Design, fabrication and thermal characterization of a magnetocaloric microcooler

Abstract

SUMMARYMagnetocaloric cooling is an alternative, high-efficiency cooling technology. In this paper, we present the design and fabrication of a micromachined magnetocaloric cooler and demonstrate its ability to work in a small magnetic field ð51:2 TÞ with a cooling test. The cooler was built by fabricating Si microfluidic channels, and it was integrated with a Gd 5 ðSi 2 Ge 2 Þ magnetocaloric refrigeration element. The magnetic properties of the Gd 5 ðSi 2 Ge 2 Þ material were characterized to calculate the magnetic entropy change at different ambient temperatures. Three different methods to integrate the channel layer and the magnetocaloric element were evaluated to test sealing and cooling performance. The cooling tests were performed by providing a magnetic field using an electromagnet. A test jig was constructed between the poles of an electromagnet to maintain a steady temperature during the test. Cooling tests were performed on the magnetocaloric element at ambient temperatures ranging from 258 to 280 K using a magnetic field of 1.2 T. Experimental results showed a maximum temperature change of 7 K on the magnetocaloric element alone at an ambient temperature of 258 K. Cooling tests of the fully integrated coolers were also performed. A solution of anti-freeze fluid (propylene glycol) and water was used as the coolant. The temperature of the working fluid decreased by 4.6 and 9 K for the glass and Si intermediate layers, respectively, confirming that the thermal conductivity of the materials is also an important factor in cooler performance.

Gd5(Si,Ge)4 thin film displaying large magnetocaloric and strain effects due to magnetostructural transition

“…Despite their properties, Gd 5 (Si x Ge 1Àx ) 4 materials were left behind in the nanoscalling race, whereas an increasing number of works have been published on Gd multilayers, 27,28 manganites, [29][30][31] FeRh, 32,33 NiMnGa, 34 and MnAs 35,36 materials and also on the MEMS development and numerical simulations. 22,[37][38][39][40] Concerning the Gd 5 (Si x Ge 1Àx ) 4 materials, there is only one not-successful report of a Gd 5 (Si x Ge 1Àx ) 4 thin film. 41 Our group has been developing and optimizing the Gd 5 (Si x Ge 1Àx ) 4 thin film deposition by femtosecond pulsed laser ablation technique, but, so far, with low amounts of desired phase and no signs of magnetostructural transition.…”

Enhancing the temperature span of thermal switch-based solid state magnetic refrigerators with field sweeping

“…2,3 The main differences are the use of a magnetocaloric material (MCM) as the working substance instead of a gas, the use of a quasi-adiabatic magnetization process to increase the temperature of the MCM instead of the compression of the gas, and the use of a quasi-adiabatic demagnetization process to reduce the temperature of the MCM instead of the expansion of the gas. [4][5][6][7] So far, rotary-based magnetic refrigerators have been the most cited designs for magnetocaloric systems, [8][9][10][11][12] with several investigations looking for the most suited parameters that results on the best performance. 13,14 Although the related prototypes already show the features required for practical applications, issues remain that make them still not competitive from a commercial point of view.…”

Magnetocaloric effect and temperature coefficient of resistance of La0.85Ag0.15MnO3epitaxial thin films obtained by polymer-assisted deposition

“…There has been an increase in the demand for localized cooling and temperature stabilization of micro and optoelectronic devices [1][2][3] since (i) the number of components in an integrated circuit continues to increase, and (ii) modern devices demand ever smaller chips at an accelerated pace. The manufacture of micro-systems using magnetic refrigeration technology seems to be a promising alternative for thermo-electric microcooler applications [3,4].…”

“…The manufacture of micro-systems using magnetic refrigeration technology seems to be a promising alternative for thermo-electric microcooler applications [3,4]. In this context, high quality and inexpensive thin films suitable for magnetic refrigeration applications near room temperature could play an important role in the development of these microrefrigeration devices.…”