Papers by Odilio Alves-Filho
Drying Technology, Sep 17, 2002
ABSTRACT There is an increased demand for convenient foods including ready-to-eat and instant pro... more ABSTRACT There is an increased demand for convenient foods including ready-to-eat and instant products. These products are desired with minimum concentration of synthetic chemicals. This creates challenges for the food industry and dryers manufactures to develop new technologies to process difficult-sensitive materials and to supply final products with high quality and improved properties. Fruits and vegetables are mainly composed of water, carbohydrates, proteins and lipids. Due to modification of chemical and physical bonds the compounds the material becomes viscous and sticky during processing. Conventional dryers have limitations in handling such sensitive materials. Heat pump dryers have been applied in the production of a diversity of ready-to-eat foods and dried instant products for the last five years at SINTEF-NTNU. Besides being energetically efficient and environmentally friendly, the heat pump drying technology provides a wide range of drying conditions as required to produce powders with improved characteristics. This work describes the new technologies and processing line for the production of instant foods as well as the measurements on the properties and quality attributes for raw, intermediate and final instant products.
This work has focused on the development of atmospheric freeze and non-freeze drying applying a h... more This work has focused on the development of atmospheric freeze and non-freeze drying applying a heat pump system as an environmental friendly and economically preferable technology compare to vacuum freeze drying. The main reason of the research is a lack of knowledge and information in the literature about the atmospheric heat pump drying, while the more common vacuum freeze drying process is widely covered.The main objective for developing atmospheric heat pump drying as a new drying technology is the desire to reduce the energy consumption compared to that of vacuum freeze drying while maintaining a high product quality.One technical solution of atmospheric freeze and non-freeze drying is combining with a heat pump system applying a new environmentally friendly natural refrigerant, such as ammonia or R717. Temperature programs make it possible to customize products for desired qualities and properties, such as color retention, instant rehydration and aroma preservation.Drying is one of the most important industrial processes, and a technology used worldwide for food processing. The vacuum freeze and high temperature drying are both well-known and extensively applied conventional technologies that have the drawback of high energy consumption. This provided the opportunity for heat pump drying development, in order to decrease operational costs while preserving the quality of the products. Heat pump drying is a relatively new technology developed at NTNU. It unifies the drying and heat pump cycles that allows energy recovery for reheating the drying air.An analysis was made on the technological aspects, product possibilities, physical properties of products, drying kinetics and modeling.This work covers the drying of green peas, applying a laboratory heat pump dryer. The drying conditions and processing time are the most important parameters for modeling and scalingup the process. Additionally, the temperature, relative humidity and residence time are essential for understanding changes in product properties, and fundamental for the designing and dimensioning of large-scale drying processes.Therefore, the various tests were done at many different temperature regimes, from -5°C to 45°C, and at varying levels of relative humidity. Some of the drying tests applied additional equipment, such as an air humidifier, infrared lamps and an oven to get the specific temperature or moisture content of the tested product. All the drying tests were performed, and each run was done in a period of three hours using a fluidized bed mode. The results on kinetics and final moisture content indicated that temperatures and relative humidity levels lead to changes in the moisture removal rates from the material as well as the quality of the product. Studies were also made to investigate the influence of drying conditions and time on product parameters such as color and water activity.This work also proposes a numerical solution for the moisture content in order to describe the drying kinetics and effective mass diffusivity. The results in this work can be useful since it reduces the number of drying experiments to be tested at a wide range of drying conditions.The proposed models have been validated by experiments with acceptable deviations. It helps in establishing the temperature and time schedule in a preliminary study on scaling up lab dryers to a pilot or commercial drying plant. This is also a good platform for further research oriented towards the unification of available laboratory data in the heat pump drying of vegetables to the overall simulation program.The coefficient of performance (COP) and specific moisture extraction rate (SMER) were calculated to characterize the energy efficiency and water removal capacity of the heat pump drying process. Ammonia or R717 was selected as the working fluid due to its thermal properties and for being an environmentally friendly refrigerant. Regarding greenhouse gases (GHGs), ammonia is a natural fluid which has zero ozone depletion potential (ODP) and zero global warming potential (GWP), that makes heat pump drying a competitive and efficient drying technology with a minimum impact on climate change.
Single layer drying tests were performed using whole English walnuts. The data were analyzed to e... more Single layer drying tests were performed using whole English walnuts. The data were analyzed to estimate apparent diffusivities for both drying and rewetting. Diffusivities were different for drying and rewetting, and depended on air temperature and initial walnut moisture. A linear relationship between diffusivity and moisture content did not fit the data well.
21<sup>st</sup> IIR International Congress of Refrigeration: Serving the Needs of Mankind., Aug 17, 2003
In the production of artificially dried ingredients in different dishes, soups and cereals we fin... more In the production of artificially dried ingredients in different dishes, soups and cereals we find today two dominating technologies, direct heated driers operated at 60 o C to 90 o C and vacuum freeze drying operated below-30 o C. Direct heated dryers have a lower production costs than vacuum freeze dryers but with a much lower quality of the dried product. Vacuum freeze dryer, on the other side, is so expensive that its use is limited. This paper presents a new technology based on heat pump drying with production costs considerably lower than vacuum freeze drying but with similar qualities of the dried product. The focus is on the design, dimensioning and operation of such heat pump dryers using a combined mode with drying temperatures below and above the product freezing point.
Drying Technology, Apr 1, 2006
Recent developments in innovative dryers and devices for pretreatment or for changing the charact... more Recent developments in innovative dryers and devices for pretreatment or for changing the characteristics of raw materials create new possibilities for drying R&D and applications. Additionally, existing dewatering equipment can be easily combined to improve overall performance and energy utilization and for better compliance with environmental issues. This work describes these new technologies and combinations with conventional processes to attain higher dryer thermal efficiency, coefficient of performance, and moisture extraction ratio. Therefore, the new technologies provide higher energy savings than conventional dryers and flexible control of the conditions for optimum moisture removal. The process stability and product quality depend on proper drying conditions, which are controlled considering the material composition and interactions with water during the process. This work describes the conventional and new technologies and possible applications as single and combined stages based upon analysis of the effects of processing conditions on dried product properties.
Heat and Mass Transfer, Jul 6, 2010
This work covers heat pump drying of protein with high quality and low cost. It consists of atmos... more This work covers heat pump drying of protein with high quality and low cost. It consists of atmospheric freeze drying to keep product quality followed by evaporation to reduce time. A sweep numerical method was applied to predict the mass transport from the porous particle to gas. The maximum deviation between predictions and mass transfer data was below 4% indicating that the method well describes mass transport during protein drying.
Chemical engineering transactions, Aug 1, 2018
Heat pump drying is a green technology with zero global warming potential and zero ozone depletio... more Heat pump drying is a green technology with zero global warming potential and zero ozone depletion potential when operating with natural fluids. A well designed heat pump dryer can be several times more energy efficient and less costly than conventional dryers. This dryer beneficially contributes to a sustainable society while providing superior products at competitive cost. It is an advanced engineered drying technology ready for implementation by modern industries wishing a return of investment while contributing to a sustainable society. This paper covers the advances in heat pump and superheated steam drying technologies. These drying processes are in the category of green technologies because they are highly effective and advantageous for the environment and climate change. Descriptions and layouts are given covering design of heat pump and steam dryers. Details are provided in their beneficial operation in single and multistage with vapor compression and drying chambers placed in series. The drying modes covered are atmospheric sublimation and evaporation for improved capacity and superior characteristics of dried materials. The future trend is heat pump drying with natural fluids and superheated steam drying complying with proper industrial practice and with regulations reducing damage to sea, soil and water as well as zeroing contribution to global warming and to climate change. These technologies have been built and extensive R&D has been done at Norwegian University of Science and Technology in Trondheim. The technology has progressed to pilot scale and industrial applications indicating a small but real contribution to a better society today and tomorrow. Lastly, this is an advanced engineered drying technology ready for implementation by modern industries wishing a return of investment while preserving the environment.
ChemEngineering, Feb 17, 2020
Drying of porous media is strictly governed by heat and mass transfer. However, contrary to the d... more Drying of porous media is strictly governed by heat and mass transfer. However, contrary to the definition that drying is simultaneous transport mechanisms of heat and mass, most past and current models either account for temperature or concentration gradient effects on drying. Even though the complexity of computations of these processes varies with area of application, in most cases, the Dufour and Soret effects are neglected. This leads to deviations and uncertainties on the assumptions and interpretations of these and other relevant effects on drying. This paper covers the theoretical methods to derive the coupled transfer effects. In addition, this work proposes and formulates relevant heat and mass transfer equations, as well as the governing equations for drying processes with Dufour and Soret effects. The application of a numerical approach to solve the equations allows for studying of the influence of these effects on the design and operation of dryers. It is shown that the Soret effect can be highly relevant on drying operations with dynamic heating operation. While for drying processes where the steady state drying process predominates, the effect is deemed negligible.
This work has focused on the development of atmospheric freeze and non-freeze drying applying a h... more This work has focused on the development of atmospheric freeze and non-freeze drying applying a heat pump system as an environmental friendly and economically preferable technology compare to vacuum freeze drying. The main reason of the research is a lack of knowledge and information in the literature about the atmospheric heat pump drying, while the more common vacuum freeze drying process is widely covered.The main objective for developing atmospheric heat pump drying as a new drying technology is the desire to reduce the energy consumption compared to that of vacuum freeze drying while maintaining a high product quality.One technical solution of atmospheric freeze and non-freeze drying is combining with a heat pump system applying a new environmentally friendly natural refrigerant, such as ammonia or R717. Temperature programs make it possible to customize products for desired qualities and properties, such as color retention, instant rehydration and aroma preservation.Drying is one of the most important industrial processes, and a technology used worldwide for food processing. The vacuum freeze and high temperature drying are both well-known and extensively applied conventional technologies that have the drawback of high energy consumption. This provided the opportunity for heat pump drying development, in order to decrease operational costs while preserving the quality of the products. Heat pump drying is a relatively new technology developed at NTNU. It unifies the drying and heat pump cycles that allows energy recovery for reheating the drying air.An analysis was made on the technological aspects, product possibilities, physical properties of products, drying kinetics and modeling.This work covers the drying of green peas, applying a laboratory heat pump dryer. The drying conditions and processing time are the most important parameters for modeling and scalingup the process. Additionally, the temperature, relative humidity and residence time are essential for understanding changes in product properties, and fundamental for the designing and dimensioning of large-scale drying processes.Therefore, the various tests were done at many different temperature regimes, from -5°C to 45°C, and at varying levels of relative humidity. Some of the drying tests applied additional equipment, such as an air humidifier, infrared lamps and an oven to get the specific temperature or moisture content of the tested product. All the drying tests were performed, and each run was done in a period of three hours using a fluidized bed mode. The results on kinetics and final moisture content indicated that temperatures and relative humidity levels lead to changes in the moisture removal rates from the material as well as the quality of the product. Studies were also made to investigate the influence of drying conditions and time on product parameters such as color and water activity.This work also proposes a numerical solution for the moisture content in order to describe the drying kinetics and effective mass diffusivity. The results in this work can be useful since it reduces the number of drying experiments to be tested at a wide range of drying conditions.The proposed models have been validated by experiments with acceptable deviations. It helps in establishing the temperature and time schedule in a preliminary study on scaling up lab dryers to a pilot or commercial drying plant. This is also a good platform for further research oriented towards the unification of available laboratory data in the heat pump drying of vegetables to the overall simulation program.The coefficient of performance (COP) and specific moisture extraction rate (SMER) were calculated to characterize the energy efficiency and water removal capacity of the heat pump drying process. Ammonia or R717 was selected as the working fluid due to its thermal properties and for being an environmentally friendly refrigerant. Regarding greenhouse gases (GHGs), ammonia is a natural fluid which has zero ozone depletion potential (ODP) and zero global warming potential (GWP), that makes heat pump drying a competitive and efficient drying technology with a minimum impact on climate change.
CRC Press eBooks, Aug 5, 2015
The paper presents new technology based on heat pump drying with production costs considerably lo... more The paper presents new technology based on heat pump drying with production costs considerably lower than vacuum freeze drying but with similar qualities of dried products. The focus is on the design, dimensioning and operation of such heat pump dryers using a combined mode with drying temperatures below and above the product freezing point. Several materials were dried in test plants, including fish products, fruits, vegetables and dairy products. The interaction between the air side of the plant and the heat pump was studied and different system solutions with ammonia as the working fluid were scrutinized. Consequences on the dryer thermal efficiency and the heat pump coefficient of performance are presented.
This work has focused on the development of atmospheric freeze and non-freeze drying applying a h... more This work has focused on the development of atmospheric freeze and non-freeze drying applying a heat pump system as an environmental friendly and economically preferable technology compare to vacuum freeze drying. The main reason of the research is a lack of knowledge and information in the literature about the atmospheric heat pump drying, while the more common vacuum freeze drying process is widely covered.The main objective for developing atmospheric heat pump drying as a new drying technology is the desire to reduce the energy consumption compared to that of vacuum freeze drying while maintaining a high product quality.One technical solution of atmospheric freeze and non-freeze drying is combining with a heat pump system applying a new environmentally friendly natural refrigerant, such as ammonia or R717. Temperature programs make it possible to customize products for desired qualities and properties, such as color retention, instant rehydration and aroma preservation.Drying is one of the most important industrial processes, and a technology used worldwide for food processing. The vacuum freeze and high temperature drying are both well-known and extensively applied conventional technologies that have the drawback of high energy consumption. This provided the opportunity for heat pump drying development, in order to decrease operational costs while preserving the quality of the products. Heat pump drying is a relatively new technology developed at NTNU. It unifies the drying and heat pump cycles that allows energy recovery for reheating the drying air.An analysis was made on the technological aspects, product possibilities, physical properties of products, drying kinetics and modeling.This work covers the drying of green peas, applying a laboratory heat pump dryer. The drying conditions and processing time are the most important parameters for modeling and scalingup the process. Additionally, the temperature, relative humidity and residence time are essential for understanding changes in product properties, and fundamental for the designing and dimensioning of large-scale drying processes.Therefore, the various tests were done at many different temperature regimes, from -5°C to 45°C, and at varying levels of relative humidity. Some of the drying tests applied additional equipment, such as an air humidifier, infrared lamps and an oven to get the specific temperature or moisture content of the tested product. All the drying tests were performed, and each run was done in a period of three hours using a fluidized bed mode. The results on kinetics and final moisture content indicated that temperatures and relative humidity levels lead to changes in the moisture removal rates from the material as well as the quality of the product. Studies were also made to investigate the influence of drying conditions and time on product parameters such as color and water activity.This work also proposes a numerical solution for the moisture content in order to describe the drying kinetics and effective mass diffusivity. The results in this work can be useful since it reduces the number of drying experiments to be tested at a wide range of drying conditions.The proposed models have been validated by experiments with acceptable deviations. It helps in establishing the temperature and time schedule in a preliminary study on scaling up lab dryers to a pilot or commercial drying plant. This is also a good platform for further research oriented towards the unification of available laboratory data in the heat pump drying of vegetables to the overall simulation program.The coefficient of performance (COP) and specific moisture extraction rate (SMER) were calculated to characterize the energy efficiency and water removal capacity of the heat pump drying process. Ammonia or R717 was selected as the working fluid due to its thermal properties and for being an environmentally friendly refrigerant. Regarding greenhouse gases (GHGs), ammonia is a natural fluid which has zero ozone depletion potential (ODP) and zero global warming potential (GWP), that makes heat pump drying a competitive and efficient drying technology with a minimum impact on climate change.
The 20th International Drying Symposium (IDS 2016), 2016
Heat pump dryers have found their application in drying of heat sensitive materials due to the po... more Heat pump dryers have found their application in drying of heat sensitive materials due to the possibilities of controlling drying conditions. In addition, this technology is energy saving and more environmentally friendly than direct heated dryers. In Norway, research on this technology has taken place over a period of 20 years and several industrial applications are seen, like drying of fish and vegetables. Several products have been dried in test plants, like fish products, fruits, vegetables, dairy products, biological active products and other heat sensitive materials. For such products quality can be controlled, like color, taste, bulk density and rehydration properties.
This work has focused on the development of atmospheric freeze and non-freeze drying applying a h... more This work has focused on the development of atmospheric freeze and non-freeze drying applying a heat pump system as an environmental friendly and economically preferable technology compare to vacuum freeze drying. The main reason of the research is a lack of knowledge and information in the literature about the atmospheric heat pump drying, while the more common vacuum freeze drying process is widely covered.The main objective for developing atmospheric heat pump drying as a new drying technology is the desire to reduce the energy consumption compared to that of vacuum freeze drying while maintaining a high product quality.One technical solution of atmospheric freeze and non-freeze drying is combining with a heat pump system applying a new environmentally friendly natural refrigerant, such as ammonia or R717. Temperature programs make it possible to customize products for desired qualities and properties, such as color retention, instant rehydration and aroma preservation.Drying is one of the most important industrial processes, and a technology used worldwide for food processing. The vacuum freeze and high temperature drying are both well-known and extensively applied conventional technologies that have the drawback of high energy consumption. This provided the opportunity for heat pump drying development, in order to decrease operational costs while preserving the quality of the products. Heat pump drying is a relatively new technology developed at NTNU. It unifies the drying and heat pump cycles that allows energy recovery for reheating the drying air.An analysis was made on the technological aspects, product possibilities, physical properties of products, drying kinetics and modeling.This work covers the drying of green peas, applying a laboratory heat pump dryer. The drying conditions and processing time are the most important parameters for modeling and scalingup the process. Additionally, the temperature, relative humidity and residence time are essential for understanding changes in product properties, and fundamental for the designing and dimensioning of large-scale drying processes.Therefore, the various tests were done at many different temperature regimes, from -5°C to 45°C, and at varying levels of relative humidity. Some of the drying tests applied additional equipment, such as an air humidifier, infrared lamps and an oven to get the specific temperature or moisture content of the tested product. All the drying tests were performed, and each run was done in a period of three hours using a fluidized bed mode. The results on kinetics and final moisture content indicated that temperatures and relative humidity levels lead to changes in the moisture removal rates from the material as well as the quality of the product. Studies were also made to investigate the influence of drying conditions and time on product parameters such as color and water activity.This work also proposes a numerical solution for the moisture content in order to describe the drying kinetics and effective mass diffusivity. The results in this work can be useful since it reduces the number of drying experiments to be tested at a wide range of drying conditions.The proposed models have been validated by experiments with acceptable deviations. It helps in establishing the temperature and time schedule in a preliminary study on scaling up lab dryers to a pilot or commercial drying plant. This is also a good platform for further research oriented towards the unification of available laboratory data in the heat pump drying of vegetables to the overall simulation program.The coefficient of performance (COP) and specific moisture extraction rate (SMER) were calculated to characterize the energy efficiency and water removal capacity of the heat pump drying process. Ammonia or R717 was selected as the working fluid due to its thermal properties and for being an environmentally friendly refrigerant. Regarding greenhouse gases (GHGs), ammonia is a natural fluid which has zero ozone depletion potential (ODP) and zero global warming potential (GWP), that makes heat pump drying a competitive and efficient drying technology with a minimum impact on climate change.
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Papers by Odilio Alves-Filho