Performance Analysis And Parametric Optimization For Two Kinds Of Irreversible Magnetic Heat Pumps

The refrigeration and the heat pump technologies have been widely applied to many fields, and in recent years the performances of the gas heat pump and refrigeration systems have been investigated by a number of researchers by using the concept of finite time thermodynamics. However, with the development of science and technology, the greenhouse effect is becoming more severe than ever. In order to solve these problems, the magnetic refrigerator and magnetic heat pump have been thought as a possible substitute of traditional refrigeration and heat pump technology and have been paid more attention. since it has small size, high efficiency, low noise and environmental friendliness even is easy to maintain. Moreover, many studies on magnetic refrigerant materials, magnetic refrigerator and magnetic refrigeration cycle theory have become an animate subject in recent year. And with the development of the studies on room-temperature magnetic refrigerators, the practical value of a magnetic heat pump is increasingly obvious. For a magnetic heat pump, it is necessary that a new models should be established. By using finite time thermodynamics and optimal-control theory, the effects of multi-irreversibilities existing in the new model will be considered, such that we may analyze and discuss the optimal performance characteristics of the magnetic heat pump systems. It is expected that the results obtained may provide some theoretical instructions for the researches and developments of magnetic heat pumps. .In Chapter 1, the concepts and principles of magnetic refrigeration as well as the significances of exploring magnetic heat pump are introduced.In Chapter 2, the new model of an irreversible Stirling heat pump cycle using ferromagnetic materials as a cyclic working substance is established. On the basis of the thermodynamic properties of ferromagnetic materials, the performance characteristic of the ferromagnetic Stirling heat pump cycle is investigated. Also, by applying the optimal-control theory, the relation between the optimal heating load and the coefficient of performance (COP) is obtained. By means of numerical value calculation, the heating load, COP and the relationship curves between them are obtained. Furthermore, some important performance of the heat pump and their optimal operating regions are determined.An irreversible magnetic Ericsson heat pump cycle is put forward in Chapter 3, in which the effects of finite-rate heat transfer, heat leak, inherent regenerative losses, additional regenerative losses and the internal irreversibility on the performance of irreversible magnetic Ericsson heat pump cycle are investigated. At the same time, by using the numerical value calculation, the influences of the multi-irreversibilities on the heat loading or COP are analyzed in detail. The important performance bounds such as the heating load, COP, power input and their optimal operating regions are determined. Some significant special cases are discussed at last.The results obtained in this thesis may provide some theoretical references for the further investigation of the performance characteristics of magnetic heat pumps as well as the optimal parameter design and performance improvement of actual magnetic heat pumps.