The subject of this invention is a method of heat transfer in the embedded structure of a heat regenerator and the design thereof. It regards the related heat regenerators, which operate on the principle of the described method and enable a reduction of the pressure drop due to the fluid flow through the heat regenerator and consequently an increase of the power density. The concept of the operation of the heat regenerator by this invention, in which for the oscillation of the flow of the primary (first) fluid (P), electromechanical elements are applied. In the housing (1) between the elements (2) for the oscillation of the primary (first) fluid (P), there are positioned a primary hot heat exchanger (PT) and a primary cold heat exchanger (PH). In the direction of the arrow (A) the unidirectional flow of the secondary (second) fluid (S) flows from the heat sink into the primary cold heat exchanger (PH). In the direction of the arrow (B) the unidirectional flow of the secondary (second) fluid (S) exits from the primary cold heat exchanger (PH) and flows towards the heat source. Meanwhile, in the direction of the arrow (C), the unidirectional flow of the secondary (second) fluid S enters the primary hot heat exchanger (PT) and exits in the direction of the arrow (D) as the unidirectional flow of the secondary (second) fluid S of the primary hot heat exchanger (PT) towards the heat sink. Between both primary heat exchangers, (PT) and (PH), the porous regenerative material is positioned, which is part of the regenerator 4, with the hydraulically separated segments.
COBISS.SI-ID: 14214659
This article reports on the novel resistive electromagnetic field source with the magnetic energy recovery, which enables the use of the static magnetocaloric regenerator. Most of the existing prototype magnetocaloric devices that operate near room temperature, use magnetic field sources consisting of permanent magnets. The alternating of the magnetic field that is required for the thermodynamic cycle often comes from the rotation of magnets over the refrigerant, that is, an active magnetocaloric regenerator (AMR). Such systems require moving parts and a motor drive, both of which cause additional costs and reduced energy efficiency. Further restrictions in existing devices result from the speed of the magnetisation/ demagnetisation process, which is, in addition to efficient heat transfer, crucial for the compactness of the device. Another drawback is that the instant change of the magnetic field is not feasible, regardless of the principle of movement. Permanent-magnet assemblies based on neodymium are also constrained by the use of this rare-earth-material. Therefore, a number of global research activities relate to the optimization of permanent-magnet-based magnetic field sources. However, ohmic loss, the active cooling of magnets, and considerable energy consumption are the reasons why another type of magnetic field source, that is, the electromagnet, was generally avoided by the magnetocaloric community. This article presents a novel and unique approach that enables substantially improved energy efficiency and applicable operation of rare-earth-free and static electromagnetic field sources, by implementing for the first time the magnetic energy recovery for magnetic refrigeration and heat pumping. To prove the advantages of such a system, a large number of numerical simulations, as well as an experimental proof, were conducted. A comparative analysis was made for the evaluation of the energy efficiency of the proposed novel system vs an example of the existing rotating-magnet assembly. The results of this study reveal that this new type of electromagnetic field sources provides a number of different and important advantages that can lead to new frontiers in research. However, the energy efficiency is still lower than that of the comparable rotating-magnet assembly.
COBISS.SI-ID: 16410139
In this work the preparation of a protective insulating alumina coating on magnetocaloric gadolinium elements was investigated. In order to prepare a dense ceramic coating at room temperature the aerosol deposition technique was used. The study reveals that the powder morphology and particle size are important parameters that influence the deposition efficiency, powder packing and consequently also the density and functional properties of the alumina coating. The optimal powder pre-deposition treatment includes heating the powder to 1150 °C, followed by milling. The deposition of this powder resulted in the preparation of dense alumina coatings with a low specific electrical conductivity of 6.4.10-14 [Omega]-1m-1.
COBISS.SI-ID: 16935195
The magnetocaloric refrigeration and heat pumping is considered to be one of the most important alternatives to existing vapour-compression technologies. In the past two decades we have witnessed a substantial increase in basic and applied research efforts to bring this technology to the market. Despite the significant research progress that has been made, there are several critical issues that need to be solved in the near future. These concern efficient heat transfer, the reduction or removal of moving parts, and rare-earth-free and stable, energy-efficient magnets and magnetocaloric materials. This article gives an overview and updated information on global research achievements in magnetic refrigeration and heat pumping. The article addresses the most important and also some overlooked solutions that could pave the way for the future developments of magnetocalorics and their realistic market applications.
COBISS.SI-ID: 16772891
Caloric refrigeration and heat pumping play important roles in a potential future substitute for vapourcompression technology. Although caloric refrigeration is foreseen as one of the most promising alternatives, the current low power density of caloric devices represents a serious hurdle to overcome prior to market applications. In order to improve the power density, the number of thermodynamic cycles per unit of time, denoted as the frequency, has to be increased. Thermal switch mechanisms, which act as a control element for the heat flux, represent a promising solution. They can enable the operation of caloric devices at up to an order higher frequencies compared to existing devices and their principles. This review covers the principles of microfluidic mechanisms that have already been or can be applied as active thermal switches in caloric technologies. The article can serve as a guideline for the future development of compact caloric devices.
COBISS.SI-ID: 16773147