Methods and Apparatus for Detecting and Making Ice

Abstract

Methods and apparatus for making and sensing ice. Also, apparatus and methods for sensing the change of phase of a substance. In one embodiment, a fringe-effect capacitor is placed proximate to a substance, such as water, which is undergoing a phase change, such as the change of phase from the liquid state to the solid state. During this change, the dielectric constant of the substance changes, and thereby changes the electrical flux between conductors of the fringe-effect capacitor. Also, apparatus and methods as described above, and using a capacitor but not a fringe-effect capacitor.

1 . An apparatus for making ice, comprising:
 a container for holding liquid water;   a refrigeration unit for removing heat from water in the container;   means for sensing the capacitance of water in the container and providing a signal corresponding to the capacitance of the water; and   a controller operably connected to said refrigeration unit, said controller operating said refrigeration unit in response to said signal.   
   
   
       2 . The apparatus of  claim 1  wherein said sensing means is a fringe effect capacitor. 
   
   
       3 . The apparatus of  claim 2  wherein said fringe effect capacitor has at least two electrodes and water in the container is a dielectric for the two electrodes. 
   
   
       4 . The apparatus of  claim 1  wherein said sensing means is a capacitor having at least two electrodes and water in the container is a dielectric between the two electrodes. 
   
   
       5 . The apparatus of  claim 4  wherein said refrigeration unit includes an evaporator having at least one tube, wherein one of the electrodes is the tube. 
   
   
       6 . The apparatus of  claim 4  wherein said controller is a digital controller having memory, the memory including data which relates the capacitance of the water to a predetermined thickness of ice in said container. 
   
   
       7 . 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.   
   
   
       8 . The apparatus of  claim 7  wherein said first member is an evaporator tube. 
   
   
       9 . The apparatus of  claim 7  wherein said first member has a first shape immersed in water, said second member having a second shape immersed in water and corresponding to said first shape. 
   
   
       10 . The apparatus of  claim 7  which further comprises a container for holding water, said refrigeration unit capable of removing heat from said container, said container having a shape, said second member having a shape corresponding to the shape of said container. 
   
   
       11 . The apparatus of  claim 7  wherein said first electrically conductive member includes a plurality of first fingers, said second electrically conductive member includes a plurality of second fingers, and said first fingers are interdigitated with said second fingers. 
   
   
       12 . 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.   
   
   
       13 . The method of  claim 13  wherein said comparing is dividing the second measurement by the first measurement. 
   
   
       14 . The method of  claim 12  wherein said comparing is subtracting one of the second measurement or the first measurement from the other of the second measurement or the first measurement. 
   
   
       15 . The method of  claim 12  which further comprises:
 determining by said comparing if a predetermined amount of ice has been made; and   stopping said removing heat after said determining.   
   
   
       16 . The method of  claim 12  wherein said providing includes a capacitor for said making a first measurement and said making a second measurement, and at least some of the changing water is the dielectric of the capacitor. 
   
   
       17 . The method of  claim 12  which further comprises:
 determining by said comparing that the water proximate to the center of the container is liquid water enclosed within a partially-formed ice cube; and   ejecting the partially-formed cube from the container.   
   
   
       18 . 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.   
   
   
       19 . The method of  claim 18  wherein said comparing is dividing the second measurement by the first measurement. 
   
   
       20 . The method of  claim 18  wherein said comparing is subtracting one of the second measurement or the first measurement from the other of the second measurement or the first measurement. 
   
   
       21 . The method of  claim 18  which further comprises:
 determining by said comparing if a predetermined portion of the quantity has been transformed; and   stopping said changing after said determining.   
   
   
       22 . The method of  claim 18  wherein said providing includes a capacitor for said making, a first measurement and said making a second measurement, and at least some of the transformed substance is dielectric for the capacitor. 
   
   
       23 . The method of  claim 22  wherein the capacitor is a fringe-effect capacitor adapted and configured so that the transformed substance changes the fringing electrical fields of the capacitor. 
   
   
       24 . The method of  claim 18  wherein said changing the heat content is by removing heat from the substance. 
   
   
       25 . The method of  claim 18  wherein said changing the heat content is by adding heat to the substance. 
   
   
       26 . The method of  claim 18  which further comprises stopping said changing the heat content based on said comparing. 
   
   
       27 . The method of  claim 26  wherein said providing includes a heat exchanger for changing the heat content of the substance in the container, and which further comprises ejecting the portion from the container based on said comparing. 
   
   
       28 . The method of  claim 26  wherein one of the first physical state or the second physical state is the solid state, and the other is either the gaseous state or the liquid state, and which further comprises ejecting the quantity with the liquid or gaseous phase being enclosed within the substance in the solid phase. 
   
   
       29 . 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.   
   
   
       30 . The apparatus of  claim 29  wherein the width increases along the length in a first direction. 
   
   
       31 . The apparatus of the  claim 30  wherein the gap between said first electrode and said second electrode increases along the length in the same direction. 
   
   
       32 . 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.   
   
   
       33 . The apparatus of  claim 32  wherein the gap monotonically increases in a direction along the first length. 
   
   
       34 . The apparatus of  claim 33  wherein said first electrode has a variable width, and the width monotonically increases in the direction. 
   
   
       35 . The apparatus of  claim 32  wherein said first electrode has a first variable width, and the first width monotonically increases in a direction along the first length. 
   
   
       36 . The apparatus of  claim 35  wherein said second electrode has a second variable width, and the second width monotonically increases in the direction. 
   
   
       37 . The apparatus of  claim 32  wherein the fluid is air and the precipitated substance is frost. 
   
   
       38 . The apparatus of  claim 32  wherein said first electrode is at a first polarity, said second electrode is at a second polarity, and which further comprises a third electrode at the second polarity and in the gap between said first electrode and said second electrode. 
   
   
       39 . The apparatus of  claim 32  which further comprises an electrical circuit which includes a reference capacitor having an input electrode and an output electrode, a source of oscillating voltage, and at least 4 diodes arranged in a four arm bridge, one of said first electrode or said second electrode and the input of said reference capacitor receiving an input from said source, and the other of said first electrode or said second electrode and the output of said reference capacitor being provided separately to opposing arms of said bridge. 
   
   
       40 . 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.   
   
   
       41 . The method of  claim 40  wherein said capacitor is a fringe-effect capacitor. 
   
   
       42 . The method of  claim 40  wherein the heat exchanger is an evaporator of a refrigeration system. 
   
   
       43 . The method of  claim 40  wherein said comparing includes differentiating between frost which has melted and frost which has evaporated.