It was concluded that the dried samples from tent dryer had good quality than open drying. It was found that the relative humidity of the drying air in a solar dryer was between 20 and 35%, while when drying in the open sun it was 50 to 65%. It was observed that the thermal efficiency of a solar dryer was found to be 16.7 to 19.3%.
It was observed that the moisture content of Bombay duck in the solar tunnel dryer was reduced from 90 to 15% in 9 hours, while it took 20 hours in the open drying method. The study reported that biological properties of fish dried in solar tunnel dryer were better than open drying and Midilli et al. The study concluded that the performance of rotary dryer was better than that of solar tunnel in terms of drying time and quality of dried fish.
Results show that the moisture content of fish in solar tunnel dryer and open solar drying was reduced to 16.78%. The results show that the final moisture content was reduced to 10% (w.b.) in 8 hours and the final yield of dried fish was 21.73 kg. The dryer's efficiency was increased by 65% thanks to an electric heater in the water tank.
It was found that the optimal value of the recycling factor and the area of the collector is 90% and 26 m2. 1996) built a solar tunnel dryer for drying bananas. It was found that dried baked banana reached equilibrium moisture content in solar dryer in 7 hours, while it took 12 hours in open sun drying method. It was mentioned that the average exergy efficiency of the solar dryer was 70 and 57% for.
It was mentioned that the fabricated indirect solar dryer was suitable for preserving the mango sample. It was mentioned that the solar dryer was more suitable for preserving pineapples and other foods. 2003) developed a solar tunnel dryer for pineapple drying and the dryer has a capacity of 120 to 150 kg of pineapple.
It was mentioned that the solar dryer was possible to reduce the drying time and most importantly the quality of the sample of dried grapes was improved compared to the open sun drying method. It was mentioned that the average effective moisture diffusion for dried grapes was found to be m2/s. It was mentioned that the correlation coefficient for dried seedless grapes was found to be 0.98.
It was found that the drying constant (k) was strongly influenced by the temperature of the drying air and the surface area of the sample.
Vegetable drying
The DPST dryer was found to reduce drying time by 30 to 50% depending on the samples. It was found that the moisture content of cucumbers in the solar dryer decreased from 92 to 7% in 8 hours, while it took 10 hours for the open drying method. It was found that the moisture content of red chili in solar tunnel dryer decreased from 2.85 to 0.05 kg/.
It was observed that the moisture content of chilli in the solar dryer was reduced from 72.8 to 9.1%. The convective heat transfer coefficient of dried green peas was reported to be 8.22 W/m2◦C. 2021b) used a solar dryer for drying ivy gourds. It was mentioned that the thermal efficiency and drying amount of the dryer were reported as 84% and 258.64 kg.
It was found that the moisture content of roots decreased by 71 and 13% within six days. It was determined that the moisture content of dried cassava was reduced from 67 to 17% on a wet basis within 30 to 36 hours. The drying efficiency of the mixed-mode solar dryer was found to be 12.3 (partial loading of the sample) and 12.5% (fully loaded sample).
It was also mentioned that drying results have better improvement after using an electric heater. It was observed that the convective mass transfer coefficient of dried onion was in the range of 3 to 2.5 W/m2◦C. It was observed that the daily drying efficiency decreased by increasing the drying period.
It was noted that the drying period increased less rapidly with increasing bed depth. It was also noted that the productivity of the dryer increased with increasing bed depth. It was also noted that the overall productivity of the dryer increased with increasing bed depth.
It was also reported that the exponential model gave better agreement with experimental results. It was reported that the moisture removed from the sample in the solar dryer was much higher compared to the open sun drying method.
Conclusions
Bio-based fuels can also be explored to increase the drying hours of the samples. Overall, it is concluded that vegetable drying needs to be aggressively explored and researched to reduce produce waste across the planet.
Basunia MA, Al-Handali HH, Al-Balushi MI, Rahman MS, Mahgoub O (2011) Drying of fish sardines in Oman using solar tunnel dryers. Berinyuy JE, Tangka JK, Weka Fotso GM (2012) Enhancing natural convection solar drying of high moisture vegetables by heat storage. Elavarasan E, Bhanu AS, Kumar Y, et al (2022a) Energy and exergy analysis of Poovan banana under single slope forced and natural convection solar drying.
Elavarasan E, Kumar Y, Mouresh R, Natarajan SK (2022b) Experimental study on drying of tomatoes in a dual slope solar dryer under natural convection. SM (2021a) Experimental study on drying of cucumber in double slope solar dryer under natural convection and open sun drying. Elangovan E, Natarajan SK (2021) Effect of pretreatments on drying of red dacca in a single slope solar dryer.
Fadhela A, Kooli S, Farhat A, Bellghith A (2005) Study of the sun drying of grapes by three different processes. Fudholi A, Bakhtyar B, Saleh H et al (2016a) Drying of salted silver jowfish in a hybrid solar drying system and under open sun: Modeling and performance analyses. Gatea AA (2011) Design and construction of a solar drying system, a cylindrical section and analysis of the performance of the thermal drying system.
Janjai S, Lamlert N, Intawee P et al (2009) Experimental and simulated performance of a PV ventilated solar greenhouse dryer for drying peeled longan and banana. Kabeel AE, Durai P, Dharmadurai L et al (2021) Experimental studies on natural convection, open and closed solar drying using external reflector. Ms N, Chauhan PM (2015) Development of greenhouse solar tunnel dryer for industrial drying of fish of selected species from western coastal region of India.
Nasri MY, Belhamri A (2018) Effects of climatic conditions and shape on drying kinetics, application to solar drying of potatoes in the Maghreb region. Ogheneruona DE, Yusuf MOL (2011) Design and fabrication of direct natural convection solar tapioca dryer. Romano G, Kocsis L, Farkas I (2009) Analysis of energy and environmental parameters during drying of apples and apples in a solar chamber.
![Fig. 7 Grape drying processes: [a] open sun drying, [b] natural convection solar drier, and [c] solar tunnel greenhouse drying (Fadhela et al](https://thumb-ap.123doks.com/thumbv2/123dok/11215631.0/15.892.90.812.849.1025/grape-drying-processes-drying-natural-convection-greenhouse-fadhela.webp)
