Tunnel Dryer Research Articles

Techno-economic feasibility of the latent heat storage material to use in a solar tunnel dryer

For efficient utilization of freely available solar energy for drying of Potato Slices (Solanum tuberosum) experiment has been carried out keeping in view to extend drying hours with efficient Latent heat storage material system was designed and installed at Department of Renewable Energy Engineering, CTAE, MPUAT, Udaipur. Techno- Economic analysis of the PCM (Phase Change Material) integrated with the unit carried out to supply the heat to the tunnel dryer. Barioum hydroxide octahydrate [Ba(oh)2 8h2o] was used as a heat storage material. It is concluded that the heat sink unit with heat storage material enables to maintain constant air temperature inside the dryer and heat stored in phase change material in heat exchanger during day time can be utilized during non-sunshine hours because of which drying time could be extended up to 4 hours. The Net Present Worth of the heat sink unit is 123785.98 ₹ with a 1.33, 1.268 years and 62% are the benefit-cost ratio, payback period and Internal Rate of Return (IRR), respectively. Considering the initial cost of the heat storage material is 60 Rs/kg with the 1000 life cycle. Based on economic analysis, it was concluded that investment on the heat storage material for solar tunnel dryer is justified.

Exergy analyses of a tunnel furnace and a tunnel dryer

Exergy analyses of a tunnel furnace and a tunnel dryer

Assessment of the Effectiveness of Coffee De-mucilager and Driers for Physical and Sensorial Coffee Quality

Coffee Arabica is an essential commodity to the livelihood of millions of Ethiopians and its quality has critical importance to the coffee industry. The objective of the present study was to evaluate the effect of newly introduced coffee post- harvest machineries and driers on coffee raw, cup and total quality as compared to the conventional processing methods. Different methods, such as normal fermentation (conventional) and drying in sun, normal fermentation and drying in artificial drier, normal fermentation dried in poly tunnel drier, demucilager pulped and dried in sun, demucilager pulped and dried in artificial drier and demucilager pulped dried in poly tunnel were used for coffee sample preparation. The experiment was conducted during the 2017/18 and 2018/19 cropping season at Limmu Kossa coffee plantation. Both raw and cup quality parameters were evaluated by a team of certified panelists at Jimma Agricultural Research Center (JARC) coffee processing and quality analysis laboratory and analyzed using completely Randomized Design (CRD). Physical coffee quality parameters such as Bean size, Bean shape and make, color and odor showed no statistically significant (P > 0.05) difference for all preparation methods. The highest values of cup quality parameters like Acidity (AC), astringency (AS), bitterness (BI), body (BO), flavor (FL) and overall quality (OAQ) were recorded for coffee samples prepared using demucilager pulper and dried in tunnel drier. Samples pulped by demucilager and dried in poly tunnel drier exhibited the highest values, 35.67, 47.50 and 83.17, for raw, cup and total quality, respectively. It seems important to further study the biochemical composion of samples prepared using in such new introduced demucilager and driers in the future.

Recent advances in solar tunnel dryer for performance improvement in food drying process: a review

The unexpected increase in demand and persistent shortage of fossil fuels continues the search for an alternative source of power. Solar energy is one of the sustainable and renewable sources of power that encouraged various researchers from all over the world. The production of food and its immediate consumption is the biggest problem to reduce the wastages of food. To overcome the wastage, drying is an excellent method to preserve the food grains, fruits and vegetables. For drying, conventional drying system is sun drying which is free and a renewable source of energy. But, there are various limitations e.g. rain, dust, animals, wind and insects. The use of solar dryers can eliminate these limitations significantly and enhance the productivity of farmers towards better revenue earned. This review attempts to provide in brief the recent developments to increase the temperature of drying chamber and applications of drying technology for different foods and agricultural produce, with particular emphasis on the modifications in the dryer and process conditions. This review paper will be helpful to know about the recent trends and different useful aspects of solar tunnel dryer to the new researchers.

Optimization of solar tunnel dryer for mango slice using response surface methodology

The performance characteristics of solar tunnel dryer used to dry mango product (mango slice) has been analysed under forced convection. A DC blower is used and it is run by a photovoltaic panel (200w). Solar drier and experimental setup has been designed and fabricated. Performance analysis of solar drier has been performed during summer season and the system is operated at 28 °C−70 °C. The experimental set up fabricated by locally available materials with simple construction which reduces the cost. The variation of thermal efficiency for different solar intensity, moisture content and moisture removal rate have been explained through experiments. Response surface methodology tool has been used for optimization and acceptability using desirability for mango slices.

Thermal Analysis of Solar Tunnel Dryer and Evaluation for Commercial Mango Leather Drying

A walk-in type semi-cylindrical shaped solar tunnel dryer (10 m x 3.75 m) was designed, developed and evaluated at Dr. B.S. Konakan Krishi Vidyapeeth, Dapoli for thermal analysis. The dryer was evaluated by conducting no-load test at laboratory to study the thermal profile, energy input/output during the winter and summer season. Based on the laboratory experience, a commercial scale solar tunnel dryer was installed and evaluated at M/s Shirodkar Food Products Pvt. Ltd., kudal, District Sindhudurg (MS) for commercial mango leather drying. The dryer was loaded with 250 kg mango pulp per batch by spreading over 210 number of grease-proof aluminium trays (1.2 kg pulp in each tray) in three layers (70 trays in each layer). Drying of mango leather was studied in comparison with open sun drying and electrical oven drying for time saving and energy consumption. The study revealed that the average rise in temperature of drying air was about 18 -22 0C over the ambient air. The average drying period reduced by 28 % over open sun drying method. The average temperature inside the solar dryer was 62+5 0C, and required 10 h for upper layer of trays, 13 h for second layer of trays, and 17 h for third level of trays as compared to 26 h in open sun drying. The operating energy cost of solar tunnel dryer was zero as compared to 102 kWh in electrical oven. Considering drying of 30 batches per season, the payback period of the system was 2.7 years.

Recent advances in solar tunnel dryer for performance improvement in food drying process: a review

The unexpected increase in demand and persistent shortage of fossil fuels continues the search for an alternative source of power. Solar energy is one of the sustainable and renewable sources of power that encouraged various researchers from all over the world. The production of food and its immediate consumption is the biggest problem to reduce the wastages of food. To overcome the wastage, drying is an excellent method to preserve the food grains, fruits and vegetables. For drying, conventional drying system is sun drying which is free and a renewable source of energy. But, there are various limitations e.g. rain, dust, animals, wind and insects. The use of solar dryers can eliminate these limitations significantly and enhance the productivity of farmers towards better revenue earned. This review attempts to provide in brief the recent developments to increase the temperature of drying chamber and applications of drying technology for different foods and agricultural produce, with particular emphasis on the modifications in the dryer and process conditions. This review paper will be helpful to know about the recent trends and different useful aspects of solar tunnel dryer to the new researchers.

Overcoming Barriers to Solar Dryer Adoption and the Promise of Multi-seasonal Use: A case study of chili drying in India

Food and income loss caused by conventional open-sun drying of crops around the world could be reduced by the use of protected solar drying equipment. Yet, solar dryers have not been widely adopted among the majority 470 million smallholder farms worldwide. For dried chili farming in India, over 55% of surveyed farmers reported at least 10% loss of harvest during open-sun drying and quality degradation in 53% of marketed yield. The latter lowered revenue by an average of 34%. Such loss significantly impacts smallholder livelihoods. Employing field data, this paper shows how technical, financial, and operational barriers combine to limit smallholder ownership of common, commercially available hoophouse tunnel dryers with necessary hectare-scale capacities. Because solar dryers are seasonally stranded assets, we assess multi-seasonal revenue streams that incorporate both drying of crops and growing of seedlings. Using service-based operational models to increase smallholder access, such dual use reduces payback time by at least 50% relative to single, drying-only uses. With available financing schemes, multi-seasonal dual-use dryers could reach payback in 1 year compared to 6.5 years for traditional single-use models. A sensitivity analysis of single- and dual-use solar dryer operations is provided and their practical implementation by smallholder farmers is discussed.

Energy Analysis of the Twin Layer Solar Tunnel Drying of Tomato Slices

Energy Analysis of the Twin Layer Solar Tunnel Drying of Tomato Slices

Solar Tunnel Drying System: A Literature Review

Production, productivity, and area under production from fruits and spices are gradually increasing. Improper processes of freshly harvested spice and fruit products will make them undergo qualitative deterioration with each passing hour. This deterioration is more pronounced in high humid areas. Drying process in one or the other form is essential. Freshly harvested spices and fruit products in average contain more than 80% moisture. The commodities need to be dried to have a moisture content below 10% in the shortest possible time for safe storage. Drying process in most cases are accomplished by the open sun. Meanwhile, the environmental condition in solar tunnel drying is enclosure type and the product is protected from rains, dust, insects, and rodents. Solar tunnel drying, a widely used bulk dryer, facilitates faster drying than open drying by virtue of the greenhouse effect. Commercial cultivators by and large choose faster drying methods using wood and fossil fuel-fired heating sources. This study attempts to review recent advances of various designs and working of the greenhouse drying system in totality, like auxiliary drying during off-sun hours, bulk drying feasibility, ease in loading and unloading along with an analysis of key features and economics involved.

Drying of mangoes (Mangifera indica L. cv. Palmer) at changeable temperature conditions—Effects on energy consumption and quality of the dehydrated fruit

AbstractThis study evaluated the influence of heat input change on the drying kinetics, energy consumption, the color, and carotenoid retention during the drying of mangoes. The drying conditions in the first stage were 95°C for 40 min and 80°C for 40 min, so that the surface temperatures of the fruit at the end of this stage were around 60°C. The temperatures of the second stage and corresponding continuous drying (control) were 70 and 60°C. As a result, the thermal intermittence influenced the drying kinetics, causing significant reductions in the overall process time and providing energy savings when compared to continuous drying. The color parameters did not show relevant changes as result of the intermittent drying while good carotenoid retention was obtained in intermittent conditions, when the second stage was 60°C. Therefore, the carotenes were more sensitive to a temperature of 70°C, which highlights the importance of limiting the temperature of the mango to 60°C during the two drying stages to better preserve the quality of the dehydrated fruit. Moreover, the high air temperatures used in the first stage were advantageous for reducing the overall process time and providing energy saving.Practical ApplicationsDrying is an operation well known for the food industry. However, in so many cases, dryers are not designed with energy consumption in mind. Moreover, simple procedures can bring savings in convective drying, as shown in the present study, where the application of two‐stages in the convective drying of mangoes was advantageous to reduce the overall drying time and provide energy savings in relation to continuous drying. Besides that, good carotenoid retention was obtained using low temperature (60°C) at the second stage. The results can be useful for design of dryers and drying process, considering different temperatures. Intermittent drying of high moisture foods by varying the drying air temperature can be applied both on an industrial scale, in continuous belt dryers or in tunnel dryers, and on a small scale, using two or more dryers with different temperatures.

Effect of packaging on phenols, flavonoids and antioxidant activity of dried wild pomegranate (Punica granatum L.) arils prepared in solar tunnel drier

Effect of packaging on phenols, flavonoids and antioxidant activity of dried wild pomegranate (Punica granatum L.) arils prepared in solar tunnel drier

Drying of Refuse-Derived Fuel (RDF) using Solar Tunnel Dryer Integrated with Flat-Plate Solar Collector: An Experimental Approach

Solar energy can be effectively used for drying, especially when the cost of fuel used for conventional dryers is high. The drying of refuse-derived fuel (RDF) is a complicated process involving mass and heat transfer and depends on external variables such as humidity, temperature, and air velocity as well as internal variables, e.g., material surface, physical structure, chemical composition, size, and shape. Herein, a solar tunnel dryer integrated with a flat-plate solar collector was designed and fabricated at the Faculty of Engineering, Suez Canal University, Egypt. The experiments were performed during July 2019. The weather characteristics as well as the variation in moisture content with time were recorded continually. The results indicated that the maximum efficiencies of the solar collector were 46.6%, 53.4%, and 40.0% on 2, 4, and 6 July, 2019, respectively. Moreover, on these days, the moisture content of RDF decreased from 35.6% to 9.6%, from 28.3% to 8.5%, and from 43.5% to 14.0%. The dryer efficiency varied over 14.1–29.5% depending on the drying air stream temperature. The maximum dryer efficiencies recorded were 23.8%, 29.5%, and 25.8% on 2, 4, and 6 July, 2019, respectively.

Thin Layer Peach Drying in Solar Tunnel Drier

This study presents performance of the solar tunnel dryer for drying of peach samples. The solar tunnel dryer consists of a flat plate solar collector, a drying tunnel, a solar cell module and a small axial fan. It has been constructed at the Department of Agricultural Machinery and Technologies Engineering at Isparta University of Applied Sciences. During the drying process, solar irradiation, drying air temperature, relative humidity, and air velocity were measured constantly in different parts of the dryer. At same time, mass loss of the peach samples was measured during the drying period at one-hour interval. In this study, the color measurements fresh and dried products were determined at the beginning and end of experiment. The fresh peach samples were sorted, graded, washed by tap water and then sliced manually as half-moon without peeling before pretreatment. Sun drying behavior of sliced peach samples pretreated with 1% sodium metabisulfit, 1% ascorbic acid and non-pretreated was investigated. The drying characteristic curves were evaluated against ten mathematical models. Results showed that the Midilli et al. model was found to be the best descriptive model for solar tunnel drying of thin layer peach.

Drying and packaging methods impact the bacoside profile and microbiological quality of Brahmi herb (Bacopa monnieri L.) during storage

Retention of quality in herbal drugs during drying and storage is of great concern and the information is lacking in an important memory enhancing medicinal herb Brahmi (Bacopa monnieri L.). This is the first ever report on effect of drying methods, packaging materials as well as storage duration on the bacoside A profile and microbiological quality. Freshly harvested herbage was dried with five different methods of drying viz., shade, sun, solar tunnel, cabinet, low cost polyhouse, followed by packing dried herbage for five months duration in different containers viz., polythene lined jute bags, woven polypropylene sacks, corrugated fiber board boxes, and 125 μm thick high density polyethylene containers. Drying of fresh herbage at 50 °C for 12 h in cabinet drier retained the highest bacoside A components compared with all other methods. Solar tunnel drying was the second best method, while conventional shade dried samples recorded lowest bacoside A level. Bacoside A profile in cabinet samples immediately after drying was 4.8 mg/g bacoside A3, 6.0 mg/g bacopaside II, 5.0 mg/g jujubogenin isomer of bacopasaponin C and 4.6 mg/g bacopasaponin C. Ambient temperature storage (23 ± 2 °C) for five months resulted in loss of bacoside A from the herbage; but packaging in high density polyethylene significantly reduced the loss compared with other packages irrespective of the drying methods. Cabinet dried samples stored in high density polyethylene packages for five months possessed 3.0 mg/g bacoside A3, 4.1 mg/g bacopaside II, 2.5 mg/g bacopasaponin C and 3.2 mg/g jujubogenin isomer of bacopasaponin C. The microbiological quality was also satisfactory during storage in high density polyethylene container. Thus, the work identified a protocol for hygienic way of drying and packaging of Brahmi to retain the bacosides during storage.

Hybrid microwave-hot air tunnel drying of onion slices: Drying kinetics, energy efficiency, product rehydration, color, and flavor characteristics

Hybrid microwave-assisted hot air (MW-HA) tunnel drying at 100, 150 and 200 W at 50 °C, 60 °C or 70 °C was evaluated with gathered data on the associated drying kinetics, energy consumption/efficiency and product quality as compared with conventional hot air drying (HA) in the same tunnel. A pilot-scale 1.5 x 4 kW magnetron microwave tunnel supplemented with a four-duct convective hot air dryer was used to dry onion slices. In the hybrid microwave (MW-HA) mode, the multistage microwave and hot air drying were used simultaneously during the drying process, while only hot air was used in HA mode, and the two were compared for drying performance and quality. Hybrid MW-HA reduced the drying time by over 90%, and increased the energy efficiency by 3.0-16.0 times as compared to HA. The rehydration capacity of all samples were well described by a first order kinetic model and MW-HA dried product had better rehydration characteristics. Verma model and Midilli & Küçük model were the best ones for describing both MW-HA and HA drying kinetics of onion slices, and the effective moisture diffusivity of MW-HA was two order of magnitudes higher than HA drying. MW-HA also improved color, flavor, antioxidant and total phenolic compounds (TPC) retention in the dehydrated product.

Effect of Variety on Rehydration Characteristics of Dried Apples

The effect of dried apple varieties on their rehydration characteristics was investigated. Four varieties of apples, Champion, Cortland, Grey Reinette and Ligol, were taken into consideration. Rehydration properties and color of apples were investigated. In order to examine the influence of apple variety on its rehydration properties, the process of rehydration was modeled. The model parameters obtained for investigated apple varieties were compared. Apple cubes were dried in a tunnel dryer (air temperature 60 °C and air velocity 2 m/s) and next rehydrated in distilled water at temperature: 20, 45 and 70 °C. Mass, dry matter mass, volume and color attributes of apples (raw, dried and rehydrated) were measured. The process of rehydration was modeled using empirical (Peleg and Weibull models) and theoretical (the Fick’s second law) models. Results of the analysis showed that the apple variety affects values of mass and volume increase, dry matter decrease and color of the rehydrated apple. Discussed parameters were also affected by rehydration temperature. Fick’s second law model can be considered as the most appropriate. Apple variety and rehydration temperature influenced the values of the model’s constants. Obtained values enabled attempts of the explanation of the rehydration course. It can be stated that apple var. Champion showed a greater rate of water absorption during the entire process of rehydration than other investigated varieties.

Methods of drying on fruit quality of Byadagi chilli

The experiment was conducted to study the effect of different drying methods in red chilli (Byadagi dabbi) at Horticultural Research and Extension Station, Devihosur, Haveri, Karnataka, during 2016 and 2017 in rabi season. Drying in solar tunnel dryer method is found to be the best option in field situation for reducing the average drying period (6.0 days) and significantly least per cent of white fruits (7.5 %), as compare to other treatments. This was mainly due to increased average maximum temperature (54.2 0C), minimum temperature (29.2 0C) and reduced relative humidity (57 %) compared to outside temperature (Tmax - 36 0 C & Tmin-18 0C and RH – 74%). This resulted in rapid loss of moisture from the fruits and ultimately reduced the drying period and fruit whitening. The fruit quality parameters were not significantly affected by the methods of drying in chilli.

Design of tunnel drier for the non-centrifugal sugar industry

Abstract The quality and shelf-life of NCS (non-centrifugal sugar) mainly depend on the moisture content present in it. NCS formed by the current practice of open sun drying contains moisture substantially greater than the acceptable level of 3%. This paper presents the work undertaken to design a tunnel dryer to achieve the required moisture content of granular NCS for various load conditions. An experimental investigation was conducted on a laboratory-scale dryer to achieve the required moisture content for various loads. This experimental data was compared with the output of two drying models and a validated one that could be used to design an industrial-scale dryer. For various load conditions on each tray and dryer exit temperature, nine different cases were determined. The number of trucks, drying time, and energy requirements were computed using the validated theoretical model. A tunnel dryer with a length, height and width of 18, 1.2 and 1 m respectively and 18 trucks with 24 trays on each truck is shown to be dry 1 tone of NCS based on the minimum energy requirement of 176.49 MJ, and a drying time of 68 min.

Comparison of Performance for Drying Leafy Vegetables for that Plate Type Tunnel Dryer and Evacuated Tubes Type Tunnel Dryer

Comparison of Performance for Drying Leafy Vegetables for that Plate Type Tunnel Dryer and Evacuated Tubes Type Tunnel Dryer