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1

Ammonia carbon adsorption cycle research at the University of Warwick

Rivero-Pacho A. M., Critoph R. E., Metcalf S. J., Pal M.

Polska Energetyka Słoneczna

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2015

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nr 1-4

47--54

EN

Active carbon-ammonia cycles have been developed from the 1980’s in the USA and are still a major research interest at the University of Warwick, where systems have been built for car air conditioning, solar refrigeration and gas-fired heat pumps. The basic cycles are introduced and a brief description of the historical development is presented. The paper then presents work to date on domestic gas fired heat pumps with preliminary results from the latest system under test, and describes plans and the prospects for future products. The possibility of using carbon-ammonia in thermal transformers for industrial use is modelled theoretically and the prospects discussed and compared with using ammonia and chemical salts.

2

Plane harmonic waves in transversely isotropic piezothermoelastic materials

Sharma J. N., Pal M.

International Journal of Applied Mechanics and Engineering

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2004

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Vol. 9, no 4

749-769

EN

The aim of the paper is to study the propagation of plane harmonic waves in homogeneous, piezothermoelastic materials having hexagonal symmetry. After deriving the secular equation, it is found that four dispersive modes are possible. The low and high frequency approximations for the propagation speeds and attenuation coefficients have been obtained for quasi-longitudinal (QL), quasi-transverse (QT), and quasi-thermal (T-mode) by using the theory of algebraic functions. The limiting cases of the frequency equation have also been discussed in addition to the paths of particles during the motion. The paths of particles during the motion have been found to be elliptic, in general. The velocities and attenuation coefficients for various waves have been computed numerically for cadmium selenide material (6mm class) having hexagonal symmetry and are represented graphically. The inclinations of major axes of the paths of particles of QL and QT waves during the motion with wave normal have also been computed and represented graphically with respect to frequency.

3

On superposed couple-stress fluids in a porous medium

Sharma R. C., Sunil, Pal M.

Studia Geotechnica et Mechanica

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2001

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Vol. 23, nr 3-4

55--66

EN

The Rayleigh-Taylor instability of two superposed couple-stress fluids of uniform densities through porous medium is studied. The stability analysis is carried out, for mathematical simplicity, for two highly viscous fluids of equal kinematic viscosities and couple-stress kinematic viscosities. The system is found to be stable for stable configuration and unstable for unstable configuration. The growth rates are found to be both increasing and decreasing with the increase in medium permeability.

PL

W porowatym środowisku badano niestateczność Rayleigha-Taylora dwóch nakładających się, sprężonych naprężeniem płynów o jednorodnych gęstościach. Ze względu na prostotę matematyczną, analizę stateczności przeprowadzono dla dwóch mocno lepkich płynów o jednakowych lepkościach kinematycznych i o sprzężonych naprężeniem lepkościach kinematycznych. Okazało się, że układ jest stabilny dla statecznej konfiguracji, a niestabilny dla niestatecznej konfiguracji. Szybkości wzrostu zarówno rosną, jak i maleją ze zwiększeniem przepuszczalności środowiska.

4

Hall effect on thermosolutal instability of Walters' (model B') fluid in porous medium

Sunil, Sharma R. C., Pal M.

Archives of Mechanics

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2001

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Vol. 53, nr 6

677-690

EN

The thermosolutal instability of Walters' (model B') fluid in porous medium is considered in the presence of uniform vertical magnetic field to include the effect of Hall currents. For the case of stationary convection, the stable solute gradient and magnetic field have stabilizing effects on the system, whereas the Hall currents have destabilizing effect on the system. The medium permeability has both stabilizing and destabilizing effects on the system depending on the Hall parameter M. The kinematic viscoelasticity has no effect for stationary convection. The kinematic viscoelasticity, stable solute gradient and magnetic field (and the corresponding Hall currents) introduce oscillatory modes in the system, which were non-existent in their absence. The sufficient conditions for the non-existence of overstability are also obtained.

5

On couple-stress fluid heated from below in porous medium in the presence of rotation

Sharma R. C., Sunil, Pal M.

Applied Mechanics and Engineering

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2000

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Vol. 5, no 4

883-896

EN

A layer of a couple-stress fluid heated from below in a porous medium is considered to include the effect of uniform rotation. For the case of stationary convection, the couple stress may hasten the onset of convection in the presence of rotation while in the absence of rotation, it always postpones the onset of convection. For the case of stationary convection, rotation postpones the onset of convection. Graphs have been plotted by giving numerical values to the parameters, to depict the stability characteristics. Rotation is found to introduce oscillatory modes in the system, which were non-existent in its absence. A sufficient condition for the non-existence of overstability is obtained.