Trygve Magne Eikevik - Profile on Academia.edu (original) (raw)
Papers by Trygve Magne Eikevik
Processes, Feb 12, 2024
In this study, the thermal transition of seaweed Saccharina latissima (raw and blanched) during d... more In this study, the thermal transition of seaweed Saccharina latissima (raw and blanched) during drying and quality stabilization was considered in view of understanding physico-chemical changes, color changes, sorption changes and thermal property changes with respect to drying kinetics. The variations in the effective moisture diffusivity coefficient with shrinkage changes and temperature lie between 1.0 and 5.0 × 10 -10 m 2 s -1 (raw) and 0.5 and 3.6 × 10 -10 m 2 s -1 (blanched), respectively. Noticeable physical and chemical changes were observed during longer drying times, especially in the case of blanched seaweeds. At the temperature of 38.0 • C, a more yellow-colored product was obtained from raw form input materials. The blanched seaweeds accumulated moisture in a linear manner with an increase in the relative humidity of the drying air in the range of 20.0~80.0%, which resulted in high level of hysteresis between the sorption and desorption behavior. Shrinkage changes during the drying of blanched and raw samples were also calculated. The thermal stabilization of raw and blanched forms started at different initial moisture contents showed changed glass transition phenomena during a wide range of temperature sand one melting endotherm between 141.9 and 167.9 • C. Some glass transitions were driven by the presence of water-soluble contents in the material. The dried seaweeds at low temperatures showed a partial glassy state and an amorphous/crystalline state. This study evaluated the effects of process parameters on the properties of dried product.
Small-scale solar-based adsorption ice maker for Indian climate
In this paper, simulation of a small scale solar-based adsorption ice maker is presented. The sys... more In this paper, simulation of a small scale solar-based adsorption ice maker is presented. The system, consisting of activated carbon (Maxsorb III) in the solar collector bed and an evaporator/cold box, can produce and store up to 10 kg of ice per day in Indian climate. The calculations are based on climatic data from India and on energy balances of the components of the system. Methanol is the best working fluid for adsorption temperatures below 28 °C and ethanol is the best working fluid for above 28 °C. The thickness of the bed is calculated to a maximum of 7.5 cm to have a required cooling time. The adsorption ice maker with 1 m2 solar collector and 20 kg of adsorbent can provide cooling capacity equivalent to 5 to 10 kg of ice per day with respect to climate conditions.
Compressors for ammonia-water hybrid absorption-compression heat pumps
In this paper, investigations on the development of industrial high temperature heat pumps are ca... more In this paper, investigations on the development of industrial high temperature heat pumps are carried out based on the analysis of the current available compressors. The compressor used for the ammonia compression is a major component of ammonia-water hybrid absorption-compression heat pump. Furthermore, the compressor is the dominant constraint on achievable process conditions due to the limitation of high pressure and discharge temperature. Ammonia-water hybrid heat pumps combine technologies of an absorption and compression heat pump with a mixture of ammonia and water as working fluid. The heat is extracted and emitted at non-constant temperature glides and the necessary ratio of compression is lower compared to conventional compression heat pumps. These properties make the hybrid heat pump interesting for use in industrial high temperature applications. In this study, currently available compressors are being investigate for a utilization of them in a hybrid heat pump test facility able to operate at high side pressures to achieve exit temperatures on the secondary side of 140 °C to 180 °C. For this purpose, available compressors are identified and evaluated based on performance indicators such as the maximum pressure and discharge temperature.
Potential evaluation of integrated high temperature heat pumps: A review of recent advances
Applied Thermal Engineering, Jul 1, 2023
Solar driven production using CO2 as working fluid
11th IIR Gustav Lorentzen Conference on Natural Refrigerants (GL2014). Proceedings. Hangzhou, China, August 31-September 2, 2014., Aug 2, 2014
三次元と二次元結合地熱源ヒートポンプ地下熱交換器複合数値モデル【JST・京大機械翻訳】
Zhileng Xuebao, 2018
Heat pumps as a sustainable bridge for global heating and cooling at multi-scale
Energy & environmental science, 2024
Numerical modelling of conjugate heat and mass transfer during hydrofluidisation food freezing in different water solutions
Innovative Food Science and Emerging Technologies, 2022
Food bioscience, Aug 1, 2021
Increasing amount of unutilized rest raw material worldwide and, particularly, in Norway leaded t... more Increasing amount of unutilized rest raw material worldwide and, particularly, in Norway leaded to the investigation of its possible utilization. In the present research, fish protein hydrolysates from cod were used as peptones for microbiological culture medias. The hydrolysates were produced with several enzymatic systems and dried by several drying techniques in order to evaluate the influence of processing on their utilization as peptones. Strains of Staphylococcus aureus and Salmonella enteriditis were used as test strains. The obtained microbiological culture medias based on the peptones from fish protein hydrolysates were compared with a reference media produced industrially. The investigated medias generally showed similar or better growth of the test strains, when compared with the reference. The influence of the enzymatic system and drying method on the growth of the tested strains was analyzed and discussed.
The drying kinetics of brown seaweed Sacharina Latissima with and without blanching were investig... more The drying kinetics of brown seaweed Sacharina Latissima with and without blanching were investigated in temperature range between 10.0 and 38.0 °C. The drying process is more rapid for raw seaweeds. The effective moisture diffusivity coefficient (with respect to shrinkage) was found in the range between 0.5 and 5.0 10-10 m-2/s. Drying temperature influence on lightness and hue color parameter of the seaweeds. The salt content in raw seaweeds influence on the shape of the sorption isotherm at high relative humidifies. The differential scanning calorimetry of raw seaweed samples revealed glass transition at ultra-low temperature range, while it was not found for blanched seaweeds. State diagram for drying and freezing of raw seaweeds was made.
Performance simulation of a refrigerated sea water system for salmon chilling with R744 as the refrigerant
The aquaculture production is steadily increasing in Norway. Typical load during one working shif... more The aquaculture production is steadily increasing in Norway. Typical load during one working shift reaches up to 100 metric tons of fish. The requirements for fish chilling is strict: the process should be as fast as possible and the final temperature in the centre of the fish should not exceed +2.0 °C. Typical chilling system are using refrigerated sea water in direct contact with the product and the cooling load is varying with product size, production rate and seasonal temperature. This case study evaluates the performance of CO2 as refrigerant in refrigerated sea water (RSW) system for chilling of salmon. The system was evaluated for different weight classes of fishes being chilled (from 3.0 to 8.0 kg). The knowledge of heat transfer and temperature fields inside the fish, which was obtained in another study, was used for simulation of the process in order to optimize the operation conditions for the system. System solutions with the highest rate of cooling capacity together with low energy consumption during operation are described and evaluated.
Energies, Dec 11, 2023
This article is an open access article distributed under the terms and conditions of the Creative... more This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY
Evaluation of natural working fluids for the development of high temperature heat pumps
For a sustainable future in energy, the use of natural fluids in heat pump systems can provide an... more For a sustainable future in energy, the use of natural fluids in heat pump systems can provide an efficient solution to combat the ozone depletion and the global warming effects of synthetic working fluids. These natural fluids, though environmentally friendly, must be able to operate at high temperature in heat pumps in an efficient and cost effective way to be viable for the industry heat demand. High temperature heat pumps with heat source and heat sink temperatures ranging from 40 oC to 200 oC have unique challenges with natural working fluids. This paper evaluates the performance and use of natural working fluids for high temperature heat pumps. The analysis is based on simple thermodynamic cycles. A simulation tool coupled with a thermodynamic properties database is used to evaluate the operating limitations of the natural fluids. Natural fluids such as ammonia, hydrocarbon and hydrocarbon mixtures are considered. The hydrocarbon mixtures, benefitting from both adjusted thermodynamic properties and a higher evaporating temperature due to better fit to heat source temperature, shows greatest potential for the development of high temperature heat pumps. The mixtures R290+R600 and R600+R601 were able to expand the working limits of their pure fluids while improving COP by up to 13.5 %.
Prestazioni di uno scambiatore di calore verticale per terreno
Energy performance of CO2 hybrid ground-coupled heat pumping system for hotel application
Proceedings of the 24th IIR International Congress of Refrigeration: Yokohama, Japan, August 16-22, 2015., Aug 16, 2015
This article attempts to investigate the energy performance of CO2 (R744) hybrid ground-coupled h... more This article attempts to investigate the energy performance of CO2 (R744) hybrid ground-coupled heat pumping system for the cooling and heating application in hotels. The developed heat pumping system, employing a reverse transcritical CO2 cycle, utilises a heat sink combination of tap water and ground in cooling mode, while only the ground is utilized as the heat source in heating mode. When the heat pump operates in cooling mode, part of heat on the high pressure side could be recovered for heating the tap water to 65°C for the hotel hot water supply. The separated gas coolers also enable simultaneous space heating and hot water supply in the heating mode. This CO2 hybrid ground coupled heat pump system is modelled in the Modelica/ Dymola environment, and several types of control strategies according to the hotel heat load demands are suggested for the energy performance investigation. Simulation result shows the COPcooling&SHW, which could reach 4.8, is superior comparing with other cooling and heating system, and the optimal high side pressure for different control strategy is acquired according to the optimal energy performance.
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.
Dimple plate heat exchangers for a sea-water chiller using CO2 as refrigerant, design and testing
Proceedings of the 24th IIR International Congress of Refrigeration: Yokohama, Japan, August 16-22, 2015., Aug 16, 2015
To ensure proper quality of high value product, cooling is a critical process in the fishing indu... more To ensure proper quality of high value product, cooling is a critical process in the fishing industry. Traditionally, on board pelagic fish cooling is achieved using Refrigerated Sea Water (RSW) refrigeration plants with halocarbon HCFC 22 as working fluid. According to EU-regulations, refilling of this fluid is not allowed from 2015. HFC alternatives have considerable greenhouse warming potential and are heavily taxed in some countries, thus only a short time solution. The main natural alternative, ammonia, has significant drawbacks that can be unacceptable particularly for smaller vessels and for rebuilding of existing ships. Carbon Dioxide (CO2) is an environmental friendly, inexpensive, non-toxic, non-flammable alternative. One drawback is the high operating pressure which could give heavy, bulky and expensive components. In this project a novel dimple plate type evaporator and condenser were developed and tested in a 300 kW cooling capacity RSW plant using CO2 as refrigerant. Optimal geometry was simulated and verified in laboratory tests. Then, new full size heat exchangers and refrigeration racks were mounted in a fishing boat replacing an existing R22 system. Measurements on-board boat showed promising results and the first mackerel catch cooling fulfilled the boat owner's expectations. The heat exchangers are smaller, lighter and cheaper than comparable shell and tube units designed for CO2. Preliminary calculations show that the production cost could be about equal to ammonia units.
Energies
This study provides an overview of new trends in the development of cooling systems for electric ... more This study provides an overview of new trends in the development of cooling systems for electric motors. It includes a summary of academic research and patents for cooling systems implemented by leading motor manufacturers at TRL9. New trends in the cooling management of air and liquid cooling systems are discussed and analyzed with a focus on temperature distribution and its influence on the power-to-dimension ratio of electric motors. The prevailing cooling method for synchronous and asynchronous motors is air cooling using external fins, air circulation ducts, air gaps, and fan impellers to enhance efficiency and reliability. Internal cooling with rotor and stator ducts, along with optimized air duct geometry, shows potential to increase the power-to-dimension ratio and reduce motor size. Liquid cooling systems offer a power-to-dimension ratio of up to 25 kW/kg, achieved through redesigned cooling ducts, stator heat exchangers, and cooling tubes. However, liquid cooling systems a...
Natural refrigerants in refrigerated seawater systems on fishing vessels
Refrigerated seawater systems (RSW) are commonly used in fishing vessels for cooling of harvested... more Refrigerated seawater systems (RSW) are commonly used in fishing vessels for cooling of harvested pelagic fish. The catch is cooled down to approximately -1 °C in large seawater tanks. In Norway, several of these RSW systems are working with ammonia as refrigerant, but carbon dioxide is introduced as an alternative and installed on a fishing vessel with good results. There are still many fishing vessels with RSW systems using refrigerant R22. This paper describes possibilities of using natural refrigerants instead of fluorocarbons, for example R22, in RSW systems on fishing boats.
Conceptual study of a transportable cooling system based on renewable energy for use on fruits and vegetables
This article is devoted to use of refrigeration and cold chain in India, with specific emphasis o... more This article is devoted to use of refrigeration and cold chain in India, with specific emphasis on agricultural products. India is found to be vastly lacking in terms of both cold storage capacity and efficiency. Thus, there is a large potential for development. A physical design of a cooling system is modelled (based on the Indian scenario), and a further logistical implementation of this system in India is constructed. A comprehensive simulation model for the complete cooling system was used to reach an optimized system configuration, which was implemented for cooling of apples, grapes and mangoes in the respective climatic regions of Dehradun, Mumbai and Kolkata. The cooling system was evaluated in relation to the Indian scenario, and it is concluded that the system offers several potential benefits.
Processes, Feb 12, 2024
In this study, the thermal transition of seaweed Saccharina latissima (raw and blanched) during d... more In this study, the thermal transition of seaweed Saccharina latissima (raw and blanched) during drying and quality stabilization was considered in view of understanding physico-chemical changes, color changes, sorption changes and thermal property changes with respect to drying kinetics. The variations in the effective moisture diffusivity coefficient with shrinkage changes and temperature lie between 1.0 and 5.0 × 10 -10 m 2 s -1 (raw) and 0.5 and 3.6 × 10 -10 m 2 s -1 (blanched), respectively. Noticeable physical and chemical changes were observed during longer drying times, especially in the case of blanched seaweeds. At the temperature of 38.0 • C, a more yellow-colored product was obtained from raw form input materials. The blanched seaweeds accumulated moisture in a linear manner with an increase in the relative humidity of the drying air in the range of 20.0~80.0%, which resulted in high level of hysteresis between the sorption and desorption behavior. Shrinkage changes during the drying of blanched and raw samples were also calculated. The thermal stabilization of raw and blanched forms started at different initial moisture contents showed changed glass transition phenomena during a wide range of temperature sand one melting endotherm between 141.9 and 167.9 • C. Some glass transitions were driven by the presence of water-soluble contents in the material. The dried seaweeds at low temperatures showed a partial glassy state and an amorphous/crystalline state. This study evaluated the effects of process parameters on the properties of dried product.
Small-scale solar-based adsorption ice maker for Indian climate
In this paper, simulation of a small scale solar-based adsorption ice maker is presented. The sys... more In this paper, simulation of a small scale solar-based adsorption ice maker is presented. The system, consisting of activated carbon (Maxsorb III) in the solar collector bed and an evaporator/cold box, can produce and store up to 10 kg of ice per day in Indian climate. The calculations are based on climatic data from India and on energy balances of the components of the system. Methanol is the best working fluid for adsorption temperatures below 28 °C and ethanol is the best working fluid for above 28 °C. The thickness of the bed is calculated to a maximum of 7.5 cm to have a required cooling time. The adsorption ice maker with 1 m2 solar collector and 20 kg of adsorbent can provide cooling capacity equivalent to 5 to 10 kg of ice per day with respect to climate conditions.
Compressors for ammonia-water hybrid absorption-compression heat pumps
In this paper, investigations on the development of industrial high temperature heat pumps are ca... more In this paper, investigations on the development of industrial high temperature heat pumps are carried out based on the analysis of the current available compressors. The compressor used for the ammonia compression is a major component of ammonia-water hybrid absorption-compression heat pump. Furthermore, the compressor is the dominant constraint on achievable process conditions due to the limitation of high pressure and discharge temperature. Ammonia-water hybrid heat pumps combine technologies of an absorption and compression heat pump with a mixture of ammonia and water as working fluid. The heat is extracted and emitted at non-constant temperature glides and the necessary ratio of compression is lower compared to conventional compression heat pumps. These properties make the hybrid heat pump interesting for use in industrial high temperature applications. In this study, currently available compressors are being investigate for a utilization of them in a hybrid heat pump test facility able to operate at high side pressures to achieve exit temperatures on the secondary side of 140 °C to 180 °C. For this purpose, available compressors are identified and evaluated based on performance indicators such as the maximum pressure and discharge temperature.
Potential evaluation of integrated high temperature heat pumps: A review of recent advances
Applied Thermal Engineering, Jul 1, 2023
Solar driven production using CO2 as working fluid
11th IIR Gustav Lorentzen Conference on Natural Refrigerants (GL2014). Proceedings. Hangzhou, China, August 31-September 2, 2014., Aug 2, 2014
三次元と二次元結合地熱源ヒートポンプ地下熱交換器複合数値モデル【JST・京大機械翻訳】
Zhileng Xuebao, 2018
Heat pumps as a sustainable bridge for global heating and cooling at multi-scale
Energy & environmental science, 2024
Numerical modelling of conjugate heat and mass transfer during hydrofluidisation food freezing in different water solutions
Innovative Food Science and Emerging Technologies, 2022
Food bioscience, Aug 1, 2021
Increasing amount of unutilized rest raw material worldwide and, particularly, in Norway leaded t... more Increasing amount of unutilized rest raw material worldwide and, particularly, in Norway leaded to the investigation of its possible utilization. In the present research, fish protein hydrolysates from cod were used as peptones for microbiological culture medias. The hydrolysates were produced with several enzymatic systems and dried by several drying techniques in order to evaluate the influence of processing on their utilization as peptones. Strains of Staphylococcus aureus and Salmonella enteriditis were used as test strains. The obtained microbiological culture medias based on the peptones from fish protein hydrolysates were compared with a reference media produced industrially. The investigated medias generally showed similar or better growth of the test strains, when compared with the reference. The influence of the enzymatic system and drying method on the growth of the tested strains was analyzed and discussed.
The drying kinetics of brown seaweed Sacharina Latissima with and without blanching were investig... more The drying kinetics of brown seaweed Sacharina Latissima with and without blanching were investigated in temperature range between 10.0 and 38.0 °C. The drying process is more rapid for raw seaweeds. The effective moisture diffusivity coefficient (with respect to shrinkage) was found in the range between 0.5 and 5.0 10-10 m-2/s. Drying temperature influence on lightness and hue color parameter of the seaweeds. The salt content in raw seaweeds influence on the shape of the sorption isotherm at high relative humidifies. The differential scanning calorimetry of raw seaweed samples revealed glass transition at ultra-low temperature range, while it was not found for blanched seaweeds. State diagram for drying and freezing of raw seaweeds was made.
Performance simulation of a refrigerated sea water system for salmon chilling with R744 as the refrigerant
The aquaculture production is steadily increasing in Norway. Typical load during one working shif... more The aquaculture production is steadily increasing in Norway. Typical load during one working shift reaches up to 100 metric tons of fish. The requirements for fish chilling is strict: the process should be as fast as possible and the final temperature in the centre of the fish should not exceed +2.0 °C. Typical chilling system are using refrigerated sea water in direct contact with the product and the cooling load is varying with product size, production rate and seasonal temperature. This case study evaluates the performance of CO2 as refrigerant in refrigerated sea water (RSW) system for chilling of salmon. The system was evaluated for different weight classes of fishes being chilled (from 3.0 to 8.0 kg). The knowledge of heat transfer and temperature fields inside the fish, which was obtained in another study, was used for simulation of the process in order to optimize the operation conditions for the system. System solutions with the highest rate of cooling capacity together with low energy consumption during operation are described and evaluated.
Energies, Dec 11, 2023
This article is an open access article distributed under the terms and conditions of the Creative... more This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY
Evaluation of natural working fluids for the development of high temperature heat pumps
For a sustainable future in energy, the use of natural fluids in heat pump systems can provide an... more For a sustainable future in energy, the use of natural fluids in heat pump systems can provide an efficient solution to combat the ozone depletion and the global warming effects of synthetic working fluids. These natural fluids, though environmentally friendly, must be able to operate at high temperature in heat pumps in an efficient and cost effective way to be viable for the industry heat demand. High temperature heat pumps with heat source and heat sink temperatures ranging from 40 oC to 200 oC have unique challenges with natural working fluids. This paper evaluates the performance and use of natural working fluids for high temperature heat pumps. The analysis is based on simple thermodynamic cycles. A simulation tool coupled with a thermodynamic properties database is used to evaluate the operating limitations of the natural fluids. Natural fluids such as ammonia, hydrocarbon and hydrocarbon mixtures are considered. The hydrocarbon mixtures, benefitting from both adjusted thermodynamic properties and a higher evaporating temperature due to better fit to heat source temperature, shows greatest potential for the development of high temperature heat pumps. The mixtures R290+R600 and R600+R601 were able to expand the working limits of their pure fluids while improving COP by up to 13.5 %.
Prestazioni di uno scambiatore di calore verticale per terreno
Energy performance of CO2 hybrid ground-coupled heat pumping system for hotel application
Proceedings of the 24th IIR International Congress of Refrigeration: Yokohama, Japan, August 16-22, 2015., Aug 16, 2015
This article attempts to investigate the energy performance of CO2 (R744) hybrid ground-coupled h... more This article attempts to investigate the energy performance of CO2 (R744) hybrid ground-coupled heat pumping system for the cooling and heating application in hotels. The developed heat pumping system, employing a reverse transcritical CO2 cycle, utilises a heat sink combination of tap water and ground in cooling mode, while only the ground is utilized as the heat source in heating mode. When the heat pump operates in cooling mode, part of heat on the high pressure side could be recovered for heating the tap water to 65°C for the hotel hot water supply. The separated gas coolers also enable simultaneous space heating and hot water supply in the heating mode. This CO2 hybrid ground coupled heat pump system is modelled in the Modelica/ Dymola environment, and several types of control strategies according to the hotel heat load demands are suggested for the energy performance investigation. Simulation result shows the COPcooling&SHW, which could reach 4.8, is superior comparing with other cooling and heating system, and the optimal high side pressure for different control strategy is acquired according to the optimal energy performance.
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.
Dimple plate heat exchangers for a sea-water chiller using CO2 as refrigerant, design and testing
Proceedings of the 24th IIR International Congress of Refrigeration: Yokohama, Japan, August 16-22, 2015., Aug 16, 2015
To ensure proper quality of high value product, cooling is a critical process in the fishing indu... more To ensure proper quality of high value product, cooling is a critical process in the fishing industry. Traditionally, on board pelagic fish cooling is achieved using Refrigerated Sea Water (RSW) refrigeration plants with halocarbon HCFC 22 as working fluid. According to EU-regulations, refilling of this fluid is not allowed from 2015. HFC alternatives have considerable greenhouse warming potential and are heavily taxed in some countries, thus only a short time solution. The main natural alternative, ammonia, has significant drawbacks that can be unacceptable particularly for smaller vessels and for rebuilding of existing ships. Carbon Dioxide (CO2) is an environmental friendly, inexpensive, non-toxic, non-flammable alternative. One drawback is the high operating pressure which could give heavy, bulky and expensive components. In this project a novel dimple plate type evaporator and condenser were developed and tested in a 300 kW cooling capacity RSW plant using CO2 as refrigerant. Optimal geometry was simulated and verified in laboratory tests. Then, new full size heat exchangers and refrigeration racks were mounted in a fishing boat replacing an existing R22 system. Measurements on-board boat showed promising results and the first mackerel catch cooling fulfilled the boat owner's expectations. The heat exchangers are smaller, lighter and cheaper than comparable shell and tube units designed for CO2. Preliminary calculations show that the production cost could be about equal to ammonia units.
Energies
This study provides an overview of new trends in the development of cooling systems for electric ... more This study provides an overview of new trends in the development of cooling systems for electric motors. It includes a summary of academic research and patents for cooling systems implemented by leading motor manufacturers at TRL9. New trends in the cooling management of air and liquid cooling systems are discussed and analyzed with a focus on temperature distribution and its influence on the power-to-dimension ratio of electric motors. The prevailing cooling method for synchronous and asynchronous motors is air cooling using external fins, air circulation ducts, air gaps, and fan impellers to enhance efficiency and reliability. Internal cooling with rotor and stator ducts, along with optimized air duct geometry, shows potential to increase the power-to-dimension ratio and reduce motor size. Liquid cooling systems offer a power-to-dimension ratio of up to 25 kW/kg, achieved through redesigned cooling ducts, stator heat exchangers, and cooling tubes. However, liquid cooling systems a...
Natural refrigerants in refrigerated seawater systems on fishing vessels
Refrigerated seawater systems (RSW) are commonly used in fishing vessels for cooling of harvested... more Refrigerated seawater systems (RSW) are commonly used in fishing vessels for cooling of harvested pelagic fish. The catch is cooled down to approximately -1 °C in large seawater tanks. In Norway, several of these RSW systems are working with ammonia as refrigerant, but carbon dioxide is introduced as an alternative and installed on a fishing vessel with good results. There are still many fishing vessels with RSW systems using refrigerant R22. This paper describes possibilities of using natural refrigerants instead of fluorocarbons, for example R22, in RSW systems on fishing boats.
Conceptual study of a transportable cooling system based on renewable energy for use on fruits and vegetables
This article is devoted to use of refrigeration and cold chain in India, with specific emphasis o... more This article is devoted to use of refrigeration and cold chain in India, with specific emphasis on agricultural products. India is found to be vastly lacking in terms of both cold storage capacity and efficiency. Thus, there is a large potential for development. A physical design of a cooling system is modelled (based on the Indian scenario), and a further logistical implementation of this system in India is constructed. A comprehensive simulation model for the complete cooling system was used to reach an optimized system configuration, which was implemented for cooling of apples, grapes and mangoes in the respective climatic regions of Dehradun, Mumbai and Kolkata. The cooling system was evaluated in relation to the Indian scenario, and it is concluded that the system offers several potential benefits.