Indirect Natural Convection Solar Dryer Research Articles

Assessment of eco‐thermal sustainability potential of a cluster of low‐cost solar dryer designs based on exergetic sustainability indicators and earned carbon credit

This research aims to establish the interconnectivity between solar dryer designs and the exegetic-sustainability performance of solar dryers. This is to assist energy policymakers and fabricators to establish design standards and make the right choice for waste exergy management strategy for environmental sustainability. Therefore, in this study, the exergy-based sustainability indicators and earned carbon credit were used to assess and compare the performance of four different designs of solar dryers of equal collector capacity under the same external environmental conditions in the same town. In terms of better sustainability indicators that include high exergy efficiency, lower waste exergy emission, higher sustainability index and lower lack of productivity, solar dryer designs with single-pass triple air movement direction with inlet air powered by wind generator had the best indices for environmental sustainability. In contrast, the natural convection mix-mode solar dryer design had the lowest environmental effect factor and destruction coefficient while the indirect natural convection solar dryer had the highest energy recovery ratio based on exergy output from water evaporation. However, the mix-mode solar dryer powered by the wind generator earned the highest carbon credit. The exergy efficiency ranged from 19.09 to 52 % for the four cases, whereas the waste exergy ratio ranged from 0.52 to 0.81. The LOP value ranged from 2.95 to 19.96. Similarly, the sustainability index ranged from 1.28 to 2.5, the average environmental destruction coefficient varied from 3.96 to 20.96, the exergy recovery ratio for the four dryers varied from 0.001825 to 0.12405, and the earned carbon credit ranged from $442. 3 to $2630.5.

Modeling and Simulation of an Indirect Natural Convection Solar Dryer with Thermal Storage Bed

Modeling and Simulation of an Indirect Natural Convection Solar Dryer with Thermal Storage Bed

Evaluation of Drying Model and Quality Analysis of Turmeric Using Solar Thermal System

This study is aimed to find the quality and appropriate thin layer mathematical model suitable for drying kinetics of turmeric which has the least impact of weather conditions. A user-friendly indirect natural convection solar dryer (INCSD) working on compound parabolic concentrator (CPC) was developed and fabricated for this purpose. It is observed that there is a dominant impact of the environmental conditions on the efficiency of solar drying. Adverse weather conditions hinder the collection of solar radiation. It was observed that the moisture content reduces from 77 to 18% in the solar dryer in 24 h as compared to open sun-drying, which requires 40 h. Six thin layer mathematical models reported in the literature have been tried for INCSD and open sun-drying. Thin layer mathematical modeling at different temperatures is presented with quality analysis. Maximum curcumin percentage 3.73% in the turmeric is found at 55°C drying air temperature. Minimum ash content is found to be 6.5% at 60°C. Experimental results reveal that the page model fits best for INCSD as well as for open sun-drying (OSD).

Investigation on indirect natural convection solar drying of anti‐diabetic medicinal products

A performance analysis of indirect natural convection solar dryer (INCSD) was carried out by drying anti-diabetic medicinal products like coccinia grandis, allium cepa, and emblica officinalis by cutting into different orientations. Drying results shows that thickness, orientation of cut, and surface area plays a vital role in the drying characteristics of the products in INCSD. The average collector and dryer efficiency of INCSD was 15% and 7%, respectively. Drying time was reduced up to 11 hr in INCSD than open sun drying. Alpha amylase inhibition assay values for products dried under open sun (15.67%, 5.89%, and 8.56%) showed better results, whereas minerals like potassium content in allium cepa (597 mg/100 g), sodium content in coccinia grandis (130.1 mg/100 g), magnesium content in allium cepa, and emblica officinalis (80 mg/100 g) were higher when dried in INCSD. Vitamin C and sugar content in products were almost same for both INCSD and open sun drying. Practical applications Indirect natural convection solar dryers are mainly benefited by small-scale farmers as it takes less drying time and possess better quality when compared to open sun drying. Drying anti-diabetic medicinal products in INCSD can be considered as a boon for pharmaceutical industries as the dryer can give good-quality dried products that can be used for preparing anti-diabetic medicines. It can also reduce the production cost of anti-diabetic medicines.

Modeling of coupled heat and mass transfer during drying of ebony wood using indirect natural convection solar dryer

This study presented the behavior of a laboratory scale solar dryer, which was designed with the objective of meeting the needs of low income carpenters of the tropical region of Africa. The following materials were used to build the solar dryer: aluminum sheets painted in black, a wooden support, and a plastic polyethylene used as a cover. Drying was carried out in the city of Yaoundé in Cameroon, and the tested boards were ebony (Diospyros crassiflora). Drying must be performed with the following conditions: slow process at a low temperature in order to maintain the proper air relative humidity. Since, no apparatus was used to force the circulation of the air, natural convection was the mode used by the dryer. The solar dryer was mathematically modeled by applying heat and mass transfer balance to the different components of the solar dryer. It is important to mention that the used heat and mass coefficients were proposed as variable with the operating conditions. The mathematical model was a reasonable description of the physical phenomena taking place in the dryer. The results show that the average relative error between numerical and experimental moisture contents was equal to 2.102%. Heat transfer convective coefficients and global mass transfer coefficients varied with drying time from 0.25 to 5.5 W/(m2K) and from 1 × 10−8 to 5.5 × 10−8 m/s, respectively. The proposed model allowed designing and dimensioning the solar dryer, to the industrial scale. It allowed following the evolution of the different temperatures and moisture content of the tested material and then optimizing the design of the dryer and the drying process conditions. Based on the model, proposing the opening of the drying chamber during the night time and the use of substances capable of retaining heat in the chamber were some proposed solutions in order to have more efficient drying process. The modeling results showed also that an improvement can be obtained at the addition of a solar collector.

A Mathematical Model of Indirect Solar Drying of Dairy Products (Jameed)

A Mathematical modeling of indirect natural convection solar dryer was designed for drying one of the famous dairy product in Jordan called Jameed. The intended solar dryer system is environmentally friendly and consumes zero electricity. The dryer consists of a flat plate solar collector having dimensions of 0.1 m height, 0.8 m width and 1.2 m length. A drying chamber consisting of four trays separated equally from each others at a distance of 0.2 m. The chamber is 1 m long made of wood. Each tray has a cross section of 0.8 m x 0.4 m. The solar collector is studied separately to establish the effect of changing its width or length on the air outlet temperature and mass flow rate. The drying chamber is used to dry 4 kilograms of jameed, each 1 kilogram is distributed on each tray. The total solar irradiation on the collector surface and chamber walls at each hour of the day was also calculated at the 21 st of May in Jordan. At these specific solar irradiation, the flat plate solar collector efficiency was almost constant having an average efficiency of 37% and a maximum outlet temperature of 41 °C at 1p.m. The drying time for trays 1, 2, 3 and 4 were 16.4, 19.14, 22.6 and 25.71 hours, respectively.