| 511. |
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| 512. |
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| 513. |
- Haglund Stignor, Caroline, et al.
(författare)
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Energy-efficient flat-tube heat exchangers for indirectly cooled display cabinets
- 2009
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Ingår i: International Journal of Refrigeration. - : Elsevier BV. - 0140-7007. ; 32:6, s. 1460-1471
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Tidskriftsartikel (refereegranskat)abstract
- Different designs of flat-tube heat exchangers with plain fins have been evaluated theoretically in a parameter study in order to evaluate their performance potential in indirectly cooled display cabinets. Two different types of flat-tube heat exchangers were considered; one with serpentine fins and one with continuous plate fins. Both flat-tube heat exchanger types were adapted to the laminar flow regime on the liquid as well as on the air side. The performance of the two heat exchanger types had previously been verified experimentally under dehumidifying conditions. The results from this parameter study show that considerable savings in the required electric drive power to compressors, pumps and fans can be obtained in comparison with the traditional cooling coil. The savings may be up to 15%. In addition, the required temperature difference for the flat-tube heat exchangers is so small that frost-free operation is possible, which would result in even larger savings. (C) 2009 Elsevier Ltd and IIR. All rights reserved.
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| 514. |
- Haglund Stignor, Caroline, et al.
(författare)
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Heat Transfer and Pressure Drop Under Dry and Humid Conditions in Flat-Tube Heat Exchangers With Plain Fins
- 2010
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Ingår i: Heat Transfer Engineering. - : Informa UK Limited. - 0145-7632 .- 1521-0537. ; 31:3, s. 179-192
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Tidskriftsartikel (refereegranskat)abstract
- Flat-tube heat exchangers could be an interesting alternative to make indirect cooling of display cabinets more energy-efficient. This application involves low air velocities in combination with condensation of water vapor on the air side, so plain fins could be suitable. Two different heat exchangers having flat tubes and plain fins on the air side were evaluated experimentally. One of the heat exchangers had continuous plate fins, and the other had serpentine fins. The performances during dry and wet test conditions were compared and related to theoretical predictions for different assumptions. The influence of air velocity, air humidity, and inclination angle was investigated. The results show that, in most cases, the heat transfer performance is somewhat reduced under wet conditions in comparison with dry test conditions, and that wet heat transfer surfaces lead to an increased pressure drop. At the lower air velocity range that was investigated, the heat exchanger having continuous plate fins drained better than the one with serpentine fins.
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| 515. |
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| 516. |
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| 517. |
- Hagman, Benjamin, et al.
(författare)
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Oxygen induced faceting of Cu(911)
- 2022
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Ingår i: Surface Science. - : Elsevier BV. - 0039-6028. ; 715
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Tidskriftsartikel (refereegranskat)abstract
- The oxidation of copper is essential for several fields, such as corrosion, catalytic methanol synthesis, and CO2 electroreduction. However, the understanding of the oxidation of copper under various conditions is not complete. Here, we study the oxidation of the vicinal Cu(911) surface by O2 with in-situ Surface X-ray Diffraction. It was found that the surface facets to (410), (401), and (100) which are stable in the parameter range of T = 25–400 °C and p = 10−10–10−5 mbar O2. The (410) and (401) facets are present until the surface is further oxidized to Cu2O, at 10−5 mbar and above. These results further the knowledge on the oxidation of copper and its surfaces, which may be of importance for a wide range of applications.
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| 518. |
- Hagman, Benjamin, et al.
(författare)
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Steps Control the Dissociation of CO2 on Cu(100)
- 2018
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Ingår i: Journal of the American Chemical Society. - : American Chemical Society (ACS). - 1520-5126 .- 0002-7863. ; 140:40, s. 12974-12979
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Tidskriftsartikel (refereegranskat)abstract
- CO2 reduction reactions, which provide one route to limit the emission of this greenhouse gas, are commonly performed over Cu-based catalysts. Here, we use ambient pressure X-ray photoelectron spectroscopy together with density functional theory to obtain an atomistic understanding of the dissociative adsorption of CO2 on Cu(100). We find that the process is dominated by the presence of steps, which promote both a lowering of the dissociation barrier and an efficient separation between adsorbed O and CO, reducing the probability for recombination. The identification of steps as sites for efficient CO2 dissociation provides an understanding that can be used in the design of future CO2 reduction catalysts.
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| 519. |
- Hagsten, Carin, et al.
(författare)
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Composition and structure of high temperature dairy fouling
- 2016
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Ingår i: Food Structure. - : Elsevier BV. - 2213-3291. ; 7, s. 13-20
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Tidskriftsartikel (refereegranskat)abstract
- The fouling structure and composition is dependent on the product, but also on the heating process applied to it. The structure will have profound effect on the cleaning process and the down time in the production plant. Here, the structure of high temperature (137 °C) milk fouling has been investigated, which so far has not been sufficiently studied in a systematic way. This particular fouling has a high content of the mineral calcium phosphate and a relatively low concentration of protein. Wide angle X-ray diffraction (WAXD) reveals a crystalline structure of calcium phosphate in agreement to the chemical analysis of the bulk layer. Microscopic investigations visualize the heterogeneous structure and energy dispersive X-ray spectroscopy (EDX) shows a spatial variation of the elements through the radius of the sample.
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| 520. |
- Hagsten, Carin, et al.
(författare)
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Structural and compositional changes during UHT fouling removal-Possible mechanisms of the cleaning process
- 2019
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Ingår i: Food Structure. - : Elsevier BV. - 2213-3291. ; 21
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Tidskriftsartikel (refereegranskat)abstract
- Ultra-high temperature (UHT) treatment of milk forms a deposit or fouling in the processing equipment that is mineral-based with an enclosed protein network. This study addresses the fundamental mechanisms that control the removal of this deposit. For this purpose, the structural and compositional changes during the cleaning process have been studied. The structure analysis was performed with scanning electron microscopy (SEM) and confocal laser scanning microscopy (CLSM) on samples that were quenched at different stages of the cleaning process. It was found for acid cleaning that the mineral content is rapidly decreasing in the fouling layer as the cleaning continues, but there is still an intact protein structure with the similar thickness as the original fouling. For alkali cleaning, part of the protein structure was subsequently removed from the outside towards the stainless steel as a function of time, while the mineral structure was mostly remaining. The break-up of the organic network structure, which likely involves depolyrnerization of protein aggregates, were found to control the cleaning efficiency. The weakening of the protein network facilitates the removal of the UHT fouling layer during the acid cleaning step and allow for an efficient cleaning cycle. The chemical reactions that occur within the fouling layer between the hydroxyl ions and the protein network was modeled according to a depolymerization reaction and a mechanistic model of the cleaning process is presented.
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