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This paper discusses the system performance of a magnetic heat pump with an active magnetic regenerator. The heat-transfer coefficient and pressure drop in the AMR are performed analytically. Measurements on the experimental magnetic heat pump test device are performed using distilled water as the working fluid. The coupling of a one-dimensional thermal model is presented. The thermal model takes into consideration the magneto-caloric effect as a source term and the energy conservation between a solid and a fluid. At cyclic steady states, the temperatures of the fluid on both sides of the regenerator are calculated numerically and compared with the measurement results. A reasonable agreement between simulations and experiments confirms the validity of the proposed model.

The main objective of this theoretical study was to investigate under which conditions a magnetic energy conversion device (MECD) - utilizing industrial waste heat - is economically feasible. Furthermore, it was evaluated if magnetic energy conversion (MCE) has the potential of being a serious concurrent to already existing conventional energy conversion technologies. Up-today the availability of magnetocaloric materials with a high Curie temperature and a high magnetocaloric effect is rather limited. Therefore, this study was mainly focused on applications with heat sources of low to medium temperature levels. Magnetic energy conversion machines, containing permanent magnets, are numerically investigated for operation conditions with different temperature levels, defined by industrial waste heat sources and environmental heat sinks, different magnetic field intensities and different frequencies of operation (number of thermodynamic cycles per unit of time). Theoretical modeling and numerical simulations were performed in order to determine thermodynamic efficiencies and the exergy efficiencies as function of different operation conditions. From extracted data of our numerical results, approximate values of the total mass and total volume of magnetic energy conversion machines could be determined. These important results are presented dependent on the produced electric power. An economic feasibility study supplements the scientific study. It shows an excellent potential of profitability for certain machines. The most important result of this article is that the magnetic energy conversion technology can be economically and technically competitive to or even beat conventional energy conversion technologies. This is true especially in those cases when large, low-exergy heat sources are at one's disposal. (C) 2012 Elsevier Ltd. All rights reserved.

At present magnetic refrigeration shows a realistic potential to penetrate into some niche markets in the field of cold and hot "production". It is well known that a refrigerator for cooling and a heat pump for heating are machines based on the same principle. A small review on magnetic heat pump studies is outlined and a simple engineering calculation scheme to determine the coefficient of performance for a magnetic heat pump with a rotary porous structure heat exchanger is presented. Magnetic heat flux line distributions are calculated by a 2-d finite element method numerical simulation program with the objective to obtain high field's mu H-0 with not too heavy permanent magnets assemblies. The porous structures are geometrically optimised to obtain maximal magnetic field inductions. It is shown that for a water/ethylene-glycol magnetic heat pump the coefficient of performance is higher than that of a conventional heat pump. (c) 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Magnetic refrigeration is a new environmentally benign technology and a promising alternative to conventional vapor-cycle refrigeration. The household refrigerator without a freezing compartment shows very good prospects for a successful application. This article starts with the general principle of magnetic refrigeration. An example of a magnet assembly is proposed and the corresponding magnetic flux lines are evaluated with a three-dimensional finite-element method (FEM). The maximum specific cooling capacity of magneto caloric materials is described. The specific cooling power of a magneto caloric material is found to be large even for medium magnetic field changes, especially if the frequency is not too small. For a domestic magnetic refrigerator, a comparison with a standard compressor refrigerator is presented. The modeling of a rotary magnetic refrigerator is described and its dynamic behavior is investigated. The physical model is based on a mapping of the magneto-thermodynamic problem from a cylinder onto two rectangles. In this model, in a basic centre cell, two coupled linear partial differential equations are solved, which have been programmed in the Modelica language. Steady-state solutions are envisaged to determine the coefficient of performance, COP, for these conditions. In future work the developed model shall be applied for an optimization of the magnetic refrigerator and to determine the related best parameters.

In conventional refrigeration the use of the T S diagram to determine thermodynamic cycle performance is a well accepted tool. This method is based on a single state description of the gaseous refrigerant during its cycling. Devices filled with a magnetocaloric refrigerant, due to slow diffusion and inhomogeneous temperature distributions, usually do not allow such a simple description. If the layered bed technique is applied, the situation is even more complex. The related problems are addressed and some new solutions are presented, e.g. a generalized T*-S* diagram containing weights w*. Furthermore, an analysis shows that an implementation of a layered bed of numerous weak magnetocaloric alloys does not substantially decrease the coefficient of performance, COP, compared to a single correspondingly better performing magnetocaloric material, but leads to an increase of the magnet size, the volume and the related price of a device. With devices operating with higher frequencies this can be counterbalanced and magnetic heating, refrigeration and energy conversion - with present available magnetocaloric materials - suddenly show a realistic chance for certain market penetrations. (c) 2012 Elsevier Ltd and IIR. All rights reserved.

A first part of the article contains a thermodynamic theory describing the temperature distribution in a Curie wheel. The occurring nonlinear ordinary differential equation has an analytical solution. If a Curie wheel is stabilized by levitation, it is named Palmy wheel. These wheels show a full structure, and because of this reason, their uptake of heat from a flame (Curie wheel) or by (solar) light absorption (Palmy wheel) only on the periphery of a cylinder is very limited. To improve the method, a modification of the principle by introducing a convective heat transport into a porous wheel is discussed. By this the power conversion rate from a heat flux to mechanical and electric power is very much increased. The second part of the article presents results of a theoretical/numerical study on the efficiencies of magnetic power conversion plants operating with porous wheels. Furthermore, these efficiencies which are promising-are compared with those of existing power conversion plants, as e.g. geothermal binary cycle power plants. (C) 2008 Published by Elsevier B.V.

In a rotary magnetic refrigerator a porous ring is turning in and out of a magnetic field region. The adiabatic demagnetization of the magnetocaloric material produces the "cold energy". This is described by a discontinuous temperature decrease, known as adiabatic temperature difference. For such a machine a physical model has been developed, based on a mapping of the magneto-thermodynamic problem. In this model, in a basic centre cell, two coupled linear partial differential equations are solved, which have been programmed in the Modelica language. The operation of a magnetic refrigerator is simulated with numerous parameters. Steady state solutions are obtained to verify the coefficient of performance under stable operation conditions. Optimal running conditions defined by maximum values of the coefficient of performance - are not presented in this article, but can now easily be obtained with the existing program. A simple regulation strategy is proposed and implemented into the program. (C) 2010 Elsevier Ltd and IIR. All rights reserved.

An investigation under which conditions industrial waste heat utilised with magnetic energy conversion machines can be a possible alternative to conventional energy conversion technologies is presented. The application of a numerical model leads to the thermodynamic efficiency, the exergy efficiency, and approximate values of the total mass and the total volume of a magnetic energy conversion machine. The exergy efficiency depends strongly on the magnetic field strength. A high frequency of operation reduces the mass and volume of a device. Magnetic energy conversion may beat conventional technologies, especially if large low-exergy heat sources are at ones disposal.

A magnetic hyperthermia cancer treatment strategy that does not operate by means of conventional heating mechanisms is presented. The proposed approach consists of injecting a gel with homogeneously distributed magnetic nanowires into a tumor. Upon the application of a low-frequency rotating or circularly polarized magnetic field, nanowires spin around their center of viscous drag due to torque generated by shape anisotropy. As a result of external rotational forcing and fluid friction in the nanoparticle's boundary layer, heating occurs. The nanowire dynamics is theoretically and experimentally investigated, and different feasibility proofs of the principle by physical modeling, which adhere to medical guidelines, are presented. The magnetic nanorotors exhibit rotations and oscillations with quite a steady center of gravity, which proves an immobile behavior and guarantees a time-independent homogeneity of the spatial particle distribution in the tumor. Furthermore, a fluid dynamic and thermodynamic heating model is briefly introduced. This model is a generalization of Penne's model that for this method reveals theoretic heating rates that are sufficiently high, and fits well into medical limits defined by present standards.