Dynamics of the thermovoltaic effect in SmS

The thermovoltaic effect in the semiconductor rare-earth compound samarium sulfide (SmS) is briefly described. The qualitative dynamic model of the effect for explaining the possibility of the long-term electric voltage generation on the basis of the thermovoltaic effect is proposed. The model uses a combination of thermal and electronic processes.     

Improvement of piston engine operation efficiency by direct conversion of the heat of exhaust gases into electric energy

A promising new way of direct conversion of the heat of piston engine exhaust gases into electric energy is investigated. An original design of a thermoelectric converter with various surface reliefs (smooth, spherical peaks, spherical dimples) is developed. The engine operation and the flow in the heat-exchanger of the thermoelectric generator are modeled. Based on the results of 3D modeling of convective heat transfer, it has been determined that the surface with heat transfer intensifiers in the form of spherical dimples is the most efficient.     

Thermoelastic interactions without energy dissipation due to a line heat source

Summary The linear theory of thermoelasticity without energy dissipation is employed to study thermoelastic interactions due to a continuous line source of heat in a homogeneous and isotropic unbounded solid. Laplace and Hankel transforms are employed to solve the problem. Exact expressions, in closed form, for the temperature and stress fields are obtained. Numerical results for a hypothetical, copper-like material are presented with the view of illustrating the theoretical results.     

Efficiency of free cooling using latent heat storage integrated into the ventilation system of a low energy building

This article presents the results of an investigation into the free cooling efficiency in a heavyweight and lightweight low energy building using a mechanical ventilation system with two latent heat thermal energy storages (LHTESs), one for cooling the fresh supply air and the other for cooling the re-circulated indoor air. Both LHTESs contain sphere encapsulated PCM (paraffin RT20). Using a developed and experimentally verified numerical model of the LHTES, the temperature response functions, based on the heat storage size, the air flow rates and the PCM's thermal properties, are established in the form of a Fourier series and empirical equations and used in the TRNSYS building thermal response model. Several mechanical ventilation, night cooling and free cooling operation modes were analysed and compared. It was found that the free cooling technique enables a reduction in the size of the mechanical ventilation system, provides more favourable temperatures and therefore enables better thermal comfort conditions, and in our studied case also fresh air for the occupants.     

Efficiency of pulse high-current generator energy transfer into plasma liner energy

The efficiency of capacitor-bank energy transfer from a high-current pulse generator into kinetic energy of a plasma liner has been analyzed. The analysis was performed using a model including the circuit equations and equations of the cylindrical shell motion. High efficiency of the energy transfer into kinetic energy of the liner is shown to be achieved only by a low-inductance generator. We considered an “ideal” liner load in which the load current is close to zero in the final of the shell compression. This load provides a high (up to 80%) efficiency of energy transfer and higher stability when compressing the liner.     

Effects of uniform radial electric field on the MHD heat and fluid flow due to a rotating disk

The flow and heat transfer of an incompressible electrically conducting fluid over a rotating infinite disk are studied in the present paper. The disk finds itself subjected to a uniform normal magnetic field. The particular interest lies in searching for the effects of an imposed radial electric field on the behavior of the physical flow. The gradient of an electric potential generated on the disk penetrates through the fluid and greatly influences the boundary layer formation. The presented model representing the fluid motion is a general case since it reduces to the traditional Karman’s viscous pump when the electric potential is ignored. The governing Navier–Stokes and Maxwell equations of the constructed model together with the energy equation are converted into self-similar forms using suitable similarity transformations. The flow and thermal boundary layers are shown to be much affected by the presence of a uniform radial electric parameter. Some parameters of fundamental physical significance such as the surface shear stresses in the radial and tangential directions and the heat transfer rate are numerically evaluated. The effects of electric conductivity of the disk on the flow and forced convection heat transfer are further discussed.     

Integration of solar thermal energy into processes with heat demand

An integration of solar thermal energy can reduce the utility cost and the environmental impact. A proper integration of solar thermal energy is required in order to achieve it. The objective of this study is to maximise the solar thermal energy delivered to the process. It is a result of trade-off between the captured solar thermal energy and maximal energy delivered to the process (process demand). Two novel curves are introduced to present this trade-off: (i) The Captured Solar Energy Curve (CSEC), which represents the available amount of heat from solar source and (ii) The Minimal Capture Temperature Curve (MCTC), indicating the minimal temperature making the heat transfer feasible. The crossing point of these two curves presents the minimal temperature of the capture being still sufficiently high to be usable for processes. The suitability of these curves for using in combination with standard heat integration methods is analysed and evaluated. The capture potential is revealed in full when the CSEC and MCTC are used with the Grand Composite Curve. In Total Site Profiles, the heat recovery is first maximised and then the CSEC and MCTC tool is applied. The implementation of CSEC and MCTC approach is illustrated by two case studies.     

Contribution to the crystal free energy due to interacting quasiparticles

The new method of calculations for the contribution to the quantum crystal free energy, due to the quasiparticles interactions, is suggested. At rather low temperatures the pare scattering approximation of quasiparticles in the lattice space is used. The commonly used condition of the perturbation theory for the small value of the potential is not superimposed.     

Effective transformation of the energy of high-voltage pulses into high-frequency oscillations using a saturated-ferrite-loaded transmission line

A new method of converting a high-voltage video pulse into high-frequency oscillations using a nonlinear transmission line with temporal dispersion has been studied. The dispersion was provided by pulsed magnetization reversal in a ferrite, which was initially magnetized to saturation in an external magnetic field. For a 9-ns pulse, an average energy conversion efficiency of about 10% was achieved. It is demonstrated that oscillations at frequencies within 600 MHz-1.1 GHz with a spectral width of about 15% (at a −3 dB level) can be excited using voltage pulses with an amplitude of 110–290 kV. The optimum bias magnetization fields are within 20–40 kA/m.     

The effect of an electric field on the surface energy anisotropy in alkali metal alloys

The effect of an electric field on the surface energy anisotropy in alloys is considered for the first time with an allowance for the surface segregation.     

Internal energy flow analysis within a single effect sorption heat pump

The knowledge of the characteristics of unused, excess and untapped exergy allows a thorough analysis of internal energy flows distribution within a sorption heat pump. It can be applied to any system based on gas–liquid absorption, adsorption or solid–gas reaction as well as to any process based on the internal recycling of the energy flux. It can also be applied for the case of a simple effect ideal machine, in particular in the definition of processes where the COP is larger than 2: the levels at which the initial exergy is downgraded on the one hand, as well as, the upgraded excess exergy produced on the other allows the designer to make a judicious choice of a system.     

Plastic energy dissipation due to a penny-shaped crack

International Journal of Fracture - A penny-shaped crack in a material which is ideally elastic-plastic has been envisaged with the assumption that the plastic zone forms a very thin layer...     

Efficiency of the conversion of radiation energy into kinetic energy of a gas-plasma flow during femtosecond laser ablation of metals in vacuum

Using the methods of combined interferometry, we obtained new data on the momentum coupling coefficient and conversion efficiency of radiation energy into kinetic energy of a gas-plasma stream during femtosecond laser ablation (τ ～ 45 fs, λ ～ 800 nm) of several metals (Ti, Zr, Mo, Cu) in vacuum (p ～ 5 × 10^?2 Pa).     

Effects of Hall current and two temperatures in transversely isotropic magnetothermoelastic with and without energy dissipation due to ramp-type heat

The present article is concerned with the investigation of disturbances in a homogeneous transversely isotropic thermoelastic rotating medium with two temperatures, in the presence of the combined effects of Hall currents and magnetic field. The formulation is applied to the thermoelasticity theories developed by Green-Naghdi theories of type-II and type-III. Laplace and Fourier transform techniques are applied to solve the problem. The analytical expressions of displacements, stress components, temperature change, and current density components are obtained in the transformed domain. A numerical inversion technique has been applied to obtain the results in the physical domain. Numerical simulated results are depicted graphically to show the effect of Hall current and two temperatures on resulting quantities. Some special cases are also deduced from the present investigation.     

Abnormal expansion due to pearlite-to-austenite transformation in high aluminium-added steels

Addition of alloying elements usually moves eutectoid point to left whilst aluminium enhances eutectoid carbon content. The carbon expands lattice parameters of austenite. High aluminium addition in steels led to volume expansion at pearlite-to-austenite transformation since specific volume of austenite is larger than that of mother phases, which is proposed to determine the volume expansion or contraction. It has been proven by calculations based on thermodynamics as well as accurate experimental observations of dilatometry study.