Indirect Forced Convection Solar Dryer Research Articles

Performance investigation of an innovative solar heating unit for a powered self-sustained solar dryer

Drying food is an efficient way to prevent crop decay. However, drying techniques are known to be intensive processes in which the energy required is usually met by fossil fuels, the main sources of greenhouse gas emissions. Thus, the development of a solar-powered sustainable drying system is not only crucial for zero CO2 emissions, but also for improved energy efficiency. This study performs a comparative analysis of four solar collectors used as heating units in an indirect forced convection solar dryer. The collectors evaluated were a flat solar collector, two solar air collectors with latent thermal storage (CaCl26H2O and paraffin), and a novel heating unit combining the latter two collectors. This study conducted a comprehensive 4E analysis, evaluating the performance of the collectors through energetic, exergetic, economic, and environmental assessments. The results showed that the pioneering heating unit caused a 30 °C increase in nocturnal temperature compared to other collectors. It demonstrated an annual energy consumption of 640 kWh/year and an energy payback period of 2.5 years. The environmental analysis revealed a significant CO2 reduction of 39 tons. Overall, the proposed heating unit allows a more sustainable and cost-effective drying process while reducing greenhouse gas emissions and promoting energy conservation.

Performance studies on indirect forced convection solar dryer without and with thermal energy storage during drying muskmelon slices

Performance studies on indirect forced convection solar dryer without and with thermal energy storage during drying muskmelon slices

Heat transfer enhancement of solar collector by placing wire mesh stainless porous material on the solar absorber plate of indirect forced convection solar dryer

Indirect forced convection solar dryers are a common technology in solar drying. The flat plate solar collector is an essential device that absorbs heat from solar radiation in order to heat the air flowing through. To improve the thermal utilization of this device, heat transfer enhancement by using the technique of changing airflow patterns into swirling or rotating flow was proposed in this research. In the experiment, wire mesh stainless porous material (WP) SUS304 with various porosities (X) of 0.747, 0.888 and 0.928, transverse pitch with duct height ratio (P/h) of 1.14, 1.43, and 1.71, rib height with duct height ratio (R/h) of 1, attack angle (α) of 30° was placed on the solar absorber plate and the investigation conducted under solar simulator of EN 12975–2 standard with a constant solar intensity of 780±20 W/m2. Air was used as the working fluid in the turbulent flow region at Reynolds number (Re) in the range of 3,700–30,000. The experiment results showed that Nusselt number (Nu), Friction factor (f) and Thermal enhancement factor (TEF) significantly increased when WP was placed on the absorber plate because the swirling airflow through WP occurred and disturbed the thermal boundary layer on absorber plate. The increase in Re resulted in increased Nu and decreased f. Nu and f increased with a decrease in X and P/h. The highest Nu and f of 303.01 and 5.14, respectively, were found at X = 0.747 and P/h = 1.14. The maximum TEF was 1.84. Besides, the developed correlations were in good agreement with the experimental results of predicting both Nu and f with the mean differences of 6.23% and 9.98%, respectively.

Thermokinetic Study by Solar Convective Drying of Argan Press-Cake

The argan tree "Argania spinosa" is a typically multi-use tree. It represents the agroforestry systems pivot which has so far succeeded in meeting the needs of the inhabitants of arid and semi-arid areas strongly marked by climatic hazards. Argan press-cake, residue from the argan oil extraction, is used in several fields, namely: cosmetics, agriculture, and pharmacology. In order to keep this argan paste with a pennyworth, solar drying is an economically appropriate solution, energy and environmentally friendly. In this work, an experimental study is performed to improve the sun-drying process of Argan press-cake using an indirect forced convection solar dryer. As a result, the evolution of the temperature and the drying kinetics inside the product have been assessed. The influence of air recycling drying on the drying time has been highlighted and the characteristic drying law was established too. Thus, the optimal storing conditions of argan press-cake were identified.

CFD Modelling and Simulation of an Indirect Forced Convection Solar Dryer

Solar dryer is a conventional device used for solar drying products. There are several types of solar dryers being employed for drying fruits and vegetables. In this research, the indirect type solar dryer is studied and computational fluid dynamics is employed to simulate the process. Ansys fluent CFD software is used to simulate and obtain dynamic and thermal performance of the dryer at different operating conditions (mass flow rate). The predicted results are validated with the help of experimental results. The average velocity at the exit of the collector was 2.89 m/s for 0.0872 kg/s mass flow rate, while for a mass flow rate of 0.0447 kg/s was 1.36 m/s. The maximum temperature at the collector outlet was 44.6°C and the maximum absorber plate temperature was 69.57°C for a magnitude of 0.0872kg/s mass flow rate. The temperature profiles of the trays are also analysed and the tray closest to the collector is found to have the maximum average temperature. The results also revealed that CFD simulations are a reliable method to predict and design solar dryers.

Investigation of the thermal performance of an indirect forced convection solar dryer for tapioca chips drying

Investigation of the thermal performance of an indirect forced convection solar dryer for tapioca chips drying

Drying kinetics of cabya (Piper retrofractum Vahl) fruit as affected by hot water blanching under indirect forced convection solar dryer

East Java Province is one of main producers of cabya (Piper retrofractum Vahl) fruit in Indonesia. The fruit has huge utilizations and economic potential, but lack in postharvest process investigation. Traditional open sun drying by farmers has deficiency, e.g. unpredictable weather and longer process. In the present study, the indirect forced convection solar dryer was used to dehydrate the cabya fruit as affected by hot water blanching. The drying behavior, drying kinetics model and shrinkage of the fruit were evaluated. One kilogram of cabya fruit at the red edible maturity stage with 70.29 ± 2.89% (wb) of average moisture content was used as raw material for each with and without hot water blanching. Two units of forced convective solar dryers with identical specification consisting of solar air collector and drying cabinet were employed in parallel for 18 h in 3 days. The obtained drying data were fitted to 12 mathematical drying kinetics models. The moisture content of cabya fruit with and without hot water blanching was reduced to the final moisture content of 6% (wb) and 9% (wb), respectively. Among examined models, The Page model satisfactorily described cabya fruit drying kinetics. The results also indicated that hot water blanching affected significantly the drying behavior of cabya fruit. Significant shrinkage was also found in the final dried product of cabya fruit.

Performance Assessment of Banana Drying using a Forced Convection Solar dryer

Among all the noteworthy preservation techniques for food items, drying is considered to be one of the most consequential one. Different types of drying systems exist bottomed on the manner in which air flow takes place in the drying chamber and method of utilising incident solar radiation for drying. An indirect forced convection solar drying system with a dryer of varying cross section was considered in the present work. Banana (Musa Paradisiaca) was the raw material to be dried. Performance of the system at discharges of 0.03 and 0.02 kg/s, respectively for the specified mass of product was obtained and compared with open sun drying in the range of 66.3% - 9.9% of wet basis moisture content. Drying process in chamber drying was completed four and two hours earlier than open sun drying at discharges of 0.03 kg/s and 0.02 kg/s, respectively. Cumulative and tray wise instantaneous drying rates were found and obtained maximum drying rates of 75 g/h and 15 g/h, respectively. Trend of moisture ratio against time was obtained by polynomial fitting which has satisfactory agreement with available mathematical model.

Exergo-environmental analysis of an indirect forced convection solar dryer for drying bitter gourd slices

In this study, a low cost indirect forced convection solar dryer integrated with porous bed sensible heat storage medium has been developed and studied under the climatic conditions of Coimbatore for drying bitter gourd slices. The experimental setup consists of a solar collector with 2 m2 area, drying chamber and a centrifugal blower to force the air. The main objective of the study is to investigate the effect of mass flow rate of air on the exegetic and pickup efficiencies of the solar drying system for drying bitter gourd slices. The results indicate that the mass of the bitter gourd slices was reduced from 4000 to 723 g in 7 h at the mass flow rate of air 0.0636 kg/s in solar drying system. The average exergy efficiency values vary from 28.74% to 40.67% for the mass flow rates of air from 0.0141 to 0.0872 kg/s respectively. The average pickup efficiency of the drying air varied from 54.29% to 17.18% for various mass flow rates of air and it decreases with increase in mass flow rate of air. The effective moisture diffusivity of bitter gourd slices was observed from 8.6293 × 10−10 to 12.9585 × 10−10 m2/s, whereas for open sun drying it gives the lowest value of 0.9568 × 10−10 m2/s. Environmental impact analysis indicated that the energy payback time for the indirect solar dryer is found to be 2.21 years only. The CO2 mitigation and earned carbon credit values for the developed system are 33.52 tons and INR 10894 to 43576 for the expected lifetime of 35 years. Impact analysis shows that the solar dryer is a suitable solution for preserving the agricultural products with environmental sustainability.

Experimental investigation of the performance of a novel solar dryer for drying medicinal plants in Western Himalayan region

This paper presents the experimental investigation of indirect forced convection solar dryer integrated with sensible heat storage material (SHSM) and phase change material (PCM) in meteorological environment of Himalayas (latitude 30.91 °N). The iron scrap mixed with gravel is placed on absorber plate and copper tubes comprising of engine oil have been used as SHSM in the solar collector. The Paraffin RT-42 as a PCM has been used in the drying chamber. Experimentations of Valeriana Jatamansi (a medicinal herb) drying have been conducted and its moisture content reduced from initial value of 89% to 9%. Using SHSM and PCM simultaneously the overall drying rate observed 0.051 kg/hr which was almost double as compared to 0.028 kg/hr and 0.018 kg/hr with no use of thermal storage medium and traditional shade drying, respectively. The drying time to reach the saturation level of 9% was recorded as 120 h in comparison to 216 and 336 h, respectively and the dried rhizomes of good quality in terms of essential oil and bio-medical compounds are obtained. From the experimental results rehydration capacity and total Valepotriates were found 7.11 and 3.47% as compared to 6.18 and 3.31%, respectively in case of traditional shade drying. The solar collector without SHSM possess an average energy and exergy efficiency 9.8% and 0.14%, respectively. The respective energy and exergy efficiency achieved with SHSM are 26.10 and 0.81%.

Experimental investigation of an active direct and indirect solar dryer with sensible heat storage for camel meat drying in Saharan environment

An indirect and direct forced convection solar dryer integrated with pebble sensible heat storage medium was developed and investigated under Saharan prevailing weather conditions. The setup consists of a direct chamber superimposed to an indirect drying one. A first pebble bed is placed in a plenum, below the direct drying chamber, a second in a cavity below the solar collector. The sensible heat storage system maintained the thermal efficiency of the solar collector until one hour after sunset and enhanced it by 28%. The thermal efficiency of the direct chamber was enhanced by 11.8%. Experiments of drying camel meat without salting were carried out under the different climatic conditions of July and November months. The drying kinetic evolution was investigated under each experiment conditions. The drying is faster in July than in November. Several mathematical models were tested to describe the best, in terms of statistical parameters, the drying behavior of camel meat slices. Logarithmic model and Midilli-Kucruk model are respectively the most suitable for July and November experiments. The average of indirect drying efficiency over diurnal period reached 18.34% in July and 15.52% in November. The direct drying efficiency reached the average of 10.35% and 7.88% respectively in July and November. In order to preserve the protein rate of the dried camel meat, salting which inhibits decay, pretreatment usually reserved for meat products before drying has been suppressed. Microbiological and physicochemical monitoring has been carried out to ensure the final quality of the dried product. The results obtained, compared to an open sun-dried samples were satisfactory according to the norms imposed by the Algerian legislation.

Thin layer solar drying of Moroccan carob pulp (Ceratonia Siliqua L.)

Most biological products are highly perishable, so the issue of their conservation during large transportation distances and storage is a sensitive problem. Solar drying is the most useful method of keeping food staff safe in terms of both energy and time. Our work aims to contribute to the optimization of solar convective drying at the pulp of carob widely produced in Morocco by an experimental approach in an indirect forced convection solar dryer. In this paper, the effect of air temperature on the drying kinetics of carob pulp was investigated in convective solar drying. The relative humidity of air was varied from 15% to 45.5%. This kinetic measurement is carried out at four temperature values of drying air (50, 60, 70 and 80 °C) and also for one value of drying air flow rate Dv (0.0833 ± 0.002 m3 s-1). Four models have been used to adjust experimental curves. In conclusion, the experimental study shows that solar drying is adapted for the valorisation of carob pulp. Middili & Kucuk model is the most appropriate to describe drying curves in various drying conditions.

Thermal performance of indirect forced convection solar dryer and kinetics analysis of mango

In this paper, an indirect forced convection solar dryer (IFCSD) with auxiliary heating device has been presented for drying mango. The dryer consists of the evacuated tube solar air collector, three phase inverter fan, auxiliary heating device, drying chamber, and automatic control system. Moreover, the influence of different drying air temperatures on the dryer performance, the drying characteristic and the drying kinetics of mango slices in this dryer have been investigated. The experimental results showed that the temperatures at four different locations of the drying chamber were varied within a narrow band. Meanwhile, the average thermal efficiency of IFCSD was between 30.9% and 33.8%, the specific moisture extraction rate (SMER) was 1.67 (kg water/kWh) with the drying temperature of 52 °C. In addition, results revealed that the Page's model was the most appropriate for describing the drying kinetics of mango slices in IFCSD. The effective moisture diffusivity (Deff) values of mango slices were obtained from the Fick’s diffusion equation varying from 6.41 × 10−11 to 1.18 × 10−10m2/s, over the temperature range of 40–52 °C. Furthermore, results revealed that Deff values increased with the increasing of drying air temperatures, due to the increase of heating energy would increase the activity of water molecules of mango slices. Thus, this study contributed to provide the basic theoretical and experimental data support for the follow-up research.

Design and Development of Solar/LPG powered Areca-nut leaf Plate Press Machine and Areca Leaf Sheath-Solar dryer

The whole idea is to produce eco-friendly plates from the sheaths of the Areca palm tree leaves. The technology developed for and employed in the project has negated the issues of production challenges that occurred due to humid weather conditions, high cost machines and low quality and fungus prone products. We have ergonomically designed the press machine. The dried sheaths are placed inside the machine using the required die size to manufacture plates and bowls of different sizes. The upper die plate made of aluminium is heated using electricity. Then the sheath is placed on the lower die and will be pressed against the upper die to create plate. In order to remove moisture content, we have designed an indirect forced convection Solar dryer. With integrated cutters in die, a separate cutter mechanism is avoided to prevent reduction of sheath waste. The most distinguished achievement of the project lies in its ability to develop entrepreneurial spirit among the rural unemployed youth, by providing them a dignified livelihood generation activity. Further the current technology will ensure to produce plates at a cost of 1 rupee which is way less than banana leaf. Most of the existing machines are costly in nature and they range from 1.5 lakhs to 3 lakh rupees. Further most of these machines lack a drying chamber. The initiative boosts the growth of palm trees ensuring year round employment and women empowerment leading towards creation of a self-sustained rural economic model.

Study of Fabricated Solar Dryer of Tomato Slices under Jordan Climate Condition

The objective of the current study was to investigate experimentally, the performance of a fabricated solar dryer under Jordan climate condition during the summer of 2013. The temporal variations of temperature difference between absorber plate and ambient temperature were obtained in the results and its influence on the performance of solar flat plate collector was examined. The effects of absorber plate temperature, ambient temperature and wind heat transfer coefficient on the top heat loss coefficient were also investigated. The results showed that the efficiency of the collector ranging between 45 to 66 % which affected significantly by the amount of solar irradiation during the day. Only top heat loss was taken into considerations, since other losses were very small and might be negligible. Also the results confirmed that the performance of collector was maximum when the difference between plate and ambient temperatures was maximum. In addition, this work presented an indirect forced convection solar dryer, which consists of solar heater, fan and drying chamber. Fan was used to force the heated air through chamber to increase the drying rate. A 500 gram of tomatoes were dried to the final moisture content 28% from 95% (w.b). The experimental moisture ratios of the tomatoes were fitted to four mathematical drying models. Comparisons between these modes are sought using statistical analysis in the results. The fit quality obtained with each model was evaluated. After the comparison with the experimental obtained values, it was concluded that polynomial equation with second order represents the drying characteristics better than the other models by indicating high value of coefficient correlation (R2= 0.999564 ) and low values of other parameters( 𝞌2= 0.000203; RMSE= 0.01011; MBE= 0.000102 ) compare with other models. The effective moisture diffusivity was estimated using Fick's second law and was m2/s with an average temperature of 306 K.Article History: Received January 14th 2017; Received in revised form April 28th 2017; Accepted June 10th 2017; Available onlineHow to Cite This Article: Olimat, A.N. (2017) Study of Fabricated Solar Dryer of Tomato Slices Under Jordan Climate Condition. International Journal of Renewable Energy Development, 6(2), 93-101.https://doi.org/10.14710/ijred.6.2.93-101

Thin layer drying characteristics of curry leaves (Murraya koenigii) in an indirect solar dryer

In this work, the thin layer drying characteristics of curry leaves (Murraya koenigii) has been studied in an indirect forced convection solar dryer with constant air mass flow rate of 0.0636 kg/s. Twelve thin layer drying models were tested for its suitability to describe the drying characteristics of curry leaves. The dryer has reduced the initial moisture content of curry leaves from 67.3% (wet basis) to the final moisture content of 4.75% (wet basis) in 3.5 hours. The pickup efficiency of indirect solar dryer for drying curry leaves was varied between 4.9% and 23.02%. Based on the statistical parameters, the Modified Henderson and Pabis model and Wang and Singh model were selected for predicting the drying characteristics of curry leaves. The payback period for the solar dryer was evaluated as 8 months, which is found to be much lower when compared with the entire life span of 15 years. The payback evaluation confirms that the solar dryer is economically viable in rural applications.

Mathematical modeling and performance analysis of thin layer drying of bitter gourd in sensible storage based indirect solar dryer

Abstract An indirect forced convection solar dryer integrated with porous sensible heat storage medium was developed. The effect of porous thermal storage and mass flow rate of air on the performance of the system for drying bitter gourd was studied. The experimental setup consists of a blower, solar flat plate collector with corrugated absorber plate (2 m 2 ) and a drying chamber. The thermal storage medium (pebble) is placed below the corrugated absorber plate, in the air passage as a porous medium. The experiments have been carried out with various mass flow rates of air and different drying models have been used for explaining the drying behaviour of sliced bitter gourd. The result shows that, (i) the initial moisture content 92% (w.b) of bitter gourd was reduced to 9% (w.b) in 7 h in the proposed drying system, while it was 10 h for open sun drying, (ii) the maximum specific moisture extraction rate was observed as 0.215 kg/kWh at the mass flow rate of 0.0636 kg/s and the corresponding specific energy consumption was 4.44 kWh/kg, (iii) the collector and drying efficiency of the system were 22% and 19% respectively. The two term model and Midilli–Kucuk model are most suitable for indirect solar dryer and open sun drying in terms of statistical parameter respectively. The drying inside sensible heat storage based indirect dryer was more consistent and produced better quality product as compared to open sun drying. Industrial relevance • Every year post harvest losses are increasing rapidly due to the lack of storage facilities. • Solar dryers are the most suitable technology that can be easily availed at low cost and in small scale and it can be used as an income generation option for farmers and women in rural areas. • The role of solar dryers in food processing industries is significant especially in developing countries in the following areas o For preserving fruits and vegetables o Dairy industries o Agricultural crop drying o Timber drying o Industrial waste drying • The utilization of thermal storage medium in the solar dryers is being focused much for the reasons of extending the availability of the system for operation and to achieve better quality of the products.

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

Experimental study and simulation of a solar dryer for spearmint leaves (Mentha spicata)

An indirect forced convection solar dryer consisting of an air flat plate collector and a drying cabin was designed and fabricated to investigate its performance under the climate of Algiers. Drying experiments have been performed for spearmint leaves at different air flow rates in order to determine the drying velocity, the characteristic drying curve, the effective diffusion coefficient and the activation energy. A mathematical model based on thermal and mass balances over the component of the solar collector and the cabinet dryer was developed. Simulations are carried out for meteorological data of Algiers (Algeria). We analyse the effect of air mass flow rate, air temperature, products mass, collector area, air recycling rate on the drying time, the solar fraction and the efficiency of the dryer.

Experimental Study on Eggplant Drying by an Indirect Solar Dryer and Open Sun Drying

In this article, an indirect forced convection solar dryer is used to study the kinetic drying of eggplant. The effective moisture diffusivity calculated by slop method follows the solar intensity with the maximum value of 1.68 E-09 at 15 PM. Performance of solar dryer is determined by defining the efficiency of collector and an effectiveness factor as the ratio of the drying rate in the indirect solar dryer to the drying rate in the open sun. The collector efficiency and the effectiveness factor vary with the drying time inversely. Results show that the drying rate in the solar dryer is 3.5 g H O. g ds . Hr and is 2 g H O. g ds . Hr for 22 11 11