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- Mannelquist, Anders, et al.
(författare)
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Near field optical microscopy in aqueous solution : implementation and characterization of a vibrating probe
- 2002
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Ingår i: Journal of Microscopy. - : Wiley. - 0022-2720 .- 1365-2818. ; 205:1, s. 53-60
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Tidskriftsartikel (refereegranskat)abstract
- Near field optical microscopy (NSOM) is one of the possible solutions to circumvent the diffraction limit, but the control of the optical probe in solution has been a technical challenge for practical applications. Most recently, it has been shown that the pipette used in the scanning ion conductance microscope can be modified to form a high resolution near field optical probe. When combined with a novel distance modulation mechanism, a robust near field microscope can be constructed for operation in aqueous solution. In this paper, we present technical details of this design and a further characterization of the NSOM system for imaging in solution. Fundamental limitations of this approach in comparison to other systems are also discussed. Based on the current technology, it is concluded that better than 50 nm resolution should be achievable with this technique for fluorescence, as well as fluorescence resonance energy transfer, imaging of biological specimens.
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| 2. |
- Shao, D. W., et al.
(författare)
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Flow pattern, heat transfer and pressure drop in flow condensation part I : Pure and azeotropic refrigerants
- 2000
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Ingår i: HVAC & R RESEARCH. - : Informa UK Limited. - 1078-9669 .- 1938-5587. ; 6:2, s. 175-195
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Tidskriftsartikel (refereegranskat)abstract
- This study concerns the flow pattern, heat transfer, and pressure drop for flow condensation. The experimental results are recorded in tests with a smooth horizontal tube of 6 mm inner diameter and 2 to 10 m long. This manuscript, which is part I of a two part series, focuses on pure and azeotropic fluids. Part II describes results with non-azeotropic refrigerant mixtures. A flow pattern map by Tandon et al. (1982) roughly predicts flow patterns associated with pure and azeotropic fluids in this work. However, the Froude number is found to be a good additional indicator to identify transition between annular and wavy flows. The transition occurs mostly at Fr = 15 to 20 for both pure and azeotropic fluids. In the case of pure and azeotropic fluids, the hear transfer coefficient was found to be independent of the mass flux in wavy flow regions, but increased with an increasing mass flux in the annular flow regions. For pure and azeotropic fluids, a modified Tandon et al. correlation agreed best with experimental data from tests with R-12, R-22, R-134a, and R-502. For the local pressure drop it is correlated within +/-15% by using the Lockhart-Martinelli parameters. The experimental data for pure and azeotropic refrigerants can be predicted by using a correlation for overall pressure drop.
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| 3. |
- Shao, D. W., et al.
(författare)
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Flow pattern, heat transfer and pressure drop in flow condensation part II : Zeotropic refrigerants mixtures (NARMs)
- 2000
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Ingår i: HVAC & R RESEARCH. - : Informa UK Limited. - 1078-9669 .- 1938-5587. ; 6:2, s. 197-209
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Tidskriftsartikel (refereegranskat)abstract
- This paper, which is parr II of a study on flow condensation is focused on zeotropic (or non-azeotropic) refrigerant mixtures (NARMs) In the experiments, condensation in a horizontal tube of inner diameter 6 mm and 10 m length were studied with fluids R-404A, R-407C, and three mixtures of R-32 and R-134a. A flow pattern map by Tandon et al. (1982) roughly predicts flow patterns associated with NARMs studied in this work. Most tests recorded are in the annular or semi annular flow region. The Froude number is, however, found to be an additional indicator to identify transition between annular and wavy flows. The transition in the experiments occurs mostly at Fr = 15 to 20 for the fluids tested. For NARMs with a small temperature glide (e.g. R-404A), as observed in the case of pure and azeotropic fluids, the hear transfer coefficient is independent of the mass flux in wavy flow regions, and increases with an increasing mass flux in annular flow regions. For other NARMs tested, the hear transfer coefficient (starting from a lower level) always increases with an increasing mass flux within the tested ranges. The heat transfer data from the tests with R-404A, R-407C, and R-32/R-134a mixtures can be predicted reasonably well by a modified Tandon et al. (1985b, 1995) equation with a correction proposed by Granryd (1989)for NARMs. The classical correlations for the pressure drop do nor work well. Instead, the data for local pressure drop are correlated within +/-15% by means of the same correlation as for the pure and azeotropic fluids. A simple correlation for the overall pressure drop based on the experimental data for pure and azeotropic fluids is good also for R-404A (with a small glide), but overpredicts the pressure drop (by up to 50%)for NARMs with glide, such as R-407C.
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