Response surface modelling and performance evaluation of solar dryer for drying of grapes

The current study focuses on the performance of Solar Greenhouse Dryer for drying of grapes for raisin making in Solar Dryer and Open sun condition in Western Maharashtra. The Maharashtra state ranks first in the production of grapes, probably Western Maharashtra produces nearly 800 thousand tons of grapes every year. The major wastage of grapes is due to low sugar content, glossy appearance, shrinkage, excess water in berry, scorching and size variation. Therefore, there is a need to preserve the grapes by drying and making raisins for a non-seasonal requirement. The experiment was conducted for drying of grapes in Solar Greenhouse Dryer and Open Sun condition from 1st of April to 4th of April for 48 hours. The initial weight of the grapes to be dried was 500 grams for both Solar Greenhouse Dryer and open sun drying conditions. The experiment was conducted at Bahe, Borgaon, Tal-Walwa, Dist- Sangli, Maharashtra, India located at 17.115o N and 74.33o E. The main aim of using DOE i.e., Response Surface Modelling is to get an optimum region for drying of grapes in Solar Greenhouse Dryer, from the Surface plot; the region of maxima and minima was obtained.

Drying characteristics and prediction of best fitted drying model for coriander leaves

Drying experiments were conducted on coriander leaves as affected by drying methods (solar greenhouse drying and open sun drying), pretreatments (dipping in a solution of magnesium chloride + sodium bicarbonate + potassium metabisulphite, boiled water blanching containing sodium metabisulphite, and untreated), and loading densities (2.0, 2.5 and 3.0 kg/m2). Validity of three commonly used drying models were examined to predict the most suitable drying model for coriander leaves. The increased drying temperature under solar greenhouse dryer (42°C) increases the amount of moisture removal from the coriander leaves and reduces the drying time by increasing the drying rate as compared to open sun drying (29°C), at all the selected levels of pretreatments and loading densities. Chemically treated coriander leaves dehydrated under a solar greenhouse dryer required less drying time than other treated leaves and dried leaves. Nevertheless, drying methods and loading densities had significant effects, while treatment effects were marginal. It was found that reduction of moisture and moisture removal rate per unit time occurred mostly in the falling rate period except some accelerated removal of moisture at the beginning up to 150 minutes. Page's model was found most appropriate for drying coriander leaves among the selected models.

Selection of a heating system based on climatic conditions of Uzbekistan and on calculations of the technical and economic indicators of alternative systems: A case study of the solar greenhouse with a transformable building

This paper presents studies on the choice of a heating system based on calculations of economic efficiency and payback periods for alternative systems, a solar greenhouse with a transformable body. The purpose of the work is to carry out calculations to determine the consumption of fuel resources necessary to ensure the required amount of energy for the heating season: consumption of natural gas, solid fuel (coal) and electricity for heating a greenhouse with a transformable (adjustable) body. Analytical methods were used to determine the cost of materials and the main units of a greenhouse with a transformable (adjustable) body. Depending on the shape of the greenhouse, the total costs, economic efficiency and payback periods are determined. The research work carried out shows that, in terms of the cost of construction and consumption of materials, the developed greenhouse with transformable (adjustable) body are quite acceptable for its successful use among farmers and private households in the Republic of Uzbekistan. Calculation of economic efficiency and payback periods for greenhouses with a transformable housing allows you to choose the most acceptable heating system and technical characteristics of alternative systems acceptable for the climatic conditions of Uzbekistan.

Effect of external thermal insulation layer on the Chinese solar greenhouse microclimate

In order to optimize the heat preservation capacity of Chinese solar greenhouse (CSG) and further reduce energy consumption, we clarified the mechanism of the external thermal insulation layer that affects the microclimate environment of CSG. The most suitable external insulation layer thickness (EILT) of the solar greenhouse envelope structure in high latitude and cold region has been indicated. A three-dimensional mathematical model was developed based on computational fluid dynamics and verified using experimental measurement. The temperature variations, heat variations and economic benefit were analysed. The results indicated that covering the outer surface of the enclosures with a thermal insulation layer could effectively increase the greenhouse temperature by 1.2–4.0°C. The influence degree of the external thermal insulation layer on the greenhouse microclimate was as follows: sidewall (SW) > north wall (NW) > north roof (NR). In high-dimensional and cold areas, covering the outer surface of all enclosures with insulation layer as the suitable solution could raise the greenhouse air temperature maximally. The suitable EILT of each maintenance structure was obtained as follows: NW 80 mm, SW 80 mm, NR 100 mm.

The Influence of Meshing Strategies on The Numerical Simulation of Solar Greenhouse Dryer

In the present study, we conduct the numerical simulation for solar greenhouse dryer performance by Ansys Fluent software. The numerical simulations compared the meshing strategies for the dryer and show the effects on both temperature distribution and relative humidity distribution of air inside the dryer. Unstructured meshes were used in the numerical simulation employing hexahedral meshing and tetrahedral meshing for mesh generation. The meshing strategies were evaluated through 2 size of cell i.e., 0.1 m and 0.05m. The results indicated that the size of cell have strong effect than the mesh type on the temperature profile and humidity of air inside the dryer. Thus, the results gave the engineers more options to select the optimum conditions for meshing and simulation the dryer.