1. Magnetic Refrigeration (at room temperature)
Behzad Monfared

2. Agenda Introduction Computer simulation Prototype
Solid-state magnetic refrigeration
Future work

3. Magnetocaloric effect
Temperature increase in presence of magnetic field (magnetocaloric effect)
Example: Gd (rare-earth metal)

4. Working principle

5. Thermodynamic cycle
Resembles Brayton cycle
Limited span
Regeneration

6. Regeneration

7. Active regeneration

8. Porous regenerator Packed bed Parallel plates
(Tusek et al. 2013)

9. A built prototype (not ours)
Cold heat exchanger
Bahl et al., 2012, Thermag V Conf., Grenoble

10. Technical Aspects of a Magnetic Refrigerator
Hydraulics
Mechanics
Material science
Magnetism
Thermodynamics
Heat transfer
- Bed of MC material
- Valves and connections
- Heat exchangers
- Pumping power
- Bed of MC material
- Heat losses
- Heat exchangers
- Power transmission losses
- Mechanisms
- Magnetic and non-magnetic properties
- Mechanics of Material
- Hysteresis, Volume change, etc.
- Magnetocaloric effect
- Bed of MC material
- Heat exchangers
- Energy balance and performance evaluation
- Design of the magnet assembly
- Field variations (spatial and temporal)
- Magnetic forces
- Magnetization of the MC materials
- Eddy currents

11. Advantages No leakage of refrigerants
Magnetization/demagnetization is reversible unlike compression/expansion
Potential for higher efficiency
the most promising alternative to vapor-compression technology (compared to Thermoelectric, Stirling, Electrocaloric, etc.)
(Qian et al. 2016)

12. Agenda Introduction Computer simulation Prototype
Solid-state magnetic refrigeration
Future work

13. Mathematical model Solid
𝑘 𝑒𝑠 𝜕 2 𝑇 𝑠 𝜕 𝑥 2 + ℎ 𝑠𝑓 𝑎 𝑇 𝑓 − 𝑇 𝑠 − 1−𝜀 𝜌 𝑠 𝑇 𝑠 𝜕𝑠 𝜕𝐵 𝜕𝐵 𝜕𝑡 =(1−𝜀) 𝜌 𝑠 𝑐 𝑝,𝑠 𝜕 𝑇 𝑠 𝜕𝑡
Fluid
𝑘 𝑒𝑓 𝜕 2 𝑇 𝑓 𝜕 𝑥 2 − 𝑉 𝐷 𝑐 𝑝,𝑓 𝜕 𝑇 𝑓 𝜕𝑥 − ℎ 𝑠𝑓 𝑎 𝑇 𝑓 − 𝑇 𝑠 + 𝑑𝑃 𝑑𝑥 𝑉 𝐷 =𝜀 𝜌 𝑓 𝑐 𝑝,𝑓 𝜕 𝑇 𝑓 𝜕𝑡
Monfared and Palm "Optimization of layered regenerator of a magnetic refrigeration device." International Journal of Refrigeration 57: doi:

14. Agenda Introduction Computer simulation Prototype
Solid-state magnetic refrigeration
Future work

15. Design specifications
200 W cooling capacity over 40 K temperature span
Estimated 1.6 COP
Magnetic field indicates cost, weight, and size
Comparison:
(Jacobs et al. 2014) 2000 W over 12 K temperature span with 1.44 T field
* defined differently
cooling capacity [W]
(zero span)
temperature span* [K]
(zero load)
magnetic field [T]
(Zimm et al. 2006) 50 25
1.5
(Okamura et al. 2007)
560 8
1.1
(Vasile and Müller 2006)
360 14
2.4
(Yao et al. 2006) 51 42
(Lozano 2014)
625
1.24

16. Regenerators

17. Magnetic circuit

18. Measured results (1/6 of the capacity)

19. Materials: the main problem
Pulverization (low mechanical strength)
Corrosion
Non-uniform size of particles
Low quality of delivery
Resulting in excessive pressure drop, low performance, clogging, etc.

20. Agenda Introduction Computer simulation Prototype
Solid-state magnetic refrigeration
Future work

21. Another work in parallel
Low cycle frequency of the conventional magnetic refrigeration systems described
Small cooling capacity per kg of magnetocaloric material
Large magnets ( 𝑚 𝑚𝑎𝑔 𝑚 𝑀𝐶𝑀 does not increase linearly)
Expensive and bulky
Solid-state magnetic refrigeration

22. Solid-state magnetic refrigeration
Enhanced conduction in one direction

23. Agenda Introduction Computer simulation Prototype
Solid-state magnetic refrigeration
Future work

24. Future work Solving the remaining problems of the prototype
Running systematic experiments to study the effect of different parameters
Adjusting the software model using the experimental data
Simulating solid-state magnetic refrigeration systems

25. Thank you