Passive Solar Dryer Research Articles

Performance parameters evaluation and comparison of passive and active indirect type solar dryers supported by phase change material during drying ivy gourd

Experimental investigations were carried out by drying ivy gourd slices to evaluate the performance of passive and active indirect type solar dryers (PITSD and AITSD) supported with a thermal energy storage unit. The PITSD was restructured with central processing unit fans powered by photovoltaic solar panels to form the AITSD. Performance parameters and drying kinetics were evaluated from the data recorded during experiments. The average values of heat supplied, activation energy and specific energy consumption of PITSD and AITSD were 735.9 and 761.2 W, 38.95 and 36.35 kJ/mol, and 00.228 and 0.265 kWh/kg, respectively. Average collector and drying efficiencies were 66.7 and 69.87%, and 13.15 and 15.2% for PITSD and AITSD, respectively. The mean values of effective diffusivity, specific moisture extraction rate, heat and mass transfer coefficients of PITSD and AITSD were 8.06 × 10−9 and 10.00 × 10−9 m2/s, 78 and 4.380 kg/kWh, 0.0041 and 0.0055 m/s, and 4.7 and 6.28 W/m2 K, respectively. Moisture diffusivity, heat and mass transfer coefficients were negatively related in a logarithmic trend with moisture content. The AITSD performed well as compared to the PITSD. Uncertainty analysis was made to ascertain the reliability of the outcomes.

Design and fabrication of box-type passive solar dryer (BTPSD) with thermal insulation material for valorizing biomass and neutral lipids of marine Chlorella vulgaris for biodiesel application

The staggering rate of population growth has augmented the reliance on fossil fuel utilization, and it kindled the society to explore alternative and sustainable sources of energy. In this regard, biodiesel from microalgae came to the limelight; but crucial energy-consuming and expensive processes like cultivation, harvesting, and drying make the microalgal biodiesel unsustainable and economically unfeasible. To surpass these impediments, in this research work, a low-cost box-type passive solar dryer (BTPSD) is designed and fabricated with zero energy consumption mode and compared with conventional hot air oven for drying the biomass, neutral lipids of the marine microalga Chlorella vulgaris for biodiesel application. The onset of the work, BTPSD with 2 cm thickness of glass wool as TIM (thermal insulation material), 4 cm TIM thickness and no TIM was simulated for thermal storage behaviour using ANSYS FLUENT 19.2 Computational Fluid Dynamics tool and based on the results, 4 cm TIM thickness was chosen for experimentation. The time taken by BTPSD and hot air oven to remove the moisture from algal biomass is 3 and 2 h, respectively, whereas for neutral lipids drying, it was 4 and 3.5 h, respectively. Though there is a little difference in drying time, neutral lipid and FAME content from both drying systems are tantamount, i.e., ~ 12% neutral lipid and 95% FAME. Further, the percentage of vital fatty acids identified from BTPSD and hot air oven methods are almost similar, i.e., C16:0 (23.4%), C18:1 (14.3%), C18:3 (11.42%), C18:1 (9.22%). Though the time taken for valorizing biomass and neutral lipids of C. vulgaris by BTPSD is slightly longer than hot air oven, low energy consumption and cost-effectiveness make the BTPSD a promising system to scale down the microalgal biodiesel production cost significantly.

PERFORMANCE EVALUATION OF A PASSIVE SOLAR CROP DRYING

This paper presents the performance evaluation of a passive solar dryer. The Dryer was designed and constructed at the Mechanical Engineering Department of Caritas University, Amorji-Nike, and Enugu, Nigeria. The Dryer was constructed using locally sourced materials from Ogbete main market, Enugu. Experimentation was carried out using samples of 20mm and 40mm sliced cassava chips weighing 46g and 80g respectively in the month of November, 2020.Temperature readings of the ambient air, the drying chamber and the collector chamber were recorded and tabulated for the hours of 10.00am to 5.00pm for the first day and 9.00am to 4.00pm for the second day. The moisture content and drying rates were evaluated for both samples using both dry and wet basis. Plots were made on the variation of temperature with time as well as moisture content with time for both dry and wet basis for the two days. Results show that the mass of the water removed were 112g and 105g for the first and second day respectively. Results also show the collector efficiency as 37.9% while the dryer efficiency was evaluated to be 37.6%. The moisture content of the 20mm samples of cassava slices were evaluated to be 53.03% and 38.8% for the first and second day respectively, while of the 40mm sample were evaluated as 112.9% and 64.6% respectively for the first and second day. The moisture loss or drying rate for the respective samples of 20mm and 40mm were evaluated to be 27.0g/hr and 34.0g/hr, showing percentage drying rates of 62.1% and 68% for the first and second day respectively. The equipment and the test therefrom have shown tremendous improvement on crop drying over the conventional open air drying method used in the region/location under study. It also provided a veritable tool for training students on heat and mass transfer analysis.

Experimental Investigations of a Simple and Cheap Passive Solar Dryer for Preserving Agricultural Products

Experimental Investigations of a Simple and Cheap Passive Solar Dryer for Preserving Agricultural Products

Moisture Adsorption potentials and energy models of Gongronema latifolium leaves dried in separate environments.

Moisture adsorption isotherm potentials and energy models of Gongronema latifolium leaf grits were investigated. Fresh leaves were dried in sun; passive solar dryer and hot air oven, while proximate composition of the dried and fresh leaves were determined using standard laboratory procedure. Equilibrium moisture content (EMC) of the leaf grits was measured using gravimetric static method. Selected mathematical and statistical models were applied on the experimental data to evaluate data fitting. Energy calculations were done based on the mathematical models. The EMCs of the leaf grits directly increased with water activity (aW) at specific temperatures. Adsorption data was better represented by GAB model than others while differential enthalpy decreased as the EMC of the oven sample increased. Differential entropy of all the samples decreased as the EMC increased. The safest monolayer moisture content varied between 7.1036 and 8.0164 gH2O/100 g solid, below 40°C, within relative humidity of 10%–50%. Sun and oven leaf grits adsorbed more moisture than solar sample. Proximate contents of the dried leaves showed higher values for protein and ash. Overall results indicated that the leaf grits when properly packaged could be used as spice or tea powder to manage household nutrient security in addition to the use as therapeutic foods.

Experimental evaluation of a passive indirect solar dryer for agricultural products in Central Mozambique

Post-harvest losses are one of the major livelihood challenges for farmers in the Global South. The use of drying technologies to preserve agricultural products has been promoted as a particular solution to address this challenge. In this regard, we designed and tested a passive indirect solar dryer for drying agricultural products as an alternative to open sun drying (OSD) in Gurue district, Central Mozambique, using amaranth leaves and maize. In addition, a sensorial analysis was conducted by randomly selecting a group of 60 adults who evaluated the texture, aroma and color of dried amaranth and maize grains. Compared to OSD, the passive indirect solar dryer reduced drying time and increased the thermal efficiency. Evaluation of sensory quality attributes showed that passive indirect solar drying outperforms OSD. Practical applications This study evaluates the performance of a passive indirect solar dryer, a sustainable alternative to conventional food preservation technologies (e.g., refrigeration) that are not affordable to resource-constrained communities. The use of passive solar dryers, if carried out correctly, creates the possibility for poor rural households to safely store and increase shelf life of food. In addition, the acceptability of products dried in the passive indirect solar dryer is evaluated. Thus, the study also provides insights on passive solar dryer potential for preserving the quality of the final product.

Study and Analysis of Solar Cabinet Dryer on Passive Mode by Using Aluminium Foil, Solar Selective Black Carbon Material and Silica Sand (Concrete)

In this research work started to study of various article which is related to solar cabinet dryer. In many article do work repetition and some having different type of work analysis. There are work mostly to increase its efficiency, workability and moisture removal rate with changes in different parameters. Some of authors work passive mode solar cabinet dryer and some was work on active solar cabinet dryer. In this study observed that some of researcher use silica sand and metals particles. Every parameter have focused on different purpose of work. After the study of various articles analyze that use of mixture black carbon material and silica concrete as a storage material. That is important for increase moisture removal rate and drying rate. It will also enhance efficiency and workability of solar cabinet dryer. That will use in industry and winter oriented season in future aspects.

Turmeric (Curcuma longa) drying in natural circulation solar dryer: An experimental evaluation

AbstractA natural circulation solar dryer has been evaluated for drying differently processed turmeric. The predrying treatments namely, hydrothermal treatment using water boiling and steam boiling; and drying methods namely, drying of sliced and unsliced turmeric rhizomes have been investigated. The open sun drying and untreated unsliced turmeric rhizome was used as control. The maximum thermal efficiency of this passive solar dryer has been obtained as 22.4% for the water boiled sliced turmeric, and while that for the steam boiled unsliced turmeric was 14.1%. The thermal efficiency was comparatively lower for untreated turmeric. The quality parameters namely, polishing loss, curcumin content, volatile oil content, total recovery, and color, were found better for steam boiled unsliced turmeric dried in solar dryer. Based on combined perspective of thermal efficiency and quality, drying of unsliced rhizome pretreated with steam in natural circulation solar dryer is recommended as compared to other processing practices. The dryer is economically feasible as indicated by the cumulative present worth of life cycle savings and payback period.Practical ApplicationsIn India, turmeric is an essential part of cuisine. The drying operation consumes maximum time and energy in postharvest processing of turmeric. The conventional practice of drying is open sun. The aim of the article was to find the best drying method and pretreatment method for drying in a natural circulation solar dryer, which will also result in saving conventional energy. It was found that the drying in this solar dryer results in lesser drying time and better quality as compared to conventional method of open sun drying.

Experimental study on drying kinetics of ivy gourd using solar dryer

AbstractVegetable preservation through drying technology is an effective method to minimize wastage while satisfying the essential nutrition requirements. It is necessary to expand the existing technologies to preserve seasonal and regional specific vegetables. The present study is intended to find suitable conditions to increase preservation capacity through solar drying. A single slope solar dryer (SSSD) is designed, fabricated and ivy gourd is taken as a vegetable sample. Experiments are carried out in the highest temperature region in South India at 10.925°N latitude, 79.838°E longitude. The safe moisture content of the passive and active mode solar dryer was attained in 9 and 7 hr whereas it took 11 hr in sun drying. During the dehydrating process, the temperature of the system varied from 35 to 71°C. Existing kinetics models are used to optimize the “goodness of fit” and proposed a novel model to suit India's environmental conditions. Exergy analysis and thin layer drying kinetic studies are performed and studied the influence of various parameters in the dehydrating of ivy gourd. The study revealed that the air temperature, RH, global radiation, and airspeed, significantly influence the drying kinetics. However, all the above four drying parameters are interconnected to enhance the drying process and which in turn enhance the drying kinetics process. Obtained results are explained with suitable discussions.Practical ApplicationAlmost 40–50% amount of food items annually are rotten all over the global due to deficiency of proper preservation methods. Solar drying is found as a sustainable approach for food preservation; however, the food items dehydrated under sun dehydrating lose their nutritional, medicinal properties due to slow and nonuniform dehydrating rate. In this article, the newly designed SSSD is developed and a thin‐layer dehydrating mathematical correlation for freshly harvested ivy gourd is conducted. The results showed that forced convection solar drying setup could enhance the product quality of ivy gourd and also decrease the dehydrating time.

Natural Convection Solar Dryers for Agricultural Products — A Comprehensive Exploration

Objectives: To make review on passive solar dryers and its performance of drying agricultural products. Methods: This article focuses on the development in various categories of passive solar dryers in last six years. The different studies carried out in direct, indirect and mixed mode types of passive dryers for drying agricultural products in the year of 2014 to 2020 have been considered this review. Investigations on forced convection solar dryers have not been included in the current paper. The various experimental setups of solar dryers, specimens used for experimentation, measured output parameters and performance have been illustrated. The changes made in construction of solar dryers for improving the performance have also been reviewed. Findings:The mixed mode passive solar dryer is found to be superior in terms of drying time, better utilization of solar energy and efficiency compared to other passive dryers. Novelty: Several review articles have been published in solar dryers. Nevertheless, no comprehensive reviews have hitherto been published on passive dryers in particular. Hence, our current review article focuses on development in passive dryers and its advancements with emphasis on dryer design features, specimen and measured output parameters. Keywords: Passive solar dryers; Natural convection solar dryers; Direct solar dryers; Indirect solar dryers; Mixed mode solar dryers

Sorption isotherms and thermodynamic properties of the dry silage of red tilapia viscera (Oreochromis spp.) obtained in a direct solar dryer

The sorption isotherms, thermodynamic properties and calculation for confirming the isokinetic theory of dry chemical silage of red tilapia viscera (Oreochromis spp.) obtained in a direct passive solar dryer were determined. Sorption isotherms were carried out at 15, 25, 35 and 45 °C using a static gravimetric method. The curves obtained were adjusted to eight equations. The isosteric heat of sorption (net and total) and the thermodynamic parameters were determined based on the Clausius-Clapeyron equation and the enthalpy–entropy compensation theory was applied to adsorption isotherms. The sorption isotherms obtained were of type III of Brunauer classification. The Peleg model best described the experimental data. In all cases, the isosteric heat decreased while the moisture content increased. The value of isokinetic temperature (TB) was found to be less than harmonic mean temperature (Thm), the sorption of water in dry chemical silage is therefore controlled by entropic mechanisms and proceeds spontaneously.

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.

Experimental investigation of drying characteristics of lima beans with passive and active mode greenhouse solar dryers

AbstractIn the study, the thermal performance of the even span and parabolic roof type solar greenhouse dryers is investigated under the active and passive modes under the same operating conditions. Dryers were covered with the 200‐μm UV stabilized polyethylene sheets to enhance the solar insolation effect. The performance of these dryers is evaluated for drying lima beans (Phaseolus lunatus). The moisture content of Lima beans was reduced from 75% (w.b.) to 11% (w.b). For both of active and passive mode conditions, the parabolic dryer could dry in 28 and 32 hr, respectively and that for the even span dryer, it could achieve the same state in 32 and 36 hr, respectively. The open sun drying took as high as 40 hr to dry time for the lima beans. The highest thermal efficiency of the dryers was estimated to be 14.7% for the active mode parabolic dryer and the minimum as 12.03% in the passive mode even span dryers. The nutrition retainment was the highest for parabolic active mode dryer with the payback period as 2.15 years, as against 10 years of expected solid life span and strong suggestion is made for the use of the small scale needful farmers.Practical ApplicationsDrying is an energy consuming processes, and industries require more amount of energy for drying a food grain. In the current scenario, more attention is toward for usage of the Solar based dryers for the abundance of availability of solar energy which makes cost effective. However, the popularly available conventional method of open Sun drying of lima beans resulted in contamination of product from external dirt, degradation due to direct heating, existence of uncontrolled dry rate and additional dry time. To solve the above constraints, in open sun drying and to improve the dried product quality, the author constructed a simple, compact and economically modified greenhouse solar dryer. The quality of dried lima beans under active mode convection parabolic roof was superior. The much needed carbohydrate and protein values, of dried lima beans of 100 g sample for forced convection parabolic roof greenhouse solar dryer had shown the increase of 2 and 10% than open sun dry sample. Among various seeds used to making food stuff, the lima beans are one of the choices for people.

A review of construction, material and performance in mixed mode passive solar dryers

One of the important global concerns is to reduce the spoiling of agricultural products for avoiding food demand. The solar drying techniques play a vital role to avoid post harvest losses. Mixed mode type, passive solar dryer is the most efficient dryer compared to other passive dryers. The performance of the solar dryer is mainly depends on its construction and material. Presenting the various studies in mixed mode passive solar dryer and its details of construction is the main objective of this paper. This paper focuses on recent development in passive type mixed mode solar dryer. This study will help the researchers find the new direction of research to improve the performance of mixed mode passive solar dryers. The basic idea is providing to the former for constructing and modifying their solar dryer.

Evaluation of Novel Portable Passive and Cabinet Solar Dryers in Sun Drying of Mint Leaves under Indiana Weather Conditions

HighlightsThe Page model best predicted the drying rates of mint leaves in thin-layer laboratory experiments under cyclical temperature change and in field experiments using open-air sun drying and Dehytray and Dehymeleon solar dryers.The total time for drying mint leaves with all solar drying methods was the same (48 h).For all drying methods, the aerobic bacterial count was significantly less on dried mint leaves than on fresh leaves.Color change was less impacted by sunlight with the Dehymeleon than with the Dehytray and open-air sun drying.Abstract. The drying kinetics and quality attributes of mint leaves (Mentha spitaca) were studied to determine the drying performance of two solar drying technologies (Dehymeleon V.2 and Dehytray) and their effect on dried mint quality. Field drying experiments were carried out under weather conditions at Purdue University, West Lafayette, Indiana. Thin-layer laboratory drying experiments were conducted for whole mint leaves at three temperatures [24°C (75°F), 35°C (95°F), and 54°C (130°F)] and airflow velocity of 1 m s-1 to determine the drying kinetics for the diurnal cycles typical for solar drying. The Page model was the most suitable model to predict the drying behavior of mint leaves for both the lab and field experiments. Even though the drying rate was higher with open-air sun drying on uncovered Dehytrays than with covered Dehytrays and the Dehymeleon, the total drying time for all methods was the same (48 h). Color change in mint leaves was less impacted by sunlight for mint leaves dried using the Dehymeleon, while the Dehytray and open-air sun drying had similar results due to their exposure to direct sunlight. For all drying methods, the aerobic bacterial count was significantly less for dried mint leaves than for fresh mint leaves. The log reductions in aerobic bacterial count achieved with open-air sun drying, Dehymeleon, and Dehytray were 0.47, 2.3, and 0.40, respectively. Keywords: Diffusion, Drying kinetics, Food quality, Mint leaves, Solar drying, Sun drying, Thin-layer drying.

Development of mathematical model for drying of crops under passive greenhouse solar dryer

The design and development of greenhouse dryer operating under passive mode is being reported in the present experimentation. The aim of the present study is to develop and fit a new proposed model for drying of tomato flakes and potato chips under greenhouse dryer operating under passive mode. The proposed model was compared with 6 different mathematical models and it was found that the proposed model highest coefficient of determination for both tomato flakes and potato chips followed by logarithmic model. Statistical evaluation of the predicted and experimental moisture ratio shows that the proposed model gives lowest root mean square error and chi square. The present result shows that the curve fitting ability of proposed model for both tomato flakes and potato chips is best compare to other model. However there is no other theoretical basis offered for the best curve fitting ability of the equation.

Passive Drying of Yum Tuber Slices (Dioscorea alata L.)

ABSTRACT Passive drying is a drying mechanism that utilizes sunlight in a drying chamber with natural air flow mechanism. The tool used is direct passive solar box dryer. Direct type passive drying is a drying mechanism in a drying chamber with an air flow mechanism where direct sunlight enters the drying chamber. This study was intended to determine the pattern of decreasing water content and moisture ratio of yum (Dioscorea alata L.) and the appropriate drying model. Passive drying of yum tuber slices is done in two stages. The first drying data is used to determine the most suitable drying model (biggest R2). While the second drying data is used to validate the accuracy of the model predictions obtained. The drying process is carried out by placing the sample at the top, middle, and bottom of the drying chamber. The samples used are two types of yum namely white yum and purple yum with a size of 3x3x1 cm. The models evaluated for compatibility are Newton, Henderson & Pabis, and Page. The results of the analysis show that the Page model with the equation MR = exp (-ktn) is the most suitable model to describe the pattern of decreasing water content and moisture ratio of yum. The values ​​of the Page equation constants are obtained as follows: k = 0.187249, n = 1.17272 and R2 = 0.999403. Keywords: Yum, Drying, Drying Model, Water Content

Design and performance evaluation of a passive flat plate collector solar dryer for agricultural products

AbstractA passive flat plate collector solar dryer (FPC‐SD) was designed and fabricated for drying of agricultural products. It has drying capacity of 7.5 kg, drying chamber cross sectional area of 0.74 m × 0.58 m, collector aspect ratio 2, collector depth of 0.25 m and hence volume of 0.5 m3. Total pressure drop across drying bed ΔPT was 1.29 kg/m2. The difference between the dryer inlet and ambient temperature was recorded for certain days and was 24.6°C at 1.30 p.m. with average solar insolation of 882.35 W/m2. Performance of FPC‐SD was evaluated by drying mushroom under sun drying and passive FPC solar dryer. The moisture ratio of the samples reached zero in 33 hr for sun drying while 21 hr for FPC‐SD. Solar drying took 36.36% lesser time than open sun drying.Practical applicationsThe designed and fabricated flat plate collector (FPC) solar dryer incorporated with a phase change material is a farmer's friendly unit, which can dry agricultural products at farm level. Traditional open sun drying is usually practiced by farmers for drying of fruits and vegetables which generates wastage and also is an energy inefficient process. It also results in loss of nutritional quality due to slow and intermittent drying. The solar dryer is a sustainable and environment friendly farmer's gadget for drying of fruit and vegetables with better retention of the quality. The phase change material helps to prolong the operation even after sunset and thus this continuous operation accomplishes the drying process sooner. Incorporation of phase change material as thermal storage unit helps in improving its performance. Present FPC‐SD helps carry out drying in nearly 35 to 40% lesser time than open sun drying.

Perkembangan Teknologi Pengering surya


 
 
 
 Solar dryers used in agriculture for food and crop drying are used for industrial drying processes. They can be proved to be a very useful device from the energy conservation point of view. It not only saves energy but also saves a lot of time, occupies less area, improves quality of the product, makes the process more efficient, and also protects the environment. Solar dryers circumvent some of the major disadvantages of classical drying. Solar drying under controlled conditions of temperature and moisture removing rate ensures perfect drying and desirable product quality. The percentage of moisture content in different agricultural products is different and varies product to product. For drying different moisture content products, the drying systems are usually classified as low and high temperature operated drying systems. The indirect, direct, and mixed mode dryers that have shown potential in drying agricultural products in the tropical and subtropical countries are discussed. A side from identifying the active and passive mode solar dryers, they also highlight the environmental influence on solar energy (harnessing) that plays a vital role in the solar drying sector. The classifications of sun drying procedures are created based on the stage of processing, the location of drying, or the apprehension to solar radiation. This paper also presents the related technologies that can help improve existing solar dryers.
 
 
 

Performance evaluation of cassava drying technologies: a case study from Uganda

Dried cassava chips have varied applications by end users that include breweries, confectionaries, starch and flour for food. In Uganda, over 80% of Cassava farmers dry their products by open sun drying and direct passive solar dryers. However, these two drying practices produce varying quality of dried products which may not be good all for the various end users. The quality of dried products depends on factors like cassava chip size, drying technology, temperature, air flow and relative humidity. The objective of this study was to assess the performance of cassava sun drying on a raised platform and drying in a direct passive solar dryer. The two drying technologies were assessed basing on drying rate and product quality of cassava using a randomized complete block design experiment. The measurements considered for drying rate and quality assessment were drying time, moisture content, pH, peak viscosity, starch content and microbial contamination in terms of Total plate count (TPC), Total coliforms (TC) and Yeast and moulds (YM). Results showed that samples dried on the raised platform had higher drying rates than those dried in solar dryer. Additionally, Cassava samples dried on the raised platform showed superior quality in terms of microbial contamination compared to samples dried in the solar dryer.