Sitesh Kumar Pandey1, Richa Soni2, Abhishek Shrivastav3 1,3

Transcription

1 IJEEE Volume Spl. Issue (6) Mathematical ing of Thin Layer Drying Process of Red Chili in Solar Dryer Under Open Sun Sitesh Kumar Pey Richa Soni Abhishek Shrivastav Mechanical Engineering Deptt. C.I.E.T Raipur India Mechanical Engineering R.I.T Raipur India Abstract: Drying is an important technique to remove the moisture of the product. Various drying techniques are employed to dry different agricultural products. All techniques have their own advantages limitations. So choosing the right drying techniques is very important in the process of drying. The raw agricultural products with 89% moisture content are brought down to equilibrium moisture content for keeping in the short or long term storages. In this present work I will experimentally investigate the drying characteristics of red chili one of the main ingredients used in almost every cooking in the world. It is mainly cultivated in the Indian states of Andhra Pradesh Karnataka Maharashtra Madhya Pradesh using thin layer solar drying technique. In this study direct-type natural convection solar dryer was developed used in the experiments. An experimental study was performed to determine the thin layer drying process in a solar dryer under open sun with natural convection of red chili. The drying data were fitted into four different thin layer drying models. The performance of these models is investigated by comparing the coefficient of determination (R) reduced chisquare(x) root mean square error (RMSE) between the observed predicted moisture ratio. Among these models Wang Singh model was found best to explain the thin layer behavior of red chili. Keywords- convection; coefficient of determination (R); reduced chi-square (X); root mean square error (RMSE) I. INTRODUCTION Quality of product depends on preservation of fruits vegetables certain food items for which it is essential to keep them for a long time without further deterioration. Up to 5% of the fruits vegetable 5% of the harvested food grain gets rotten in the tropical countries. During the harvest season either the high quantity of food cannot be sold or the price is not good. Hence drying is the oldest simplest method of preserving fruits vegetables food. It is defined as the process of moisture removal due to simultaneous heat mass transfer. But drying in the direct sun has the risk of damaging the complete harvest by rainfall. Also risk of animals decreases the quality of the product. By drying the farmer can have more income for a longer time. Dried food generates a much better benefit on the market than the unprocessed fruit. By drying the taste of the fruits is intensified the nutrients are contained more intensely they taste more sweet richer. Dried fruit vegetables are free from preservatives. Dried food has a very good nutritive quality (vitamins etc). RES -6 The requirement of energy for drying can be supplied from various resources namely electricity fossil fuel natural gas wood forest residual solar. According to the source of energy used there are different types of drying process. Amongst all the sun is the biggest carbon-free energy resource for human being. It is used to extend agricultural product life improves quality minimize losses during storage lower transportation cost. As per the solar energy used for drying it can be categorized as open sun drying solar drying. In India red chili is one of the important spices of meal is compulsory course in the kitchen. There is main ingredient in all cooking while has high nutritional value. For red chili it was found to contain very nutritious with high vitamin C calcium protein. The use of chili is not just for adding food palatability because there are a number of studies have shown that is very beneficial for human health. Furthermore chili is a good source of antioxidants being rich in vitamins A C minerals other photochemical which an important source of nutrients in the human diet. Traditionally chili was dried in the open sun drying. The farmers expose their chilies to the open sun on a mat earthen floor cemented floor or on a tin shed. In this method drying cannot be controlled a relatively low quality dried product is obtained. Open sun drying requires large open space area long drying times very much dependent on the availability of sunshine susceptible to contamination with foreign materials. Otherwise insects fungi which thrive in moist conditions render them unusable. Moreover in this method a low quality dried products was obtained. Most agricultural commodities require drying process in an effort to preserve the quality of the final product including the drying temperature duration of drying time. As an alternative approach to open sun drying solar drying system is one of the most attractive promising applications of solar energy systems. It is renewable environmentally friendly technology also economically available in most developing countries. II. LITERATURE REVIEW Akpinar et al. [5] performed an experimental study mathematical modeling of thin layer drying process of red pepper. The thin layer drying behavior of red pepper slices was experimentally investigated in a forced convective dryer consisting of fan heaters drying chamber instrument for measurement. Experiments regarding drying were conducted at inlet temperatures of drying air of C at a drying air velocity of.5 m/s. Initial

2 IJEEE Volume Spl. Issue (6) moisture of the red peppers was 87.5% (wb) drying of the pepper continued until no further changes in their mass were observed. Final moisture content of the red pepper obtained was about % (wb). The time taken to reach % moisture content from the initial moisture content at the various drying air temperatures were found to be between 6 min. According to the results of the multiple linear regression analysis among the thin layer-drying models the approximation of the diffusion model could adequately describe the thin layer drying behavior of red peppers. Constant drying rate period was not observed under any of the test conditions of this investigation the red pepper drying process occurring in the falling rate. Madamba et al. [6] studied the thin layer drying characteristics of slices of garlic. The thin-layer drying characteristics of garlic slices (- mm) were investigated for a temperature range of 5-9 ºC a relative humidity range 8-% an airflow range (.5-l) m/s. Initial moisture content by garlic slice varied from 6-6% wet basis was determined in a vacuum oven under certain condition. The effects of temperature thickness RH air velocity were analyzed using analysis of variance (ANOVA) this clearly showed that temperature slice thickness are significant factors in drying. In this experiment it was concluded that most of the drying of garlic slices takes place in the falling rate period. Four mathematical models available in the literature were fitted to the experimental data among which the Page the two-compartment models gave better predictions in comparison to single-term exponential Thompson s model. Rafiee et al. [7] studied thin layer drying properties of soybean. The experiments were conducted at inlet drying air temperatures of ºC at a fixed drying air velocity of m/s. The thin layer drying behavior of soybean was experimentally investigated the mathematical modeling performed by using thin layer drying models provided in the literature. The experimental moisture ratio was fitted to thirteen thin layer drying models. Midilli [] model gave the lowest RMSE the highest regression coefficient values. Hence the Midilli model was chosen to represent the thin layer drying of soybeans. Akpinar [8] investigated suitable thin layer drying curve model for some vegetables fruits. It is a study of mathematical modeling of thin layer drying of potato apple pumpkin slices in a convective cyclone dryer. He performed experiment in convective cyclone dryer. The dryer consists of fan resistance heating control system air duct drying chamber in cyclone type measurement instruments. In which Potato slices of 8% (wb) apple slices of 87% (wb) pumpkin slices of 9% (wb) average initial moisture content were dried to % (wb) % (wb) 6% (wb) respectively at temperatures of ºC in the velocities of drying air of.5 m/s. It was noticed that the Midilli Kucuk model [9] gave the highest correlation coefficient r the lowest chi-square (X) for all drying conditions. RES -6 III. EXPERIMENTAL PROCEDURE AND SETUP A. EXPERIMENTAL SETUP Fig.. shows the arrangement of the experimental setup of the solar dryer. The solar dryer consist of wooden block insulating foam aluminum sheet mm glass plate. The dryer consists of aluminum plate of thickness.5 mm. Aluminum plates is painted by black color because black color enhances the absorbtivity of a material. Sheet of aluminum is used as an absorber plate. Insulating material foam is provided at all side of the dryer to minimize the heat loss. Fig..Pictorial view of the experimental setup of solar dryer B. EXPERIMENTAL PROCEDURE Solar drying experiments were performed during periods of Nov.-Dec 5 in RIT Rewa India. The initial moisture content of freshly harvested red chili was determined by hot air oven method before carrying out the drying experiment. g of chili was dried in a hot air oven. On wet basis average initial moisture content obtained from the experiment was 8.6%. Fig... Flow diagram of thin layer natural convection solar drying process g fully ripe chili sample was taken placed on the drying tray of the solar dryer in a single layer another g was taken for the open-sun drying. Experiment was conducted at a regular interval of time of hr. From fig..6 it is clear that fresh air enters into the solar dryer it takes heat available inside the dryer due to intense solar radiation.air also extracts moisture from the chili gets

3 IJEEE Volume Spl. Issue (6) humidified. Weight loss of the chili was measured at a regular interval of time of hr. Reduction in weight of the chili provided the amount moisture removed during the drying process. Drying process was continued till the moisture content of the chili was reduced up to % on wet basis. During experiment it was clear that chili drying inside the drying chamber dried faster comparison to chili drying under open sun. C. MATHEMATICAL MODELING PROCEDURE OF DRYING CURVES Mathematical modeling of the chili was done on the basis of drying characteristics obtained from the experimental investigation. Thin layer drying requires some of the important parameters to get the drying characteristics of the product. D. IMPORTANT PARAMETERS a) Moisture content The quantity of moisture present in a material can be expressed either on the wet basis or dry basis also can be expressed either as decimal or percentage. The moisture content on the wet basis is the weight of moisture present in a product per unit weight of the undried material represented as Mwb = (w-wd)/w () If the relative humidity of the drying air fluctuates continuously then the moisture equilibrium continuously varies so MR is determined as in Eq.(5) given by Diamante Munro[6] MR=Mt / M (5) d) Drying rates Drying rate is expressed as the amount of evaporated moisture over time. Drying rate = (Mt+dt Mt)/ dt (6) Where Mt+dt Mt (g water /g dry matter.h) are the moisture content at the moment t the moisture content at the moment t+dt respectively. E. DETERMINATION OF THE APPROPRIATE MODEL Mathematical modeling of the drying of chili often requires the statistical methods of regression correlation analysis. Thin layer drying equations require MR variation versus time t. Therefore MR data plotted with time t curve fitting was done for the models shown in Tab... The validation of models can be checked with different statistical methods. no. Table. Thin layer drying curve models References name While the moisture content on the dry basis is the weight of moisture present in the product per unit weight of dry matter in the product represented as Newton MR=exp(-kt) Mujumdar [] Mdb = (w-wd)/wd Page MR=exp(-ktn) Diamante Munro [] () The moisture contents on the wet dry basis are interrelated according to the following equation Mwb = - [/Mdb+] Henderson Pabis MR=a exp(-kt) Zhang Litchfield [] Wang Singh MR=+at+bt Wang Singh [] () b) Equilibrium moisture content (Me) A crop has a characteristic water vapor pressure at a particular temperature moisture content. The equilibrium moisture content is the moisture content at which the product is neither gaining nor losing moisture. It is a dynamic equilibrium which changes with relative humidity temperature. c) Moisture ratio (MR) Moisture ratio is one of the important criteria to determine the drying characteristics of agricultural product. MR can be determined according to external conditions. If the relative humidity of the drying air is constant during the drying process then the moisture equilibrium will be constant too. In this respect MR is determined as in Eq. (). MR= (Mt - Me) / (M Me) () The coefficient of determination (R) is one of the primary criteria to select the best model compare with the experimental data. In addition to R reduced chisquare(x) root mean square error(rmse) are also be used to compare the goodness of the fit. Reduced chi-square (X) = ( Root mean square error (RMSE)RMSE = [ ( MR Correlation coefficient (r)- RES -6 ) MR (7) ) ] (8)

4 ( ) IV. (9) a) DRYING CHARACTERISTICS OF RED CHILI The variation of moisture content of g of red chili with drying time is shown in Fig. 5. Fig. 5.. The final moisture content (% wb) of the chili was achieved in 7 h in solar dryer while it was achieved in 8 h in open-sun drying. The open-sun drying took more time to reach the final moisture content due to slow drying rate. It is observed that the drying of chili occurred only in the falling rate period the constant rate period was completely absent in the drying period. (hr) (gm) 96.7 Weight reduction Moisture content Drying time (hr) Table. Experimental data of solar drying Weight of the sample Open sun drying.5 RESULT AND DISCUSSION Time.5 Moisture contentdb(g/g of dm) IJEEE Volume Spl. Issue (6) r= Fig... Moisture content variation with drying time on dry basis Moisture ratio (MR) The variation of drying rates with drying time is shown in Fig. 5.. It is obvious that the drying rate in solar drying is faster than the open-sun drying the drying rates decrease continuously with drying time. The drying rate is found to be fluctuating in nature both in the solar drying the open-sun drying which is mainly caused by variation of solar radiation during the experiment. During summer solar radiation changes frequently due to clouds in the sky. The drying rate in 9 Moisture contentwb(%) 8 solar drying Drying time (hr) Fig.. Moisture content variation with drying time on wet basis. RES -6 Fig..Solar dryer with T T hole solar drying is faster than the open-sun drying till the first 8 h of the drying hour. However the drying rate in the solar drying is almost same as the open sun drying in the later part of the drying hour.

5 IJEEE Volume Spl. Issue (6) Time Inlet temperature (T) Outlet temperature (T) In C 7 In C : 8: 9: : : : : : : 9 : Table. Experimental data of open sun drying b) TEMPERATURE MEASUREMENT OF INLET AND OUTLET AIR DURING EXPERIMENT T Inlet air temperature T Outlet air temperature During experiment temperature at position position was obtained by placing the thermometer at that position. Temperature at the inlet outlet depends upon the solar radiation intensity higher the solar radiation intensity higher the temperature of the air vice versa. During solar drying of red chili in our experimental setup inlet outlet temperature obtained is shown in the above table. From the table it is clear that temperature at the outlet reaches at its maximum level during mid day. Temperature depends upon the solar radiation intensity. During sunny days solar radiation intensity is maximum when sun is overhead. Table. Temperature during one day experiment of open sun drying Time (hr) Weight of the sample (gm) Weight reduction Moisture Moisture content ratio (MR) Thermometer is used to measure ambient temperature. Ambient temperature is almost same during the experiment. c) MODELING OF MOISTURE RATIO ACCORDING TO DRYING TIME FOR THIN LAYER DRYING Open sun drying of Red chili Table. Temperature during one day experiment of solar Time Ambient temperature (Tamb) In C 7 7: 7.5 8: 8 9: 8 : 9.5 : : : 9.5 : 9 : : RES -6 Fig.. Newton model fit 9 drying 5

6 IJEEE Volume Spl. Issue (6) Solar drying of red chili Fig..5 Page model fit Fig..8 Newton model fit Fig..6 Wang singh model fit Fig..9 Page model fit Table.5 Results of the fitting statistics of various thin layer models for open sun drying Coefficients RMSE no. name constants Newton k= Page K=6n= Hender son Pabis Wangh Singh a=.955k= a=87b= Fig..7 Henderson pabis model fit RES -6 6

7 IJEEE Volume Spl. Issue (6) Thin layer drying modelling equation for open sun drying of red chilli is given by MR=+(-7)t+7t Thin layer drying modelling equation for solar drying of red chilli is given by MR=+(-555)t+75t Fig.. Henderson pabis model fit Fitting of the four thin layer drying models has been done with the experimental data of chili drying using open sun solar drying. s of drying which were fitted with the experimental data of drying were the Newton Page Henderson Pabis Wang Singh model. Experimental data for drying were fitted to the model of drying in the form of changes in moisture ratio versus drying time. These drying models were fitted into experimentally obtained moisture ratio versus drying time curve with the help of origin pro 8.5 software. The results of the statistical analysis undertaken on these models for open sun drying solar drying are given in table... The models were evaluated based on R X RMSE.The model which was having the higher value of R the lower values of X RMSE was selected to better estimate the drying curve. For the thin layer open sun drying of red chili Wang Singh model gave R = X =5 RMSE=7. For the thin layer solar drying of red chili Wang Singh model gave R =.9966 X = RMSE=8.Wang Singh model is considered as best model for thin layer solar drying open sun drying of red chili. Fig... A view of freshly harvested red chilli Table.6 Results of the fitting statistics of various thin no. name Coefficients constants k=7696 RMSE Newto n Page K=5 n= a=.769k = Hender son Pabis Wangh a= b= 6 Singh.75 layer models for solar drying Fig.. Wang singh model fit RES -6 7

8 IJEEE Volume Spl. Issue (6) Fig... A view of red chili after open sun drying Fig.. A view of red chili after solar drying In solar drying good quality red chili was found color was not degraded after drying. In open sun drying red chili quality was not as good color quality was also degraded. REFERENCES [] Sharma A. Chen C.R. Lan N. V Solar-energy drying systems: A review Renewable Sustainable Energy Reviews (9) pp [] Singh S. Singh P.P. Dhaliwal S.S. Multi-shelf portable solar dryer. Renewable Energy 9 () [] Sreekumar A Manikantan P.E. Vijayakumar K.P. Performance of indirect solar cabinet dryer Energy Convers Manage 9(8) [] Seveda M SJhajhariaD.Design performance evaluation of solar dryer for drying of large cardamom (amomumsubulatum).journal of renewable sustainable energy 69 (). [5] Akpinar E.K. Bicer Y. Yildiz C..Thin layer drying of red pepper. Journal of Food Engineering 59() 99. [6] Madamba P.S. Driscoll R.H. Buckle K.A. Thin-layer drying characteristics of garlic slices. Journal of Food Engineering.9 (996)75 97 [7]Rafiee Sh. Sharifi M JafariA Mobli H. Tabatabaeefar A..Thin Layer Drying Properties of Soyabean (ViliamzCultivar).Journal of J. Agric. Sci. Technol. (9) Vol. : 89-. [8] Midilli A. Kucuk H. Mathematical ling of Thin Layer Drying of Pistachio by Using Solar Energy. Energy Conversion Manage.(7) (): [9] Akpinar E.K. Determination of suitable thin layer drying curve model for some vegetables fruits. Journal of Food Engineering 7(6) []Rao G.VMeSKishorev V.V.N. Study of drying characteristics of large-cardamom. Journal of Biomass Bioenergy ()7-. []Aghbashlo M Kianmehr M.H. Arabhosseini A. ing of thinlayer drying of potato slices in length of continuous b dryer. Journal of Energy Conversion Management 5 (9) []Garav A.T.Rafiee s. Keyhania A Mathematical ing of Thin Layer Drying Kinetics of Tomato Influence of Air Dryer Conditions. International Transaction Journal of Engineering Management & Applied Sciences & Technologies (). []Panchariya P.C. Popovic D. Sharma A.L. Thin layer modelling of black tea drying process. Journal of Food Engineering (5) () 9-57 []Meisamiasl E. Rafiee S. Mathematical ing of Kinetics of Thin-layer Drying of Apple.Agricultural Engineering International: the CIGR. journal.manuscript 85.Vol. XI.(9). [5]Ertekin C. Yaldiz O. Drying of eggplant selection of a suitable thin layer drying model.journal of Food Engineering.6() Madamba P.S.Thin layer drying models for osmotically pre-dried young coconut. Drying Technology.() RES -6 8