Effective Energy Conversion Research Articles

Transient characteristics of combined conduction, convection and radiation heat transfer in porous media

This paper presents transient heat transfer characteristics of an effective energy conversion between high-temperature gas enthalpy and thermal radiation by means of porous media. A theoretical analysis is conducted for the one-dimensional system where conduction, convection and radiation take place simultaneously. The porous medium is assumed to be a homogeneous continuum which absorbs and emits thermal radiation. The coupled energy equations for gas and porous media are solved numerically. To confirm the validity of the analysis, experiments which strictly correspond to the analytical model are performed. The predicted results agree well with those of the experiments.

Temperature Equalization by the Radiative Converter for a Slab in Continuous Casting Direct Rolling

This paper reports the experimental results on heat transfer performance of a newly suggested temperature equalizer with the radiative converter for a slab in the continuous casting direct rolling process. The present temperature equalization is based on the effective energy conversion method between gas enthalpy and thermal radiation using a porous media. The model temperature equalizer used is about one fifth of the actual one its dimensions. To simulate the continuous casting direct rolling process in the experiment, the uniformly preheated model slab was first cooled by thermal radiation, and subsequently fed into the temperature equalizer. By measurements of transient slab temperatures, it is proved that the radiative converter equalizes the slab temperature quickly owing to local heating of the slab edge. Furthermore, estimation of the overall energy balance in the temperature equalizer demonstrated that efficient temperature equalization is feasible if the available energy flowing out of it is recovered.

Theory of the radio emission of pulsars

A consistent theory of excitation, stabilization, and propagation of electromagnetic oscillations in a relativistic one-dimensional electron-positron plasma flowing along curved magnetic field lines is presented. It is shown that in such a medium which is typical of the magnetosphere of a neutron star there exist unstable natural modes of oscillations. Nonlinear saturation of the instability leads to an effective energy conversion into transverse oscillations capable of leaving the magnetosphere of a pulsar. The polarization spectrum and the directivity pattern of generated radiation are determined. A comparison with observations has shown that the theory makes it possible to explain practically all the basic characteristics of observed pulsar radio emission.

A study on a high-performance radiant heater with a porous medium energy converter.

This study aims to develop a high-performance radiant heater which would be able to convert almost all energy released by combustion into thermal radiation. A compact radiant heater was produced, which was an application of the effective energy conversion method from flowing gas enthalpy to thermal radiation emitted from the porous medium of an appropriate optical thickness placed in a duct of high-temperature gas. It consists of a porous medium energy converter and a quartz window. It is also equipped with a convective heat exchanger between the burnt and unburnt gases. The thermal radiation emitted from the porous medium energy converter is taken out in the opposite direction to the burnt gas flow. The temperature profiles in the heater were examined and the energy balance of the heater has been elucidated. The results shows that 80 to 90% of the energy released by combustion is converted into thermal radiation.

Dependence of fast magnetic reconnection on electrical resistivity in an isolated current-sheet system

Computer simulation shows that, initiated by a resistive disturbance, the rarefaction of the current-sheet plasma and the subsequent remarkable thinning of the current-sheet region occur; once the fast reconnection builds up, the plasma density is extremely rarefied near the neutral point. The development of fast reconnection provides a situation favorable to the occurrence of a current-driven instability. The energy conversion rate associated with the fast reconnection is found to have a weak dependence on the magnetic Reynolds number Rm0 and tends to scale as (log10 Rm0)−1 for large Rm0. These results come from the fact that for larger Rm0 the diffusion region that is spontaneously established has a smaller width and hence a larger current density to compensate for the smaller magnitude of electrical resistivity. Effective energy conversion can be realized even in the presence of rigid walls.

ふく射エネルギ利用の新しい要素技術 : 顕熱とふく射エネルギ間の効果的変換法の原理と応用

ふく射エネルギ利用の新しい要素技術 : 顕熱とふく射エネルギ間の効果的変換法の原理と応用

303 - On the current generated by a galvanic cell driven by photosynthetic electron transport

Photosynthetic electron transport of isolated chloroplasts was used to convert light energy to a potential difference of a galvanic cell. A current through an external circuit of the cell requires a transfer of electrons between the endogenous electron carriers and a redox mediator, and a subsequent transfer between the mediator and the electrode in each of the joined half—cells. With 2,3,5,6-tetramethyl- p-phenylenediamine or N,N,N′,N′-tetramethyl- p-phenylenediamine as mediator the second electron transfer step was found to be limiting. To increase the current through the external circuit we increased the concentration of salt and mediator as well as the surface area of the electrodes. Upon illumination the system generated a short—circuit current of up to 800 μA at a current density of 16 μA/cm 2. The results are discussed with respect to the interdependence of the successive electron transfer steps and the properties of components for effective energy conversion by the cell.

Low‐grade thermal energy conversion engine

Abundant, undeveloped, and essentially ‘free’ thermal energy exists in the form of low‐temperature water from sources such as geothermal hot water, oceanic and fresh water thermal gradients, and industrial waste heat. Recovery of useful mechanical and electrical energy from these vast and inexpensive resources has been hampered by lack of effective and economical thermal energy conversion systems (heat engines). A research team at McDonnell Douglas Astronautics Company (MDAC) is developing low‐temperature heat engines which use Joule effect solid state materials as the working media. These materials, when heated, contract with substantially greater force than is required to stretch them at lower temperatures, and the force difference is translated into work. Heat engines built by using one of these materials, Nitinol—a nickel titanium alloy—have operated successfully at temperature differences as low as 5°C.

On the current generated by a galvanic cell driven by photosynthetic electron transport

Abstract Photosynthetic electron transport of isolated chloroplasts was used to convert light energy to a potential difference of a galvanic cell. A current through an external circuit of the cell requires a transfer of electrons between the endogenous electron carriers and a redox mediator, and a subsequent transfer between the mediator and the electrode in each of the joined half—cells. With 2,3,5,6-tetramethyl- p -phenylenediamine or N,N,N′,N′-tetramethyl- p -phenylenediamine as mediator the second electron transfer step was found to be limiting. To increase the current through the external circuit we increased the concentration of salt and mediator as well as the surface area of the electrodes. Upon illumination the system generated a short—circuit current of up to 800 μA at a current density of 16 μA/cm 2 . The results are discussed with respect to the interdependence of the successive electron transfer steps and the properties of components for effective energy conversion by the cell.

Electrofluid Dynamic Energy Conversion Present Status and Research Areas

This paper presents in depth the major basic performance characteristics of electrofluid dynamic (EFD) energy conversion processes, which are shown to be complementary to magnetofluid dynamic processes. With a view toward making possible effective thermal-electric energy conversion without moving parts, the potential compatibility of incorporating low pressure ratio EFD processes into high pressure ratio thermodynamic cycles is shown. Investigations of scaling, similarity, performance characteristics, and the effects of physical properties of working media containing electric charges of one polarity are used as a basis to determine the major problems and corresponding research areas in EFD energy conversion. In general these are: Generation of Charged Colloids; Electrode and Conversion Duct Geometry; and Fluid Dynamic Energy Transfer Phenomena in Multicomponent, Multiphase Flows. Also given are typical configurations of EFD energy converters, and a look at potential applications, especially those associated with encapsulated, long-duration power supply for operations in space, under the ocean, or at remote unattended sites.