Javad Ashrafi Varkani; Shiva Gorjian; Barat Ghobadian
Abstract
Concentrators have many functions, one of which is their use in the process of evaporation of liquids. Since high heat is present in concentrator-absorbers, it is possible to develop a heat exchanger system that allows the evaporation of salt water. One of the main components of these systems is the ...
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Concentrators have many functions, one of which is their use in the process of evaporation of liquids. Since high heat is present in concentrator-absorbers, it is possible to develop a heat exchanger system that allows the evaporation of salt water. One of the main components of these systems is the heat absorber, which is located at the focal point. In this research, an attempt was made to study two geometries of annular and hollow absorbers using the Computational Fluid Dynamics (CFD) method. For this purpose, the working fluid was defined based on the properties of seawater in Fluent Ansys software and the creation of geometry and thermal analysis were considered based on the initial and boundary conditions of the system. The results of the validation of the grid quality showed that the use of a tetrahedral grid with square grid order is suitable for the cavity geometry. Due to the dimensional symmetry of the geometry of the ring converter, the use of the simplest grid method leads to a high accuracy of the solver. The thermal analysis of the absorber showed that for the cavity geometry, the heat distribution at the bottom of the geometry is larger than at the top. The results of the Nusselt number change analysis showed the concentration of thermal stress in the liquid outlet region. This stress concentration leads to the shifting of the evaporation process from the inside of the chamber to the transfer tubes.
Samane Torabi; S. R. Hasanbeigi; Behzad Sattari; Barat Ghobadian
Abstract
Bread waste is the common part of food biomass in the world. The aim of this study was to investigate the effects of saccharification time and also substrate concentration on the amount of glucose as well as bioethanol obtained from bread wastes folowing hydrolysis processing. The bread wastes were crushed ...
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Bread waste is the common part of food biomass in the world. The aim of this study was to investigate the effects of saccharification time and also substrate concentration on the amount of glucose as well as bioethanol obtained from bread wastes folowing hydrolysis processing. The bread wastes were crushed to small parts and then mixed with water at ratio of 10-15 (w/v%). Alpha-amylase and glucoamylase enzymes were used for liquefaction and saccharification, respectively. The effects of saccharification time and substrate loading parameters on the amount of glucose were investigated by using response surface methodology (central composite design) with Design Expert software. The glucose-derived from hydrolysis processing was measured by glucose kit. Aflatoxin contents of the bread wastes (as control sample) and optimum sample obtained from the hydrolysis processing (sample with the maximum glucose) were measured. Fermentation processing was carried out by using Saccharomyces cerevisiae yeast. The results showed that the highest amount of glucose (100.21 g/l) in enzymatic hydrolysis was obtained at the saccharification time of 48 h and substrate loading of 150 g/l. The hydrolysis processing at the higher concentrations and longer duration, due to high viscosity and adhesion, reduced the concentration of glucose, so high concentration did not have any favorable effect on the hydrolysis processing. The hydrolysis processing reduced Aflatoxin B1 and B2 at a ratio of 76% and 16%, respectively. The greatest amount of bio-ethanol in the fermentation phase (45.35 g/l) was obtained at 36 hours with efficiency of 88.7%. It could be related to the consumption of glucose produced in the hydrolysis phase due to proper growth of the cell mass during fermentation phase in this duration. The recommended time for the fermentation processing is 36 hours.
