[en] Abstract only

[en] This paper reports on Vuilleumier heat pumps with balanced compounding which have been under investigation for about fifteen years but have not yet reached the stage of commercial utilization. Previously published analytical treatment based upon isothermal treatment of the variable-volume spaces resulted in closed form solution of considerable complexity of the coupled differential equations but applied only to free piston machines. In contrast, the procedure presented here is based on previously demonstrated sinusoidal excursions of the reciprocators. It is of the same order of accuracy, but much more simple and usable. It was found that there is only negligible difference between the results of the present and the previous approach. Additionally, the treatment presented here is applicable to kinematic machines, as well as to free piston machines. For the latter design, an equation for the natural frequency is also derived. Ideal proportions and practical expressions for the energy streams are derived. Gas forces are plotted versus displacement and it is shown that they are equivalent to a linear spring, which is of importance for the concept of a free-piston design

[en] The most attractive application for fuel cells seems to be in decentralised combined heat and power generation (CHP). The market for energy efficient CHP is growing, partly as a result of the wish to decrease CO₂ emissions. Gas utilities are facing this development and can react in different ways. One of these is to operate natural gas powered CHPs themselves. The attractiveness of fuel cell powered CHPs for gas utilities depends firstly on the economy and reliability of CHP in general in the markets considered and secondly on the competitiveness of fuel cells versus, for example, the gas engine and gas turbine based CHP. Important possible activities for a gas utility in relation to fuel cell commercialisation are helping develop the market for CHP, defining the requirements for fuel cells in CHP and helping the fuel cell manufacturers to build up practical experience by participating in demonstration projects. The situation in the Netherlands will be used for examples. (orig.)

[en] This paper reports that the transported entropy of oxygen ion S*_O²-, in yttria-stabilized zirconia (YSZ) has been determined from measurements of Seebeck coefficients of the cell (T₁,p)(Pt)O₂(g)|YSZ|O₂(g)(Pt)(T₂,p). The value obtained, 51 J K^-1 F^-1, is substantially different from results for YSZ which can be calculated from other investigations. The value does not vary with oxygen pressure, in accordance with results obtained for calcia-stabilized zirconia. The results indicate that the sintering temperature for YSZ is important for obtaining uniform temperature conditions in fuel cells

[en] The instrumented Fast-Reactor Accelerated Component-Sheath Insulator test (IFAC-SI) is a key experiment of the Thermionic fuel Element (TFE) Verification Program designed to allow continuous monitoring of sheath insulator specimens with an applied voltage during the in-reactor test. The IFAC-SI experiment is designed to monitor the applied voltage, resistance, and temperature of two sets of three specimens while maintaining the sets at two desired operating temperatures. This paper contains a description of the test section of the IFAC-SI experiment which includes the sheath insulator samples, heat pipes, fins, and enclosing container. The thermal models developed are described and their results and effects on the experiment design are presented

[en] Short communication

[en] This patent describes a high surface area platinum catalyst which has been prepared by the electrochemical processing of uranium platinum carbide. This Raney-type catalyst has a roughness factor exceeding 3000. The methanol oxidation current at this catalyst was about 1.8 A/cm² at 60 degrees C and a polarization of 1.2 V. Due to the high activity of the catalyst, the inhibition of methanol oxidation at more positive potentials and the consequent hysteresis in the oxidation response were not observed. The preparation, characterization, and evaluation of this catalyst material are also described

[en] The presented LMMHD cycles (Rankine MHD or Brayton MHD) show a potential superior to conventional power plants and their realisation is possible with available techniques. For the high temperature components ceramic materials can be used, which are compatible with alkali metals up to high temperatures. One can mention, that the greatest losses in the LMMHD cycles are localised in the two-phase flow region and especially in the separator. The calculations of the efficiencies of the separator are based on experimental results with low rates. Probably these efficiencies will be better for larger power installations, this could drive to an increased actual efficiency of η>0.50

[en] Spalling of the oxide scale from 316 stainless steel hardware in the molten carbonate environment is likely due to the presence of frozen electrolyte in the porous scale. If the thickness of the scale can be kept to a minimum and the active components can be kept under compression, then spalling will not occur during thermal cycling in the area of contact between the cathode current collector and the bipolar separator plate

[en] This paper reports on magnetohydrodynamic (MHD) thrusters which have long been recognized as potentially attractive candidates for ship propulsion because such systems eliminate the conventional rotating drive components. The MHD thruster is essentially an electromagnet (EM) pump operating in seawater. An electrical current is passed directly through the seawater and interacts with an applied magnetic field; the interaction of the magnetic field and the electrode current in the seawater results in a Lorentz force acting on the water, and the reaction to this force propels the vessel forward. The concept of EM propulsion has been examined periodically during the past 35 years as an alternative method of propulsion for surface ships and submersibles. The conclusions reached in early studies were that MHD thrusters restricted to fields of 2T (the state-of-the-art at that time) were impractical and very inefficient. With the evolution of superconducting magnet technology, later studies investigated the performance of MHD thrusters with much higher magnetic field strengths and concluded that at higher fields (>6 T) practical MHD propulsion systems appear possible