Convection Solar Dryer Research Articles

Thermal performance of novel indirect passive solar dryer

An experimental investigation was conducted to study the performance of a novel indirect type free convection solar dryer. The novel and a conventional indirect passive solar dryer were built. Solar irradiation and temperature of different locations were recorded. The air at the drying chamber entrance, lower space, and upper space temperatures besides the thermal efficiency of the novel dryer were 68, 39, 49 and 85%, respectively, higher than the conventional one.

Comparative study on thermal performance of cross-matrix absorber solar collector with series and parallel configurations

This paper presents an experimental study comprising two CMA solar collectors with parallel and series arrangements on a forced convection solar drying system. The parallel and series solar collectors were investigated to evaluate the arrangement type's effect on the thermal performance. The experiments were conducted using artificial solar radiation that varies from 300 to 900W/m2 with the air velocity of 0.5–2 m/s. The arrangement's efficiency was evaluated based on the drying chamber's thermal delivery from the collectors, thermal gains, and drying efficiencies, including air velocity effect and pressure drop. Results show that the solar collectors' parallel arrangement leads to higher air temperature inside the drying chamber than the series by 3.87 °C. The thermal efficiency of 33.89% is achieved for the parallel setup than the series of 27.73%. The series arrangement is superior to the parallel in terms of the pressure drop across the solar drying system. Drying efficiency is observed at a higher air velocity of 2 m/s for both arrangements than lower airflow of 0.5 and 1 m/s. Parallel configuration showed promising performance in drying efficiency and low energy usage compared to the series arrangement in which the negative impact of higher pressure-drop was compensated.

Energy and exergy analyses of drying medicinal herb in a novel forced convection solar dryer integrated with SHSM and PCM

This article examined the performance of a low cost, economically viable and a novel forced convection solar drying system. To control the thermal fluctuations during the day-night drying process, solar air collector (SAC) was equipped with sensible heat storage medium (SHSM) while, drying unit contained paraffin RT-42 as a thermal energy storage (TES) medium. The experiment was conducted considering a sample size of 9.0 kg of Valerian rhizomes. The rhizomes were dehydrated to saturation value of 9% from preliminary moisture content of 89% on wet basis and took 120 (216) hours with (without) use of TES. The performance evaluation of each element of the dehydrating system was carried out on the basis of energy and exergy analyses. The mean values of energy and exergy efficiencies of SAC without (with) TES were computed to be 9.8(26.10) % and 0.14(0.81) % respectively. The overall drying rate without (with) applying TES was 0.028(0.051) kg/hour. The exergy efficiency of the drying unit was assessed to vary from 3.7% to 75.15% with a mean value of 30.28%. The specific energy consumption (SEC) of the rhizomes and the overall efficiency of the drying system were 11.33 kWh/ kg of moisture and 10.53%, respectively.

Drying kinetics and energy analysis of carob seeds (Ceratonia siliqua L.) convective solar drying

The drying process is a fundamental operation in the industry that demands much energy and time, this method is used in order to increase the shelf life of the products as well as the mass and volume during the storage and the transportation. The moisture content permits the deterioration of quality through the microorganisms and the enzymatic reactions. This work aims to study the carob seeds (Ceratonia Siliqua L.) solar drying using a convective solar dryer in order to study and understand the drying kinetics and obtain the characteristic drying curve in different temperatures (50, 60, 70 and 80 °C) and drying air velocities (0.18 and 0.10 m s−1). It was concluded that the increase in the drying temperature reduces the drying time. Six mathematical models were used to appropriately interpret the experimental data; it was found that Verna was the perfect model to represent the drying curves of the carob seeds. The variation of the diffusivity coefficient was found in a range of 1.1968 10−9–4.1482 10−9 m2 s−1, an increase in this coefficient is noticed with the increase in the drying temperature. In order to evaluate the activation energy of the studied product, the Arrhenius relation was called and the average activation energy was found to be 41.46 kJ mol−1. An energy analysis has conducted in order to evaluate the performances of the studied solar dryer. The energy efficiency of the convective dryer was varied in a range of 2.6–4.2%.

Energy Efficiency of Drying Kinetics Process of Hydroxide Sludge Wastes in an Indirect Convection Solar Dryer

Abstract The treatment of sludge, which is produced from raw water treatment, has been considered as an ecologically sensitive problem in terms of energy and pollution. In this context, this study presents many series of solar drying tests that were carried on three samples of sludge obtained from several drinking water treatment plants in Marrakech-Safi regions, Morocco. The main aim is to develop further management processes of these wastes such as upgrading or storage. A partially solar indirect convective dryer operating in forced convection was used to run experiment tests. The temperature of air has ranged from 50 to 90°C and the relative humidity from 24% to 46%. The drying airflow was kept at about 0.0833 m3/s. An estimation of the mass diffusion coefficient and the activation energy during vacuum drying besides the characteristic convective drying curve were established. In addition, six semi-theoretical and/or empirical and statistical models were used to predict experimental data. It was found that the temperature was the most important factor during the drying process. Furthermore, the obtained results of mass diffusion coefficient and activation energy were found consistent with those already existing in the literature. The mathematical model called “Midilli–Kucuk” was found to be the most appropriate to describe the drying curves of the three samples. The total energy consumption was also studied. It showed a downward tendency with the increase in temperature. The efficiency of drying energy ranged from 4.89% to 7.5%. Although it was found to be low, it can be improved by increasing the load.

Exergy Analysis on Performance of Groundnut Solar Dryer with Forced Convection

The moisture present in the farming yields and in seeds is one of the greatest affecting factors which are playing a major role in storing it for longer days. The quality of products can be increased by preventing the formation of bacteria, yeast, etc. The moisture content present in the groundnut must be between 10 to 15% (weight basis). In this study a numerical analysis was investigated on a solar dryer, which is used to diminish the moisture content present in the groundnut to preserve it for longer days. The performance analyses of forced convection solar dryer with dryer compartment were analysed based on local ambient conditions at sathyamangalam for various required design and operating parameters such as moisture removal rate, air mass flow rate, air inlet, and outlet temperature. The proposed basic solar collector aperture area is about 2 m2 which is made of the copper plate as an absorber plate coated with black powder coating for better absorption. The moisture content present in the freshly harvested groundnut varies from 25-30 % (weight basis). The analysis was done for drying groundnut to remove the moisture content to the required moisture level of 10% by utilizing solar energy. The results from the study illustrate that the Efficiency of dryer is a maximum of 39.2% for the optimized mass flow rate of 0.022 kg/s and also it was found that the dryer overall efficiency and average collector temperature is gradually decreasing for increasing the mass flow rate.

Evaluation of the influence of ambient air temperature and air velocity on mortar cement durability using a forced convection solar dryer

PurposeThis work aims to study the hydrothermal behavior of mortar cement toward certain environmental factors (ambient air temperature and air velocity) based on its drying kinetics data. The objective is to provide a better understanding and controlling the stability of mortar structures, which integrate the sorption phenomenon, drying process, air pressure and intrinsic characteristics. This leads to predict the comportment of mortar structures in relation with main environmental factors and minimize the risk of cracking mortar structures at an early age.Design/methodology/approachThermokinetic study was carried out in natural and forced convection solar drying at three temperatures 20, 30 and 40°C and three air velocities (1, 3 and 5 m.s-1). The empirical and semiempirical models tested successfully describe the drying kinetics of mortar. These models simulate the drying process of water absorbed by capillarity, which is the most common humidity transfer mechanism in building materials and contain parameters with physical significance, which integrate the effect of several environmental factors and intrinsic characteristics of mortar structures.FindingsThe models simulate the drying process of water absorbed by capillarity, which is the most common humidity transfer mechanism in building materials and contain parameters with physical significance, which integrate the effect of several environmental factors and intrinsic characteristics of mortar structures. The average activation energy obtained expressed the temperature effect on the mortar diffusivity. The drying constant and the diffusion coefficient can be used to predict the influence of these environmental factors on the drying behavior of various building materials and therefore on their durability.Originality/valueEvaluation of the effect of several environmental factors and intrinsic characteristics of mortar structures on their durability.

Improved solar drying performance by ultrasonic desiccant dehumidification in indirect forced convection solar drying of ginger with phase change material

One of the vital crops used in the recent times of pandemic COVID-19 for making medicines is ginger. It is essential to reduce the drying time compared to open sun drying while maintaining the quality of the dried ginger. The current work highlights about the novel arrangement in indirect forced convection solar drying of ginger by the combined application of liquid desiccant supplied as droplets using ultrasonic atomizer for dehumidification of air stream and paraffin wax as the thermal energy storage medium. The present study is a performance comparison of forced convection solar drying of ginger against open sun drying with and without dehumidification of air stream using liquid calcium chloride as desiccant at air flow rates of 0.153 kg/s and 0.077 kg/s. Using the dryer, fresh ginger having initial moisture content of greater than 80% is reduced to nearly 10% using liquid desiccant at the flow rate of 0.153 kg/s taking 13 h less compared to open sun drying while it is 9 h less without using desiccant. At a flow rate of 0.077 kg/s, moisture content is reduced to nearly 20% with saving of 11 and 6 h, respectively. Three drying models are also presented with the experimental data, amongst which the parabolic fit is found to be the best model for both with and without using desiccant.

Experimental Research of Drying Characteristic of Red Banana in a Single Slope Direct Solar Dryer Based on Natural and Forced Convection.

SUMMARYResearch backgroundTraditionally, open sun drying method serves to dry the products for long time preservation. Solar drying is also employed to minimise the drying time to achieve the required moisture content. This method inherently contains complex heat and mass transfer mechanisms, which makes difficult to describe drying kinetics at the micro level.Experimental approachIn this paper, research is carried out to investigate the drying of 5 mm thick slices of red banana (Musa acuminata ’Red Dacca’) in a single slope solar dryer based on natural and forced convection. Based on the experiments, a new semi-empirical thin layer drying kinetics is proposed and compared with other existing models. The proposed model with the correlation coefficient (R2) of 0.997 is in very good agreement with other well-known models. Based on the model, we calculated the moisture diffusivity and activation energy of the red banana drying process.Results and conclusionsIt was found that the moisture diffusivity of the red banana samples was in the range 0.87-1.56·10-9 m2/s for natural convection solar drying and 0.84-2.61·10-8 m2/s for forced convection solar drying. The activation energy of the red banana varied from 24.58 to 45.20 kJ/mol for passive and 22.56 to 35.49 kJ/mol for active drying. Besides, we carried out energy and exergy analyses of red banana in the dryers and found that the average exergy losses in the forced and natural convections were 16.1 and 6.63 kJ/kg and the average exergic efficiency of the natural and forced convection dryers was 57.7 and 70.9%, respectively.Novelty and scientific contributionA single slope direct solar dryer was designed and built to maintain the desired temperature for a specified period in both natural and forced convection mode. A novel drying kinetics model with higher correlation coefficient (R2) than the other drying kinetic models is proposed for the preservation of red bananas.

Drying behaviour observations for wood chips of grade EN14961

Solid biofuels such as woodchips have always been a significant source of fuel in the field of renewable energy. However, the drying of wood chips has been a challenge in preparing biofuels and other applications. The moisture content of below 25% in the wood chips of grade EN 14961 is considered the premium wood chip material. Solar drying emerged as a leading solution for the drying of wood chips. The paper investigates the comparison of moisture removal rate using a natural convective solar dryer compared to open sun drying developed at Miskolc, Hungary (48°06'15.0"N 20°47'30.0"E).

Performance investigation of natural and forced convection cabinet solar dryer for ginger drying

In this paper, a Cabinet type solar dryer has been designed and developed with natural and forced convection air circulation. This paper aimed to study the performance of solar dryer for fruits to analyze the moisture content loss and weight loss of Ginger during the drying process by comparing with natural convection and forced convection solar dryers. The Objective of the current experimentation is to present the several parameters of the solar cabinet dryer in a table and graphical form. Study of drying behaviour of Ginger drying has been done with natural and forced air circulation. In this work 4000 gm ginger used for drying and various calibrated instruments used for the measurement. Various tabular data has been prepared on ginger drying with natural and forced Convection. Analysis of per day weight removal of ginger and moisture removal has been done. After analysis, it has been found that the initial moisture content in the ginger is 80% for 4000 gm weight. After drying for three days 830gm in natural air circulation and 620gm in forced air circulation. The Design and specification of the solar Dryer are shown here. Drying has been done in the region Ahmedabad (23.0732N, 72.5515E) Gujarat, India. Comparison of temperature indicated at inlet–outlet of solar dryer in Natural and forced convection mode is represented.

Financial and Economic Analysis of a 1-Tonne Capacity Mobile Solar-Biomass Hybrid Dryer for Maize Drying

Drawbacks associated with natural convection solar dryers are encouraging the development of low-capacity hybrid drying systems which integrate renewable energy in their operation. However, information on the cost-effectiveness of such drying systems for decision-making by investors is lacking. This study seeks to assess the financial and economic feasibility of a solar-biomass hybrid dryer for maize drying. A cost-benefit analysis was done using net present value (NPV), benefit-cost ratio (BCR), and internal rate of return (IRR) as well as payback period to measure the financial viability of the dryer operation and the profitability of the investment. The results show that the total capital expenditure required to establish the drying system is $ 5,263 with a running cost of $ 1,166 per year. Using an economic utilisation period of 10 years, the investment in the dryer was determined to be viable with an NPV of $ 4,876 and an IRR of 38% at a capital cost of 24%. At a drying charge of $2.11/bag, the results show the initial capital invested can be recouped in a PBP of 2.7 years at a BCR of 1.48. These financial indicators suggest that investment in the dryer is profitable. Further analysis shows that, at a projected 30, 266.80 tonnes of maize produce per season by smallholder maize farmers in the study area, about 210 of the hybrid dryers are needed to provide drying services to the farmers. This translates into about 420 direct job opportunities created for the youth and the potential to prevent economic loss of maize grains equivalent to $ 5,684.2 per year due to post-harvest losses of maize in the study area. The adoption and scale-up of the dryer have implications in addressing maize post-harvest loss at the smallholder level and job creation for the youth in the country.

Investigation on indirect solar dryer for drying sliced potatoes using phase change materials (PCM)

The solar dryers are playing a pivotal role in the food industries for preserving edible items such as grains, vegetables, fish, etc., through the removal of moisture content from them. They are having benefit over the open air drying by protecting the food items from dust, insects and other detrimental things. Further, they are attributed to save a greater amount of energy and protect the ecosphere from degradation. The indirect type solar dryers are primarily consisting of a solar collector and a space to place sliced potatoes. Their moisture removal rate is high and the quality of the end product would also be improved by them. In this present work, an indirect type single-pass forced convection solar dryer was fabricated and paraffin was integrated with solar collector as phase changing material (PCM) to improve the off-sunshine hour performance of the solar dryer. The process parameters such as, moisture removal rate, moisture ratio and the dryer inlet temperature were investigated for drying sliced potatoes in two cases, namely, solar dryer without PCM (Plain Dryer) and solar dryer with PCM (PCM Dryer). The mass flow rate of air was maintained as 0.065 kg/s and the dryer was operated from 10.00 a.m. to 7.00 p.m. The obtained results were compared and the influence of amalgamating PCM with the solar dryer was analyzed and presented. The results demonstrated that the presence of PCM within the solar collector enhanced the drying room temperature significantly, two more hours after solar period. In addition, the percentage weight of moisture removal from potato slices was enhanced by 5.1% per day with the aid of paraffin.

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

Design and development of natural convective solar dryer

Solar drying has emerged as a potential drying solution for agricultural products in many developing nations. The drying behavior of the product to be dried depends on many parameters of the dryer. A box-type natural convective solar dryer was developed to analyze the drying performance of Wood chips. Experiments revealed promising drying results with drying efficiency. The design of the dryer could further be enhanced by hybridization with an external heat source.

An Experimental and Numerical Investigation of Absorber Positioning in a Natural Convection Solar Drying System

An Experimental and Numerical Investigation of Absorber Positioning in a Natural Convection Solar Drying System

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.

Application of solar drying on the apple peels using an indirect hybrid solar-electrical forced convection dryer

Apple peels are available worldwide as organic waste from the food processing industries which have many functional groups that can be exploited for industrial such as food supplements. The valorization and conservation of this organic waste with good quality at a low cost still remains a big problem in the agro-food industry. Hence, a forced convection solar drying is deemed as an environmentally friendly solution. This paper tackles the drying kinetics of the apple peels at four temperatures 50, 60, 70, and 80 °C, with two mass air flow rate 150 and 300 m3 h−1. The results are represented in a drying characteristic curve. The impact of aerothermal parameters on the drying behavior, the color, the dimension, and the bioactive profile of this co-product is also studied. An energetic study demonstrates that the total energy consumed during the drying experiments reaches the minimum at a higher temperature and a lower airflow while the energy efficiency gets a maximum value at a higher temperature and airflow.

The effect of drying sweet basil in an indirect solar dryer integrated with phase change material on essential oil valuable components

In the present work, the quality of sweet basil leaves volatile oil dried by indirect mode forced convection solar dryer (IMFCSD) integrated with thermal storage material was investigated and compared with the traditional air-drying method. It is found that the indirect solar dryer is capable of drying the basil leaves for 31 h (including the night hours) when the phase change material was used, while it is required 60 h to dry the basil leaves in natural air. In order to ensure that the proposed solar drying method preserves the basil valuable components, an untargeted gas chromatography-mass spectrometry (GC/MS)-based metabolomic technique was used to investigate the impact of the indirect solar drying process on the Volatile organic compounds (VOCs) profile of the basil essential oil. GC/MS analysis revealed that 62 different VOCs were detected in either natural-air dried, indirect solar-dried samples or both together. The usage of indirect solar dryer resulted in higher abundances of 31 detected VOCs. There was no significant difference in the abundance of methyl eugenol, however, there were significant differences in the abundance of most minor components for the favor of IMFCSD. Collectively, these findings indicate that the IMFCSD is much better than natural air drying which might be referred to the controlled drying environment and the stability of drying temperature.

Design, Fabrication and Characterization of a Solar Fish Dryer

Herein, a forced convection solar fish dryer is designed, constructed and characterized to yield a better main of drying fish. The designed dryer incorporated a heat storage unit which complimented the drying rate of the product during off sunshine hours. The device was characterized during raining and dry seasons and results clearly indicated the influence of seasonal variation on the performance of the device. Average hourly variation of the dryer and ambient temperatures measured on the selected days of the different months of measurement during the two seasons, clearly indicated that temperatures were significantly enhanced by the device. This was due to the high ability of the designed solar collector to trap large amount of long waves. Maximum dryer and ambient temperatures during raining season were measured to be (58.9±2) oC and (40±2) oC whereas, (73.5±1.3) oC and (45±1.8) oC respectively, were measured during the dry season. Average daily moisture loss from the drying fish was notably high, especially during dry season which was due to the high dryer temperatures and decrease in atmospheric humidity. The efficiency of the solar dryer was estimated to be 76 %. The fishes with initial moisture content of 87 % was dried to 13 %. This moisture content is in range with the United Nations Economic Commission for Europe (UNECE) Standard DDP-19 concerning the marketing and commercial quality control of dried fish.