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The present work reports on an experimental study carried out on a solar dryer with an external reflector to remove the moisture content available in the grapes. The thermal behavior of the solar dryer with external reflector and open solar drying technique were compared. Using an external reflector on the solar dryer increased the energy input. Results showed that using a solar dryer with external reflectors reduced the drying time while compared to that of open solar drying. The temperature of the dryer tray using an external reflector is increased to about 20% than open basket solar drying. Similarly, the relative humidity of open solar drying is higher as compared to that of the drying chamber with an external reflector. The time required for removing the moisture using a modified solar dryer is found as 5 days, whereas, using open basket solar drying, the time required to remove moisture is 8 days.

Phosphate sludge generated at the end of the phosphate enrichment operations can be reused after being subject to drying processes. For efficient drying treatment and also for saving storage, the hygroscopic properties of the phosphate sludge have to be determined. In this paper, the adsorption and desorption behaviors were studied. The drying of phosphate sludge in a hybrid solar dryer requires between 90 min at 60 °C and 180 min at 40 °C. The isosteric energy was calculated from the experimental tests and varies from 2 kJ/mol to 25 kJ/mol respectively from the wetted to dried product. From the moisture content evolution, the computed water diffusivity inside tailing varies from 1.70 10-7 m2/s at 30 °C to reach 2.49 10-7 m2/s at 60 °C.

Solar energy is a widely used green energy resource that is used for drying processes. Through this assessment, the performance of an Indirect Solar Dryer (ISD) with three different cases, namely solar collector - without Thermal Energy Storage (TES), with TES unit having Phase Change Material (PCM) and with TES having fins inserted PCM have been experimentally analyzed during spring and summer seasons for drying Momordica charantia. Totally six experiments were undertaken to compare temperature, drying kinetics, and energy analyses. The initial moisture level of 2 kg of specimen decreased from 1.84 kg of water (92% w. b) to 0.24 kg of water (12% w. b) in 10.5 h utilizing ISD with TES having fins inserted PCM (Test 6). The maximum thermal efficiency achieved about 19.41% on Test 6. Exergy efficiency increased from 8.66% to 79.02% at Test 6. Environmental impacts assessment has revealed that the Energy Payback Time for the ISD was 1.42 years. The CO2 emission, mitigation, and carbon credit gained (Test 6) are 23.88 kg/year, 20.13 tons, and $100.642 to $402.569 for the 35 years’ intended lifespan. The assessment report showed that the device established was a potentially effective commercial drying technique, both in energy utilization and environmental sustainability.

Solar drying has received great interest as a viable alternative solution to fossil fuel dryers. However, due to the intermittency of the solar resource, solar dryers suffer from discontinued drying and thus, long drying time. In this paper, the use of sorption materials to enhance the performance of solar dryers is reviewed. The main aspects regarding their use as thermal energy storage or dehumidification materials are highlighted. The paper shows that solid adsorbents, especially silica gel, are the most used materials. The use of composite materials, for instance the mixture of bentonite, CaCl2, vermiculite, and cement proved to be promising. The incorporation of a sorption dehumidifier in a solar dryer, usually at the solar collector inlet, generally leads to a reduction of the drying time of 15–30%, although values up to 50% and even 64% have been reported. On the other hand, introducing sorption materials as thermal storage in a solar dryer, mostly integrated at the top in the drying chamber, usually leads to a reduction of the drying time in a range of 30–45%. There are still various aspects to be investigated in depth before a large-scale utilization of these techniques in solar drying technology.

This work reports the use of tubular solar dryer for drying the Mexican mint (Plectranthus amboinicus) under various mass of leaves. Experiments were carried out in a tubular solar dryer under natural convection mode with direct solar heating. Parameters such as the temperature of dryer tray, relative humidity, and moisture content were recorded for 0.25, 0.5, 0.75 and 1 kg of P. amboinicus leaves placed in the dryer tray. Results showed that under an increased mass of P. amboinicus leaves in the tray the parameters such as dryer tray temperature are reduced, and the moisture content available with 0.75 kg of P. amboinicus leaves is higher as compared to 0.25 kg of P. amboinicus leaves. Also, it is found that the relative humidity inside the drying chamber is higher with increased mass of P. amboinicus leaves in the drying chamber.

Solar energy as a clean energy source is widely investigated to find out the effective mechanisms to meet a large part of energy demand in the near future. In the present research, a square-spiral finned quadruple-flow solar collector assisted dryer has been designed, and numerically compared with finless collector. Main aim of the current work is to develop and analyze a sustainable solar drying system. In this study, different from similar works, heat transfer surface area has been enhanced by using square spiral geometry which is an unconventional fin type. According to the numerical findings, a finned quadruple-flow collector which found more efficient has been manufactured, integrated with a drying chamber and performance experiments have been conducted. In the manufactured solar dryer, a PV panel has been used to run utilized fan. CFD simulation and empirical outcomes of this research exhibited the successful design of finned quadruple-flow collector. Experimentally obtained average efficiency of quadruple-flow collector varied in the range of 73.27-78.19%. Also, mean exergy efficiency of drying chamber was found between 44.16 and 58.38%. Sustainability index and waste exergy ratio values as important factors were attained between the ranges of 1.93-2.73 and 0.52-0.56, respectively. (c) 2021 Elsevier Ltd. All rights reserved.

This research study presents the experimental assessment of two sensible heat materials originating from the State of Yucatan, Mexico, which were incorporated into three compartments within an indirect type solar dryer with a storage system (ITSD-TSS). The experimental tests were carried out under different environmental conditions and were compared with the results obtained from a conventional solar dryer without thermal storage. Temperature and humidity were measured during the different tests and various indicators were used to compare both drying systems. The results revealed that the solar dryer that used limestone as storage material indicated better performance than the dryer that utilized beach sand, since the drying efficiency with limestone was higher by 1.55% and allowed to extract 0.0257 kg more water per unit kWh. Similarly, beach sand stored 1.5 times more energy than limestone, however, this material is very susceptible to variations of solar radiation, so it is not recommended to implement it in areas with high cloudiness. Finally, the implementation of the three storage compartments in the ITSD-TSS allowed an increase between 3 and 4% of the drying efficiency as compared to the conventional solar dryer. The findings of the work can contribute to sustainable development in the agricultural drying process in rural communities.

Solar drying is an important industrial technology with expanding segment in the industrial solar market. The main drawback in commercializing solar dryers is the non-appropriate design of the drying chamber to perform uniform drying and hence producing a nonhomogeneous product. Uniformity of airflow inside the drying chamber has a significant role in the drying process. The current article presents an experimental and computational analysis of a hybrid solar-thermal dryer with a multi-chamber drying cabinet. A prototype was designed and fabricated to including three separate chambers, and each has one angular-movable tray for experimental measurements. The computational model was developed in ANSYS Fluent software for CFD simulation and validated by comparing the experimental results. A statistical analysis of the simulation results has been performed. The focus was made on the effect of tray inclination angle, 0°, 10°, 20°, 30° and 35°, air velocity and turbulence intensity distribution inside the drying cabinet at various operational conditions. Experimental and numerical analysis results indicate that the best uniformity is achieved in the tray with 30° inclination. Statistical analysis results revealed that around 93% of velocity frequency is obtained at 0.7–0.8 m/s air velocity level for 30° tray angle.

Solar Drying or solar dehydration is one of the important processes required for preservation of food and agriculture products. Bacterial growth and moisture is being removed in this process. It helps for preserving the food products for more long time. Solar drying is the oldest & effective method used for drying food products. The device used for preservation of food products using solar energy is called as solar dryer or solar dehydrator. The solar dryer is classified on the basis of mode of drying, circulation of air, type and arrangement of solar air collector. In this project, a solar powered indirect type food dryer is designed and developed. The dryer design is consisting of solar collector unit along with absorber made up of extended surface of aluminum sheet with staging, drying chamber with three columns of each rack shelves, chimney for exhaust air, a solar powered fan. The dryer collector and drying chamber are connected with a hose pipe clamped to both ends. The project model of solar dryer is consisting of a monitoring unit for data logging of continuous updatation of parameters like temperature inside the dryer and temperature at ambient condition, humidity at inside and outside of dryer also the atmospheric pressure, etc. At the end we are going to investigate the effectiveness of solar dryer with above parameters.

Global energy demand continues to increase with the expansion of the economy activities and sustainable development. Meanwhile, the world is suffering from pollution and harmful greenhouse gases originated from burning of fossil fuels where the consequences of climate changes are also alarming. Solar energy is an alternative energy source that is abundant, safer and cleaner. This article provides a comprehensive review of works pertaining to solar thermal energy utilization in the drying process. In this article, the classification of solar dryers, the main components which includes solar collector, drying chamber and auxiliary systems, prospects, challenges, recent advancement and performance are discussed. The existing literature reported that solar dryer and solar collector maximum efficiency of 54% and 81% respectively, with superior products quality than the open solar drying. Solar drying is economical method with the payback period of 0.54–4.69 years. Solar dryer can also reduce 34% of CO2 emission to the atmosphere with less consumption of fossil fuel. Improvements such as in the design of solar collector, drying chamber, new auxiliary system, and material are essential to elevate the solar drying system performance. A review of the technologies can provide a base for the next generation of sustainable solar drying systems and helps policymakers to frame strategies aiming for clean technology and sustainable development.

Cover material of solar dryers influences on fruit properties due to the temperature and ultraviolet radiation (UV) during drying. Polyethylene (P) is the most used material for covering solar dryers. Cellular polycarbonate (CP) is a material that promotes UV protection; hence, it has recently been proposed as a covering material for greenhouse dryers. However, it is unknown whether CP cover will have any effect on bioactive compounds of foods treated by solar drying. Especially, if CP has advantages in preserving sensitive compounds compared to traditional materials as P. In this work the effect of CP and P covers on anthocyanins (TA) and total phenolic compounds (TPC) of strawberries during solar drying was evaluated. Open sun drying was used as a reference. Drying temperature, solar radiation, external and internal UV radiation was measured. The results indicated that the drying temperature and UV radiation influenced the moisture content and bioactive compounds. Direct radiation increased the drying temperature and reduced the final moisture content, while the partial incidence of UV radiation in the dried samples with P covers favored the remaining 40.7% of TA and 42.5% of TPC. With CP covers, where the ultraviolet radiation was zero, the 15.5% of TA and 14.4% of TPC were retained. Activation energy indicated that bioactives were more stable in the solar dryer with P and transparent cellular polycarbonate covers, demonstrated that they can be used as coatings in solar dryers destined for drying fruits, producing high-quality dehydrated products and efficient solar drying processes.

Low thermal efficiency is one of the main problems in using solar collectors in different fields. In the present study, the effect of using phase change materials (PCM) inside the Flat plate collector (FPC) on the thermal performance and overall drying efficiency of FPC was investigated. Four PCM positions were considered inside of the collector, and the results compared with the collector without PCM. Experimental results implied that specific energy consumption for drying tomato slices is between 11.12 and 9.01 MJ/kg. The drying time of the slices using the collector with PCM at the end section was decreased about 21.87%. Based on the position of PCM, the thermal efficiency of FPC increased by about 5.02%-10.13%. The overall efficiency varied from 21.92% to 25.72% for different PCM positions. CFD simulation of the system was performed by Ansys 2015, and it showed that the thermal performance of the collector could be predicted with good accuracy (R2 > 0.9432). Moreover, the result of evolutionary polynomial regression models applied for each PCM position. It confirmed that outlet temperature and thermal efficiency of collector predicted with acceptable accuracy (R2 > 0.98). Due to the use of PCM at the end section of the collector, a homogeneous drying process, normal temperature, and short drying time resulted. The quality of tomato slices dried by the solar dryer was higher than other positions.

In this study, the manufacturing and testing of an infrared dryer equipped with a PV/T solar collector were investigated. The total energy for the drying process is provided by solar energy. This study sought to compare the experimental results of glazed and unglazed modes and observe the effect of volume flow rate variations on the drying process of the products to determine the dryer’s energy and exergy efficiency and analyze the drying kinetic of potato slices. The amount of inlet airflow to the PV/T was controlled during the experiment. The power of the fan is supplied directly from two photovoltaic panels and the surplus amount of electrical energy is assigned to an infrared radiation source to enhance the process. Despite the low energy consumption of the current system, the products’ drying time was significantly reduced compared to similar systems. As a result, in glazed experiments, the drying time is prolonged in a range of 12–25% for 3 mm thicknesses and between 5 and 25% for 7 mm thicknesses compared to unglazed experiments. The maximum system energy efficiency and system exergy efficiency were 9% and 0.5%, respectively, calculated for 7 mm slices in unglazed tests.

Improper handling of fruits and vegetables causes a significant postharvest loss. Among the postharvest preservation mechanisms, solar dryers are reported as sustainable and suitable preservation systems for fruit and vegetable products. This paper summarizes the recent advances, opportunities, and challenges in solar drying of fruit and vegetable products. Besides, the review discusses the commonly used mathematical models for the evaluation, design, and optimization of solar dryers. The review discusses the factors that affect the performance of solar drying systems concerning drying time, drying rate, and product quality attributes. Short drying time, uniform drying air velocity, temperature, and product moisture distribution in the drying chamber are the critical parameters that are required for an efficient operation of a solar dryer. There is a good prospect in the application of mathematical modeling techniques such as computational fluid dynamics (CFD) in identifying the optimum solar drying conditions and dryer design that can maintain the required quality of the product. CFD has been used extensively in studying the airflow, heat, and mass transfer processes for optimizing the design and operation of different drying systems, similarly different quality models have been applied to evaluate the quality of dried products. However, most CFD studies did not include the quality aspect for dryer performance evaluation or optimization studies. To get the best result, CFD based performance evaluation or optimization studies of the solar dryers should have the capacity to predict the product quality in addition to the airflow, heat, and moisture transfer characteristics.

The design and development of an evacuated tube collector-based solar dryer with heat pipe for drying of garlic clove were carried out in the present work. For the experimental performance evaluation, garlic cloves (10 kg) were dried from 69% to 8% moisture content (wb). The thermal performance of the evacuated tube solar dryer (ETSD) was tested on no-load and full load conditions at different air flow velocities (1, 2, and 3 m/s). The highest temperature of 86.7 °C, at no load condition, was obtained in the drying chamber at 2 m/s air flow velocity with the maximum solar radiation of 1204 W/m2 while the maximum peak sun hour was 6.27. The maximum drying rate, solar collector efficiency, and dryer efficiency were found to be 1.56 kg H2O/kg dry solid/h, 45.86%, and 56% respectively at 2 m/s air flow velocity. The highest average exergy efficiency of 56.59% was found at 2 m/s, and the average lowest exergy loss of 4.74 W was found at 1 m/s. ETSD performed efficiently at 2 m/s air velocity and was capable to dry the garlic clove within 8 h. The payback period of the developed ESTD was found to be 1.3 years.

Solar air heaters (SAHs) are commonly utilized in different applications due to their simple structure and low setup cost. Optimizing operating parameters of the SAH is highly linked to the desired application. The aim of this study is to determine the optimal geometric and operational parameters of finned SAH for food drying. In order to achieve this goal, response surface methodology was combined with an experimentally validated thermal model of the SAH system. Multi-objective optimization is carried out according to energy-exergy analysis, improvement potential (IP) and outlet temperature suitable for food drying (40–70 °C). Length/width ratio (L/W) (1–5), height of air duct (0.02–0.2), and number of fins (0-60) were the operating variables. The experimental tests were carried out on the indirect type solar dryer composed of SAH and the drying chamber. The developed code led to consistent numerical results that have been confirmed by experimental tests. The optimal parameters were defined as 1.28 L/W, 0.067 m air duct height and 49 fins. In these optimal conditions, the outlet temperature, thermal efficiency, and IP were 52 °C, 51.78% and 1397.34W, respectively. The optimal design improved the thermal efficiency by 15.76% and IP by 19.33%.

Determination of the drying curves characteristics of date fruits at tamar (fully ripe) stage of Khalas and Ruzeiz varieties by using two constructed solar dryers namely; direct solar dryer (DSD) and indirect solar dryer (ISD), Modelling of drying curves data of date fruits for both varieties and solar dryers, and the effect of solar drying process on four physico-chemical properties of the date fruits for both varieties and solar dryers were investigated. The four physico-chemical properties included linear dimensions of length and width, mass, colour L, a, and b values and pH. The two solar dryers were constructed from local materials and were used in the date fruits drying. Study experiments were carried out at The Research and Training Station of King Faisal University, Al-Ahsa, KSA. Results for both varieties and solar dryers showed that Khalas date fruits dried more than Ruzeiz ones and date fruits drying took place predominantly in the falling rate period i.e. diffusion was the main physical mechanism governing moisture movement in date fruits. Page model was more accurate in predicting the measured drying curve data. Generally, under the present study solar drying conditions, some physico-chemical properties of mass and pH of date fruits were affected, while properties of linear dimensions (length and width) and colour L, a, and b values were not. This concluded that under similar drying conditions of the study some unit operations of date fruits processing such packaging, sorting and grading they will not be affected.

This study focusses on the experimental analyses of two active horizontal solar dryers viz., mixed mode (Case-I) and indirect solar dryer (Case-II) integrated with latent heat storage system designed for drying Piper nigrum (black pepper). The drying time required to reach the desired moisture content of 0.14(d.b) from 3.46 (d b) in both cases were 14 h and 23 h, respectively. While, it took 59 h in open sun drying (case-III). The developed dryers operated in case-I and case-II saved 76% and 60% of drying time respectively compared to case-III. Form economic point of view, the developed solar dryers are more beneficial. It is seen that the overall dryer efficiency of the case-I is 20% higher than case-II. Quality analyses in terms of proximity analysis and anti-oxidants of the fresh and dried samples in all the three cases were carried out. The carbohydrates and protein values were rich in case-I compared to other two cases. The anti-oxidant contents of samples dried in case-I and case-III were 45.69 μ mol TE/g sample and 23.25 μ mol TE/g sample, respectively. The ash substance of the samples dried under case-III was high compared to the other two cases.

Present work is focused on the assessment of energy and exergy flow in a mixed-mode solar dryer during the drying of pineapple slices by utilizing first and second law of thermodynamics. Moreover, drying kinetics and effective moisture diffusivity with shrinkage correction were also investigated at natural convection (NC) and forced convection (FC) conditions. The initial moisture of pineapple slices (90%, wb) was reduced to 29.66, 23.06, 24.05 and 19.68% (wb) in 6.5 h under NC, air mass flow rates of 0.006, 0.01 and 0.015 kg/s, respectively. Results revealed that diffusivity determined by assuming negligible shrinkage demonstrated 3.5–5.3 times overestimation than shrinkage consideration. Energy analysis exhibited that about 55–78% of total input solar energy constituted thermal losses from the absorber plate. Remarkably, an increase of air mass flow rate caused an augmentation in useful heat gain by air and a simultaneous reduction in thermal losses from collector along with its efficiency improvement. Exergetic investigation of dryer identified that the exergy efficiency of the solar collector and drying chamber was positively influenced by increasing air velocity. Furthermore, exergy efficiency of the dryer for NC and drying air mass flow rate of 0.006, 0.01 kg/s was 85.45%, 46.15%, and 18.88% lesser than 0.015 kg/s, respectively.

In this paper, a concentrated photovoltaic-thermal solar dryer (CPV/TSD) using nano-enhanced PCM (Al2O3Paraffin wax) is experimentally studied. A comprehensive thermodynamic analysis of the system according to the first and second laws is discussed. Besides, the drying parameters (moisture content and moisture ratio) are predicted using the two machine learning algorithms (ANN and SVM) and compared the prediction success with four evaluation metrics (R2, rRMSE, MBE, and rMAE). The overall thermal energy efficiency and exergy efficiency of the CPV/TSD system are found to be 20% and 8%, respectively. Although solar radiation to the environment has decreased a lot, it has been found that the thermal energy transferred to the nano-enhanced PCM prevents the decrease in greenhouse temperature for the first 100 min. In the system, mushrooms are dried from the initial moisture content of 17.45 g water/g dry matter to the final moisture content of 0.0515 g water/g dry matter. Then the drying rate value for CPV/TSD system is calculated to be 0.436 g matter/g dry matter.min. On the other hand, even if both ANN and SVM algorithms have exhibited very satisfying results, ANN is coming to the fore in the prediction of the drying parameters considering all evaluation metrics together. WOS:000637191800006 2-s2.0-85102023951

In this work, an indirect solar dryer for drying cassava root chips was modelled and experimentally validated using the environmental conditions of Yaoundé in Cameroon and Yamoussoukro in Ivory Coast. The dryers were operational in natural convection mode. Resolution of the equations was achieved by finite differences and the 4th order of Runge–Kutta methods. A model was proposed for performing heat and mass transfer using thermophysical properties of cassava roots, and the obtained results were satisfactory for all conditions, with moisture content difference of less than 0.2 kg/kg between the experimental and theoretical results. The model showed that the core of the product takes more time to dry, which always prolongs the drying duration. The heat and mass transfer coefficients vary during the entire process of solar drying. The drying kinetics vary during the drying with values lower than 1.2 × 10−4 kg/(kg.s). The great gradients of humidity were observed in the thickness of the sample with a regular distribution of the temperature each drying time in the thickness of the sample.

This work describes the thermal behavior and evaluation of kinetics drying of natural rubber sheets using two solar drying technologies: direct and indirect. The solar drying tests were carried out simultaneously in order to compare the behavior under same weather conditions. The moisture content of the rubber sheets was reduced from 45.8 to 0.59% and from 49.7 to 0.33% on a dry basis (d.b.) for direct solar drying and indirect solar drying, respectively. The direct drying mode was carried out for 12 days with average temperature and relative humidity inside the greenhouse, during sunny hours, of 37.04 °C and 14.1%, respectively. Meanwhile, the indirect drying operation was carried out in 9 days (61.62 h intermittently) with 61 °C and 4.77%, respectively. The average global energy efficiency of the field of SAH was 33.77%. Thirteen thin layer models were used to evaluate the drying behavior of which the Modified Henderson and Pabis model was the best to describe the solar drying of rubber sheets for the direct and indirect system. As a conclusion, the direct greenhouse-type solar dryer is recommended for small producers and the indirect tunnel-type solar dryer for companies with high and continuous production.

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%.

A prototype hybrid Photovoltaic Thermal (PV – T) solar dryer aided with Evacuated Tube Collector (ETC) is presented for drying of cassava slices under the meteorological conditions of Thanjavur, Tamilnadu, India. Further the morphological, structural and physical properties of thin layer drying kinetics are studied and compared with natural sun drying. The designed dryer reduces the moisture content of cassava from 91.5% (wb) to 10.67% (wb) which is considered to be a safe level for storage in 8 h. There is a wide scope to save the conventional fuel by adopting the designed solar dryer as the air temperature inside the chamber rise is 30–40 °C than the ambient temperature. Non – linear regression analysis is performed to find out the drying kinetics of cassava using IBM SPSS 23 statistical package. Two - term model is proved to be the most suitable model for predicting thin-layer drying behaviour of cassava slices with R2 = 0.982, χ2 = 0.017553 for hybrid dryer and R2 = 0.998, χ2 = 0.001247 for open sun drying. XRD results exhibit ‘A’ type crystalline pattern that indicates semi–crystalline nature of cassava for both hybrid and sun dried cassava. Structural, morphological and proximate composition analysis reveals that the quality of hybrid dried cassava is better in terms of physical and chemical compositions than sun dried cassava. The proposed hybrid dryer is capable of producing high standard dried products for exporting and can make a good profit.

Three designs of a direct solar dryer for wood were evaluated with computer simulations. Calculations were performed using a heat and mass transfer model to obtain and compare the wood moisture content (MC) variation, as well as other drying parameters within the three designs. The findings showed higher drying temperatures and shorter drying times for solar dryers with large transparent cover areas (i.e., greenhouse-type dryers). Comparisons between glass covered and Plexiglas (PMMA) covered systems were also performed and the results indicated reasonably similar drying curves. The effect of using plastic cover was more prominent for dryers with low transparent areas (i.e., semi-greenhouse-type dryers), that is, 5% increase in the drying time for the greenhouse-type design and 10% increase for the semi-greenhouse-type designs. The economic analysis of the three designs revealed that double-glazing reduced the drying time, though it increased the cost of the covers by more than 130%. Inserting a Plexiglas cover over the glass cover resulted in a 25% decrease in the drying time and only a 57% increase in cost. Additionally, the combined plastic-glass configuration for the semi-greenhouse-type design resulted in a drying time comparable to this of the single glazing greenhouse-type design, though at a lower cost.

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.

Many studies have been conducted in the field of drying technology. The traditional dryingmethods are considered less effective and time consuming. The present study aims to develop the indirect solar dryer for agro-food products from El-Oued region (South-East of Algeria). The dryer is assisted by a parabolic dish concentrator to improve its performances through increasing its temperature and decreasing drying time. the realized solar dryer was tested on the red chilies during April 2018, the temperature in the drying chamber is reached intoxicating 55 °C with a drying time of 5 h.

In regards to the highly perishable character of most food products and plants, their conservation during large transportation distances and storage is a sensitive issue. The drying process is a method used to increase the shelf life of the products. It is a fundamental operation in the industry that requires energy and time. This process permits to avoid the deterioration of product quality through the microorganisms and the enzymatic reactions. The aim of this work is to study the carob pulp (Ceratonia Siliqua L.) solar drying using a convective solar dryer. Besides, to understand the drying kinetics and to obtain the characteristic drying curve under different temperatures (50, 60, 70, 80 °C) and different drying air velocities. As results, the increase of drying temperature leads to a drying time decrease. In addition, the variation of the diffusivity coefficient is found to be ranged between 1.56 10−9 and 6.98 10−9, moreover, it is influenced by the increase of the drying temperature. As well an energy-exergy analysis is conducted to evaluate the performance of the studied solar dryer. The energy and exergy efficiencies of the convective dryer are varied in a range of 4.23–7.25% and 30.12–80.5%, respectively.

The solar energy is very plenty which is used to remove the moisture level in the food material and to preserve the food material. The aim of this experiment is to evaluate the performance of greenhouse solar dryer using North Wall insulation. When the food products are placed inside the dryer, due to the high temperature inside the dryer when compared to the atmospheric temperature will lose the moisture content in them quickly and gets dried within a short span of time. The dryer is covered with PVC sheet and the construction of the dryer is made up of Wood. The dimensions of the dryer are 1 m length and 0.75 m height are constructed. Inside the dryer stainless steel tray is placed in which the food materials are kept for drying. Below the tray a black sheet is kept at certain distance for absorbing the maximum heat from sun which helps to increase the temperature inside the dryer. Through drying in solar dryers the food material temperature can be observed till 61 °C as a result the moisture inside the food material can be dried more quickly, also there will be a steady decrease in the moisture inside the solar dryer from 60% to 32%. By these observations and results the food material placed in the parabolic dryer with insulation has given the best drying performance which took 5 days to complete the drying process followed by the triangular dryer with insulation took 5 and half days to complete the drying process. The parabolic dryer without insulation took 6 days and triangular dryer without insulation took 6 and half days to complete the drying process and the open drying process has taken 8 days to complete the entire drying process.

The drying process is generally carried out by burning wood and fossil fuels. However, this method is expensive and may damage the environment which has an adverse impact on climate. The world is facing the problem of shortage of fossil fuels. Some researchers did historical work on design and development of solar technology which is faster, more efficient, and hygienic and better quality of the product. Several solar dryers reviewed and enlisted the performance of dryers as per application. This paper gives an idea about the recent development in solar dryers. Some solar dryers are equipped with thermal storage to enhance the efficiency and drying rate in off-sunshine hours. To overcome the sunshine irregularity, some solar dryers have come up with solar thermal reservoirs. A comprehensive review on different dryers according to the product has been carried out, which helps in development and redesign of the solar dryer. From this paper, an idea regarding products drying likes chili, turmeric, peanut, grapes, copra and fish are presented. Which type of dryer is suitable and what kind of improvement could be possible in the future is obtained. For performance evaluation of the solar dryer, researchers used parameters like moisture reduction, moisture removal rate and different efficiencies. Solar dryer did not receive commercial utility because of high initial investment, long payback period and intermittent application. The study shows that the solar dryer not only saves fossil fuel for drying but also adds great worth to improve the product quality in terms of taste and color. It also doesn’t have any harmful effect on the environment. Solar dryer is therefore ideal to use for preservation of food in rural areas. This study may help farmers and new researchers for the design new type of solar dryer for products.

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.

A mixed cabin solar dryer was designed and tested in Brazil in the spring equinox, for the drying of corn grains. The key advantage of the current design is its ability to work even in locations with no electricity because a photovoltaic module is used to power an electrical heater and fans. The analysis of the drying process was performed based on the first and second laws of thermodynamics. For average solar radiation and ambient temperature of 710 W/m2 and 30 °C, respectively, the average thermal efficiency obtained was 21% and the exergy efficiency ranged between 10% and 66%, with an average value of 23%. It was observed that the corn grains reached the desired moisture content of 13% in 8.5 h, while a similar sample subjected to natural sun drying failed to reach this moisture content in 24 h. The PV module was also used to preheat the drying air, allowing an average increase in the airflow temperature of 14 °C, reaching a maximum of 27 °C.

The solar drying of agricultural products is considered the most excellent green and sustainable agricultural product conservation method. The advancement of effective drying system design and agricultural products drying characteristics will increase product conservation. The current research work focuses on the investigation analysis of evacuated tube assisted solar dryer in eliminating the moisture ratio present in the crops. The temperature can be controlled and maintained by regulating the flow rate of flowing hot water inside the drying chamber with heat exchanger. The thermal performance of evacuated tube solar collector assisted solar dryer and open sun drying method were compared. Due to advancements in solar dryers, its drying cabin temperature increased. Consequences indicated that using a hybrid greenhouse solar dryer decreased the drying period while equating to open sun drying. All the experiments are performed under the environmental condition of Gwalior-India (26.2183° N, 78.1828° E) during the days of February 25, 2021 and February 26, 2021. The temperature difference between drying methods during the experiment was recorded 14.35℃ and 13.95℃ on the first day and second day of experiments, respectively. Also the relative humidity of open sun drying method is more in comparison to hybrid greenhouse solar drying. Time need to reduce moisture by using advanced solar dry systems recorded 7 h, while in open sun drying 10 h. The results show that drying time is 30% more in open sun drying.

Thermal Numerical modeling and aerodynamic processes taking place in a V-corrugated solar air heater and wavy shaped fins is performed. The analysis of this study is done through ANSYS software. The technological variables (the Reynolds number) on heat-exchange processes influence of design (the step between the fins) and flow aerodynamics was also established. Pictorial contours are determined for the velocity distribution, pressure, and other characteristics of the airflow in the solar air-heater box. Thermodynamic characteristics and effective values of technological parameters for the effective use of a solar air heater also studied. V-corrugated and wavy fin used Heat transfer correlations were created with the help of experimental outcomes with respect to the parameter considered for this investigation.

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.

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.

A solar dryer assisted by biomass back-up heater was designed and manufactured from locally available materials to dry maize, and the drying model is selected, which better fits the dryer test results. This study tried to address the problem associated with the fact that solar dryers are efficiently operational only when there is sufficient solar energy. The dyer comprises a solar air heater, drying chamber, biomass back-up heater, and airflow systems. The solar heater has a length and width of 2 m × 1 m respectively and is enclosed with a transparent glass that allows the solar energy into the collector. The measurement taken to evaluate this dryer's performance is temperature, moisture content, solar irradiation, and airspeed. The average temperature difference between the ambient and the collector outlet was recorded as 9.6 °C, and 12.8 °C in the solar and biomass assisted dryer. The daily average solar insolation for the test periods of October and December at the site was 673 W/m2. When the system is loaded with 50 kg of wet maize grain at an initial moisture content of 21.3% and dried to 14.4% moisture content in 45 h drying time in the solar dryer, 4.03 kg of moisture is removed. A 50 kg of wet maize grain at an initial moisture content of 22.9% and dried to 14.2% moisture content in 27 h in solar dryer assisted by biomass back-up heater, 5.06 kg of moisture is removed. Solar dryer collector efficiency was estimated as 64.2% with an average drying rate of 0.0746 kg/hr. The solar dryer system efficiency was 20.8%, and solar assisted dryer efficiency was 4.3%.

The abundant and unpredictable use of fossil fuel accelerate the continuous search in that field of an alternative source. Most of the researchers are attracted to the solar power, that is one of therenewable and sustainable energy sources. Based on the current scenario, in futurethe energy requirement will be tremendously high. The effectiveuse of solar energy can be reduced the problem of huge energy demand in all agricultural, industrial, domestic and power production sectors. In agricultural sector, one of the areas is drying technology. The drying technique is one of the applications of the solar energy. Drying is the process of removing moisture from the agricultural produce. From our ancestor to modern humanbeing, various improvement occurs in the solar drying system. The indirect solar drying with integrated flat plate collector is most popular, simple in design, cost effective, maintenance free and easy to operatevegetable drying system. The flow of air movement, thermal leak proof cabinet structure, flat plate collector’s (FPC) absorber plate design, optimum thickness of selective coating materials, etc. directly affect the efficiency and moisture removing rate of the solar drying system. Here, the 15 kg green chili has been taken for drying in solar drying system. The dryer is integrated with phase change materials (PCM) in drying trays, flat plate collector’s absorbing plate coated with activated charcoal and black board paint, the variable air mass flow rate of the blower. It has been found that, at 0.008 kg/s air mass flow rate the outlet temperature of the FPC is 96 °C and efficiency is 33%. The drying time was 16 h as compared with open sundrying time 28 h for the 15 kg chili. It was compared with indirect solar dryer without thermal energy storage and found that the time required for drying chili with thermal energy storage is 4 h less than the without thermal enrgy storage solar dryer.

The present work focuses on drying of Garcinia pedunculata in an efficiently developed free convection corrugated solar dryer (FCCSD) and conventional open sun. The experimental solar drying results for two batches are presented. The moisture contents of Garcinia pedunculata in the dryer was reduced to 7.22% (wb) for the first batch and 7.1% (wb) for the second batch in 28 h from the initial of 88% (wb) of moisture content. Moisture content was reduced to 10.18% (wb) and 10.08% (wb) for the first and second batches respectively in 55 h in open sun drying. Midilli and Kucuk model was found the most suitable for drying process in the developed solar dryer. Two-Term model was suitable for open sun drying. The average thermal efficiencies of the solar dryer for the first and second batches were evaluated as 33.29% and 33.45% respectively. The average specific energy requirement and average thermal efficiency of the FCCSD were estimated as 68.00 kWhkg−1 and 10.69% for the first batch 65.54 kWhkg−1 and 10.77% respectively for the second batch. For the newly developed FCCSD, the payback period was estimated as 0.6 year.

In the present study, a low-cost solar fruit and vegetable dryer was designed, constructed, and tested for small-scale production, especially in households. An optimizing procedure was performed to convert a typical widely-used direct cabinet dryer into a new indirect dryer using experimental data and numerical simulations. Several well-designed experiments accompanied by CFD simulations using finite volume method were carried out. It was concluded that the proposed conversion procedure could be achieved utilizing a blackened absorber plate, an air circulating unit, and a honeycomb air manifold. The drying capacity of the dryer could be increased by more than 50% in comparison with the direct type by adding a new tray to the optimized dryer. The thermal efficiency of the proposed solar dryer was estimated 16.4%, indicating that the desirable energy performance of the dryer was superior to some available designs of solar dryers. Besides, it was observed that the proposed numerical approach was able to produce a reliable qualitative and quantitative insight into both the thermal and fluid mechanical behavior of the dryer. Finally, it was claimed that not only was the developed apparatus suitable and efficient for the household usage, but also the optimized version of the dryer could be inspiring for those who are currently using typical direct cabinet dryers to convert their dryers into indirect ones.

It is an essential and most abundant energy resource on earth. Solar energy can be caught and utilized in a few different ways and as a sustainable energy source is a significant part of our virtuous energy future. Its technology can be passive solar or active solar depending on how it can store excess energy and converting into solar power the storage of solar energy require a storage medium or accumulator. It can help to store excess solar energy for future use. One of the best methods to store heat energy from the sun is by making use of phase change material (PCMs) due to a huge ton of captured latent heat and isothermal kind of PCM during heat expansion and dismissal during phase change. PCM becomes an ideal candidate for a thermal energy storage medium in building applications. Now a day PCM gained special attention in building applications like water and air heating application, building-integrated system (ceilings, walls, and floor), H.V.A.C/solar absorption system for building, and other useful applications PCM concrete, PCM shutters, solar cooker, and solar dryer. In this paper, an attempt has been made to provide an overview of the progress and application of PCM in solar thermal energy.

The agricultural and food products may be enhanced by reducing their moisture contents, by means of a drying process. The aim of the work is to evaluate a mathematical modelling based on the experimental analysis of forced circulation of mixed mode solar dryer. From previous literature four different models (Newton, Page, Henderson & Pabis and Wang & Singh) are chosen for testing the performance of 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 mixed mode solar dryer at air flow rate 0.009 Kg/s based on the experimental analysis.

Building cooling is achieved by the extensive use of air conditioners. These mechanically driven devices provide thermal comfort by deteriorating the environment with increased energy consumption. To alleviate environmental degradation, the need for energy-efficient and eco-friendly systems for building cooling becomes essential. Evaporative cooling, a typical passive cooling technique, could meet the energy demand and global climatic issues. In conventional direct evaporative cooling, the sensible cooling of air is achieved by continuous water circulation over the cooling pad. Despite its simple operation, the problem of the pad material and water stagnation in the sump limits its usage. Moreover, the continuous pump operation increases the electrical energy consumption. In the present work, a porous material is used as the water storage medium eliminating the pump and sump. An experimental investigation is performed on the developed setup, and experiments are conducted for three different RH conditions (low, medium, and high) to assess the porous material’s ability as a cooling medium. Cooling capacity, effectiveness, and water evaporation rate are determined to evaluate the direct evaporative cooling system’s performance. The material that replaces the pump and sump is vermicompost due to its excellent water retention characteristics. There is no necessity to change material each time. However, the vermicompost is regenerated at the end of the experiment using a solar dryer. The passing of hot air over the vermicompost also avoids mould spores’ transmission, if any, present through the air. The results show that vermicompost produces an average temperature drop of 9.5°C during low RH conditions. Besides, vermicompost helps with the energy savings of 21.7% by eliminating the pump. Hence, vermicompost could be an alternate energy-efficient material to replace the pad-pump-sump of the conventional evaporative cooling system. Further, if this direct evaporative cooling system is integrated with solar-assisted drying of vermicompost, it is possible to provide a clean and sustainable indoor environment. This system could pave the way for year-round thermal management of building cooling applications with environmental safety.

Tomato (Solanum lycopersicum) and brinjal (Solanum melongena) are food products that are frequently wasted in Indian markets as their shelf lives are only a few days. An indirect type solar dryer (ITSD) has been developed. It’s performance and drying kinetics of brinjal and tomato slices have been analyzed. The moisture content of tomato decreased from 15.667 to 0.803 kg/kg of dry basis (db) and that of brinjal reduced from 10.111 to 0.498 kg/kg of db. The drying curve was fitted with the different models of existing studies. The average effective moisture diffusivity is estimated and it is 3.60 × 10−9 and 4.00× 10−9 m2/s for tomato and brinjal, respectively. Mass transfer coefficient was in the range of 0.82 × 10−4 to 2.85 × 10−3 m/s for tomato and 1.11 × 10−4 to 3.32 × 10−3 m/s for brinjal. The heat transfer coefficient was in the range of 0.089 to 2.888 W/m2 K and 0.1066 to 3.3564 W/m2 K for tomato and brinjal, respectively. The activation energy for tomato and brinjal was 21.19 and 19.46 kJ/mol, respectively. The average thermal efficiency of the collector and dryer was 59.05% and 31.4% during tomato drying and 58.42% and 25.16% for brinjal drying, respectively.

The most noteworthy advantage of solar power as compared to other forms of energy is that it is clean and might be supplied with no contamination to the environment. Over the past centuries, it is believed that energy from fossil fuels is less expensive and more helpful than energy from other sources. This research thus results to the successful fabrication of a solar dryer with tests distributed for various performance comparisons like No-load and load performance of the dryer. Direct sun-drying comparisons depicted discernable contrasts within the final moisture content specified. The utmost temperature recorded within the drying chamber and solar dish for No-load are 44.5 and 52 respectively. Whereas when the cupboard is loaded, the highest temperature of 34.5 and least temperature of 23 are recorded. An average temperature of 27 was obtained, thereby giving the solar dryer an exegetic efficiency between 70% and 80%. Performances of the tests were done from 9am to 5pm. The solar store that was designed to heat to the drying chamber within the night was found to possess its most elevated temperature at 43 . These performance results were achievable due to daily precipitation, and in some cases, cloudy days when the sun was not shining at its peak. The load outcome was done with red-sweet pepper and yam food items.

Drying characteristics of stevia leaves were investigated in an infrared (IR)‐assisted continuous‐flow hybrid solar dryer. Drying experiments were conducted at the inlet air temperatures of 30, 40, and 50°C, air inlet velocities of 7, 8, and 9 m/s, and IR lamp input powers of 0, 150, and 300 W. The results indicated that inlet air temperature and IR lamp input power had significant effect on drying time (p, A comparative study was performed among mathematical, artificial neural networks (ANNs), and Adaptive Neuro‐Fuzzy System (ANFIS) models for predicting the experimental moisture ratio (MR) of stevia leaves during the drying in an infrared (IR)‐assisted continuous‐flow hybrid solar dryer. The drying time was decreased significantly by increasing the inlet air temperature and increasing IR lamp input power (p

The world is acting towards the reduction of use of fossil fuels. Therefore, a big number of innovations are utilized that adopt sources of renewable energy such as wind, solar, tidal etc. Solar radiation is used for different applications, one of them is drying different products from thousands of years. Thus, solar energy was the only used energy until the discovery of fossil fuel sources, especially utilized for solar dryers. These dryers are not very commercialized, and their designs are based on empirical and semi-empirical systems. Therefore, theoretical studies will be of high importance in this field. The majority designs of solar dryer available in the market, are used mainly for drying of various crops either for family use or for small-scale industrial production. In this article a simulation of the Lebanese ambient temperature and the relative humidity will be conducted then compared to the meteorological experimental data. After that, a modeling of a direct solar dryer system is developed based on the heat transfers phenomena inside and outside the dryer. This model is simulated using five different products that helps us to determine the instant temperatures of the product, of the internal air of the dryer and of its cover, in addition to the instant water content of the product dried. Finally, a linear relation between the thermal capacity of the product dried with a range going from 1100 to 2300 J/kg.K and a defined drying characteristic time will be concluded from this work.

Cyclic drying has been reported as an innovative drying technique for the drying of food materials in terms of drying time, energy cost and product quality. In this study, drying characteristics and product quality of continuous and cyclic drying of Mytilus galloprovincialis in a convective solar dryer were investigated. A two-stage increasing–decreasing drying air temperature (sinusoidal pattern) of the solar dryer was used to obtain the desired cyclical variation of the drying temperature while keeping other drying air parameters constants. The advantages of employing cyclic heating on the drying kinetics, energy consumption are demonstrated. Analytical results illustrated an effective drying time of mussels by a reduction of 1.5% and optimum energy consumption does not exceed 23 kWh of drying process by applying cyclic drying technique compared to continuous drying of air temperature. Furthermore, According to the proximate composition of AOAC method and following Total viable count (TPC) of the dried mussels, it was observed that cyclic air temperature allows to yield higher retention of protein, glycogen, reduce significantly the effect of stresses compared to the constant conditions of drying, and it is possible the reduce the overall color change as well as an accepted texture. Several empirical and semi-empirical models were used to fitting drying curves of experimental data. It was found that the Page model seems to be most suitable to describe the drying curves of Mytilus galloprovincialis. The second law of Fick’s was used to determine the effective moisture diffusivity at different conditions of drying. As results, the values of effective diffusivity obtained by applying cyclic drying were in the margin with the drying at constant conditions that was reached 2.84 × 10−9 m2/s.

An innovative design of front loaded multi-rack tray (MRT) solar cabinet dryer is presented having optimally inclined reflective north wall (RNW) which utilizes reflected component of the solar radiation in addition to the beam radiation for efficient drying particularly in winter when conventional dryer does not perform well at higher latitudes (>30°N). A modified global solar radiation capture model coupled with RNW is presented to determine the effect of RNW on its performance. A thermal model is also developed for chamber air temperature (Tch) and crop surface temperature (Tc) with experimental validation and solved using Modified Euler’s method using FREEMAT software with experimental validation at Ludhiana climate (30.56°N) India. Use of RNW enhances the radiation capture by 37.58%, 31.57% and 23.24% at 30°, 40° and 50°N latitude respectively in winter. Daily average efficiency η(avg) with RNW was 5% and 4.35% higher under natural and forced convection modes respectively as compared to without using RNW. By using RNW, 4–7 °C and 2–5 °C higher Tch was observed as compared to when RNW was not used under natural and forced convection modes respectively. Total reduction in drying time for carrot drying was observed to be 20% and 15% under natural and forced convection modes respectively. Predicted and experimental values for Tch were successfully validated with root mean square error (RMSE) ranging between 2.6 and 4.9. Uncertainty was found to be 20.5 out of which 19.3 was internal and 1.2 external which indicates the accuracy of observed data to determine the performance of solar dryer.

The simplicity of solar flat plate air collector and free availability of solar energy sources attract attention to the optimization of the collector. This study aims to assess the effect of double pass air flow on the performance of flat plate air collectors. The analysis of the performance characteristics of the indirect solar dryer was carried out by CFD simulation with three different smooth, rough and V-grooved surfaces, keeping the lower and lateral collector well insulated and the drying chamber acting as a vertical chimney. The average thermal efficiency of the V-grooved surface, smooth surface, and rough surface is 90%, 78%, and 62% respectively. The total area of the collector is 1.20 × 2.0 = 2.40 m2 with the dimension of drying cabinet width, depth, and height 1200 × 650 × 1000 mm respectively. The pressure drop observed at the entrance to the drying chamber is high in the case of a smooth surface, medium in a rough surface and low in a V-grooved plate which will allow sufficient gas pressure to pass through completely.The air mass flow rate is the most important and effective factor during drying. The humidity of the air, as well as air velocity, is also an important factor in improving the drying rate. ©2020. CBIORE-IJRED. All rights reserved