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- Danielsson, Carl-Ola, et al.
(författare)
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A Model for the Enhanced Water Dissociation On Monopolar Membranes
- 2009
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Ingår i: Electrochimica Acta. - : Elsevier BV. - 0013-4686 .- 1873-3859. ; 54:11, s. 2983-2991
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Tidskriftsartikel (refereegranskat)abstract
- A model for the enhanced water dissociation that takes place at the solution/membrane interface in electromembrane processes is presented. The mechanisms behind the enhanced water dissociation are poorly understood and therefore a semi-empirical approach is suggested. The enhanced water dissociation is introduced as a heterogeneous surface reaction similar to the well established Butler–Volmer law for electrode reactions. In the model there are two parameters that need to be determined through experiments. A 1D diffusion boundary layer problem is presented and solved in order to show that a sufficient rate of water dissociation can be obtained with the model. The advantage of the presented model is that it can easily be incorporated into simulations of electromembrane processes such as electrodialysis, electrodeionization and electropermutation. The influence of the enhanced water dissociation on these processes can then be studied.
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| 4. |
- Danielsson, Carl-Ola
(författare)
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Electropermutation assisted by ion-exchange textile : removal of nitrate from drinking water
- 2006
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Increased levels of nitrate in ground water have made many wells unsuitable as sources for drinking water. In this thesis an ion-exchang eassisted electromembrane process, suitable for nitrate removal, is investigated both theoretically and experimentally. An ion-exchange textile material is introduced as a conducting spacer in the feed compartment of an electropermutation cell. The sheet shaped structure of the textile makes it easy to incorporate into the cell. High permeability and fast ion-exchange kinetics, compared to ion-exchange resins, are other attractive features of the ion-exchange textile. A steady-state model based on the conservation of the ionic species is developed. The governing equations on the microscopic level are volume averaged to give macro-homogeneous equations. The model equations are analyzed and relevant simplifications are motivated and introduced. Dimensionless parameters governing the continuous electropermutation process are identified and their influence on the process are discussed. The mathematical model can be used as a tool when optimising the process parameters and designing equipment. An experimental study that aimed to show the positive influence of using the ion-exchange textile in the feed compartment of an continuous electropermutation process is presented. The incorporation of the ion-exchange textile significantly improves the nitrate removal rate at the same time as the power consumption is decreased. A superficial solution of sodium nitrate with a initial nitrate concentration of 105 ppm was treated. A product stream with less than 20 ppm nitrate could be obtained, in a single pass mode of operation. Its concluded from these experiments that continuous electropermutation using ion-exchange textile provides an interesting alternative for nitrate removal, in drinking water production. The predictions of the mathematical model are compared with experimental results and a good agreement is obtained. Enhanced water dissociation is known to take place at the surface of ion-exchange membranes in electromembrane processes operated above the limiting current density. A model for this enhanced water dissociation in presented in the thesis. The model makes it possible to incorporate the effect of water dissociation as a heterogeneous surface reaction. Results from simulations of electropermutation with and without ion-exchange textile incorporated are presented. The influence of the water dissociation is investigated with the developed model.
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| 5. |
- Danielsson, Carl-Ola, et al.
(författare)
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Modeling Continuous Electropermutation with Effects of Water Dissociation Included
- 2010
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Ingår i: AIChE Journal. - : Wiley. - 0001-1541 .- 1547-5905. ; 56:9, s. 2455-2467
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Tidskriftsartikel (refereegranskat)abstract
- The repeating unit consisting of a cell pair of one concentrate and one feed compartment of an electropermutation stack is modeled. Both the feed and the concentrate compartments are filled with an ion-exchange textile material. Enhanced water dissociation taking place at the surface of the membrane is included in the model as a hetrogeneous surface reaction. Results from simulations of nitrate removal for drinking water production are presented and comparisons with previous experimental results are made. The influence of both conductive and inert textile spacers on the process is investigated via simulations
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| 6. |
- Danielsson, Carl-Ola, et al.
(författare)
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Nitrate Removal by Continuous Electropermutation Using Ion-Exchange Textile : II. Experimental Investigation
- 2006
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Ingår i: Journal of the Electrochemical Society. - : The Electrochemical Society. - 0013-4651 .- 1945-7111. ; 153:4, s. D62-D67
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Tidskriftsartikel (refereegranskat)abstract
- Water with nitrate concentrations above 100 ppm has been treated with continuous electropermutation which partially substitutes the nitrate with chloride. The performance of a textile anion exchanger as conducting spacer in the feed compartment of an electropermutation cell was investigated. Experiments with and without textile are compared and the influence of the textile is discussed. The process could, using the textile, successfully treat feed water with 105 ppm nitrate to produce a water with less than 25 ppm nitrate. The importance of establishing a good contact between the membranes and the textile spacer was pointed out. The experimental results were compared to model predictions and a good agreement was found.
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| 7. |
- Danielsson, Carl-Ola, et al.
(författare)
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Nitrate Removal by Continuous Electropermutation Using Ion-Exchange Textile : I. Modeling
- 2006
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Ingår i: Journal of the Electrochemical Society. - : The Electrochemical Society. - 0013-4651 .- 1945-7111. ; 153:4, s. D51-D61
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Tidskriftsartikel (refereegranskat)abstract
- This paper presents a steady-state model of the feed compartment of an electropermutation cell, used for nitrate removal, with ion exchange textiles incorporated as a conducting spacer. In the model the ion-exchange textile is treated as a porous medium and volume averaging is applied to obtain a macrohomogeneous two-phase model. The ion-exchange between the two phases is modeled assuming that the rate-determining step is the mass-transfer resistance on the liquid side of the phase interface. Analysis of the model equations reveals appropriate simplifications. The influence of the governing dimensionless numbers is investigated through simulations based on the model.
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| 8. |
- Lundgren, Henrik, et al.
(författare)
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Thermal Management of Large-Format Prismatic Lithium-Ion Battery in PHEV Application
- 2016
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Ingår i: Journal of the Electrochemical Society. - : Electrochemical Society. - 0013-4651 .- 1945-7111. ; 163:2, s. A309-A317
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Tidskriftsartikel (refereegranskat)abstract
- Thermal effects are linked to all main barriers to the widespread commercialization of lithium-ion battery powered vehicles. This paper presents a coupled 2D electrochemical - 3D thermal model of a large-format prismatic lithium-ion battery, including a thermal management system with a heat sink connected to the surface opposite the terminals, undergoing the dynamic current behavior of a plug-in hybrid electric (PHEV) vehicle using a load cycle with a maximum current of 8 C, validated using potential and temperature data. The model fits the data well, with small deviations at the most demanding parts of the cycle. The maximum temperature increase and temperature difference of the jellyroll is found to be 9.7 degrees C and 3.6 degrees C, respectively. The electrolyte is found to limit the performance during the high-current pulses, as the concentration reaches extreme values, leading to a very uneven current distribution. Two other thermal management strategies, short side and long side surfaces cooling, are evaluated but are found to have only minor effects on the temperature of the jellyroll, with maximum jellyroll temperatures increases of 9.4 degrees C and 8.1 degrees C, respectively, and maximum temperature differences of 3.7 degrees C and 5.0 degrees C, respectively.
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| 9. |
- Åvik Persson, Helene, et al.
(författare)
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Early and late signs that precede dying among older persons in nursing homes : the multidisciplinary team's perspective
- 2018
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Ingår i: BMC Geriatrics. - : BioMed Central. - 1471-2318. ; 18
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Tidskriftsartikel (refereegranskat)abstract
- Background: Nursing home residents in Sweden are old, frail and usually have multiple morbidities which often make dying a prolonged suffering. It has been found that older persons at nursing homes receive far less palliative care than younger persons, partly because it is difficult to identify when the final stage of life begins. The identification may help the staff to enable the older person and their families to participate in planning the care in accordance with their own preferences and values. With this in mind the aim was to explore the experiences of early and late signs preceding dying in older persons in nursing homes from the multidisciplinary team's perspective. Methods: The focus group method was used to interview 20 health-care professionals on the basis of semi-structured questions. Four focus groups were conducted at four nursing homes in two counties in southern Sweden. The groups included different professionals such as assistant nurses, registered nurses, occupational therapists, physiotherapists, social workers and unit managers. The analysis was conducted according to the focus group method developed by Kruger and Casey. Results: The analysis revealed one major theme, from unawareness to obviousness, which illustrates that the participants experienced dying as a happening, not a process, and found it difficult to identify early signs. Even though it was a new way of thinking, several suggestions of early signs were presented. The main category "Going into a bubble" illustrates early signs, which meant that the older person showed signs of wanting to withdraw from the outside world. The main category "The body begins to shut down" illustrates late signs, which meant that the older person showed signs that indicate that the body starts to prepare for death. Conclusions: This study conveys new knowledge concerning the multidisciplinary team's collective experience of early and late signs that precede dying. This knowledge can increase the understanding of when a palliative care approach needs to be in place at nursing homes. The use of a palliative care approach in care planning requires consensus in the perception of the dying process of frail older persons.
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