Magnetic Refrigeration down to 1.6K for FCC_ee Jakub Tkaczuk Supported by: DRF Energy Program – DESA41K CERN FCC Collaboration
Contents Magnetic refrigeration State of the Art Active Magnetic Regenerative Refrigerator Static Magnetic Refrigerator o Heat exchange conditions o Heat losses o Possible improvements Perspectives
Contents Magnetic refrigeration State of the Art Active Magnetic Regenerative Refrigerator Static Magnetic Refrigerator o Heat exchange conditions o Heat losses o Possible improvements Perspectives
Magnetic refrigeration Magnetic refrigeration is based on the Magneto-Caloric Effect (MCE) (reversible variation of internal energy when applied magnetic field in a suitable material) Remove magnetic field spins randomize temperature decreases Apply magnetic field spins align temperature increases
Magnetic refrigeration Ideal Carnot cycle 2 adiabatic transformations 2 isothermal transformations
Contents Magnetic refrigeration State of the Art Active Magnetic Regenerative Refrigerator Static Magnetic Refrigerator o Heat exchange conditions o Heat losses o Possible improvements Perspectives
State of the Art CEA design Hitachi rotating design Hitachi static design CERN design MIT design
State of the Art Cold source Temperature 1.8K Warm source temperature 4.2K 4.5K4.2K Useful power1.35 W1.8 W0.5 W10 W12 mW Q / m_GGG10.6 W/kg1.7 W/kg0.7 W/kg1 W/kg0.1 W/kg η ?0.12 See presentation: FCC Week 2015
Contents Magnetic refrigeration State of the Art Active Magnetic Regenerative Refrigerator Static Magnetic Refrigerator o Heat exchange conditions o Heat losses o Possible improvements Perspectives
Active Magnetic Regenerative Refrigerator Large DT possible But : More material More exchanged power ADR Adiabatic Demagnetization Refrigerator AMRR Active Magnetic Regenerative Refrigerator Every part of magneto-caloric material goes through its own cycle
Active Magnetic Regenerative Refrigerator
Inputs for one GGG core: Outputs for AMRR: Limited efficiency in comparison to other designs
Contents Magnetic refrigeration State of the Art Active Magnetic Regenerative Refrigerator Static Magnetic Refrigerator o Heat exchange conditions o Heat losses o Possible improvements Perspectives
Static Magnetic Refrigerator
Contents Magnetic refrigeration State of the Art Active Magnetic Regenerative Refrigerator Static Magnetic Refrigerator o Heat exchange conditions o Heat losses o Possible improvements Perspectives
Static Magnetic Refrigerator – Heat exchange conditions Warm source Kutateladze correlation: Nucleate boiling – far from film boiling transition
Cold source Condensation is limited by Kapitza resistance For small temperature differences: For larger temperature differences: Static Magnetic Refrigerator – Heat exchange conditions
L5 cm D No heat losses taken into account yet
Contents Magnetic refrigeration State of the Art Active Magnetic Regenerative Refrigerator Static Magnetic Refrigerator o Heat exchange conditions o Heat losses o Possible improvements Perspectives
Energy balance with Kapitza resistance Static Magnetic Refrigerator – Heat losses Largest heat losses: GGG – warm source So large heat loss is not possible Conclusion: GGG temperature is not homogeneous, it is significantly influenced by the heat exchange with the warm source.
Diffusion inside GGG: Static Magnetic Refrigerator – Heat losses Largest heat losses: GGG – warm source
Other heat losses Static Magnetic Refrigerator – Heat losses negligible Scaling the SMR: 670 kg of GGG is needed to obtain 1kW. GGG dimensions: D = 50 cm, L = 50 cm
Contents Magnetic refrigeration State of the Art Active Magnetic Regenerative Refrigerator Static Magnetic Refrigerator o Heat exchange conditions o Heat losses o Possible improvements Perspectives
50 µm Static Magnetic Refrigerator – Possible improvements Gas heat switch “off ” conduction is satisfying “on” conduction is not satisfying – 2-5 µm heat switch required – technically impossible
Contents Magnetic refrigeration State of the Art Active Magnetic Regenerative Refrigerator Static Magnetic Refrigerator o Heat exchange conditions o Heat losses o Possible improvements Perspectives
Short term Study of heat switch solution on the warm source interface Experimental, cryogenic validation of selected heat switch Mid-term design of a 0.3 W magnetic refrigerator for laboratory demonstration Long term design of kW range refrigerator for FCC
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