Objectives: To make review on passive solar dryers and its performance of drying agricultural products. Methods: This article focuses on the development in various categories of passive solar dryers in last six years. The different studies carried out in direct, indirect and mixed mode types of passive dryers for drying agricultural products in the year of 2014 to 2020 have been considered this review. Investigations on forced convection solar dryers have not been included in the current paper. The various experimental setups of solar dryers, specimens used for experimentation, measured output parameters and performance have been illustrated. The changes made in construction of solar dryers for improving the performance have also been reviewed. Findings:The mixed mode passive solar dryer is found to be superior in terms of drying time, better utilization of solar energy and efficiency compared to other passive dryers. Novelty: Several review articles have been published in solar dryers. Nevertheless, no comprehensive reviews have hitherto been published on passive dryers in particular. Hence, our current review article focuses on development in passive dryers and its advancements with emphasis on dryer design features, specimen and measured output parameters. Keywords: Passive solar dryers; Natural convection solar dryers; Direct solar dryers; Indirect solar dryers; Mixed mode solar dryers
The physical health of human beings and the environment will be negatively influenced by the improper use of cutting fluid, which is an important factor for achieving sustainable machining. Turning is a basic process of all machining operations. Using a minimum quantity lubrication (MQL) system is the best way for achieving sustainable turning process. Improvements made in the MQL system to achieve better performance of the turning process have been discussed in this paper. Search categories that have been used to carry out the study are MQL system with the conventional cutting fluid, MQL system with nano-fluid, MQL system with cryogenics and restructured MQL system. The advancements in MQL turning process published over a span of four most recent years from 2018 to 2021 have been chosen for this review. In this study, the details of experimentation such as materials used for the workpiece, cutting tool materials, environments for lubrication, machining parameters, MQL fluids and performance parameters such as surface roughness, tool wear, cutting force, cutting temperature, etc. have been critically considered. Results investigated from various articles mostly show that advanced MQL systems such as MQL system with nano-fluid, MQL system with cryogenics and restructured MQL system are better than the conventional MQL system in terms of producing better output performance.
This study aimed to produce fuel briquettes from khat waste at Dire Dawa Ethiopia, which is the most serious invasive plant waste, spreading throughout the world particularly at an alarming rate in Ethiopia. Utilization of biomass like invasive waste plant such as khat waste in Ethiopia has a greater advantage for the discovery of clean renewable energy sources and for reduction of deforestation of indigenous trees. Producing the fuel briquetting of khat waste branch and the raw material of khat waste branch of the plant is carried out by using ASTM procedure. The mean average value for fixed carbon content (FCC) and calorific value of the khat waste branch of fuel briquette of the sample were 39.268% and 4143.269 (cal/g) respectively. Also, the result for fixed carbon content(FCC) and calorific value of khat waste branch of raw material waste 20.9% and 3688.3946(cal/g) respectively. The finding shows that by eco-friendly utilization of khat waste plant as a clean energy fuel briquette. It is possible to manage the spread of such type alien invasive plant as well as to increase farmer's crop production, access for livestock grazing land; reduce deforestation of indigenous trees and reduce indoor air pollution.
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