A comparison between electrocaloric and magnetocaloric materials for solid state refrigeration

et al. 2018

IJHT

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Caloric refrigeration is an emerging class of cooling technologies based on caloric effects detected in ferro-caloric solid-state materials. Depending of the nature of the driving field, it is possible distinguishing four main caloric refrigerations: magnetocaloric, electrocaloric, elastocaloric and barocaloric. Therefore, caloric refrigeration is based on solid-state materials, unlike vapor compression, nowadays still the most diffused cooling technique, whom employs fluids as refrigerants. Solid-state materials do not provide a direct contribution in global warming, since they do not disperse in the atmosphere, but only an indirect impact is registered when they are employed as refrigerants in cooling systems. On the other side, a vapor compression plant is characterized by both direct and indirect contributions to global warming. The main parameter to evaluate global warming impact and carbon-dioxide emissions coming out from a cooler is the Total Environmental Warming Impact (TEWI) index, which accounts both the direct and indirect contributions produced. In this paper a numerical ∆TEWI analysis is presented, comparing the environmental impact of a caloric refrigerator, operating with different caloric materials, with the one of a vapor compression cooler working with HFC134a.

Section: -D Modelmentioning

confidence: 99%

The environmental impact of solid-state materials working in an active caloric refrigerator compared to a vapor compression cooler

Aprea¹,

Greco²,

et al. 2018

IJHT

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“…TEWI provides a measure of the environmental impact of greenhouse gases originating from operation, service and endof-life disposal of the equipment. TEWI is the sum of the direct contribution of the greenhouse gases used to make or operate the systems and the indirect contribution of carbon dioxide emissions resulting from the energy required to run the systems over their normal lifetimes [6][7][8][9][10][11][12][13][14]. The TEWI is calculated as:…”

Section: The Tewi Conceptmentioning

confidence: 99%

An experimental evaluation of the greenhouse effect in the substitution of R134a with pure and mixed HFO in a domestic refrigerator

Aprea¹,

Greco²,

2017

IJHT

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Due to the UE Regulation n. 517/2014 refrigerants with a GWP higher than 150 are not allowed from January 1, 2015 in new domestic refrigerators. Thus, a replacement for HFC134a is needed. In this paper attention is devoted to the evaluation of the environmental impact in terms of greenhouse effect of the substitution of HFC134a with low GWP, HFO refrigerant fluids. The greenhouse effect is accounted for by the experimental evaluation of the TEWI index (Total Equivalent Warming Impact) that takes into account both direct and indirect contributions to global warming. The refrigerant fluids that have been tested as a drop-in are: pure HFO1234yf, the mixture HFO1234yf/HFC134a (90/10 % in weight), pure HFO1234ze, the mixture HFO1234ze/HFC134a (90/10 % in weight). In particular, with the mixture HFC134a/HFO1234yf (10/90 % in weight) there is a reduction of the TEWI of -295% respect to HFC134a.

“…The nature of the driving field Y particularizes the caloric effect. Magnetic fields applied to a magnetocaloric materials give rise to magnetocaloric effect (MCE) where Y=H and X=M, electric fields to electrocaloric effect (ECE) [8] where Y=E and X=P, mechanical stress to elastocaloric effect (eCE) [9], where Y=σ and X=ε, pressure field to barocaloric effect (BCE) [10] where Y=-p and X=V.…”

Section: Introductionmentioning

confidence: 99%

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

Greco¹,

Aprea²,

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.