Abstract
High cooling power of magnetocaloric refrigeration can be achieved only at large amounts of heat, which can be transferred in one cycle from cold end hot end at quasi-isothermal conditions. The simple and robust experimental method of direct measuring of the transferred heat of materials with magnetocaloric effect (MCE) in thermal contact with massive copper block with definite heat capacity in quasi-isothermal regime was proposed. The vacuum calorimeter for the specific transferred heat ∆Q and adiabatic temperature change ∆T measurements of MCE materials in the fields of Bitter coil magnet up to H = 140 kOe was designed and tested on samples of Ni43Mn37.9In12.1Co7 Heusler alloy with inverse MCE in the vicinity of meta-magneto- structural phase transition (PT). It was found, that the magnetic field H = 80 kOe produces complete PT from martensite to austenite with ∆Q = - 1600 J/kg at initial temperature 273 K.
Highlights
A big interest is attracted to the application of materials with a large magnetocaloric effect (MCE) at phase transition (PT) for creation of household and industrial refrigerators, operating at room temperature
High cooling power of such devices can be achieved only at high frequency of heat transfer cycles and at large amounts of heat, which can be transferred in one cycle from cold end to hot end
The maximal frequency of cycles depends on the geometry of the working body made of MCE material and the fundamental restrictions on the rate of PT in this material
Summary
A big interest is attracted to the application of materials with a large magnetocaloric effect (MCE) at phase transition (PT) for creation of household and industrial refrigerators, operating at room temperature. High cooling power of such devices can be achieved only at high frequency of heat transfer cycles and at large amounts of heat, which can be transferred in one cycle from cold end to hot end. The maximal frequency of cycles depends on the geometry of the working body made of MCE material and the fundamental restrictions on the rate of PT in this material. The rate of PT depends on the relaxation processes in the vicinity of PT. The magnetization relaxation time of Gd near the Curie point is discussed in terms of Landau-Khalatnikov equation and is experimentally estimated as τ ≈ 50 ms in [2]. In the present work we suggest the experimental approach for the direct measurement of transferred heat in one cycle
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