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  • 1. Andersson, Odd E.
    et al.
    Sundqvist, Bertil
    Umeå University, Faculty of Science and Technology, Physics.
    Low temperature calibration of Manganin pressure gauges1997In: Review of Scientific Instruments, ISSN 0034-6748, E-ISSN 1089-7623, Vol. 68, no 2, p. 1344-1345Article in journal (Refereed)
    Abstract [en]

    High pressures are often measured using the resistance of Manganin wires. However, the pressure coefficient of resistance is known to depend on temperature. We have measured this temperature dependence by comparing the output from a Manganin gauge with that of a well calibrated Zeranin gauge and determined a correction factor which enables us to measure the pressure at any temperature between 150 and 300 K with a temperature dependent error well below 0.5%.

  • 2.
    Chadi, Abd Alrahman
    et al.
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Mejean, G.
    Grilli, R.
    Romanini, D.
    Note: Simple and compact piezoelectric mirror actuator with 100 kHz bandwidth, using standard components2013In: Review of Scientific Instruments, ISSN 0034-6748, E-ISSN 1089-7623, Vol. 84, no 5, p. 056112-Article in journal (Refereed)
    Abstract [en]

    We propose a mounting scheme to control the displacement of a mirror (or other small object) by a cylindrical piezoelectric actuator, giving uniform response and no phase lag up to high frequencies. This requires a simple ring holder, and unmodified off-the-shelf components. In our implementation, the piezo-mirror assembly has its first mechanical resonance around 120 kHz, close to the resonance for the bare piezo. The idea is to decouple the fundamental elongation mode of the piezo-mirror assembly from the holder by side-clamping the assembly at its zero-displacement plane for this mode. The main drawback is a reduced mirror displacement, by a factor 2 in our case (mirror displacement is similar to 2.5 mu m). Also, the mirror needs to be light with respect to the piezo: still, we use a standard half-inch mirror. The resulting system is very compact as it fits inside a 1-in. commercial steering mirror post.

  • 3.
    Forsberg, Christer
    et al.
    Vattenfall AB Nordic Heat, S-162 87 Stockholm, Sweden .
    Broström, Markus
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics, Energy Technology and Thermal Process Chemistry.
    Backman, Rainer
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics, Energy Technology and Thermal Process Chemistry.
    Edvardsson, Elin
    Vattenfall Research and Development AB, S-814 26 Älvkarleby, Sweden.
    Badiei, Shahriar
    Vattenfall Research and Development AB, S-814 26 Älvkarleby, Sweden.
    Berg, Magnus
    Vattenfall Research and Development AB, S-814 26 Älvkarleby, Sweden.
    Kassman, Håkan
    Vattenfall Power Consultant AB, Box 1046, S-611 29 Nyköping, Sweden.
    Principle, calibration, and application of the in situ alkali chloride monitor2009In: Review of Scientific Instruments, ISSN 0034-6748, E-ISSN 1089-7623, Vol. 80, no 2, p. 023104-1-023104-4Article in journal (Refereed)
    Abstract [en]

     The extended use of biomass for heat and power production has caused increased operational problems with fouling and high-temperature corrosion in boilers. These problems are mainly related to the presence of alkali chlorides (KCl and NaCl) at high concentrations in the flue gas. The In-Situ Alkali Chloride Monitor (IACM) was developed by Vattenfall Research and Development AB for measuring the alkali chloride concentration in hot flue gases (>650 oC). The measurement technique is based on molecular differential absorption spectroscopy in the UV range. Simultaneous measurement of SO2 concentration is also possible. The measuring range is 1-50 ppm for the sum of KCl and NaCl concentrations, and 4-750 ppm for SO2. This paper describes the principle of the IACM as well as its calibration. Furthermore, an example of its application in an industrial boiler is given.

  • 4.
    Sundqvist, Bertil
    Umeå University, Faculty of Science and Technology, Physics.
    Improving thermal insulation in high pressure experiments1998In: Review of Scientific Instruments, ISSN 0034-6748, E-ISSN 1089-7623, Vol. 69, no 9, p. 3433-3434Article in journal (Refereed)
    Abstract [en]

    The use of internal ovens is common in high-temperature–high-pressure experiments. Improving the thermal insulation means better efficiency and lower thermal strain on pressure vessels and feedthroughs, but is difficult when using solid media. The addition of a layer of amorphous solid (glass) in the form of a mixed powder is reported to give a significant reduction (20%–50%) in the power dissipated in a high pressure oven.

  • 5.
    Sundqvist, Bertil
    Umeå University, Faculty of Science and Technology, Physics.
    Simple electronic resistance bridge with µOhm resolution at low current1985In: Review of Scientific Instruments, ISSN 0034-6748, E-ISSN 1089-7623, Vol. 56, no 11, p. 2166-2167Article in journal (Refereed)
    Abstract [en]

    A simple electronic resistance bridge is described. The bridge compares an unknown four-terminal resistor in the mOmega range with a precision resistance decade in the kOmega range. A lock-in amplifier is used as zero detector. With 10-mA exciting current a resolution better than one part in 3000 is obtained for unknown resistors in the range 3–100 mOmega. Experimental results are shown for a gold sample under pressure in the range 0–35° C and 0–1.3 GPa.

  • 6.
    Sundqvist, Bertil
    Umeå University, Faculty of Science and Technology, Physics.
    Thermal diffusivity measurements under hydrostatic pressure1981In: Review of Scientific Instruments, ISSN 0034-6748, E-ISSN 1089-7623, Vol. 52, no 7, p. 1061-1063Article in journal (Refereed)
    Abstract [en]

    The original Ångström method has been modified to allow, for the first time, measurements of the thermal diffusivity of metals and other very good conductors under high hydrostatic pressure. The method can also be used to obtain at the same time the pressure dependence of the thermal properties of the pressure transmitting medium, although with reduced accuracy. Some other modifications of the Ångström method are commented on and improved.

  • 7.
    Sundqvist, Bertil
    et al.
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Bäckström, Gunnar
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Low noise and drift by parallel amplifiers1975In: Review of Scientific Instruments, ISSN 0034-6748, E-ISSN 1089-7623, Vol. 46, no 7, p. 928-929Article in journal (Refereed)
    Abstract [en]

    A low noise and low drift amplifier has been constructed using several monolithic operational amplifiers in parallel. It is shown that each amplifier may be connected by only three resistors. An input noise of 0.15 µV (p–p) in the band 0.1–10 Hz was obtained with six amplifiers, and the noise is expected to decrease as N−1/2 as the number of units is increased.

  • 8.
    Sundqvist, Bertil
    et al.
    Umeå University, Faculty of Science and Technology, Physics.
    Bäckström, Gunnar
    Umeå University, Faculty of Science and Technology, Physics.
    Thermal conduction of metals under pressure1976In: Review of Scientific Instruments, ISSN 0034-6748, E-ISSN 1089-7623, Vol. 47, no 2, p. 177-182Article in journal (Refereed)
    Abstract [en]

    It is shown that the original Ångström method of determining the thermal diffusivity of metals is not valid in the case of a specimen surrounded by a solid medium, and an appropriate modification is described. Several simplifications of this method are also presented and criteria for their validity given. An electronic system has been developed for automatic sampling and analysis of the temperature data. The new method has been applied to Cu under pressure, and the results show that the thermal conductivity rises by 6.4% up to 2.5 GPa (25 kilobar).

  • 9.
    Wagner, David R.
    et al.
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics. Department of Chemical and Materials Engineering, San Jose State University, One Washington Square, San Jose, California, USA.
    Holmgren, Per
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Skoglund, Nils
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Broström, Markus
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Design and validation of an advanced entrained flow reactor system for studies of rapid solid biomass fuel particle conversion and ash formation reactions2018In: Review of Scientific Instruments, ISSN 0034-6748, E-ISSN 1089-7623, Vol. 89, no 6, article id 065101Article in journal (Refereed)
    Abstract [en]

    The design and validation of a newly commissioned entrained flow reactor is described in the present paper. The reactor was designed for advanced studies of fuel conversion and ash formation in powder flames, and the capabilities of the reactor were experimentally validated using two different solid biomass fuels. The drop tube geometry was equipped with a flat flame burner to heat and support the powder flame, optical access ports, a particle image velocimetry (PIV) system for in situ conversion monitoring, and probes for extraction of gases and particulate matter. A detailed description of the system is provided based on simulations and measurements, establishing the detailed temperature distribution and gas flow profiles. Mass balance closures of approximately 98% were achieved by combining gas analysis and particle extraction. Biomass fuel particles were successfully tracked using shadow imaging PIV, and the resulting data were used to determine the size, shape, velocity, and residence time of converting particles. Successful extractive sampling of coarse and fine particles during combustion while retaining their morphology was demonstrated, and it opens up for detailed time resolved studies of rapid ash transformation reactions; in the validation experiments, clear and systematic fractionation trends for K, Cl, S, and Si were observed for the two fuels tested. The combination of in situ access, accurate residence time estimations, and precise particle sampling for subsequent chemical analysis allows for a wide range of future studies, with implications and possibilities discussed in the paper.

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