STUDY ON ENERGY REQUIREMENT FOR DEHYDRATION OF CHICKPEA
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Date
2015-09
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jau,junagdh
Abstract
ABSTRACT
Energy is god gift and categorized mainly in two forms. i.e. conventional and non-conventional energy. Conventional energy sources not only depleting fast but are becoming costly too. Non-conventional energy resources are solar, wind, ocean, tidal, geothermal, hydrogen energy and energy from biomass and biogas, etc. Among all these sources; solar energy source is the most perceptive source of energy.Due to uncertainty and intermittent nature in the availability of solar radiation, it can be best utilized as a supplementary source of energy in the indirect mode forced convection solar dryer.In these dryers, an auxiliary heating arrangement can be used for supply of hot air under controlled conditions. In addition to this, from the cost of energy and reliability point of view, it is now realized that application of solar energy for industrial dryer, instead of standalone solar systems, the hybrid system using combination of renewable sources was more appropriate. Therefore a detailed study on energy required and the contribution of solar air heater, electrical back-up heater, and electrical blower for the drying of chickpea was carried out using solar assisted forced convection dryer.
Chickpea is one of the most readily produced and consumed pulses (grain legume) worldwide, particularly in the Indian subcontinent and Mediterranean countries.Food legumes decreased incidence of several diseases, such as cancer, cardiovascular diseases, obesity and diabetes.Dried legumes (pulses) are well known for their nutritional and functional value.Drying of cooked chickpeas using hot (convection) air is a promising method, which could produce highly rehydratable products in short times. In the Present study, thin layer drying behaviour of cooked and soaked chickpea at four levels of drying air temperature (50°C, 60°C, 70°C and 80 °C) and four levels of air velocity (0.25 m/s, 0.50 m/s, 0.75 m/s and 1.00 m/s). The Exponential model and Page's model were obtained for each experimental run. Page's model was more suitable than the Exponential model based on the COD (r2) and lower value of reduced chi-square as compare to Exponential model.Page’s equation drying constant k and N were obtained for each experimental condition.
Correlations of drying rate constant k with drying air condition variables T and V was determined in terms of Arrhenius type model and power model. The drying rate constant k was found more influenced by air temperature as compared to air velocity of the drying air. For ascertaining, the dependence of k on the drying air condition variables (temperature and velocity), Arrhenius model was more suitable than the Power model based on the COD (r2) and lower value of reduced chi-square as compared to Power model. The obtained values of Arrhenius type model parameters for cooked chickpea α0, α1 and α2were 1.2349 x 104, 0.27 and 3712.91respectively. The obtained values of Arrhenius type model parameters for soaked chickpea α0, α1 and α2were 2.5251 x 106, 0.16 and 5395.09respectively.The data fitted well in to the Arrhenius type model as compared to Power model.
In this study also evaluated the energy requirement for drying of cooked chickpea form initial moisture content of 67% (w.b.) to final moisture content of about 7% (w.b.) and soaked chickpea form initial moisture content of 58% (w.b.) to final moisture content of about 7% (w.b.). It was found that the total energy required per unit mass of water removed for cooked chickpea, ranged between 12.86 MJ per kg water to 66.97 MJ per kg water and for soaked chickpea, ranged between 11.28 MJ per kg water to 66.09 MJ per kg water during all the experimental runs conducted at different air mass flow rates (118.02 kg/h - 478.54 kg/h) and different air temperatures (50 °C – 80 °C). Rehydration and organoleptic evaluation showed that very good quality of dehydrated cooked and soaked chickpea can be obtained at 50 °C and 60 °C of drying air temperature and good quality of dehydrated cooked and soaked chickpea can be obtained at 70 °Cof drying air temperature. However, a fair quality of dehydrated cooked and soaked chickpea was obtained at 80 °C of drying air temperature.
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Rural Engineering