Use of unidirectional flow modes of magnetic cooling systems
A dual-mode magnetic refrigeration apparatus includes beds of magnetocaloric material, a magnet to apply a time-varying magnetic field to the beds, a heat transfer fluid (HTF), a pump to circulate the HTF, a hot side heat exchanger (HHEX), a cold side heat exchanger (CHEX), valves to direct flow of the HTF, and a controller configured to control periodic switching of the valves to allow the apparatus to operate in a first mode and in a second mode. The first mode transfers heat from the CHEX to the HHEX. In the second mode of operation, the periodic switching of the valves is suspended to allow unidirectional flow of the HTF through the HHEX, the beds, and the CHEX such that heat is transferred from the HHEX to the CHEX.
1. A combination magnetic refrigerator-freezer apparatus, comprising:
a refrigerator compartment that is maintained above 0 C;
a freezer compartment that is maintained below 0 C;
a controller;
one or more magnets configured to generate one or more time-varying magnetic fields;
a first magnetic refrigeration system for the refrigerator compartment comprising:
a first set of one or more beds of magnetocaloric material;
a first heat transfer fluid (HTF);
a first pump to drive flow of the first heat transfer fluid;
a hot side heat exchanger (HHEX);
a first cold side heat exchanger (CHEX);
a first section of an inter-stage heat exchanger (IHEX);
one or more first valves to direct flow of the first heat transfer fluid; and
wherein the controller is configured to control the periodic switching of the one or more valves to direct the first HTF to a cold end of the first set of one or more beds through the first set of one or more beds to a hot end of the first set of one or more beds and through the HHEX when the time-varying magnetic field applied to the first set of one or more beds is high, and to the hot end of the first set of one or more beds through the first set of one or more beds to the cold end of the first set of one or more beds and through the first CHEX and the first section of the IHEX when the time-varying magnetic field applied to the first set of one or more beds is low, in order to transfer heat from the first CHEX and the first section of the IHEX to the HHEX; and
a second magnetic refrigeration system for the freezer compartment comprising:
a second set of one or more beds of magnetocaloric material;
a second heat transfer fluid;
a second pump to drive flow of the second heat transfer fluid;
a second CHEX;
a second section of the IHEX;
one or more second valves to direct flow of the second heat transfer fluid; and
wherein the controller is configured to control the periodic switching of the one or more valves to direct the second HTF to a cold end of the second set of one or more beds through the second set of one or more beds to a hot end of the second set of one or more beds and through the second section of the IHEX when the time-varying magnetic field applied to the one or more beds is high, and to the hot end of the second set of one or more beds through the second set of one or more beds to the cold end of the second set of one or more beds and through the second CHEX when the time-varying magnetic field applied to the second set of one or more beds is low, in order to transfer heat from the second CHEX via the second section of the IHEX to the first section of the IHEX.
2. The apparatus of claim 1 , wherein the controller controls the one or more first valves to be maintained in a bypass arrangement to allow unidirectional flow of the first heat transfer fluid through the first set of one or more beds, the HHEX, the first CHEX, and the first section of the IHEX, and wherein the controller controls the one or more second valves to be maintained in a bypass arrangement to allow unidirectional flow of the second heat transfer fluid through the second set of one or more beds, the second CHEX, and the second section of the IHEX, such that heat is transferred from the HHEX to the first CHEX and the second CHEX.
3. The apparatus of claim 1 , wherein the controller controls the one or more second valves to be maintained in a position to allow unidirectional flow of the second heat transfer fluid through the second set of one or more beds, the second CHEX, and the second section of the IHEX such that heat is transferred from the first CHEX to the second CHEX.
4. The apparatus of claim 1 , wherein the second heat transfer fluid has a lower freezing point than the first heat transfer fluid.