or treat the product. In the 1 st method moisture is vaporized, while at the same time the humid air is constantly being removed. In the 2 nd method, the product is treated to be dried so that the moisture barriers, such as dense hydrophobic skin layers or long water migration paths, will be minimized. The convection dryer in which the product is exposed to warm air which is heated by means of a solar absorber.
Dryers combining the principles of the above two, where the product is exposed to the sun and a stream of pre-heated air simultaneously. Also solar dryers are usually classified according to the mode of air flow into natural convection and forced convection dryers. There is no need for a fan to pump air in the dryer in the natural convection. Therefore, research efforts will be focused on designing the solar dryer.
The use of solar technology has been often suggested for the dried fruit industry for both reasons of reducing the energy cost and economically speeding the drying process to improve the final product quality in the terms of color and flavor.
The solar energy can be economically used for drying only if the purpose can be coordinated with specific characteristics of solar radiation which are that the incident radiation energy must be considerably higher than the world average 3. In Jordan, the calculated average radiation intensity is 5. For this reason economic use of solar energy could be achieved in Jordan.
Accordingly, the availability of solar energy and the operational marketing and economy reasons offer a good opportunity for using solar drying all over the world. A great number of successful practical applications have already been reported [9] [10] [11] [12] [13].
Solar drying is in practice since time immemorial for preservation of food and agriculture crops. This was done particularly by open sun drying under the open sky. Since traditional sun drying is a relatively slow process, considerable losses can occur. In addition, a reduction in the product quality takes place due to insect infestation, enzymatic reactions, microorganism growth, and mycotoxin development. This process has several disadvantages like spoilage of product due to adverse climatic condition like rain, wind, moist, and dust, loss of material due to birds and animals, deterioration of the material by decomposition, insect infestation and fungal growth.
Solar drying can be an effective means of food preservation since the product is completely protected during drying against rain, dust, insects and animals [14]. Significant developments, during the past decade, in the area of solar crop drying were reviewed by [15] , stating the fact that solar energy is considered more applicable to low-temperature in-storage drying systems and it has gained more importance work to facilitate a comparison of the financial feasibility of solar drying as against open sun drying, having presented the results of some exemplifying calculations and a brief discussion.
Also they presented a comprehensive review of the fundamental principles and theories governing the drying process, along with basic definitions [16] [17]. A comprehensive review of the various designs, details of construction and operational principles of the wide variety of practically-realized designs of solar energy drying systems was presented [18] - [26]: Asys-dryers, mixed-mode solar dryers, and hybrid solar dryers [27]. Low cost drying technologies suitable for rural farming areas were presented by [28].
A brief introduction on each of the drying technology considered namely fluidized bed, spouted bed, infrared, solar, simple convective, and desiccant drying were presented followed by some technical details on their working operations.
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Write a customer review. Most helpful customer reviews on Amazon. I bought several books on food drying and received mostly recipes and almost no information about how to prepare the raw food and carry out the drying process. This twin book lists almost every imaginable fruit and vegetable and clearly states how to properly prepare and dry it.
Very useful and a great help for a beginner like me. This book is a Godsend for anyone just getting into dehydrating food. How to select the best vegetables of that type for drying. How to prepare the vegetable for drying. How to blanch the vegetable, if necessary.
The drying temperature range that works best. Approximate drying times for the oven, the dehydrator and sun-drying. How to tell when the vegetable is dry. Conditioning, pasteurizing and storing the dried vegetable. How to rehydrate the dried vegetable before use, if applicable. The following recipes are included in this helpful guide: Popcorn on the cob. Cajun spiced green beans.
Buy this book today and learn to preserve your harvest by drying vegetables. Kindle Edition , pages. To see what your friends thought of this book, please sign up. To ask other readers questions about Food Drying vol. Lists with This Book.
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