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Dr Chandan Kumar

Queensland University of Technology, Engineering, Post-Doc

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I am a motivated, output-driven and committed Mechanical Engineer with more than 5 years experience in industrial and academic projects. With my strong academic background, quality of work, knowledge, skill and original ideas, I am confident about my professional expertise that I can contribute to any organization.
Key Skills:
-Mechanical design and testing (using Solidworks, AutoCAD)
-Mathematical modeling and simulation ( COMSOL Multiphysics)
-Power plant operation and maintenance
-Improving Energy efficiency and product quality during Agricultural product drying
-Heat and mass transfer analysis and modeling during drying
-Expert in sensing and controlling temperature, relative humidity, and flow

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Papers by Dr Chandan Kumar

Multiphase transfer model for intermittent microwave-convective drying of food: Considering shrinkage and pore evolution

Intermittent microwave convective (IMCD) drying is an advanced drying technology that improves bo... more Intermittent microwave convective (IMCD) drying is an advanced drying technology that improves both energy efficiency and food quality during drying. Although many experimental studies on IMCD have been conducted, there is no complete multiphase porous media model describing the physics of the process available in the literature. A multiphase porous media model considering liquid water, gases and the solid matrix of food during drying can provide in-depth understanding of IMCD process. Currently there is no IMCD model that have taken shrinkage and pore evolution during drying into consideration. In this study, first a multiphase porous media model with shrinkage (IMCD2) has been developed for IMCD. Then the model has been compared with IMCD model without shrinkage (IMCD1). Simulated temperature , moisture content, density, porosity from IMCD2 are then validated against experimental data. The profile of vapour pressures and evaporation during IMCD are also presented and discussed.

Preliminary investigation of the flow distribution in an innovative intermittent convective microwave dryer (IMCD

Intermittent Microwave Convection Drying (IMCD) is an innovative concept that has the potential t... more Intermittent Microwave Convection Drying (IMCD) is an innovative concept that has the potential to reduce drying time and improve both energy efficiency and product quality. However very few studies on flow or temperature distributions on IMCD can be found in the literature. In this study, an innovative U shaped continuous flow IMCD has been proposed. In order to take full advantage of the IMCD technology, a uniform airflow distribution in the drying chamber is critical. Uneven airflow in the drying chamber significantly deteriorate the food quality and energy efficiency and increase the drying time. This research investigates the flow distribution in the proposed U shaped IMCD using computational fluid dynamics (CFD). Effects of varying inlet air velocity on the airflow distribution were investigated. The geometry, mesh and turbulence model were kept constant throughout the investigation. COMSOL Multiphysics software alongside a SST k-turbulence model was utilised. The investigation revealed that the distribution of the U shaped geometry minimises the 'dead flow' regions compared to rectangular shaped geometry. However, two small 'dead zones' were still found in U shaped geometry. This study further investigates how these dead zones can be minimised by changing the location of inlets and outlets.

Multiphase porous media modelling: A novel approach to predicting food processing performance

The development of a physics-based model of food processing is essential to improve the quality o... more The development of a physics-based model of food processing is essential to improve the quality of processed food and optimize energy consumption. Food materials, particularly plant-based food materials, are complex in nature as they are porous and have hygroscopic properties. A multiphase porous media model for simultaneous heat and mass transfer can provide a realistic understanding of transport processes and thus can help to optimize energy consumption and improve food quality. Although the development of a multiphase porous media model for food processing is a challenging task because of its complexity, many researchers have attempted it. The primary aim of this paper is to present a comprehensive review of the multiphase models available in the literature for different methods of food processing, such as drying, frying, cooking, baking, heating, and roasting. A critical review of the parameters that should be considered for multiphase modelling is presented which includes input parameters, material properties, simulation techniques and the hypotheses. A discussion on the general trends in outcomes, such as moisture saturation, temperature profile, pressure variation, and evaporation patterns, is also presented. The paper concludes by considering key issues in the existing multiphase models and future directions for development of multiphase models.

Effect of Cell Wall Properties on Porosity and Shrinkage of Dried Apple

Water removal during drying depends on the pathway of water migration from food materials. Moreov... more Water removal during drying depends on the pathway of water migration from food materials. Moreover, the water removal rate also depends on the characteristics of the cell wall of plant tissue. In this study, the influence of cell wall properties on porosity and shrinkage of dried product was investigated. Cell wall stiffness depends on a complex combination of plant cell microstructure, composition of food materials and the water-holding capacity of the cell. In this work, a preliminary investigation of the cell wall properties of apple was conducted in order to predict changes of porosity and shrinkage during drying. Cell wall characteristics of two types of apple (Granny Smith and Red Delicious) were investigated under convective drying to correlate with porosity and shrinkage. A scanning electron microscope (SEM), 2kN Intron, pycnometer and ImageJ software were used in order to measure and analyse cell characteristics, water holding capacity of cell walls, porosity and shrinkage. The cell firmness of the Red Delicious apple was found to be higher than for Granny Smith apples. A remarkable relationship was observed between cell wall characteristics when compare with heat and mass transfer characteristics. It was also found that the evolution of porosity and shrinkage are noticeably influenced by the nature of the cell wall during convective drying. This study has revealed a better understanding of porosity and the shrinkage of dried food at microscopy (cell) level, and will provide better insights to attain energy-effective drying processes and improved quality of dried foods.

A micro-level investigation of the solid displacement method for porosity determination of dried food

Porosity is one of the key parameters of the macroscopic structure of porous media, generally def... more Porosity is one of the key parameters of the macroscopic structure of porous media, generally defined as the ratio of the free spaces occupied (by the volume of air) within the material to the total volume of the material. Porosity is determined by measuring skeletal volume and the envelope volume. Solid displacement method is one of the inexpensive and easy methods to determine the envelope volume of a sample with an irregular shape. In this method, glass beads are used as a solid displacement media due to their uniform size, compactness and fluidity properties. The smaller size of the glass beads means that they enter into the open pores that have a larger diameter than the glass beads. Although extensive research has been carried out on porosity determination using displacement method, no study exists which adequately reports the micro-level observation of the sample during measurement. This study set out with the aim of assessing the accuracy of solid displacement method of bulk density measurement of dried foods by micro-level observation. Solid displacement method of porosity determination was conducted using a cylindrical vial (cylindrical plastic container) and 57 lm glass beads in order to measure the bulk density of apple slices at different moisture contents. A scanning electron microscope (SEM), a profilome-ter and Image J software were used to investigate the penetration of glass beads into the surface pores during the determination of the porosity of dried food. A helium pycnometer was used to measure the particle density of the sample. Results show that a significant number of pores were large enough to allow the glass beads to enter into the pores, thereby causing some erroneous results. It was also found that coating the dried sample with the appropriate coating material prior to measurement can resolve this problem.

Food structure: Its formation and relationships with other properties

Food materials are complex in nature as it has heterogeneous, amorphous, hygroscopic and porous p... more Food materials are complex in nature as it has heterogeneous, amorphous, hygroscopic and porous properties. During processing, microstructure of food materials changes which significantly affects other properties of food. An appropriate understanding of the microstructure of the raw food material and its evolution during processing is critical in order to understand and accurately describe dehydration processes and quality anticipation. This review critically assesses the factors that influence the modification of microstructure in the course of drying of fruits and vegetables. The effect of simultaneous heat and mass transfer on microstructure in various drying methods is investigated. Effects of changes in microstructure on other functional properties of dried foods are discussed. After an extensive review of the literature, it is found that development of food structure significantly depends on fresh food properties and process parameters. Also, modification of microstructure influences the other properties of final product. An enhanced understanding of the relationships between food microstructure, drying process parameters and final product quality will facilitate the energy efficient optimum design of the food processor in order to achieve high-quality food. KEYWORDS Microstructure; drying; heat and mass transfer; food quality; drying parameters CONTACT M. A. Karim

Critical Reviews in Food Science and Nutrition Food structure: Its formation and relationships with other properties

Food materials are complex in nature as it has heterogeneous, amorphous, hygroscopic and porous p... more Food materials are complex in nature as it has heterogeneous, amorphous, hygroscopic and porous properties. During processing, microstructure of food materials changes which significantly affects other properties of food. An appropriate understanding of the microstructure of the raw food material and its evolution during processing is critical in order to understand and accurately describe dehydration processes and quality anticipation. This review critically assesses the factors that influence the modification of microstructure in the course of drying of fruits and vegetables. The effect of simultaneous heat and mass transfer on microstructure in various drying methods is investigated. Effects of changes in microstructure on other functional properties of dried foods are discussed. After an extensive review of the literature, it is found that development of food structure significantly depends on fresh food properties and process parameters. Also, modification of microstructure influences the other properties of final product. An enhanced understanding of the relationships between food microstructure, drying process parameters and final product quality will facilitate the energy efficient optimum design of the food processor in order to achieve high-quality food. KEYWORDS Microstructure; drying; heat and mass transfer; food quality; drying parameters CONTACT M. A. Karim

Effective Diffusivity and Evaporative Cooling in Convective Drying of Food Material

This article presents mathematical models to simulate coupled heat and mass transfer during conve... more This article presents mathematical models to simulate coupled heat and mass transfer during convective drying of food materials using three different effective diffusivities: shrinkage dependent, temperature dependent, and the average of those two. Engineering simulation software COMSOL Multiphysics was utilized to simulate the model in 2D and 3D. The simulation results were compared with experimental data. It is found that the temperature-dependent effective diffusivity model predicts the moisture content more accurately at the initial stage of the drying, whereas the shrinkage-dependent effective diffusivity model is better for the final stage of the drying. The model with shrinkage-dependent effective diffusivity shows evaporative cooling phenomena at the initial stage of drying. This phenomenon was investigated and explained. Three-dimensional temperature and moisture profiles show that even when the surface is dry, the inside of the sample may still contain a large amount of moisture. Therefore, the drying process should be dealt with carefully; otherwise, microbial spoilage may start from the center of the dried food. A parametric investigation was conducted after validation of the model.

Multiphase porous media model for intermittent microwave convective drying (IMCD) of food

Intermittent microwave convective (IMCD) drying is an advanced drying technology that improves bo... more Intermittent microwave convective (IMCD) drying is an advanced drying technology that improves both energy efficiency and food quality during the drying of food materials. Despite numerous experimental studies available for IMCD, there is no complete multiphase porous media model available to describe the process. A multiphase porous media model considering liquid water, gases and the solid matrix inside the food during drying can provide in depth understanding of IMCD. In this article, firstly a multiphase porous media model was developed for IMCD. Then the model is validated against experimental data by comparing moisture content and temperature distributions after each heating and tempering periods. The profile of vapour pressures and evaporation during IMCD are presented and discussed. The relative contribution of water and vapour fluxes due to gas pressure and diffusion demonstrated that the fluxes due are relatively higher in IMCD compared to convection drying and this makes the IMCD faster.

Mathematical model for intermittent microwave convective drying of food materials

Intermittent microwave convective drying (IMCD) is an advanced technology that improves both ener... more Intermittent microwave convective drying (IMCD) is an advanced technology that improves both
energy efficiency and food quality in drying. Modeling of IMCD is essential to understand the physics
of this advanced drying process and to optimize the microwave power level and intermittency
during drying. However, there is still a lack of modeling studies dedicated to IMCD. In this study, a
mathematical model for IMCD was developed and validated with experimental data. The model
showed that the interior temperature of the material was higher than the surface in IMCD, and that
the temperatures fluctuated and redistributed due to the intermittency of the microwave power.
This redistribution of temperature could significantly contribute to the improvement of product
quality during IMCD. Limitations when using Lambert’s law for microwave heat generation were
identified and discussed.

Temperature redistribution modelling during intermittent microwave convective heating

Microwave power is used for heating and drying processes because of its faster and volumetric hea... more Microwave power is used for heating and drying processes because of its faster and volumetric heating capability. Nonuniformtemperature
distributionduring microwaveapplication is a major drawbackof these processes. Intermittent application of
microwavepotentially reduces the impact of non-uniformity and improves energy efficiencyby redistributing the
temperature.However, temperature re-distribution during intermittent microwave heating has not been investigated adequately.
Consequently, in this study, a coupled electromagnetic with heat and mass transfer model was developed using the finite element
methodembedded in COMSOL-Multyphysics software. Particularly, the temperature redistribution due to intermittent heating
was investigated. A series of experiments were performed to validate the simulation. The test specimen was an apple and the
temperature distribution was closely monitored by a TIC (Thermal Imaging Camera). The simulated temperature profilematched
closely with thermal images obtained from experiments.

Heat and mass transfer modeling of the osmo-convective drying of yacon roots (Smallanthus sonchifolius)

Osmotic treatments are often applied prior to convective drying of foods to impart sensory appeal... more Osmotic treatments are often applied prior to convective drying of foods to impart sensory appeal aspects. During this process a multicomponent mass flow, composed mainly of water and osmotic agent, takes place. In this work, a heat and mass transfer model for the osmo-convective drying of yacon was developed and solved by the Finite Element Method using COMSOL Multiphysics®, considering a 2-D axisymmetric geometry and moisture dependent thermophysical properties. Yacon slices were osmotically dehydrated for 2 h in a solution of sucralose and then dried in a tray dryer for 3 h. The model was validated by experimental data of temperature, moisture content and sucralose uptake (R2 > 0.90).

Intermittent drying of food products: A critical review

Drying is very energy intensive process and consumes about 20–25% of the energy used by food proc... more Drying is very energy intensive process and consumes about 20–25% of the energy used by food processing industry. The energy efficiency of the process and quality of dried product are two key factors in food drying. Global energy crisis and demand for quality dried food further challenge researchers to explore innovative techniques in food drying to address these issues. Intermittent drying is considered one of the promising solutions for improving energy efficiency and product quality without increasing the capital cost of the drier. Intermittent drying has already received much attention. However, a comprehensive review of recent progresses and overall assessment of energy efficiency and product quality in intermittent drying is lacking. The objective of this article is to discuss, analyze and evaluate the recent advances in intermittent drying research with energy efficiency and product quality as standpoint. Current available modelling techniques for intermittent drying are reviewed and their merits and demerits are analyzed. Moreover, intermittent application of ultrasound, infrared (IR) and microwave in combined drying technology have been reviewed and discussed. In this review article the gaps in the current literature are highlighted, some important future scopes for theoretical and experimental studies are identified and the direction of further research is suggested.

Effect of moisture and temperature distribution on dried food microstucture and porosity

Multiphysics modelling of convective drying of food materials

by Dr Chandan Kumar and Dr. Suvash C Saha (ড. সুভাষ সাহা)

Multiphase transfer model for intermittent microwave-convective drying of food: Considering shrinkage and pore evolution

Intermittent microwave convective (IMCD) drying is an advanced drying technology that improves bo... more Intermittent microwave convective (IMCD) drying is an advanced drying technology that improves both energy efficiency and food quality during drying. Although many experimental studies on IMCD have been conducted, there is no complete multiphase porous media model describing the physics of the process available in the literature. A multiphase porous media model considering liquid water, gases and the solid matrix of food during drying can provide in-depth understanding of IMCD process. Currently there is no IMCD model that have taken shrinkage and pore evolution during drying into consideration. In this study, first a multiphase porous media model with shrinkage (IMCD2) has been developed for IMCD. Then the model has been compared with IMCD model without shrinkage (IMCD1). Simulated temperature , moisture content, density, porosity from IMCD2 are then validated against experimental data. The profile of vapour pressures and evaporation during IMCD are also presented and discussed.

Preliminary investigation of the flow distribution in an innovative intermittent convective microwave dryer (IMCD

Intermittent Microwave Convection Drying (IMCD) is an innovative concept that has the potential t... more Intermittent Microwave Convection Drying (IMCD) is an innovative concept that has the potential to reduce drying time and improve both energy efficiency and product quality. However very few studies on flow or temperature distributions on IMCD can be found in the literature. In this study, an innovative U shaped continuous flow IMCD has been proposed. In order to take full advantage of the IMCD technology, a uniform airflow distribution in the drying chamber is critical. Uneven airflow in the drying chamber significantly deteriorate the food quality and energy efficiency and increase the drying time. This research investigates the flow distribution in the proposed U shaped IMCD using computational fluid dynamics (CFD). Effects of varying inlet air velocity on the airflow distribution were investigated. The geometry, mesh and turbulence model were kept constant throughout the investigation. COMSOL Multiphysics software alongside a SST k-turbulence model was utilised. The investigation revealed that the distribution of the U shaped geometry minimises the 'dead flow' regions compared to rectangular shaped geometry. However, two small 'dead zones' were still found in U shaped geometry. This study further investigates how these dead zones can be minimised by changing the location of inlets and outlets.

Multiphase porous media modelling: A novel approach to predicting food processing performance

The development of a physics-based model of food processing is essential to improve the quality o... more The development of a physics-based model of food processing is essential to improve the quality of processed food and optimize energy consumption. Food materials, particularly plant-based food materials, are complex in nature as they are porous and have hygroscopic properties. A multiphase porous media model for simultaneous heat and mass transfer can provide a realistic understanding of transport processes and thus can help to optimize energy consumption and improve food quality. Although the development of a multiphase porous media model for food processing is a challenging task because of its complexity, many researchers have attempted it. The primary aim of this paper is to present a comprehensive review of the multiphase models available in the literature for different methods of food processing, such as drying, frying, cooking, baking, heating, and roasting. A critical review of the parameters that should be considered for multiphase modelling is presented which includes input parameters, material properties, simulation techniques and the hypotheses. A discussion on the general trends in outcomes, such as moisture saturation, temperature profile, pressure variation, and evaporation patterns, is also presented. The paper concludes by considering key issues in the existing multiphase models and future directions for development of multiphase models.

Effect of Cell Wall Properties on Porosity and Shrinkage of Dried Apple

Water removal during drying depends on the pathway of water migration from food materials. Moreov... more Water removal during drying depends on the pathway of water migration from food materials. Moreover, the water removal rate also depends on the characteristics of the cell wall of plant tissue. In this study, the influence of cell wall properties on porosity and shrinkage of dried product was investigated. Cell wall stiffness depends on a complex combination of plant cell microstructure, composition of food materials and the water-holding capacity of the cell. In this work, a preliminary investigation of the cell wall properties of apple was conducted in order to predict changes of porosity and shrinkage during drying. Cell wall characteristics of two types of apple (Granny Smith and Red Delicious) were investigated under convective drying to correlate with porosity and shrinkage. A scanning electron microscope (SEM), 2kN Intron, pycnometer and ImageJ software were used in order to measure and analyse cell characteristics, water holding capacity of cell walls, porosity and shrinkage. The cell firmness of the Red Delicious apple was found to be higher than for Granny Smith apples. A remarkable relationship was observed between cell wall characteristics when compare with heat and mass transfer characteristics. It was also found that the evolution of porosity and shrinkage are noticeably influenced by the nature of the cell wall during convective drying. This study has revealed a better understanding of porosity and the shrinkage of dried food at microscopy (cell) level, and will provide better insights to attain energy-effective drying processes and improved quality of dried foods.

A micro-level investigation of the solid displacement method for porosity determination of dried food

Porosity is one of the key parameters of the macroscopic structure of porous media, generally def... more Porosity is one of the key parameters of the macroscopic structure of porous media, generally defined as the ratio of the free spaces occupied (by the volume of air) within the material to the total volume of the material. Porosity is determined by measuring skeletal volume and the envelope volume. Solid displacement method is one of the inexpensive and easy methods to determine the envelope volume of a sample with an irregular shape. In this method, glass beads are used as a solid displacement media due to their uniform size, compactness and fluidity properties. The smaller size of the glass beads means that they enter into the open pores that have a larger diameter than the glass beads. Although extensive research has been carried out on porosity determination using displacement method, no study exists which adequately reports the micro-level observation of the sample during measurement. This study set out with the aim of assessing the accuracy of solid displacement method of bulk density measurement of dried foods by micro-level observation. Solid displacement method of porosity determination was conducted using a cylindrical vial (cylindrical plastic container) and 57 lm glass beads in order to measure the bulk density of apple slices at different moisture contents. A scanning electron microscope (SEM), a profilome-ter and Image J software were used to investigate the penetration of glass beads into the surface pores during the determination of the porosity of dried food. A helium pycnometer was used to measure the particle density of the sample. Results show that a significant number of pores were large enough to allow the glass beads to enter into the pores, thereby causing some erroneous results. It was also found that coating the dried sample with the appropriate coating material prior to measurement can resolve this problem.

Food structure: Its formation and relationships with other properties

Food materials are complex in nature as it has heterogeneous, amorphous, hygroscopic and porous p... more Food materials are complex in nature as it has heterogeneous, amorphous, hygroscopic and porous properties. During processing, microstructure of food materials changes which significantly affects other properties of food. An appropriate understanding of the microstructure of the raw food material and its evolution during processing is critical in order to understand and accurately describe dehydration processes and quality anticipation. This review critically assesses the factors that influence the modification of microstructure in the course of drying of fruits and vegetables. The effect of simultaneous heat and mass transfer on microstructure in various drying methods is investigated. Effects of changes in microstructure on other functional properties of dried foods are discussed. After an extensive review of the literature, it is found that development of food structure significantly depends on fresh food properties and process parameters. Also, modification of microstructure influences the other properties of final product. An enhanced understanding of the relationships between food microstructure, drying process parameters and final product quality will facilitate the energy efficient optimum design of the food processor in order to achieve high-quality food. KEYWORDS Microstructure; drying; heat and mass transfer; food quality; drying parameters CONTACT M. A. Karim

Critical Reviews in Food Science and Nutrition Food structure: Its formation and relationships with other properties

Food materials are complex in nature as it has heterogeneous, amorphous, hygroscopic and porous p... more Food materials are complex in nature as it has heterogeneous, amorphous, hygroscopic and porous properties. During processing, microstructure of food materials changes which significantly affects other properties of food. An appropriate understanding of the microstructure of the raw food material and its evolution during processing is critical in order to understand and accurately describe dehydration processes and quality anticipation. This review critically assesses the factors that influence the modification of microstructure in the course of drying of fruits and vegetables. The effect of simultaneous heat and mass transfer on microstructure in various drying methods is investigated. Effects of changes in microstructure on other functional properties of dried foods are discussed. After an extensive review of the literature, it is found that development of food structure significantly depends on fresh food properties and process parameters. Also, modification of microstructure influences the other properties of final product. An enhanced understanding of the relationships between food microstructure, drying process parameters and final product quality will facilitate the energy efficient optimum design of the food processor in order to achieve high-quality food. KEYWORDS Microstructure; drying; heat and mass transfer; food quality; drying parameters CONTACT M. A. Karim

Effective Diffusivity and Evaporative Cooling in Convective Drying of Food Material

This article presents mathematical models to simulate coupled heat and mass transfer during conve... more This article presents mathematical models to simulate coupled heat and mass transfer during convective drying of food materials using three different effective diffusivities: shrinkage dependent, temperature dependent, and the average of those two. Engineering simulation software COMSOL Multiphysics was utilized to simulate the model in 2D and 3D. The simulation results were compared with experimental data. It is found that the temperature-dependent effective diffusivity model predicts the moisture content more accurately at the initial stage of the drying, whereas the shrinkage-dependent effective diffusivity model is better for the final stage of the drying. The model with shrinkage-dependent effective diffusivity shows evaporative cooling phenomena at the initial stage of drying. This phenomenon was investigated and explained. Three-dimensional temperature and moisture profiles show that even when the surface is dry, the inside of the sample may still contain a large amount of moisture. Therefore, the drying process should be dealt with carefully; otherwise, microbial spoilage may start from the center of the dried food. A parametric investigation was conducted after validation of the model.

Multiphase porous media model for intermittent microwave convective drying (IMCD) of food

Intermittent microwave convective (IMCD) drying is an advanced drying technology that improves bo... more Intermittent microwave convective (IMCD) drying is an advanced drying technology that improves both energy efficiency and food quality during the drying of food materials. Despite numerous experimental studies available for IMCD, there is no complete multiphase porous media model available to describe the process. A multiphase porous media model considering liquid water, gases and the solid matrix inside the food during drying can provide in depth understanding of IMCD. In this article, firstly a multiphase porous media model was developed for IMCD. Then the model is validated against experimental data by comparing moisture content and temperature distributions after each heating and tempering periods. The profile of vapour pressures and evaporation during IMCD are presented and discussed. The relative contribution of water and vapour fluxes due to gas pressure and diffusion demonstrated that the fluxes due are relatively higher in IMCD compared to convection drying and this makes the IMCD faster.

Mathematical model for intermittent microwave convective drying of food materials

Intermittent microwave convective drying (IMCD) is an advanced technology that improves both ener... more Intermittent microwave convective drying (IMCD) is an advanced technology that improves both
energy efficiency and food quality in drying. Modeling of IMCD is essential to understand the physics
of this advanced drying process and to optimize the microwave power level and intermittency
during drying. However, there is still a lack of modeling studies dedicated to IMCD. In this study, a
mathematical model for IMCD was developed and validated with experimental data. The model
showed that the interior temperature of the material was higher than the surface in IMCD, and that
the temperatures fluctuated and redistributed due to the intermittency of the microwave power.
This redistribution of temperature could significantly contribute to the improvement of product
quality during IMCD. Limitations when using Lambert’s law for microwave heat generation were
identified and discussed.

Temperature redistribution modelling during intermittent microwave convective heating

Microwave power is used for heating and drying processes because of its faster and volumetric hea... more Microwave power is used for heating and drying processes because of its faster and volumetric heating capability. Nonuniformtemperature
distributionduring microwaveapplication is a major drawbackof these processes. Intermittent application of
microwavepotentially reduces the impact of non-uniformity and improves energy efficiencyby redistributing the
temperature.However, temperature re-distribution during intermittent microwave heating has not been investigated adequately.
Consequently, in this study, a coupled electromagnetic with heat and mass transfer model was developed using the finite element
methodembedded in COMSOL-Multyphysics software. Particularly, the temperature redistribution due to intermittent heating
was investigated. A series of experiments were performed to validate the simulation. The test specimen was an apple and the
temperature distribution was closely monitored by a TIC (Thermal Imaging Camera). The simulated temperature profilematched
closely with thermal images obtained from experiments.

Heat and mass transfer modeling of the osmo-convective drying of yacon roots (Smallanthus sonchifolius)

Osmotic treatments are often applied prior to convective drying of foods to impart sensory appeal... more Osmotic treatments are often applied prior to convective drying of foods to impart sensory appeal aspects. During this process a multicomponent mass flow, composed mainly of water and osmotic agent, takes place. In this work, a heat and mass transfer model for the osmo-convective drying of yacon was developed and solved by the Finite Element Method using COMSOL Multiphysics®, considering a 2-D axisymmetric geometry and moisture dependent thermophysical properties. Yacon slices were osmotically dehydrated for 2 h in a solution of sucralose and then dried in a tray dryer for 3 h. The model was validated by experimental data of temperature, moisture content and sucralose uptake (R2 > 0.90).

Intermittent drying of food products: A critical review

Drying is very energy intensive process and consumes about 20–25% of the energy used by food proc... more Drying is very energy intensive process and consumes about 20–25% of the energy used by food processing industry. The energy efficiency of the process and quality of dried product are two key factors in food drying. Global energy crisis and demand for quality dried food further challenge researchers to explore innovative techniques in food drying to address these issues. Intermittent drying is considered one of the promising solutions for improving energy efficiency and product quality without increasing the capital cost of the drier. Intermittent drying has already received much attention. However, a comprehensive review of recent progresses and overall assessment of energy efficiency and product quality in intermittent drying is lacking. The objective of this article is to discuss, analyze and evaluate the recent advances in intermittent drying research with energy efficiency and product quality as standpoint. Current available modelling techniques for intermittent drying are reviewed and their merits and demerits are analyzed. Moreover, intermittent application of ultrasound, infrared (IR) and microwave in combined drying technology have been reviewed and discussed. In this review article the gaps in the current literature are highlighted, some important future scopes for theoretical and experimental studies are identified and the direction of further research is suggested.

Effect of moisture and temperature distribution on dried food microstucture and porosity

Multiphysics modelling of convective drying of food materials

by Dr Chandan Kumar and Dr. Suvash C Saha (ড. সুভাষ সাহা)