The Magnetic Refrigeration (MR) technique is going to replace the conventional vapour compression refrigeration cycle, which is based on the magnetic property of materials i.e. Magneto Caloric Effect (MCE). Magneto Caloric Effect is a technology that came into existence around a century ago. A rebirth of this technology seeks to the research endeavours for better performance of systems with various magnetic materials.
In 1881, E. Warbung found that due to the presence of some magnetic field carrying constituents in them, some materials when exposed to a magnetic field heat up and cool down instantaneously after removal of the field. This phenomenon is termed as Magneto Caloric Effect (MCE) where such materials are called Magneto Caloric Materials (MCM). It took a century to implement this technology into a concept that was given by the Ames Laboratory in 1997, developing magnetic refrigeration systems for commercial applications. In between, Giaque in 1933, used this effect and achieved a very low temperature of 0.25 K in the magnetocaloric system. He also received a Nobel prize for that.
As compared to conventional refrigeration system, in which the refrigerant with compression/expansion process gives cooling effect, in MR system it uses MCM under magnetization/demagnetization process. So, the main parameters that affect the working are adiabatic temperature or curie temperature of material that depends on the entropy of the system and some external parameters of the system.
In MR system a series of Magnetization-Demagnetization fields are applied in a controlled manner to the MCM. Each field creates a temperature gradient in the material. A rapid sequence of these fields yields the final and stabilized hot and cold temperatures in the refrigerated system. An environmentally friendly coolant fluid ensures the heat transfers between cold to hot sources.
Magneto Caloric Materials
The experiments are conducted from early days when Giaque first performed it in 1933. He experimented with the Gadolinium Sulphate and achieved 0.25 K. then after that many researchers experimented on various MCMs like Cerium Fluoride, Dysprosium ethyl sulphate, Manganese Ammonium Sulphate, Lanthanum Calcium Magnate, Terbium Silicon Geranium, Anti-ferromagnets like FeRh, various Gadolinium alloys, Paramagnetic Salts like cerium magnesium nitrate, ADR, Germanium alloy, Holmium, etc. for increasing the performance and optimizing system capabilities of MR systems.
Benefits of MR System
The technology resolves the two main issues affecting conventional refrigeration systems that are:
The environmental challenge via a gas-free solution.
The economic challenge by reducing energy consumption and increasing efficiency.
Apart from that, it also has advantages like:
- More efficient than conventional technologies
- No gases or volatile liquids involved
- Low vibration and noise
- Re-usable and recyclable parts and components
- Energy savings up to 50%
- Safety and cost reduction
- In household refrigerators
- Magnetic room air conditioning unit and heat rejection system
- In central cooling systems
- Magneto caloric material that can be effectively used for cancer treatment side effects of hyperthermia
- In blood plasma storage refrigerators, chromatography
- In food-storage units
- High-temperature magneto caloric materials are used in aircraft and military systems.
Karan Khatke is an Assistant Professor (ME Deptt) at Prestige Institute of Engineering Management & Research Indore, Madhya Pradesh, India.