Solar Cabinet Dryer Research Articles

PERFORMANCE OF LOW-COST DUAL CIRCUIT SOLAR ASSISTED CABINET DRYER FOR GREEN BANANA

A low-cost solar cabinet dryer was designed to dry green banana. The dryer was made of low-cost material readily available locally. The dryer consists of two types of solar collector (air and fluid collectors), water tank, automotive radiator and a drying cabinet. The experiment was conducted in Iligan City, Philippines and placed at the roof top. Banana slices were placed in the cabinet and dried for the whole day. Temperature and moisture were observed during different solar conditions. The temperature of the chamber, output temperature of the air heater and water heater were enough for low temperature drying. Chamber temperature has a mean maximum value of 48 C and an average temperature of 41 C. The overall dryer efficiency was 18 %. The dryer efficiency is lower than the projected simulated dryer efficiency but good enough considering the low-cost construction of the dryer.

Performance evaluation of a cabinet solar dryer for drying red pepper in Bangladesh

A cabinet type solar dryer was designed and fabricated over a collector and dryer area of 4.00 m2 and 7.5 m2 respectively for the geographical condition of Bangladesh. Red pepper was used to test the performance of the dryer. The upper tray and lower tray pepper drying needed 36 and 41 h to reduce moisture from 73% (wet basis) to 10% (wet basis) respectively and found 9 kg dried pepper from 30 kg fresh red ripe pepper. In contrast, open sun drying needed 85 h to reduce moisture from 73% (wet basis) to 11% (wet basis) and produced 2.43 kg dried pepper from 8 kg red ripe pepper. The average global radiation was about 133 W/m2 while the flux incidence and flux absorbed on collector was about 128 W/m2 and 103 W/m2 respectively. The average collector and dryer efficiency was about 48% and 34% respectively. The average exergy efficiency was obtained 63%. The average rate of top, bottom and side collector loss was 37 W/m2, 20 W/m2 and 3 W/m2 respectively. The upper tray, lower tray and open sun pepper seed germination was 76%, 81% and 85% respectively (P≥0.01). The redness value of lower tray pepper (a*=27.1) was higher followed by upper tray (a*=24.7) and open sun pepper powder (a*=21.1), which means direct exposure of sunlight diminishes the quality of pepper colour. The redness value of fabricated solar drying was significantly (P≤0.01) higher than that of open sun drying.

Effect of Different Processing Conditions on Proximate and Bioactive Contents of Solanum aethiopicum (Shum) Powders, and Acceptability for Cottage Scale Production

The purpose of this study was to investigate the effects of different processing conditions for production of dried Solanum aethiopicum (S.) leaf powder by comparing solar drying and cabinet drying processing techniques. Four (4) pre-treatments were done on S. aethiopicum leaves to inhibit enzyme action and prolong storage life. Treatments included dipping in; 10% saline solution, 10% vinegar solution, water (as the control), and steam blanching; done for both whole and sliced S. aethiopicum leaves. Each of the resultant samples were dried in both solar and cabinet dryers for a period of 24 hours. The dried leaf samples were grounded into powder using a coffee grinder and subjected to different laboratory analyses including; catalase activity, moisture content, vitamin C retention capacity and phytate content analyses. The results obtained were analysed using MINITAB version 16.0 at 5% significance level. The results showed that there was a reduction in catalase activity after pre-treatment and drying from 5.0±0.0 cm3 for the fresh un-treated leaves to a range of 4.5±0.7 – 3.0±0.0 cm3 for whole solar dried; 4.5±0.7-4.0±0.0 cm3 for sliced solar dried; 4.0±0.0 - 3.0±0.0 cm3 for whole cabinet dried and 3.5±0.7-2.3±0.7 cm3 for sliced cabinet dried leaf powder. Solar dried S. aethiopicum leaf powder contained significantly high moisture content than hot air cabinet dried one (24.9±0.5 % for saline treated sliced leaves to 8.9±0.8 % for blanched sliced leaves, than hot air cabinet dried one with 9.3±0.0 % for sliced plain water treated leaves to 7.0±0.2 % for sliced vinegar treated leaves; respectively). Cabinet dried S. aethiopicum contained significantly more vitamin C content (1.1±0.2 mg for whole blanched leaves compared to 0.6±0.1 mg for sliced vinegar treated leaves) than the solar dried one (1.0±0.2 mg for sliced plain water treated leaves to 0.6±0.1 mg for sliced vinegar treated leaves). There was no significant difference in phytate content between the hot air cabinet dried and solar dried i.e. 0.7±0.1 - 0.2±0.1 mg for solar and 0.7±0.1 - 0.3±0.3 mg for cabinet dried. Solar dried S. aethiopicum powder contained significantly higher catalase than the hot air cabinet dried one (4.5±0.7 - 3.0±0.0 and 4.0±0.0 - 2.5±0.7 cm3; respectively). However, in terms of acceptability, there was high preference for saline treated leaf powder soups compared to other soups. It can be concluded that High activity of catalase, moisture retention and high loss of Vit.C occurs in the solar drier than in cabinet drier. Whole leaf saline pretreated leaf powder soup is rated high compared to other dried soups. Therefore, the best method for production of dried S. aethiopicum powder is by slicing, dipping it in plain water and drying using a cabinet dryer. Under circumstances where cabinet drying is not achievable, solar drying is recommended using whole leaf, pretreated with saline water to promote preservation and consumption of the vegetable.

Performance Evaluation of Solar and Oven Drying for Tropical Fruits

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. Operational cost of solar dryer can be cheaper but the drying time using 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.

Use of Eco-Friendly Solar Cabinet Dryer for Drying of Agricultural Products-A Boon to Rural Farmers of Manipur

Use of Eco-Friendly Solar Cabinet Dryer for Drying of Agricultural Products-A Boon to Rural Farmers of Manipur

CFD simulation of corn drying in a natural convection solar dryer

ABSTRACTA computational fluid dynamics model was developed to simulate the corn drying process in a solar cabinet dryer. Incident solar radiation was modeled using a dual-band spectrum to simulate the absorption of shortwave radiation by corn and account for the greenhouse effect caused by glazing materials. The performance of the dryer was simulated at fair and overcast weather conditions. The model allowed visualization of temperature, humidity, and air velocity profiles in the dryer. The model was validated with experimental results, which showed an overprediction of temperature (8.5%) and humidity (21.4%). The experimental humidity profile suggests that there was stagnation in the airflow of the dryer, which was accurately predicted by the model. The model was used to simulate the dryer’s performance under overcast conditions, and the predicted moisture removal was 32% less than the simulated fair-weather case.

Meat Products Drying with a Compact Solar Cabinet Dryer

The present paper presented the results of meat products drying with a compact solar cabinet dryer. To meet the requirements of the user, the participation research (PAR) and scientific research is required for investigation. Thus this paper will present both in term of qualitative and quantitative results. The methodology of this study comprises of four main steps such as (1) determine the conceptual design of the solar dryer cabinet (2) selection technology (3) design and fabricate of the solar cabinet dryer and (4) performance testing. For all of these four steps the user and the researcher team have been involved and participated closely. The results from the study found that the developed solar cabinet dryer is suitable for specific use of drying meat products. It is noticed that with the special design of preheating ambient air will enhance the ambient air temperature pass through the solar collector house. The drying results of the seasoning raw pork for the duration of two days showed that the average temperature of each drying tray is in the range of 45.75-48.63 degree Celsius. The temperature at uppermost tray is highest and the temperature at the upper tray is higher than the lower tray. The temperature difference among the tray is in the range of 1- 3 degree Celsius. In which showed that the temperature distribution of the drying tray is almost uniform throughout the cabinet dryer. The quality of the drying products was accepted by the users. With the uniform temperature within the solar dryer cabinet will help to control the quality of the drying products The comparison results between the percentage of weight loss for open sun drying and solar cabinet drying showed that under the same environment of drying, using solar cabinet dryer get the weight loss higher than using open sun dryer. The designed solar cabinet dryer is suitable for the drying products that require the optimum temperature in the range of 47-50 degree Celsius.

Development of Solar Biomass Drying System

The purpose of this paper focuses on the experimental pre-treatment of biomass in agricultural site using solar energy as power source and contribution of common use and efficiency solar dryer system for consumer. The main purpose of this design for solar cabinet dryer is to dry biomass via direct and indirect heating. Direct heating is the simplest method to dry biomass by exposing the biomass under direct sunlight. The solar cabinet dryer traps solar heat to increase the temperature of the drying chamber. The biomass absorbs the heat and transforms the moisture content within the biomass into water vapour and then leaves the chamber via the exhaust air outlet. This problem however can be solved by adopting indirect solar drying system. High and controllable temperatures can be achieved as a fan is used to move the air through the solar collector. This project has successfully created a solar cabinet dryer that combines both direct and indirect solar drying systems and functions to dry biomass as well as crops effectively and efficiently with minimal maintenance. Hence, it is indeed a substitution for conventional dryers which are affordable to local farmers.

Drying Kinetics of Fig (Ficus carica L) under Various Drying Methods

A study was conducted to evaluate different drying methods for pre-treated (2% KMS) fig fruits. Figure fruit was dried under different drying methods (sun drying, solar cabinet dryer, and microwave oven and cabinet tray dryer) to elicit their effect on drying rate, drying time, biochemical properties and sensory attributes. Microwave oven drying showed highest drying rate, and took less time to reach required final moisture content. Higher drying rate was observed in the pre-treated samples as compared to the untreated samples under all drying methods. The drying time required for cut-fig fruits was nearly half of that for whole fig fruits. The sulphited samples showed higher biochemical properties irrespective of drying methods. The samples dried in microwave oven, solar cabinet and sun drying had higher values of biochemical properties than the cabinet tray dried samples. Acceptable sensory quality was obtained in products dried with microwave oven, solar cabinet and sun drying. Among five thin-layer drying models (Newton, Page, Modified Page, Logarithmic and Henderson and Pabis) for evaluating the drying kinematics, the Logarithmic, model yielded the best fit (R2 = 0.9998, χ2 = 0.000017).

EXPERIMENTAL INVESTIGATION AND NEURAL NETWORK PREDICTION OF THE PERFORMANCE OF A MIXED MODE SOLAR DRYER FOR COCONUT

The shelf life of agricultural food products may be enhanced by reducing their moisture contents, by means of a drying process. The present work aims at drying coconut yielding copra. This paper presents the design, analysis of a mixed mode solar dryer for food preservation and energy saving. In the mixed mode solar dryer, the drying cabinet absorbs solar energy directly through the transparent roof and during the same time the heated air from a solar collector is passed through a tray. Various measurements like solar radiation, mass flow rate, and moisture content and relative humidity have been observed. From previous literature four different models (Newton, Page, Henderson & Pabis and Wang & Singh) are chosen for testing the performance of mixed mode solar dryer. Selected models are evaluated by using EMD, ERMS, R2 and 𝜒2 and it is concluded that page model is more suitable for the fabricated cabinet solar dryer at air flow rate 0.009Kg/s based on the experimental analysis. The direct radiant solar energy and a convective hot air stream dry the products, resulting in longer life for the products which are also free from impurities. The experimental results are utilized to evolve a suitable mathematical model, among the different models that are chosen, for copra. This will help in designing suitable dryers for actual users. Also, a multilayer neural network approach has been used to predict the performance of a mixed mode solar dryer for drying coconut. The simulation of neural network is based on the feed forward back propagation algorithm.

DRYING OF CUCUMBER SEEDS USING A FORCED AIR CABINET SOLAR DRAYER

This research work aims at studying the factors affecting the solar drying of cucumber seeds using a cabinet solar dryer. The experimental work was conducted on the roof of Agricultural Engineering Research Institute (latitude angle of 30o 2' 35.2N and longitude angle of 31o 12' 20E) during summer season of 2015. Three different layers thickness of cucumber seeds (5, 10, and 15 mm thick) were functioned during the experimental work. The thermal performance analysis of the cabinet solar dryer (forced convection system) was evaluated. The obtained results revealed that, the daily average solar radiation recorded on the horizontal surface during the experimental period was 7.215 kWh/m2 while, the actual solar radiation recorded on the tilted surface of the cabinet solar dryer was 10.220 kWh/m2. Accordingly, the stationary non-tracking cabinet solar dryer increased the actual received solar radiation during that period by 41.65%. The daily average solar radiation recorded outside and inside the cabinet solar dryer was 7.215 and 5.740 kWh/m2, respectively, with cover effective transmittance of 79.56%. The solar radiation available inside the cabinet solar dryer was converted into useful heat gain for the drying process, resulting in increasing the dying air temperatures above the outdoor air (31.8oC) by 16.2oC, and reduce the air relative humidity under the outside (60.5%) by 20.4%. The daily average overall thermal efficiency of the cabinet solar dryer during the drying period was 46.64%, accordingly, 53.36% of the solar energy available was lost. The obtained results also showed that, the germination percentage of cucumber seeds dried by cabinet solar dryer was ranged between 97.1 and 97.4% under different drying times, drying air temperature, and air relative humidity. The minimum drying cost (292 LE/ton) was obtained by the dryer operated at layer thickness of 5 mm.

EXPERIMENTAL FORCED SOLAR THIN LAYER GINGER DRYING

In this research paper, the convective and the evaporative heat transfer coefficients of ginger (zingiber officinale) drying in an indirect solar cabinet dryer under the induced forced convection mode is presented. Experiments were conducted during the month of March 2015 under the climatic conditions of Hisar, India (29°5’5”N latitude and 75°45’55”E longitude). The experimental data obtained for solar drying of a constant ginger mass of 150 g has been used to determine constants ‘C’ and ‘n’ in the Nusselt number expression using linear regression analysis; consequently, the convective and the evaporative heat transfer coefficients have been evaluated. The average value of constants ‘C’ and ‘n’ were evaluated as 0.999 and 0.318, respectively. The average values of the convective and the evaporative heat transfer coefficients were found to be 3.95 W/m2 °C and 160.47 W/m2 °C, respectively, for the given mass samples of ginger. The average collector efficiency was observed to be 14.5%. The experimental error in terms of percentage uncertainty was found to be 20.87%.

Exergy Analysis of Solar Cabinet Dryer and Evaluate the Performance Enhancement of Solar Cabinet Dryer by Addition of Solar Reflectors

Solar dryer dehumidifies the moisture for food preservation using solar radiation. In this paper performance evaluation of cabinet dryer by using energy and exergy analysis tool has been presented. Â Experimental work on proposed design of cabinet dryer has been carried out at Abraka, Nigeria. Analysis has been performed by solving the model equation of solar radiation of Abraka, Nigeria and mathematical model of solar cabinet dryer. Mathematical model has been solved by using Engineering Equation Solver. Solution of mathematical model will give the available useful energy and exergy of solar cabinet dryer. Performance of system is evaluated by making calculation of energy utilized in drying process using experimental data. The analysis highlights the energy losses, irreversibility, exergy losses and exergy destruction at different stages. This study will help improve the efficiency of the system so that maximum energy can be utilized. Performance comparison of cabinet dryer with and without a reflector is also discussed. It has been concluded that cabinet drier without a reflector is able to convert 39% of solar energy as available useful energy of dryer and convert about 13% of useful energy to exergy of the dryer system. While dryer with a reflector converts 42% of solar energy into available useful energy of dryer and converts about 17% of available energy to exergy of dryer. If we compare the performance of both dryers it can be observed that dryer without reflector has twice the exergy as compared to dryer with reflector.

Innovative solar cabinet dryer technology

The new solar cabinet dryer technology is designed and developed with innovative features. This dryer has unique feature of forced circulation of air with solar fans run by power generated by Solar Photovoltaic panels. The working principle of this dryer is closed large cabinet for dehydration of fruits and agri-horticultural products as processed food products. The top cover of the cabinet is fitted with transparent glazing glass through which solar radiation passes into the cabinet chamber and simultaneously incident on solar photovoltaic panels of suitable wattage. The cabinet chamber always maintains between 20–30°C higher over the ambient on good sunny days resulting in maximum temp. 70°C due to green house effect. The forced circulation created by the solar fans will give the maximum efficiency of the dryer. Basing on this principle, the different sizes of the dryers were designed and successfully operated in the dehydration process. 70 commercial products of fruits, vegetables and non-timber forest produce were processed in these dryers. The results were tabulated and stored in the data bank. The operation of these dryers resulted in zero energy cost and protected the climate by sizable volume of reduction carbon emission.

Analysis of ginger drying inside a natural convection indirect solar dryer: An experimental study

In this paper, a natural convection indirect solar cabinet dryer has been fabricated to study the drying behaviour of ginger rhizomes in terms of its convective heat transfer coefficient and moisture removing rate (% db). Various experiments were conducted during the months of March and April 2014 at Guru Jambheshwar University of Science and Technology, Hisar (295’5’’N, 7545’55’’E), India. Experimental data obtained were used to evaluate the Nusselt number constants using linear regression method. Considering these constants, the average value of convective heat transfer coefficient was obtained and observed to decrease with increase in mass of ginger samples and progression of drying days with variation from 0.59 to 5.42 W/m C for different mass of ginger samples. The moisture removing rate was reported to increase with increase in mass of ginger samples and decreases significantly with the progression of drying days. The average collector efficiency was also observed to vary from 14.97 to 16.14% under increasing and decreasing trends of solar radiations from morning to noon and noon to evening respectively. Modified page model was reported best for describing the drying behaviour of different mass of ginger samples. The experimental error in terms of percent uncertainty ranged from 29.19 to 46.25%.

Modeling and Improving the Performance of Cabinet Solar Dryer Using Computational Fluid Dynamics

Abstract In this study, a new approach for numerically modeling of an entire cabinet solar dryer is proposed. Collector, drying chamber and chimney are the three principle sections considered in the present modeling. The collector section containing a cover and an absorber plate is modeled applying energy and fluid flow equations to obtain temperature distribution inside the collector. Due to the non-linear behavior of the governing equations as well as variety of effective variables, an iterative method is employed for solution. Regarding the geometry complexity of the drying chamber along with the air compressibility (that in turn causes coupling of momentum and energy equations) drying chamber is simulated by CFD method. Chimney’s effect and effective parameters in suction are comprehensively considered in the present model. The numerical results are in line with experimental results which show that the model can be applied with certainty to employ the dryer for drying highly demanded and time-consuming products in a scientific, sanitary, and timely manner. The model is then optimized by adding some baffles to achieve higher efficiencies and accelerate the drying process.

English

In spite of the high global demand for fish which is a major source of animal protein, nearly 10% (13 million tons) of the world’s total fish production is lost through spoilage due to inadequate cold storage and poor marketing/distribution channels. Fish is a highly perishable product that is processed by freezing, canning, salting and drying. About 40% of fish landings in developing countries are preserved through traditional processing methods (smoking, drying and salting) organized at artisanal level. As a result of increased trade and co-operation among neighboring African countries over the past years, processed products from the artisanal sector now form a significant part of the small pelagic fish products traded intra-regionally. Lake Victoria provides about 95% of the total fish landings in Kenya, with Rasrineobola argentea (one of the pelagic species) being the second commercially important fish. It is harvested in very large quantities and is readily available at affordable price and widely used for both domestic and industrial purposes. Open-sun drying is the main preservation method employed by the fish farmers and involves spreading the fish on open ground where it is exposed to contamination, infestation and adverse weather conditions. It is estimated that post harvest losses of between 20 and 50% occur especially during rainy seasons. Although, the landings of R. argentea are higher as compared to other fish species, the value of the catch is often very low due to these huge losses. In an effort to curb these losses, a model of an indirect forced convection solar dryer was developed and tested for thin layer drying of R. argentea fish. The fish, in 10 kg batches were loaded onto the dryer and the moisture content reduced from an initial value of 73% (w. b.) to between 16 and 20% (w. b.) after 11 h of drying at average air flow rate of 0.017 kg/s, where open sun drying took 18 h. The mean efficiencies of collector and drying systems were 9.36 ± 3.95% and 11%, respectively. The drying rate constants of the fish in dryer were found to be: 0.146, 0.206 and 0.148 for the fish in the top, middle and bottom trays, respectively.   Key words: Twin collector, indirect, forced convection, cabinet solar dryer, Rastrineobola argentea fish

Effect of Blanching on Drying Kinetics and Quality of Solar Dried Cabbage

Cabbage (Brassica oleracea var. capitata) 250 g samples were blanched in water at 100˚C for 2 min, and subjected to solar cabinet drying to observe qualitative changes of the dried product. Blanching pre-treatments were done in plain water for 2 min (T1 ), and 0.5% potassium metabisuphite (T2 ). Sample without blanching was considered as control ( UT ) . The samples were then dried in a solar cabinet dryer (57 ±3˚C) . Six thin layer drying models were used to fit the experimental moisture ratio obtained for cabbage by nonlinear regression analysis using NLREG Statistical programme. Page model showed a good fit with the highest correlation for cabbage samples. Solar cabinet dried product were found good and acceptable in sensory quality. Cabbage blanched in KMS solution was the best, followed by blanching in water. The rehydration ratio (5.5) and coefficient of rehydration (0.488) were highest for cabbage blanched with KMS solution among all samples. The result showed that the rehydrated products could be well utilized for substituting the fresh product in off-season.

CSD Type Family Solar Drying Technology and Its Potential Impact on Rural Development and Nutrition – A Case Study

Globalization has adversely affected development of rural areas in developing countries. Rural areas are unable to absorb new technologies due to low literacy rates. Local Products, mostly from agricultural produces, are increasingly replaced by cheaper products from organized mechanized farming from one or the other corner of the globe. In this paper, family type cabinet solar dryer designs are presented in commensuration with the contemporary requirement of rural Bihar. Design objective includes simplification of technology and process, easy maintenance and low price to dry exotic produces which has significant export potential. Field trials are conducted, social surveys are undertaken and nutritional values of the products are determined in actual condition. Results indicate that simpler technology with state-of-art control of temperature by a combination of high heat capacity material and phase change material is most suitable to dry vegetables and spices, commonly called “Cash Crops”. Their nutritional values remain within 80% limits even after six months. The technology is appropriate as it uses local materials; sustainable as it is cost-effective and employment generating ability and; robust as it uses very simple way for controlled drying.

Investigation of Solar Drying of Ginger (Zingiber officinale): Emprical Modelling, Drying Characteristics, and Quality Study

Drying is a simultaneous heat and mass transfer energy intensive operation, widely used as a food preservation technique. In view of improper postharvest methods, energy constraint, and environmental impact of conventional drying methods, solar drying could be a practical, economical, and environmentally reliable alternative. In the present paper applicability of mixed mode solar cabinet dryer was investigated for drying of commercially important and export oriented ginger. Freshly harvested ginger slices were successfully dried from initial moisture content of 621.50 to 12.19% (d.b.) and their drying characteristics, quality parameters, and kinetics were evaluated. The results showed that present solar dryer could be successfully applied for drying of ginger in view of quality, reduced drying time, and zero energy requirement as compared to conventional open sun drying and convective drying techniques, respectively. Drying curves showed that drying occurred in falling rate period and no constant period was observed. The effective moisture diffusivity was determined by using Fick’s second law and found to be 1.789×10-9 m2/s. The drying data was fitted to five thin layer drying models and compared using statistical criteria. Page model was found to be most suitable to describe the drying kinetics of ginger in solar dryer under natural convection among the tested models.