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The magnetocaloric effect can be quantified with the following equation: = ((,)) ((,)) where is the adiabatic change in temperature of the magnetic system around temperature T, H is the applied external magnetic field, C is the heat capacity of the working magnet (refrigerant) and M is the magnetization of the refrigerant.
In a typical two-stage refrigerator, the first stage will offer higher cooling capacity but at higher temperature (≈ 77 K) with the second stage reaching ≈ 4.2 K and < 2.0 W of cooling power. In use, the first stage is used primarily for ancillary cooling of the cryostat with the second stage used primarily for cooling the magnet.
The refrigeration requirements for HTSC and low-temperature superconductor (LTSC) toroidal coils for the baseline temperatures of 77 K, 20 K, and 4.2 K, increases in that order. The refrigeration requirements here is defined as electrical power to operate the refrigeration system.
For commercial and industrial refrigeration systems, the kilowatt (kW) is the basic unit of refrigeration, except in North America, where both ton of refrigeration and BTU/h are used. A refrigeration system's coefficient of performance (CoP) is very important in determining a system's overall efficiency. It is defined as refrigeration capacity ...
The term is most often used for smaller systems, typically table-top size, with input powers less than about 20 kW. Some can have input powers as low as 2–3 W. Large systems, such as those used for cooling the superconducting magnets in particle accelerators are more often called cryogenic refrigerators. Their input powers can be as high as 1 MW.
The current is fed through a conducting liquid. Two permanent magnets are arranged to produce a magnetic field B ap as shown in the figure. The supplied current has a current density (J) and the magnetic field associated with this current can be called "Reaction magnetic Field (b rc)". The two magnetic fields B ap and b rc attempt to align with ...
Engine cooling systems (21 P) H. Heat exchangers (39 P) ... Magnetic refrigeration; Alfred Mellowes; MERLIN (refrigerator) Micro-loop heat pipe; Mini-split air ...
Assuming the external magnetic field is uniform and shares a common axis with the paramagnet, the extensive parameter characterizing the magnetic state is , the magnetic dipole moment of the system. The fundamental thermodynamic relation describing the system will then be of the form U = U ( S , V , I , N ) {\displaystyle U=U(S,V,I,N)} .