Sun and artificial air drying kinetics of some agricultural products (original) (raw)
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Drying Characteristics of Fruits using Solar Drying
2016
In this study, a solar dryer system designed to use convection sources of energy for drying agricultural product it is expensive process in developing countries. This research is a try to develop a solar dryer for figs. The aim is to produce a drying fig with good quality and decrease the drying time. Five different indirect design concepts were presented. All concepts that generated are indirect forced and natural convection of solar energy. All generation consists of the same dimensions and material made. One design concept was chosen after screening process which consists of a solar collector, a drying chamber, and chimney. Finally, the result was discussing five experiments that did to obtain the higher performance of solar dryer. The result recorded the average chamber temperature is 59°C compared with average ambient temperature is 32 °C. The theoretically result presented the dryer efficiency is 17.6%.
Solar drying of natural and food products: a review
Natural and food products are dried to improve self-life, reduce packaging cost, increase shipping capacity, enhance appearance, encapsulate original flavor and maintain nutritional value. The main objective of drying is to withdraw moisture from the food so that bacteria, yeast and mold cannot grow and spoil the food. Mostly fossil fuel is used for heating air for drying purpose. Due to exponential rise in the price of fuel and depletion of fossil fuel, there is a need to look for other alternatives like nonconventional energy resources viz. solar energy. India is blessed with good sunshine hours. A review is made to use solar energy for drying of agricultural and food products with different dryers available and with various parameters affecting the drying process and the product. Effect of drying on texture and oil content of the natural products are discussed. A comparison is made between conventional drying and solar energy assisted drying. Work done on different solar dryers with different natural agricultural products along with parameters, result obtained are compared from different literatures.
Performance characteristics of solar drying system for agricultural products
Drying has important influences on agricultural products' quality and storage. Drying characteristics of different agricultural products vary. Temperature and velocity of drying airflow affect greatly drying quality and drying efficiency of agricultural products. Two types of solar drying systems for different drying temperature requirement were designed and characterized in this paper: solar air drying system with plate air collector and solar parabolic trough concentrating drying system. In solar air drying system with plate air collector, the drying oven has two ventilation modes. With top inlet and bottom outlet ventilation mode, the overall temperature in drying oven is relatively high, however large vertical temperature difference exists in drying oven. With bottom inlet and top outlet ventilation mode, the temperature in drying oven is uniformity, however relatively low. In notoginseng drying experiment, the drying time is shortened to half of that in nature drying. The average thermal efficiency is 66.5%. The solar trough concentrating drying system utilizes a low cost and reliable V-type metal cavity to collect solar irradiation. In the system, the heat conducting oil can be heated to 230℃, and the air flow from heat exchanger reaches above 200℃. The tobacco shred drying experiments verifies that the drying temperature of the system meets the tobacco shred drying requirement. Solar trough concentrating drying system matchts the drying temperature scope of 80℃~200℃.
Drying of agricultural products using forced convection indirect solar dryer
Drying of three agricultural products namely potato slices, onion slices and whole grapes was done using an indigenously designed and fabricated forced convection indirect solar dryer and under open sunlight. The diurnal variation of temperature, relative humidity in the solar dryer was also compared with the ambient temperature and relative humidity during March and April 2017 for all the three products. The study showed increase of temperature and lower humidity inside the drying chamber at different time interval. Hourly moisture loss for all the three agricultural products in the drying chamber and open sun drying was also compared and the percentage of moisture loss in the drying chamber was found to be higher compared to open sun drying for all the products. The mass of water removed for all the three products in the drying chamber was also found to be higher than the open sun drying. Results of the study showed that forced convection indirect solar dryer is better than the open sun drying method for drying the agricultural products more efficiently.
Performance Evaluation of Solar and Oven Drying for Tropical Fruits
Sretechjournal Publication
Solar drying is the common traditional method to preserve fruits by reducing its moisture content and the microorganisms’ activities, hence, slowing down the mold growth, which affect the quality of fruits. The operational cost of the solar dryer can be cheaper but the drying time using the solar dryer is usually longer than other drying techniques that use electricity due to the lower and inconsistent temperature within its drying chamber. In this work, bananas, papaya and pineapple were dried using an oven at temperatures of 65-85oC, and the results were compared with the outcomes of drying using a simple wood solar cabinet dryer, done in Kota Samarahan, Sarawak Malaysia. The drying profiles for the fruits dried in the oven were found to be quite similar, indicating the insignificant variation in the cell matrix structure of the fruits, and in addition, these results were supported by the small range of the estimated drying constants between 1.32 - 1.83 10-1 hr-1. Moreover, the results showed that the increase in the temperature of drying in the oven from 65 to 75oC did not change the drying time significantly, but the drying time was reduced significantly to 70% when the temperature was increased to 85oC. The fluctuation of temperature and air flow within the solar dryer between 27-34oC and 0.12 -1.52 m/s, respectively, slowed down the drying process, resulting to prolong of drying time. The drying time to reduce the moisture content from 80-60% for the solar drying was between 31 to 74 hours while for oven drying with temperatures of 65-85oC was between 1-5 hours.
Evaluation of Indirect Solar Dryer for Drying of Some Wild Fruits Grown in Western Himalayan Region
Studies were undertaken to evaluate the indirect solar dryer for drying of some wild fruits vis-a-vis mechanical dryer and open sun drying on the basis of physico-chemical and sensory characteristics. Three major wild fruits i.e. wild ber (Zizyphus mauritiana L.), wild anola (Phyllanthus emblica L.) and wild bael (Aegle marmelos L. Corr.) were selected for the present study. Indirect solar dryer consists of two main parts viz. solar collector and drying chamber with thermal backup system. Average drying rate of 0.35 gm/h (open sun), 0.63 gm/h (solar dryer) and 4.32 gm/h (mechanical cabinet dryer) was recorded when the samples were dried intermittently in open sun, indirect solar dryer and mechanical cabinet dryer. Water activity of dried fruits ranged between 0.276 to 0.364, when dried with different modes of drying. All the hysicochemical characteristics of dried fruits were at par with those dried in cabinet drier and differ significantly with those dried in open sun. Further, the treated fruits dried in indirect solar dryer were rated best among all drying modes on the basis of highest sensory scores of colour, texture, taste and overall acceptability even after 3 months of storage of dried samples at ambient conditions. Hence, drying of such perishable crops in the indirect solar dryer could be a best option to prevent the postharvest losses and to extend the shelf life of these crops.
Intensification of the Plant Products Drying Process by Improving Solar Dryer Design
Journal of Engineering Thermophysics, 2018
The article presents the rationale for production of dried fruits and vegetables using a solar drying unit. To intensify the drying process, convection of drying agent flow in the proposed drying chamber is studied using Navier–Stokes equations. Numerical methods are used for solving equations describing the process of convective heat transfer. As a result, graphical interpretations of isolines of drying agent flow are obtained and location of passive zones in the dryer chamber are identified. Uniformity of the temperature zones in the chamber is ensured by supplying additional drying agent into the passive zones. Temperature values at various levels of the drying chamber are experimentally obtained. Results for drying cut-up mass of vegetables and fruits are presented.
Drying is a popular and oldest preservation technique in which the moisture content is reduced to a level to keep the product at a relatively chemically stable state . Although, open sun drying is the cheapest method, the dried products are of poor quality due to contamination by insects, pests, birds and dusts and attack by wild animals . Further, there is an increasing realization that the use renewable sources to meet the growing energy needs of a burgeoning population cannot be delayed any further . India stands second in vegetables and fruits production, hardly 2% of the produce is processed and 25-30 % is being wasted due to lack of processing and preservation infrastructure . Many a times, when the production is high, the farmers have to either sell their produce at very low price or it goes waste, there by incurring great economic loss to the farmers. However, this loss can be minimized by dehydrating fruits and vegetables . Moisture removal from food products is one of the critical factors responsible for prevention of growth and reproduction of spoilage causing microorganisms . Solar drying results in quicker drying rates compared to open sun drying by achieving higher temperatures, lower humidity, and increased air movement . Drying food items in short times better preserves nutritional values of the products and optimal temperatures as compared to traditional dried [2,3]. Additionally, research has shown that solar drying can improve the quality of a product w.r.t. colour, flavour, appearance and other organoleptic qualities, which enhances the marketability of product and consequently allows for improved financial opportunities for farmers . Therefore, in the present energy crisis, it is desirable to harness the potential of solar technology for dehydration of fruits and vegetables, so that gas, oil and electricity can be saved. The indirect solar dryers are not only more effective than open sun drying, but have lower operating costs than that of mechanized industrial driers. Keeping the above facts in view, indirect solar drier having thermal backup system was evaluated for drying of some important wild fruits viz. aonla, bael, and ber grown in western Himalayan region.
Experimental analysis of solar drying system for vegetable and fruits
Journal of Thermal and Fluid Science, 2020
A performance analysis of a sun drying system for vegetables and fruits is the subject of this study (Grapes, Potato, Onion and Banana). Drying 5 kg of Vegetable & Fruits using the dryer Study the influence of drying, as well as environmental and operational conditions, on the performance of the drier. The experiment was conducted both with and without a reflecting mirror, and the results were compared. In the absence and presence of reflecting mirrors, the highest collector outlet temperature was 66 o C and 81 0 C, respectively. According to the results, ginger can tolerate a maximum of 65 0 C in a dryer without a reflecting mirror, but not one with one. The maximum temperature for ginger is 65 0 C when the dryer has a reflective mirror installed. On average, efficiency without and with a mirror was 53.14% and 79.39% whereas it was 53.14% when using a mirror and 61.84% when using a mirror, respectively Reflectors enhance the average efficiency of the collector by 8.04%, according to the study. Ginger's original moisture content was 82.95%, and it required 16 hours of daytime drying in a solar dryer to achieve its equilibrium moisture level of 12%, and 48 hours of open sun drying with 8 hours of drying each day to reach the same level. Fruits and vegetables dried in a dryer took 66.7% less time and had better quality than those that were sun-dried.
Solar drying of agricultural products: A review
The use of solar energy in recent years had reached a remarkable edge. The continuous research for an alternative power source due to the perceived scarcity of fuel fossils is its driving force. It had become even more popular as the cost of fossil fuel continues to rise. Of all the renewable sources of energy available, solar energy is the most abundant one and is available in both direct as well as indirect forms. Solar energy applications were divided mainly into two categories: the first is the direct conversion to electricity using solar cells (electrical applications). The second is the thermal applications. The latter include solar heating, solar cooling, solar drying, solar cooking, solar ponds, solar distillation, solar furnaces, solarthermal power generation, solar water heating, solar air heating, etc. Detailed description, fundamentals and previous work performed on solar dryers and solar air heaters, as the vital element for the indirect and mixed modes of solar dryers, were presented in the present review paper.