Query: Solar dryer

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

title: Development of a low cost wind powered active solar dryer integrated with glycerol as thermal storage
abstract: The paper presents an active mix mode wind powered fan solar dryer (AWPFS) with a passive mix mode non wind powered solar dryer (PNWPS) evaluated with pre treated potato slices. The two dryers were tested with and without glycerol as thermal energy storage. The objective was to present a non electricity powered active solar dryer using only clean energy sources. Evaluation of the dryer took place at ambient temperature range of 24 50 degC and humidity of 10 52% The results indicate that drying with AWPFS integrated with glycerol showed shorter drying time than drying with AWPFS only or PNWPS. Dipping the potato in a salt solution and blanching for 30 s before drying quickened the drying rate of the potato compared to other treatments. The energy consumed for drying ranged from 4.10 to 4.98 MJ, while the specific energy consumption ranged from 2.846 to 3.686 kWh/kg. The drying efficiencies ranged from 25.031% to 31.5% while the exergy efficiency ranged from 14.5 to 80.9% With low electricity penetration density across Africa, this dryer with naturally powered fan will help crop processors dry their product faster and about 15.3 290.4 /year could be saved at 10 100% rate of usage

title: Thermal analysis of a solar dryer equipped with PTSC and PCM using experimental and numerical methods
abstract: This paper was aimed to evaluate the effect of fluid type on thermal performance of parabolic trough solar collector (PTSC) The simulation process was performed to predict thermal variations in receiver tube and storage tank by CFD. The experiments were conducted with 0.025 kg/s as air flow rate. Four fluid types including Nano fluid (Al2O3, 4% engine oil (10W40) glycerin and water and were considered for the performance analysis. Moreover, the drying process of the solar dryer was considered during the drying of apple slices with 5 mm thickness. The results showed that overall input thermal energy for dryer was about 17.36 MJ, 18.46 MJ, 17.76 MJ and 16.80 MJ for Nano fluid, oil, glycerin and water, respectively. It also implied that using Nanofluid, oil and glycerin improved the overall efficiency of the dryer about 9.7% 20.2% and 12.4% related to water. The comparison of simulated and predicted results it is implied that CFD method can predict the performance of PTSC with different working fluids with good accuracy. Using different working fluids assisted with PCM did not have undesired effect on the quality of dried apples.

title: Numerical analysis and validation of a natural convection mix mode solar dryer for drying red chilli under variable conditions
abstract: The objective of this paper is to model a natural convection mix mode solar dryer (NCMMSD) for drying agricultural products in an environment with short sunshine duration. The solar dryer was used to dry red chilli and was operating under the climate of the coastal area of South Eastern Nigeria characterized by low solar radiation intensity with a short duration of sunshine hours. The model took into consideration the thermophysical properties of the drying air and dried red chilli. The simultaneous heat and mass transfer equations were solved using the fourth order Runge Kutha method. The numerical solution allows for the determination of temperature and relative humidity of drying air at different points within the dryer as well as the moisture profile of the dried product. The experimental values of moisture ratios, temperature, and relative humidity during the mix mode solar drying process with and without NaCl were used to validate the proposed model. Numerical simulation results were in close agreement with experimental results. The present model can serve as good reference bases to explain the drying phenomenon of mix mode solar drying of other agricultural products when necessary thermophysical properties of these products are known. Using this model, the potential of mitigating gross fossil (coal) CO2 in Africa is annually estimated to 1280148 tons of CO2.

title: Thermal performance of a passive, mixed type solar dryer for tomato slices (Solanum lycopersicum)
abstract: In this work, a passive, mixed type solar dryer was designed, constructed and evaluated. The solar dryer evaluated has the option of working as an indirect direct dryer (mixed solar dryer, MSD) or in indirect solar dryer mode (ISD) since the drying chamber has a mobile opaque cover. The energy efficiency, drying efficiency, and the drying kinetics were the evaluation criteria for thermal performance of the dryer during the drying of tomato. During the experiments, the temperature inside the drying chamber at solar noon was in a range of 65@C 70 degC operating in MSD and 55@C 60 degC in ISD. The results showed that drying the tomato in ISD (26 h) took longer than the MSD (17 h) The efficiency of the solar collector was between 52.30% and 55.45% The overall dryer efficiency in MSD and ISD mode were between 10.66% and 8.80% respectively, while the drying efficiency was in a range of 5.47% and 4.48% respectively. The experimental data of the tomato drying kinetics were adjusted to five different mathematical models; the Modified Henderson Pabis model showed the better fit with an r2 of 0.9888 and 0.9996 and an RMSE of 0.0027 and 0.008 for the MSD and ISD respectively.

title: Energy and exergy analysis of an indirect solar dryer based on a dynamic model
abstract: Sun is a clean and available sustainable energy source. The usage of sustainable energy in various industries such as agriculture is taking into consideration during the early years. One application is dehydration by using an indirect solar dryer, which was adopted in this study. A dynamic model was presented in which the calculation of the solar radiation received in the tiled surface of the collector, temperature variation along the collector, the kinetics of moisture reduction and temperature variation of the drying material were taken into consideration. The model was validated and confirmed with high accuracy by test results in three states of mass flow rates of air. The effects of air velocity, the glass cover thickness and the length of the collector took into consideration in the analysis as effective parameters. The thermal analysis was accomplished by using energy and exergy analysis. To energy analysis, the values of received and used energy were calculated in addition to energy utilization ratio and for exergy analysis, the irreversibility at collector was calculated as well as the exergy efficiency of drying in the chamber. Energy and exergy analysis revealed more stream exergy for higher speed air and hence, lower irreversibility. Besides, the defined exergy efficiency was independent of the material mass despite the exergy destruction or energy efficiency, which means a suitable criterion for the system analysis. The model was in good agreement with the experiments so that the deviation from the best fit line (y x) in the model experiments curves were 2.37% for radiation estimation, 4% for the outlet air temperature of the collector, 1% for the material temperature and 4.8% for the moisture ratio of the drying material. The model also revealed two critical moisture ratio of 0.75 and 0.23 in the drying process so that the maximum exergy destruction was observed at the first one and the maximum exergy efficiency was 22% for the dryer.

title: Development of indirect type solar dryer and experiments for estimation of drying parameters of apple and watermelon
abstract: In the present paper, an indirect type solar dryer (ITSD) has been developed for apple and watermelon drying. The performance of ITSD and drying kinetics of watermelon and apple slices have been analyzed. From the experimental analysis, diffusion coefficient, surface transfer coefficients and activation energy of apple and watermelon were estimated. Experimental outcomes showed that the temperature inside the drying cabinet varied with time because of frequent variation in solar intensity. The average thermal efficiency of the collector and dryer was 54.5% and 25.39% during apple drying and 56.3% and 28.76% for watermelon drying, respectively. Moisture content of apple decreased from 6.16 to 0.799 kg/kg of dry basis (db) and that of watermelon reduced from 10.76 to 0.496 kg/kg of db. Drying curve was fitted with different models of existing studies. Average effective moisture diffusivity was estimated and it was 4.28 x 10 9 m2/s and 4.01 x 10 9 m2/s for apple and watermelon, respectively. Mass transfer coefficient is found to be in the range 1.584 x 10 4 to 3.158 x 10 3 m/s for apple and 5.17 x 10 4 to 4.98 x 10 3 m/s for watermelon. Heat transfer coefficient was in the range of 0.16 to 3.19 W/m2 K and 0.52 to 5.04 W/m2 K for apple and watermelon, respectively. Activation energy for apple and watermelon is 17.34 and 18.71 kJ/mol, respectively.

title: Experimental and CFD survey of indirect solar dryer modified with low cost iron mesh
abstract: In the present work, double pass indirect solar dryer (DPISD) and double pass indirect solar dryer with mesh absorber modification (DPISDMA) have been designed, analyzed, manufactured and tested. The main aim of this study is improving the thermal efficiency of double pass solar air collector by integrating iron meshes. Pepino fruit (Solanum muricatum L. samples in two thicknesses have been used in the experimental study. Also, CFD analysis of both solar air collectors and drying chamber and quality metrics such as phenolic, total flavonoid contents and antioxidant activity have been conducted. Numerical simulation and experimental results showed that using mesh modification has positive influence on the performance of the collector. The highest value of the average efficiency of the dryer was obtained in DPISDMA for the thin sample thickness as 23.08% According to quality analyses, the experiments which done in DPISDMA gave the best results with highest values of TPC, TFC and antioxidant activity values (p

title: Energy and Exergy Analysis on Drying of Banana Using Indirect Type Natural Convection Solar Dryer
abstract: Energy and exergy analysis, in the thermodynamics, is an important tool used to predict the performance of drying system. In this work, energy and exergy analyses are made during the drying process of banana using an indirect type passive solar dryer. Solar flat plate air collector is used to heat the air. Banana gets sufficiently dried at temperatures between 28 and 82 degC. Solar radiation is measured and it is ranged from 335 to 1210 W/m2. Using the first law of thermodynamics, energy analysis was carried out to estimate the amounts of energy gained from solar air heater. Also, applying the second law of thermodynamics, exergy analysis was carried out to determine exergy losses during the drying process. The exergy losses varied from 3.36 to 25.21 kJ/kg. In particular, the exergy efficiency values vary from 7.4 to 45.32%

title: Thermal performance enhancement of tube type alternative indirect solar dryer with iron mesh modification
abstract: Clean and sustainable energy generation is a substantial necessity for developing world. Solar energy is an extensively utilized renewable energy resource and it can be utilized for both electricity and thermal energy generation. Solar thermal applications could be utilized in various processes like space heating and drying. In this study, two cost effective and simple structured solar air heaters were designed and manufactured. The first heater is a hollow tube type heater. Second heater has the same basic properties but iron meshes were added in the flow channel to extend its heat transfer surface area. The mesh modified tube type heater was manufactured regarding to numerical simulation findings using Ansys Fluent software. Both heaters were integrated with a drying chamber and drying tests were conducted at three air mass flow rates (0.014, 0.011 and 0.009 kg/s) The maximum instantaneous thermal efficiency in iron mesh modified solar heater was obtained as 74.71% Utilizing mesh modification enhanced thermal efficiency of the tube type heater up to 11% Also, the highest values of the average energy efficiency of the drying system was achieved as 50.85% as well in iron mesh modified solar assisted dryer. It is observed that this tubular SAH design is promising in view of renewable hot air generation with its simple and cost effective structure since it includes no casing, no insulation material and fabricated from sheet metal.