In global industrialization, efforts have been made to increase the rate of heat transfer in heat exchanger, minimizing the size of heat exchanger to reduce cost as well as increasing the effectiveness. Helical coil h...In global industrialization, efforts have been made to increase the rate of heat transfer in heat exchanger, minimizing the size of heat exchanger to reduce cost as well as increasing the effectiveness. Helical coil heat exchanger (HCHE) has been proven to be effective in improving heat transfer due to its large surface area. In this study, HCHE was designed to provide hot air needed for fluidized bed drying processes. The HCHE design model was fabricated and evaluated to study the efficiency of the hot air output for a laboratory fluidized bed dryer. The mathematical model for estimation of the final (output) temperature of air, Taf, passing through the HCHE was developed and validated experimentally. The drying of bitter kola particulates was carried out with a drying temperature of 50C 3C and a bed height-to-bed diameter ratio (H/D) of 1.5. The time taken to dry bitter kola particulates to 0.4% moisture content was 1 hour 45 minutes. Hence, HCHE is recommended for use in the production of hot for laboratory-scale fluidized bed dryers.展开更多
This research entails the study of heat and mass transfer of nanofluid flow in a fluidized bed dryer used in tea drying processes in presence of induced magnetic field. A mathematical model describing the fluid flow i...This research entails the study of heat and mass transfer of nanofluid flow in a fluidized bed dryer used in tea drying processes in presence of induced magnetic field. A mathematical model describing the fluid flow in a Fluidized bed dryer was developed using the nonlinear partial differential equations. Due to their non-linearity, the equations were solved numerically by use of the finite difference method. The effects of physical flow parameters on velocity, temperature, concentration and magnetic induction profiles were studied and results were presented graphically. From the mathematical analysis, it was deduced that addition of silver nanoparticles into the fluid flow enhanced velocity and temperature profiles. This led to improved heat transfer in the fluidized bed dryer, hence amplifying the tea drying process. Furthermore, it was noted that induced magnetic field tends to decrease the fluid velocity, which results in uniform distribution of heat leading to efficient heat transfer between the tea particles and the fluid, thus improving the drying process. The research findings provide information to industries on ways to optimize thermal performance of fluidized bed dryers.展开更多
The effect of vertical internal baffles on the particle mixing and graindrying characteristics in a batch fluidized bed column is investigated. Experimental work wascarried out in a 3m high rectangular fluidized bed d...The effect of vertical internal baffles on the particle mixing and graindrying characteristics in a batch fluidized bed column is investigated. Experimental work wascarried out in a 3m high rectangular fluidized bed dryer of cross sectional area of 0.15 m x 0.61 mat different operating conditions using paddy, a group D particle, as the fluidizing material. Theresults of the study showed that the fluidized bed dryer system with vertical internal baffles gavebetter particle mixing effect in the bed of particles than that without vertical internal baffles.This is due to the fact that the vertical internal baffle act as gas bubble breakers by breaking upthe large gas bubbles into smaller ones. The smaller bubbles cause a more vigorous mixing in the bedof particles before finally erupting at the bed surface. This improves the contacting efficiencyand enhanced the heat and mass transfer of the fluidized bed system. Thus a higher drying rate wasobtained in the falling rate period because the higher contacting efficiency increases theevaporation rate at the particle surface. However, the drying rate in the diffusion region showslittle improvement because the moisture diffusivity does not depend on the contacting efficiency.The fluidized bed dryer with vertical internal baffles could therefore be used in the initial rapiddrying stage in a two stage drying strategy for paddy. The insertion of vertical internal bafflesinto a fluidized bed system improves the processing of Group D particles in a fluidized bed systemespecially if the system is large in scale.展开更多
This paper attempts to analyze the kinetics involved in the drying of green peas in‘with blanching’and‘without blanching’techniques.Blanching by hot water mixed with a solution of citric acid(0.1–0.2 mg/ml)at 70...This paper attempts to analyze the kinetics involved in the drying of green peas in‘with blanching’and‘without blanching’techniques.Blanching by hot water mixed with a solution of citric acid(0.1–0.2 mg/ml)at 70C–100C is the treatment provided to the samples of green peas.Experimental analysis shows that the moisture content in green peas of three different sizes is reduced at different temperatures and demonstrates the effect of the rate of drying of the moisture content.Under different diameters and temperatures,the parameters are analyzed using‘with blanching’and‘without blanching’techniques.It is observed that‘with blanching’process plays a significant role in the reduction of moisture content under different temperatures and diameters in a lesser time as compared to‘without blanching’.The operative activation energy and moisture diffusivity are described by using Fick’s law of diffusion.The calculation of effective moisture diffusivity can be done via the utilization of slope.The drying data is subjected to two models of mathematical nature:Simple Exponential model,and Page model.The performance of these models is examined by means of comparing the coefficient of determination(R2),chi-square(v2)and root mean square error(RMSE)between the experimental and forecasted value of moisture ratio obtained‘with blanching’and‘without blanching’.The experimental data was seen to be in accordance with the Page model.The comparisons of energy consumption,energy efficiency and also the cost of the drying processes for‘with blanching’and‘without blanching’have been accomplished to optimize and reduce process condition and the cost of the process,respectively.展开更多
文摘In global industrialization, efforts have been made to increase the rate of heat transfer in heat exchanger, minimizing the size of heat exchanger to reduce cost as well as increasing the effectiveness. Helical coil heat exchanger (HCHE) has been proven to be effective in improving heat transfer due to its large surface area. In this study, HCHE was designed to provide hot air needed for fluidized bed drying processes. The HCHE design model was fabricated and evaluated to study the efficiency of the hot air output for a laboratory fluidized bed dryer. The mathematical model for estimation of the final (output) temperature of air, Taf, passing through the HCHE was developed and validated experimentally. The drying of bitter kola particulates was carried out with a drying temperature of 50C 3C and a bed height-to-bed diameter ratio (H/D) of 1.5. The time taken to dry bitter kola particulates to 0.4% moisture content was 1 hour 45 minutes. Hence, HCHE is recommended for use in the production of hot for laboratory-scale fluidized bed dryers.
文摘This research entails the study of heat and mass transfer of nanofluid flow in a fluidized bed dryer used in tea drying processes in presence of induced magnetic field. A mathematical model describing the fluid flow in a Fluidized bed dryer was developed using the nonlinear partial differential equations. Due to their non-linearity, the equations were solved numerically by use of the finite difference method. The effects of physical flow parameters on velocity, temperature, concentration and magnetic induction profiles were studied and results were presented graphically. From the mathematical analysis, it was deduced that addition of silver nanoparticles into the fluid flow enhanced velocity and temperature profiles. This led to improved heat transfer in the fluidized bed dryer, hence amplifying the tea drying process. Furthermore, it was noted that induced magnetic field tends to decrease the fluid velocity, which results in uniform distribution of heat leading to efficient heat transfer between the tea particles and the fluid, thus improving the drying process. The research findings provide information to industries on ways to optimize thermal performance of fluidized bed dryers.
文摘The effect of vertical internal baffles on the particle mixing and graindrying characteristics in a batch fluidized bed column is investigated. Experimental work wascarried out in a 3m high rectangular fluidized bed dryer of cross sectional area of 0.15 m x 0.61 mat different operating conditions using paddy, a group D particle, as the fluidizing material. Theresults of the study showed that the fluidized bed dryer system with vertical internal baffles gavebetter particle mixing effect in the bed of particles than that without vertical internal baffles.This is due to the fact that the vertical internal baffle act as gas bubble breakers by breaking upthe large gas bubbles into smaller ones. The smaller bubbles cause a more vigorous mixing in the bedof particles before finally erupting at the bed surface. This improves the contacting efficiencyand enhanced the heat and mass transfer of the fluidized bed system. Thus a higher drying rate wasobtained in the falling rate period because the higher contacting efficiency increases theevaporation rate at the particle surface. However, the drying rate in the diffusion region showslittle improvement because the moisture diffusivity does not depend on the contacting efficiency.The fluidized bed dryer with vertical internal baffles could therefore be used in the initial rapiddrying stage in a two stage drying strategy for paddy. The insertion of vertical internal bafflesinto a fluidized bed system improves the processing of Group D particles in a fluidized bed systemespecially if the system is large in scale.
文摘This paper attempts to analyze the kinetics involved in the drying of green peas in‘with blanching’and‘without blanching’techniques.Blanching by hot water mixed with a solution of citric acid(0.1–0.2 mg/ml)at 70C–100C is the treatment provided to the samples of green peas.Experimental analysis shows that the moisture content in green peas of three different sizes is reduced at different temperatures and demonstrates the effect of the rate of drying of the moisture content.Under different diameters and temperatures,the parameters are analyzed using‘with blanching’and‘without blanching’techniques.It is observed that‘with blanching’process plays a significant role in the reduction of moisture content under different temperatures and diameters in a lesser time as compared to‘without blanching’.The operative activation energy and moisture diffusivity are described by using Fick’s law of diffusion.The calculation of effective moisture diffusivity can be done via the utilization of slope.The drying data is subjected to two models of mathematical nature:Simple Exponential model,and Page model.The performance of these models is examined by means of comparing the coefficient of determination(R2),chi-square(v2)and root mean square error(RMSE)between the experimental and forecasted value of moisture ratio obtained‘with blanching’and‘without blanching’.The experimental data was seen to be in accordance with the Page model.The comparisons of energy consumption,energy efficiency and also the cost of the drying processes for‘with blanching’and‘without blanching’have been accomplished to optimize and reduce process condition and the cost of the process,respectively.
