RF controlled freezing
Disclosed is a method of freezing a body or a portion thereof. The method comprises exposing at least a part of the body to a coolant having a temperature below the freezing point of the body, and at the same time operating an electromagnetic heater, as to maintain the at least part of the body at a temperature above its freezing point; and reducing the electromagnetic heating to allow the at least a part of the body to freeze. The electromagnetic heater comprises a resonator, and the heated part of the body is heated inside the resonator.
1. An apparatus for freezing an RF absorbing body, the apparatus comprising:
a cooler, comprising a coolant at a temperature below a freezing point of the RF absorbing body;
a heater, comprising:
a solid state amplifier as a source of at least one of microwave energy and UHF energy;
a resonant cavity, configured to create a heating zone in the RF absorbing body, such that regions of the RF absorbing body that are within the heating zone are selectively heated;
a feed configured to feed the resonant cavity with at least a portion of the at least one of the microwave energy and the UHF energy; and
a controller, configured to control one or more of the cooler, a position of the RF absorbing body and the heater to heat the RF absorbing body by the at least one of the microwave energy and the UHF energy fed to the resonant cavity through the feed to a substantially uniform temperature above the freezing point of the RF absorbing body while maintaining the temperature of the coolant below the freezing point of the RF absorbing body,
wherein the controller is configured to control the heater to produce electromagnetic waves having a frequency higher than or equal to a resonant cutoff frequency of the resonant cavity.
2. The apparatus according to claim 1 , comprising a shield for shielding at least a portion of the RF absorbing body from being selectively heated.
3. The apparatus of claim 2 , wherein the controller is configured to control the position of the RF absorbing body with respect to the shield so as to shield different portions of the RF absorbing body by the shield.
4. The apparatus of claim 2 , wherein the shielding comprises a cut-off wave guide.
5. The apparatus of claim 2 , wherein the shielding comprises a hollow absorbing body.
6. The apparatus according to claim 1 , wherein the heater is configured to heat the RF absorbing body by applying microwave energy.
7. The apparatus according to claim 1 , wherein the controller is configured to control a location of the heating zone.
8. The apparatus according to claim 7 , wherein the controller is configured to control a shape of the heating zone.
9. The apparatus according to claim 1 , wherein the coolant comprises a cooling fluid, which is less susceptible to heat generated by the heater than is a heated portion of the RF absorbing body.
10. The apparatus according to claim 1 , wherein the cooler comprises at least one solid block.
11. The apparatus of claim 1 , wherein the controller is configured to:
first, reduce electromagnetic heating applied in a first region of the RF absorbing body so that the first region freezes; and then
reduce the electromagnetic heating applied in a second region of the RF absorbing body, so that the second region freezes.
12. The apparatus of claim 11 , wherein the first region is adjacent to the second region.
13. The apparatus of claim 12 , wherein the controller is configured to reduce the electromagnetic heating applied in the second region responsive to a signal indicative of a temperature in the first region or presence of a frozen aqueous portion in the first region.
14. The apparatus of claim 11 , wherein the controller is configured to selectively reduce the electromagnetic heating to move a freezing front created in a border between a region where the electromagnetic heating is reduced and another region where the electromagnetic heating is not reduced.
15. The apparatus of claim 14 , wherein the controller is configured to move the freezing front in a rate responsive to a signal indicative of a temperature or presence of one or more frozen aqueous portions in the region where the electromagnetic heating is reduced, the region being at the freezing front or adjacent thereto.
16. The apparatus of claim 1 , wherein the controller is configured to control the heater to:
heat with RF energy a heating zone inside the heater; and
change a shape of the heating zone.
17. The apparatus of claim 1 , wherein the controller is configured to control the heater to:
heat with RF energy a heating zone inside the heater; and
move the RF absorbing body in or out of the heating zone.
18. The apparatus of claim 1 , wherein the controller is configured to control the heater to:
heat with RF energy a heating zone inside the heater; and
change a location of the heating zone.
19. The apparatus according to claim 1 , wherein the at least one of the microwave energy and the UHF energy has a frequency of 300 MHz to 3 GHz.
20. The apparatus according to claim 1 , wherein the at least one of the microwave energy and the UHF energy has a frequency of 300 MHz or higher.
21. An apparatus for freezing an RF absorbing body, the apparatus comprising:
a cooler, comprising a coolant at a temperature below a freezing point of the RF absorbing body;
a heater, that heats the RF absorbing body in a resonant cavity, the heater comprising:
a solid state amplifier as a source of at least one of microwave energy and UHF energy;
the resonant cavity;
a feed that feeds the resonant cavity with at least a portion of the at least one of the microwave energy and the UHF energy output by the solid state amplifier; and
a controller, that controls one or more of the cooler, a position of the RF absorbing body and the heater to heat the RF absorbing body by the at least one of the microwave energy and the UHF energy fed to the resonant cavity through the feed,
wherein the controller is configured to control the heater to produce electromagnetic waves having a frequency higher than or equal to a resonant cutoff frequency of the resonant cavity.
22. The apparatus according to claim 21 , wherein the controller controls one or more of the cooler, a position of the RF absorbing body and the heater to heat the RF absorbing body to a substantially uniform temperature above the freezing point of the RF absorbing body while maintaining the temperature of the coolant below the freezing point of the RF absorbing body.
23. The apparatus according to claim 21 , wherein the at least one of the microwave energy and the UHF energy has a frequency of 300 MHz to 3 GHz.
24. The apparatus according to claim 21 , wherein the at least one of the microwave energy and the UHF energy has a frequency of 300 MHz or higher.