Press Release Back Number(2006)

Development of refrigeration systems to replace gas refrigeration systems using CFCs or other fluorocarbon refrigerants is one approach to preventing global warming. Because they are used for such long periods of time, electrical equipment such as air conditioners and refrigerators that use refrigeration systems have long been the target of development for energy conservation.

It is a well known phenomenon (known as the magnetocaloric effect) that if magnetic field changes are applied to some types of magnetic bodies (referred to as magnetic working materials), then their temperature will change. Magnetic refrigeration technology taking advantage of this phenomenon is potentially eco-friendly, promising efficiency and energy conservation, and Chubu Electric is actively developing the technology for practical use. Our efforts have recently resulted in the successful development of a magnetic refrigeration system with the world's highest refrigerating capacity, sufficient to be used in air conditioners and refrigerators.

Magnetic refrigeration takes advantage of the phenomenon that a magnetic working material generates heat when it is exposed to a magnetic field and drops in temperature when the magnetic field is removed (i.e. the magnetocaloric effect). Compared to gas refrigeration, magnetic refrigeration has the following characteristics:

Effective ways of improving the refrigerating capacity of magnetic chillers include:

The recently developed equipment was able to achieve large magnetic field change (1.1 tesla) because the permanent magnet form and position were modified to maximize the magnetic field (the repulsion of the magnetic field was increased by placing the magnet in a V-groove).

The refrigerating capacity of the equipment was increased by optimizing the structure of the heat exchanger (shortening the length of the tubing in which the water flows) and more than tripling the flow velocity of the heat exchange fluid.

Additionally, while rotation of the permanent magnet causes magnetic working materials to be exposed to changes in the magnetic field, heat generation resulting from the eddy current in the tubing external to the system (the iron yoke) is reduced by optimizing the structure of the magnetic circuits (cutting the external tubing into round segments and putting in insulation), thus successfully limiting heat infiltration.

These improvements have resulted in the world's highest performance of 540 W, almost 10 times the 60 W refrigerating capacity achieved in FY2003.

In addition, to achieve a system that is highly efficient and limits energy consumption, it is necessary to reduce the power of the motor that drives the permanent magnet and that of the pump that circulates the heat exchange medium.

The recently developed equipment limits the power of the water pump by widening the tubing, which alters the way the circulating heat exchange medium (water) flows, and by minimizing pressure loss, so that the system exchanges heat efficiently.

Furthermore, motor power was reduced by mitigating the magnetic resistance resulting from rotation of the permanent magnet.

These improvements have resulted in the achievement of the world's highest coefficient of performance (COP) of 1.8 for a magnetic refrigeration system.

Hereafter, Chubu Electric aims to achieve practical use of air conditioners, refrigerators and so on with magnetic refrigeration technology. We will develop technology for the stable production of materials with high magnetocaloric effect and develop equipment that is more compact and efficient.