Investigation of thermal expansion, phase diagrams, and barocaloric effect in the (NH4)2WO2F4 and (NH4)2MoO2F4 oxyfluorides

Горев, М. В.; Bogdanov, E. V.; Flerov, I. N.; Kocharova, A. G.; Laptash, N. M.

doi:10.1134/s1063783410010294

Cited by 45 publications

(27 citation statements)

References 14 publications

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“…For simplicity reason, we consider the basic cooling element made of Pb(Mg 1/3 Nb 2/3 )-PbTiO 3 [13] and (NH 4 ) 2 MoO 2 F 4 [14], while the whole system contains 3 elements, see Fig.1. Obviously, the cooling rate mostly depends on the thickness of the whole structure so we impose the condition that this value does not exceed 12.5mm.…”

Section: Computational Detailsmentioning

confidence: 99%

Temperature Change in the Piezoelectrocaloric Element under Periodic External Fields

Starkov

Starkov²

2015

Ferroelectrics

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The paper presents the analysis of the cooling structure consisted of alternate electroand piezocaloric layers. The temperature distribution in such a system under periodic electric and elastic fields is investigated. It is demonstrated that the simultaneous application of the external forces allows to increase the temperature difference at the outer surfaces of the system in 2-3 times compared with the operation by a single force. The obtained results can be used for design and optimization of a new generation of cooling devices.

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Section: Computational Detailsmentioning

confidence: 99%

Temperature Change in the Piezoelectrocaloric Element under Periodic External Fields

Starkov

Starkov²

2015

Ferroelectrics

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“…The barocaloric oxyfluorides (NH4)2MoO2F4 [25] showing a maximum direct barocaloric effect at 272 K which remains remarkable until 360 K, ensures a good applicability for heat pumps application. The considered drop of applied pressure field is 0.9 GPa that guarantees a maximum of 18 K due to barocaloric effect.…”

Section: The Selected Caloric Materialsmentioning

confidence: 99%

Nanofluids as Heat Transfer Fluids for High-efficiency Caloric Heat Pumps

Greco¹,

Aprea²,

Maiorino³

et al. 2019

IJES

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Solid-state is the new frontier of Not-In-Kind technologies arisen as possible future replacement of vapor-compression-based systems. Caloric cooling and heat-pumping found their operation on caloric effect; a class of thermo-physical effects detected in caloric materials following an adiabatic change of the intensity of an applied external field, that results in a variation of the temperature in the material itself. A Brayton-based thermodynamical cycle, called Active Caloric Regenerative cycle, is used to build caloric cooling systems or heat-pumps. In ACR cycle the caloric material acts both as refrigerant and as regenerator and an auxiliary Heat-Transfer Fluid (HTF) is employed to vehiculate heat fluxes between the cold and hot environments. The most common HTF is water but advanced solutions could be adopted to enhance the heat exchange coefficients, like nanofluids. Nanofluids are suspensions consisting of solid high-thermal-conductivity nanoparticles dispersed in a base fluid to enhance the global thermal conductivity of the fluid. In this paper we investigate, numerically, the energy performances of a caloric heat pump employing water-based Al2O3 nanofluids as HTF. The analysis is perpetuated changing both the nanofluid volume concentrations and the caloric materials employing electrocaloric, elastocaloric and barocaloric ones.

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“…The results of investigations into the influence of the anisotropy of the crystal lattice on the barocaloric effect in related oxyfluorides (NH 4 ) 2 WO 2 F 4 and (NH 4 ) 2 MoO 2 F 4 are no less interesting and impressive [42]. At room temperature, these crystals have the orthorhombic symmetry Cmcm, but upon cooling, they undergo phase transitions of different natures: the tungstate at T 1 = 201 K becomes a ferroelastic (space group P ), while the molybdate at T 1 = 271 K trans forms into an antiferroelectric (space group Pnma).…”

Section: Individual Caloric Effectsmentioning

confidence: 99%