Modeling of an Elastocaloric Cooling System for Determining Efficiency

When it comes to covering the growing demand for cooling power worldwide, elastocalorics offer an environmentally friendly alternative to compressor-based cooling technology. The absence of harmful and flammable coolants makes elastocalorics suitable for energy applications such as battery cooling. Initial prototypes of elastocaloric systems, which transport heat by means of thermal conduction or convection, have already been developed. A particularly promising solution is the active elastocaloric heat pipe (AEH), which works with latent heat transfer by the evaporation and condensation of a fluid. This enables a fast and efficient heat transfer in a compression-based elastocaloric cooling system. In this publication, we present a simulation model of the AEH based on MATLAB-Simulink. The model showed very good agreement with the experimental data pertaining to the maximum temperature span and maximum cooling power. Hereby, non-measurable variables such as efficiency and heat fluxes in the cooling system are accessible, which allows the analysis of individual losses including the dissipation effects of the material, non-ideal isolation, losses in heat transfer from the elastocaloric material to the fluid, and other parasitic heat flux losses. In total, it can be shown that using this AEH-approach, an optimized system can achieve up to 67% of the material efficiency

Phenomenological model for first-order elastocaloric materials [Modèle phénoménologique pour les matériaux élastocaloriques de premier ordre]

Elastocaloric cooling systems may offer a potentially more efficient as well as environmentally friendly alternative to compressor-based cooling technology. These cooling systems use stress-induced phase transformation in elastocaloric materials to pump heat. Thermodynamically consistent material models can be used to design and quantify the efficiency of these cooling systems. In this paper, we present a phenomenological material model that depicts the behavior of first-order materials during stress-induced phase transformation. This model is based on a phenomenological heat capacity equation, from which the parameters adiabatic temperature change and isothermal entropy can be derived. Hysteresis of the materials, which determines it dissipative effects, is also taken into account. Based on this model, these parameters can be calculated as a function of stress and temperature. The performance coefficients derived from the model can be used to evaluate the materials efficiency. Furthermore, the data obtained using this model coincided very closely with experimental data

Elektronik entwärmen mit pulsierenden Heatpipes

Eine vielversprechende Lösung zur gezielten Entwärmung von Hotspots sind pulsierende Heatpipes. Die Wärmeleitfähigkeit dieser speziellen Wärmerohre ist gleich gut oder sogar besser als die von Diamant

Jean Christophe Pfeilius, Mi-corps, 3/4 à g., en méd. ov. avec armoiries

Appartient à l’ensemble documentaire : BNUStr003Appartient à l’ensemble documentaire : BNUStras

D. Joh. Conradus Dannhawerus, Theol. et Prof. Argentoratensis Senior ac Primar. Conventus Ecclesiastici Praeses atque Capituli Thomani Decanus, Mi-corps, face, en méd. ov

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New concept for magnetocaloric heat pumps based on thermal diodes and latent heat transfer

Since the beginning of the last decade, several dozens of magnetocaloric heat pump systems have been built by different groups. Basically all of these systems are based on the Active Magnetic Regenerator (AMR) concept, where a heat transfer fluid is actively pumped through a bed of magnetocaloric material in order to transfer thermal energy to hot and cold side heat exchangers. Hereby several powerful systems were built, generating large temperature spans of more than 50 K while others provided large cooling capacities of several kW. However, up to now no system has been built which provides large temperature span and cooling capacity while having a coefficient-of-performance (COP) better than standard compressor-based cooling systems [1]. In this work a new concept and first experimental data of a magnetocaloric heat pump will be presented. In this concept, the heat transfer is realized by the combination of magnetocaloric material with thermal diodes which are based on latent heat transfer. Similar to thermosyphons, thermal energy is efficiently transported by condensation and evaporation processes leading to heat transfer rates which are several orders of magnitude larger than in conventional systems. At the same time, no additional pumps are required for transporting the heat exchange fluids, enabling systems which large temperature spans and competitive COPs