Transient Exergetic Efficiency of a Forced Convection Drying Process With and Without Electrohydrodynamic (EHD) Enhancement

2014 ◽  
Author(s):  
Erik Bardy ◽  
Merouane Hamdi ◽  
Michel Havet ◽  
Olivier Rouaud
Keyword(s):  
Forced Convection ◽  
Electrostatic Field ◽  
Air Flow ◽  
Food Product ◽  
Convective Drying ◽  
Wire Electrode ◽  
Exergetic Efficiency ◽  
Drying Process ◽  
Initial Results ◽  
Flow Velocities

Electrohydrodynamic (EHD) drying is a novel drying method used to enhance forced convective drying by using a wire-electrode to create an electrostatic field. In this study, it was hypothesized that an EHD enhanced forced convective drying process will not only increase the drying rate, but also the exergetic efficiency over time. A transient exergetic efficiency was defined as the ratio of the exergy use rate in the removing of moisture from the drying product, to the exergy rate of the drying air supplied. In the case of EHD enhanced forced convection, the exergy rate supplied by the wire electrode was also accounted for. Forced convection drying experiments were run on a test specimen simulating a food product (methylcellulose gel) using an air flow channel with and without EHD enhancement with varying air flow velocities. Initial results show that the moisutre loss rate of the methylcellulose gel increased with the application of the electrostatic field. In addition, for low velocities, the exergetic efficiency of EHD enhanced forced convection was higher for the first few hours of drying as compared to conventional forced convection. The exergetic efficiency of both conventional and EHD enhanced forced convection converged at greater air flow velocities.

scholarly journals Drying Kinetics Comparison of Methylcellulose Gel Versus Mango Fruit in Forced Convective Drying With and Without Electrohydrodynamic Enhancement

2016 ◽  
Vol 138 (8) ◽  
Author(s):  
Erik Bardy ◽  
Sabrine Manai ◽  
Michel Havet ◽  
Olivier Rouaud
Keyword(s):  
Moisture Content ◽  
Food Product ◽  
Drying Kinetics ◽  
Area Measurement ◽  
Convective Drying ◽  
Drying Rate ◽  
Wire Electrode ◽  
Exergetic Efficiency ◽  
Mango Fruit ◽  
Drying Time

Electrohydrodynamic convective drying (EHD drying) is a novel drying method used to enhance forced convection drying (FC drying) by using a wire-electrode to create an electrostatic field. In a previous study, the efficiency of EHD drying (using three different wire-electrode configurations) was compared to classical FC drying by measuring the drying rate of methylcellulose gel. Efficiency was quantified in terms of exergy (transient exergetic efficiency) through the use of a proposed model. In that previous study, it was stated that methylcellulose gel can be used to simulate a food product and can be controlled to a predetermined moisture content. The purpose of this current work was to compare how methylcellulose gel compares to a real food product (mango fruit) in terms of drying kinetics for both EHD and FC drying. Drying kinetics were quantified in terms of a per unit area measurement of the exergetic efficiency, exergy supplied and used, drying rate, and total drying time to reach a moisture content of 50%. Initial results show that for both EHD and FC drying, methylcellulose gel and mango fruit exhibit similar drying kinetics.

Influencia de las condiciones de secado solar en la coloración de plantas medicinales

2019 ◽  
pp. 28-34
Author(s):  
Margarita Castillo-Téllez ◽  
Beatriz Castillo-Téllez ◽  
Juan Carlos Ovando-Sierra ◽  
Luz María Hernández-Cruz
Keyword(s):  
Medicinal Plants ◽  
Forced Convection ◽  
Rural Areas ◽  
Color Change ◽  
Drying Process ◽  
Scientific Medicine ◽  
Drying Time ◽  
Bacterial Proliferation ◽  
Wide Range ◽  
Very High

For millennia, humans have used hundreds of medicinal plants to treat diseases. Currently, many species with important characteristics are known to alleviate a wide range of health problems, mainly in rural areas, where the use of these resources is very high, even replacing scientific medicine almost completely. This paper presents the dehydration of medicinal plants that are grown in the State of Campeche through direct and indirect solar technologies in order to evaluate the influence of air flow and temperature on the color of the final product through the L* a* scale. b*, analyzing the activity of water and humidity during the drying process. The experimental results showed that the direct solar dryer with forced convection presents a little significant color change in a drying time of 400 min on average, guaranteeing the null bacterial proliferation and reaching a final humidity between 9 % and 11 %.

Experimental Investigation on the Heat Transfer of a Portable Forced-Convection Solar Air Heater

2010 ◽  
Author(s):  
Mohammad Fakoor Pakdaman ◽  
Pejman Zohorian Izadi ◽  
Mohammad Javadinia Azari ◽  
Amir Lashkari
Keyword(s):  
Forced Convection ◽  
Air Flow ◽  
Bottom Plate ◽  
Solar Air Heater ◽  
Air Flow Rate ◽  
Flow Conditions ◽  
Maximum Enhancement ◽  
Air Heater ◽  
Weather Changes ◽  
Plate Absorber

A cross-corrugated portable forced-convection solar air heater has been designed, fabricated, and developed. A wavelike bottom plate has been positioned crosswise to the air flow while rectangular baffles have been attached to the flat-plate absorber. The relative corrugation height, (e/Dh) ranges between 0.24 and 0.4, and relative baffles distance (l/L) varies between 0.21 and 0.48. The air flow rate in the heater duct has been varied in the range of 0.001 kgs−1 to 0.01kgs−1 (Reynolds number ranges from 350 to 3500), while other thermal specifications such as inlet, outlet, and plate temperatures have varied due to weather changes. Results of this study have been compared with those related to smooth ducts and other literatures, and the maximum enhancement in Nusselt number is observed to be approximately five times of that of the smooth duct under similar flow conditions. Finally, thermal efficiency of the device for different case studies has been determined and compared with other researches.

Evaluation of the influence of ambient air temperature and air velocity on mortar cement durability using a forced convection solar dryer

2021 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Younes Bahammou ◽  
Mounir Kouhila ◽  
Haytem Moussaoui ◽  
Hamza Lamsyehe ◽  
Zakaria Tagnamas ◽  
...  
Keyword(s):  
Environmental Factors ◽  
Forced Convection ◽  
Air Temperature ◽  
Building Materials ◽  
Ambient Air ◽  
Physical Significance ◽  
Drying Process ◽  
Air Velocity ◽  
Content Type ◽  
Ambient Air Temperature

PurposeThis work aims to study the hydrothermal behavior of mortar cement toward certain environmental factors (ambient air temperature and air velocity) based on its drying kinetics data. The objective is to provide a better understanding and controlling the stability of mortar structures, which integrate the sorption phenomenon, drying process, air pressure and intrinsic characteristics. This leads to predict the comportment of mortar structures in relation with main environmental factors and minimize the risk of cracking mortar structures at an early age.Design/methodology/approachThermokinetic study was carried out in natural and forced convection solar drying at three temperatures 20, 30 and 40°C and three air velocities (1, 3 and 5 m.s-1). The empirical and semiempirical models tested successfully describe the drying kinetics of mortar. These models simulate the drying process of water absorbed by capillarity, which is the most common humidity transfer mechanism in building materials and contain parameters with physical significance, which integrate the effect of several environmental factors and intrinsic characteristics of mortar structures.FindingsThe models simulate the drying process of water absorbed by capillarity, which is the most common humidity transfer mechanism in building materials and contain parameters with physical significance, which integrate the effect of several environmental factors and intrinsic characteristics of mortar structures. The average activation energy obtained expressed the temperature effect on the mortar diffusivity. The drying constant and the diffusion coefficient can be used to predict the influence of these environmental factors on the drying behavior of various building materials and therefore on their durability.Originality/valueEvaluation of the effect of several environmental factors and intrinsic characteristics of mortar structures on their durability.

Quality Assessment and Mathematical Modeling of Hot-Air Convective Drying of Persimmon (Diospyros kaki L.) Fruit

2017 ◽  
Vol 13 (7) ◽  
Author(s):  
Claudia Giovagnoli-Vicuña ◽  
Nelson O. Moraga ◽  
Vilbett Briones-Labarca ◽  
Pablo Pacheco-Pérez
Keyword(s):  
Quality Parameters ◽  
Time Function ◽  
Convective Drying ◽  
Diospyros Kaki ◽  
Drying Process ◽  
Temperature Function ◽  
Persimmon Fruit ◽  
Hot Air ◽  
Volume Method ◽  
Good Agreement

Abstract The influence of drying on the color, porosity, shrinkage and moisture of persimmon fruit during convective drying was determined by computer vision. The experiments were performed with persimmon fruit that were cut into slab 20 × 20 mm, which were arranged into a bigger slab, 60 × 60 mm. Drying process was carried out at 60 °C. Noticeable changes in quality parameters (color, porosity and shrinkage) could be observed during the drying process, where the central region of the sample evidenced less changes. Persimmon’s physical properties were experimentally obtained as the temperature function and heat and mass convective coefficients were adjusted as a time function. A numerical simulation using the Finite Volume Method allowed to describe the evolution of temperature and moisture content distributions during drying. The numerical and experimental results of temperature and moisture during persimmon drying were found to be in a good agreement.

scholarly journals Study of the drying kinetics of the malt bagasse in a pneumatic transporter

2020 ◽  
pp. 14-14
Author(s):  
Bruna Costa ◽  
Carolina Coelho ◽  
Cássia Souza ◽  
Gabriela Duarte ◽  
Maria Pinto ◽  
...  
Keyword(s):  
Statistical Tests ◽  
Air Flow ◽  
Average Energy ◽  
Moisture Diffusivity ◽  
Pneumatic Transport ◽  
Drying Process ◽  
Brewing Industry ◽  
Transport Costs ◽  
Drying Kinetic ◽  
Kinetics Of

Malt bagasse is a by-product of the brewing industry that has high moisture making it very unstable and susceptible to fast microbial deterioration. This work evaluated drying kinetic models of malt bagasse during pneumatic transport with air flow at 30, 45 and 60?C and layout of 4.5 and 7.0 m. The results showed that the decrease of moisture from malt bagasse was favored at higher air temperature due to the higher diffusion coefficient. In the ranges measured, the values of the effective moisture diffusivity and heat transfer coefficient were obtained between 2.05?10?10 to 12.74?10?10 m2/s and 175 to 363 W/m2K, respectively. Average energy for liquid diffusion in the malt bagasse drying process was 44.30 kJ/mol. Pneumatic transport with air flow at 60?C and layout of 7.0 m reached rapidly the final moisture of 12% (w.b), which it may reduce transport costs and allow long periods of stable storage for malt bagasse. The statistical tests results showed that the experimental datas presented excellent fit using the Modified Henderson-Pabis model, in the temperature range for both layouts.

Optimization of Drying Kinetics and Quality Parameters of Broccoli Florets

2011 ◽  
Vol 7 (2) ◽  
Author(s):  
Andrea V Mahn ◽  
Paola Antoine ◽  
Alejandro Reyes
Keyword(s):  
Antioxidant Activity ◽  
Air Temperature ◽  
Flow Rate ◽  
Air Flow ◽  
Radical Scavenging ◽  
Particle Diameter ◽  
Drying Kinetics ◽  
Convective Drying ◽  
Air Flow Rate ◽  
Drying Time

Drying kinetics of broccoli florets in a tunnel dryer was studied. Effective moisture diffusivity (Deff) and activation energy for moisture diffusion (E0) were estimated. The effect of air temperature, air flow rate and particle size on antioxidant capacity, greenness and texture were calculated through a 23 factorial design. Air flow rate and temperature significantly affected drying time. Deff fluctuated between 2.82 x 10-10 and 2.00 x 10-9 (m2/s), and E0 was around 42 KJ/mol, agreeing with values reported in literature. The maximum antioxidant activity was obtained at 60°C, air flow rate of 4 m/s and 1.5 cm particle diameter, resulting in a 70 percent reduction in free radical scavenging ability and a 29 percent increase in total reductive capability. Air temperature had significant effect on greenness, and air flow rate significantly affected texture. The optimization of convective drying of broccoli allows maximizing antioxidant activity and minimizing cost by saving energy and time.

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