Methods and Apparatus for Detecting and Making Ice

An apparatus for sensing the capacitance of water, comprising:

• a refrigeration unit for removing heat from water, said refrigeration unit including a first electrically conductive member located proximate to a location where liquid water transitions to ice;
• a second electrically conductive member located proximate to the location where liquid water transitions to ice, said first member being electrically insulated from said second member and spaced apart from said second member;
• and
• a circuit in electrical communication with said first member and said second member, said circuit producing a signal corresponding to the capacitance of the water proximate said first member and said second member.

A method for making ice, comprising:

• providing a container holding liquid water;
• making a first measurement of the capacitance of the water;
• removing heat from the water and changing some of the liquid water into ice;
• making a second measurement of the capacitance of the water after said removing;
• and
• comparing the first measurement to the second measurement.

A method for detecting the phase change of a substance, comprising:

• providing a container which includes a quantity of a substance in a first physical state;
• making a first, measurement of the capacitance of the substance;
• changing the heat content of the substance and transforming at least a portion of the substance to a second phase different than the first phase;
• making a second measurement of the capacitance of the substance including the portion after said changing;
• and
• comparing the first measurement to the second measurement.

An apparatus for exchanging heat, comprising:

• an evaporator having at least one tube and a plurality of fins attached to the exterior of said tube, said fins being arranged and configured for exchange of heat with a fluid flowing within the tube;
• a capacitor thermally coupled to said tube or one said fin, said capacitor having a first planar electrode being spaced apart by a gap from a second planar electrode, the first electrode having a length and a width, and one of the gap or the width varying along the length;
• and
• wherein said first electrode and said second electrode are adapted and configured to change the capacitance therebetween in response to the formation of frost therebetween.

An evaporator for a refrigeration system which transfers heat from a fluid, comprising:

• a tube having an outer wall defining a lumen for the flow therethrough of a refrigerant, said tube being adapted and configured to encourage the flow of heat into the refrigerant;
• and
• a capacitive sensor in thermal communication with said tube, said sensor including a first electrode separated by a gap from a second electrode, said first electrode having a first length in electrical communication with a second length of said second electrode, the gap between the first length and the second length being nonconstant along the first length;
• wherein a substance from the fluid precipitates proximate to the gap as a result of the flow of heat, the precipitated substance altering the electrical flux between the first length and the second length.

A method for defrosting a heat exchanger, comprising:

• providing a heat exchanger and a capacitor, the heat exchanger and capacitor both having at least a partial buildup of external frost;
• making a first measurement of the capacitance of the capacitor with the frost;
• heating the heat exchanger and the capacitor;
• making a second measurement of the capacitance of the capacitor after a period of said heating;
• comparing the first measurement to the second measurement;
• and
• stopping said heating in response to said comparing.