The effectiveness of deep-bed filtration with respect to suspension formed during the preceding processes is evaluated by the test of filterability. The properties and concentration of the suspension being filtered ar...The effectiveness of deep-bed filtration with respect to suspension formed during the preceding processes is evaluated by the test of filterability. The properties and concentration of the suspension being filtered are affected by the efficiency of the preceding aggregation and separation processes. The basic principles of the test of filterability are based on the mechanistic model of filtration. The equations in the mathematical model of the mechanistic conception of filtration are derived from the theory of filtration. The arrangement of the pilot filtration plant for the determination of filterability of flocculent suspension is presented in this paper. The test of filterability is carried out with a thin-layer filter element. The design of a filter element arrangement and its installation are also disclosed in this paper. The inter-dependence of the coefficient of filtration efficiency on the specific volume of intercepted suspensions, filter media grain sizes and different filtration velocities are graphically presented. In addition, the effect of the filter bed clogging resulting from the properties of different suspensions on the head loss generated, the length of filtration cycle and quality of filtrate produced are also shown in this paper.展开更多
Quality of dried product depends on the temperature and velocity at each position in the dryer.Simultaneous microscopic and macroscopic simulation on Computational Fluid Dynamic(CFD)is a general problem of fixed bed d...Quality of dried product depends on the temperature and velocity at each position in the dryer.Simultaneous microscopic and macroscopic simulation on Computational Fluid Dynamic(CFD)is a general problem of fixed bed dryer consisting of water transportation in porous media and dynamic flow of hot air in the dryer.Simplifying the dryer by assuming the packed bed as porous volume,viscous and inertial resistances(1/α and C_(2))are necessary for calculating the pressure drop and velocity change in the bulk.Comparing theDP/L of the standard packing with experimental results,the porosity and resistance parameters can be estimated.Simulation of unmodified,adding false floor and invest mesh,and insulating the dryer wall are used for validation with previous results.Adding the round holed sieve as false floor and invert mesh can produce better profile but cannot obtain uniform distribution.Air velocity distribution shows similar but the calculating temperature is higher than that from the experiment.By analysis of thermal efficiency of dryer without insulator,the heat loss rates with flue gas and heat flux at wall are in the range 14%-17%and 5.5%-7.3%.Integrating with single fruit or thin layer drying kinetic in the future,the CFD simulation can be used for optimal design of fixed bed dryer.展开更多
Aqueous filtration systems with granular media are increasingly implemented as a unit operation for the treatment of urban waters.Many of these aqueous filtration systems are designed with coarse granular media and ar...Aqueous filtration systems with granular media are increasingly implemented as a unit operation for the treatment of urban waters.Many of these aqueous filtration systems are designed with coarse granular media and are therefore subject to finite granular Reynolds numbers(Reg).In contrast to the Reg conditions generated by such designs,current hydrosol filtration models,such as the Yao and RT models,rely on a flow solution that is derived within the Stokes limit at low Reg.In systems that are subject to these finite and higher Reg regimes,the collector efficiency has not been examined.Therefore,in this study,we develop a 3D periodic porosity-compensated face-centered cubic sphere(PCFCC)computational fluid dynamics(CFD)model,with the surface interactions incorporated,to investigate the collector efficiency for Reg ranging from 0.01 to 20.Particle filtration induced by interception and sedimentation is examined for non-Brownian particlesfanging from 1 to 100 μm under favorable surface interactions for particle adhesion.The results from the CFD-based PCFCC model agreed well with those of the classical RT and Yao models for Reg<1.Based on 3150 simulations from the PCFCC model,we developed a new correlation for vertical aqueous filtration based on a modified gravitation number,NG^*,for the initial deep-bed filtration efficiency at lower yet finite(0.01 to 20)Reg.The proposed PCFCC model has low computational cost and is extensibile from vertical to horizontal filtration at low and finite Reg.展开更多
文摘The effectiveness of deep-bed filtration with respect to suspension formed during the preceding processes is evaluated by the test of filterability. The properties and concentration of the suspension being filtered are affected by the efficiency of the preceding aggregation and separation processes. The basic principles of the test of filterability are based on the mechanistic model of filtration. The equations in the mathematical model of the mechanistic conception of filtration are derived from the theory of filtration. The arrangement of the pilot filtration plant for the determination of filterability of flocculent suspension is presented in this paper. The test of filterability is carried out with a thin-layer filter element. The design of a filter element arrangement and its installation are also disclosed in this paper. The inter-dependence of the coefficient of filtration efficiency on the specific volume of intercepted suspensions, filter media grain sizes and different filtration velocities are graphically presented. In addition, the effect of the filter bed clogging resulting from the properties of different suspensions on the head loss generated, the length of filtration cycle and quality of filtrate produced are also shown in this paper.
基金This work was financed by Department of Material Science and Engineering and Faculty of Engineering and Industrial Technology,Sipakorn Univesity,THAILAND.
文摘Quality of dried product depends on the temperature and velocity at each position in the dryer.Simultaneous microscopic and macroscopic simulation on Computational Fluid Dynamic(CFD)is a general problem of fixed bed dryer consisting of water transportation in porous media and dynamic flow of hot air in the dryer.Simplifying the dryer by assuming the packed bed as porous volume,viscous and inertial resistances(1/α and C_(2))are necessary for calculating the pressure drop and velocity change in the bulk.Comparing theDP/L of the standard packing with experimental results,the porosity and resistance parameters can be estimated.Simulation of unmodified,adding false floor and invest mesh,and insulating the dryer wall are used for validation with previous results.Adding the round holed sieve as false floor and invert mesh can produce better profile but cannot obtain uniform distribution.Air velocity distribution shows similar but the calculating temperature is higher than that from the experiment.By analysis of thermal efficiency of dryer without insulator,the heat loss rates with flue gas and heat flux at wall are in the range 14%-17%and 5.5%-7.3%.Integrating with single fruit or thin layer drying kinetic in the future,the CFD simulation can be used for optimal design of fixed bed dryer.
基金Funding was provided through the University of Florida Graduate School Fellowship.
文摘Aqueous filtration systems with granular media are increasingly implemented as a unit operation for the treatment of urban waters.Many of these aqueous filtration systems are designed with coarse granular media and are therefore subject to finite granular Reynolds numbers(Reg).In contrast to the Reg conditions generated by such designs,current hydrosol filtration models,such as the Yao and RT models,rely on a flow solution that is derived within the Stokes limit at low Reg.In systems that are subject to these finite and higher Reg regimes,the collector efficiency has not been examined.Therefore,in this study,we develop a 3D periodic porosity-compensated face-centered cubic sphere(PCFCC)computational fluid dynamics(CFD)model,with the surface interactions incorporated,to investigate the collector efficiency for Reg ranging from 0.01 to 20.Particle filtration induced by interception and sedimentation is examined for non-Brownian particlesfanging from 1 to 100 μm under favorable surface interactions for particle adhesion.The results from the CFD-based PCFCC model agreed well with those of the classical RT and Yao models for Reg<1.Based on 3150 simulations from the PCFCC model,we developed a new correlation for vertical aqueous filtration based on a modified gravitation number,NG^*,for the initial deep-bed filtration efficiency at lower yet finite(0.01 to 20)Reg.The proposed PCFCC model has low computational cost and is extensibile from vertical to horizontal filtration at low and finite Reg.
