Abstract:
The system disclosed in my U.S. Pat. No. 4,897,099 for deriving purified ice pieces and purified water from tap water is modified by providing a metal or thermally conductive heat flow path from an alternative refrigerant condenser to the ice collection bin. In one embodiment the size/shape of the heat flow path provides sufficient heat flow resistance to maintain a temperature gradient thereacross whereby the bottom of the bin is at approximately 32° F. and the condensing rejection temperature is at least 60° F. In another embodiment the alternative condenser is undersized relative to the primary condenser (used in the non-melting mode). In a further embodiment the second condenser is operated in a partially flooded condition during the ice-melting mode to reduce its effective condensing surface area.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application is a Continuation-In-Part of my prior U S. patent application Ser. No. 07/278,447 filed Dec. 1, 1988, now U.S. Pat. No. 4,897,099. The entire disclosure in that patent is expressly incorporated herein by this reference. 
     BACKGROUND OF THE INVENTION 
     The present invention relates to a method and apparatus for providing purified ice pieces and purified liquid water from a source of unpurified liquid water. More particularly, the present invention provides an alternative approach to melting ice pieces in a method and apparatus of the type generally disclosed in my aforementioned U.S. Pat. No. 4,897,099. 
     In my U.S. Pat. No. 4,897,099 I disclose a method and apparatus for forming purified ice pieces from unpurified water, such as tap water. The ice pieces are periodically harvested and collected in a bin, the bottom of which is heated as necessary to melt desired quantities of the ice to provide a supply of purified water. In the embodiment disclosed in FIG. 6 of my aforesaid patent, heat for melting the ice is derived from an alternative condenser connected in the refrigerant flow path and disposed near the bottom of the ice bin. An air gap for material of low thermal conductivity is placed between the alternative condenser and the bin bottom, thereby avoiding the need for undesirably low condensing temperatures. Specifically, this technique permits the condensing temperature in the condenser coil to be maintained at approximately 110° F. while the melting temperature of the ice is approximately 32° F., resulting in a temperature gradient of approximately 78° F. extending through the separating gap/material. 
     The present invention provides an alternative method and apparatus for applying thermal energy to the ice collection bin bottom from the alternative condenser. 
     OBJECTS AND SUMMARY OF THE INVENTION 
     It is an object of the present invention to provide an alternative method and apparatus to that disclosed in my U.S. Pat. No. 4,897,099 for applying thermal energy to a collection bin for purified ice, thereby melting some of the ice to provide and collect purified water. 
     In accordance with the present invention, metal or other material of relatively high thermal conductivity is utilized to conduct heat from the alternative refrigerant condenser to the ice collection bin. The conductive material is configured with a small thickness and long path length to provide a high resistance to heat flow, thereby maintaining the necessary temperature gradient across the heat flow path to assure that the condensing function occurs at a temperature considerably higher (i.e., at least thirty or so degrees higher) than the ice melting temperature of approximately 32° F. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     These and other objects, features and many of the attendant advantages of the present invention will be appreciated more readily as they become better understood from a reading of the following description considered in connection with the accompanying drawings wherein like parts in each of the several figures are identified by the same reference numerals, and wherein: 
     FIG. 1 is a schematic flow diagram of a system for forming purified ice pieces, collecting the ice pieces and melting the ice pieces to provide purified liquid water, in which system the present invention has utility; 
     FIG. 2 is a front view in elevation of one embodiment of the present invention that may be employed in the system of FIG. 1; 
     FIG. 3 is a side-view in elevation of the embodiment of FIG. 2; 
     FIG. 4 is a partially diagrammatic front view in elevation of one alternative embodiment of the present invention; 
     FIG. 5 is a partially diagrammatic front view in elevation of the embodiment of FIG. 4 made from a different material; 
     FIG. 6 is a front view in elevation of another embodiment of the present invention; 
     FIG. 7 is a view in perspective of still another embodiment of the present invention; 
     FIG. 8 is a schematic flow diagram of an overall system employing a further embodiment of the present invention; and 
     FIG. 9 is a front view in elevation of yet another embodiment of the present invention. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     In order to facilitate reference to the disclosure material incorporated herein from my U.S. Pat. No. 4,897,099, two-digit reference numerals appearing in the accompanying drawing are chosen to correspond to those reference numerals employed in the aforesaid patent for like elements. Three-digit reference numerals appearing in the accompanying drawings designate elements not present in the aforesaid patent. In the interest of brevity, and to facilitate understanding of the subject matter of the present invention, the following description omits discussion of the portions of the system not directly related to the invention subject matter. 
     Referring now to FIG. 1 of the accompanying drawings, the overall ice-forming and melting system is illustrated schematically. The harvested ice pieces in collection bin 18 are heated at selected times by alternative condenser 102 via a separation region 103 functioning to provide some degree of resistance to heat flow. Hot gas line 73 delivers compressed refrigerant vapor to condenser 102, and liquid flow line 75 conveys tho condensed refrigerant liquid to other parts of the system. 
     Referring to FIGS. 2 and 3, one embodiment of present invention utilizes one or more heat conducting members 107 located in separation region 103 and extending between and in direct contact with alternative condenser 102 and the bottom of collection bin 18. Members 107 have a length dimension (A in FIG. 3) extending in the direction of heat flow between condenser 102 and bin 18, and a thickness dimension extending perpendicular to the direction of heat flow between the condenser and bin and generally transverse to the direction of refrigerant fluid flow in the condenser. The length dimension A and the thickness dimension, are selected to provide a significant resistance to heat flow between condenser 102 and the bottom of collection bin 18. This resistance permits the condensing function in condenser 102 to occur at a substantially higher temperature (typically, at least 60° F.) than the temperature (approximately 32° F.) at the bottom of bin 18, but still permits heat to flow from the condenser to the bin to effect melting and condenser heat rejection. The heat conduction rate varies directly with the thickness of the conductor members 107 and the temperature difference between the bin bottom and the condenser. The heat conduction rate varies inversely with the length A of the heat path through conductor members 107. To achieve a given heat flow rate at a required temperature differential, any decrease in the thickness of heat conducting members 107 requires a proportional decrease in the length A of these members. In effect, both the length and thickness have to be decreased in the same proportion to maintain the same heat flow rate for the desired temperature differential. 
     The heat flow rate also varies directly with the width dimension (from left to right in FIG. 2; into the plane of the drawing of FIG. 3) of conducting members 107. In this regard, condenser 102 may take the form of plural tubes conducting refrigerant flow in parallel as illustrated in FIG. 3, and including a heat conducting member 107 for each condenser tube section. Condenser 102 may also be configured as a single tube in a serpentine or other pattern beneath bin 18. As a further alternative, a plurality of heat conducting members can extend in side-by-side relation from all or sections of the condenser tube 102. 
     An alternative heat flow path arrangement in accordance with the present invention is illustrated in FIG. 4 and involves securing a condenser tube 109 in direct contact with the bottom of bin 18 at location 110. For purposes of this embodiment, at least, condenser tube 109 is constructed of a metal of low thermal conductivity such as stainless steel. Typical stainless steels have a thermal conductivity (K) on the order of thirteen, whereas copper, for example, has a thermal conductivity value approximately seventeen times greater (i.e., K=220 or thereabout). Thus, as illustrated in FIG. 5, if a conventional copper condenser tube 111 is attached to the bottom of bin at location 112, there is much less resistance to heat flow. Specifically, rejected heat of condensation flows relatively easily from locations 113, 114, 115 and all other parts of the condensing area on tube 111 to location 112 to thereby transfer heat to bin 18 directly to melt the ice, the efficiency of heat transfer between location 112 and the melting ice being quite high. However, there would be little resistance to such heat flow, and the desired difference between the condensing temperature and the ice-melting temperature would not be achieved. Conventional condensers, in which minimal temperature differential is required, invariably use copper, aluminum, or other tubing material having relatively high thermal conductivity. 
     On the other hand, the use of the stainless steel condenser tube 109 (FIG. 4), or a condenser tube of any other metal having a relatively low thermal conductivity, results in the required temperature differential across the heat flow path pursuant to the present invention. The rejected heat of condensation from location 118, for example, must flow around approximately one half the circumference of tube 109 in order to reach location 110. Actually, there is a double flow path, one clockwise past location 116 and another counter-clockwise past location 117. By comparison, the heat of condensation rejected at location 119 travels only a short distance to attachment location 110. Condensation occurs at all locations on the inside of tube 109; therefore, it is clear that the average distance traveled by all of the rejected heat of condensation is one half the distance between locations 118 and 110, or the distance from location 116 to location 110 (in a clockwise direction) and the distance from location 117 to location 110 (in a counter-clockwise direction). The result is two parallel flow paths each being one quarter of the circumference of condenser tube 109. An exemplary embodiment for condenser tube 109 has the following parameters and dimensions: inside diameter, 3/8 inch; K=13; length, twelve feet; heat rejection rate, 6,000 btu/hr; temperature differential between condensing temperature and melting temperature, 80° F.; and wall thickness of condenser tube 109, 0.070 inch. These parameters and dimensions result in satisfactory operation and are achieved by virtue of calculations based on the following formula: K=V T  d/A(dT); wherein K is the thermal conductivity of the metal employed in condenser tube 109, V T  is the heat flow rate through that material in btu/hr, d is the flow distance of the flow path in feet, A is the cross-sectional area of the heat flow conductor in square feet, and (dT) is the temperature difference (in °F) or gradient between the rejection temperature at the condenser and the ice melting temperature at the bin. In the exemplary dimensions, the twelve foot length of condenser tube can be arranged in the form of a number of passes under bin 18, such passes being arranged in parallel or series flow circuits depending on the overall condenser design. 
     By way of comparison, a design for the same performance described above, but utilizing a copper condenser tube 111 having a length of twelve feet and a value for K of 220, would require a thickness of 0.004 inch for condenser tube 111. Accordingly, it has been determined that condenser tube materials having a value of K greater than one hundred fifty would not be appropriate for the present invention. 
     The embodiment illustrated in FIG. 6 is an alternative arrangement for providing resistance to heat flow from condenser 102 to bin 18. More particularly, direct spot contacts are provided between the condenser and bin bottom by conductors 125, 126, 127, 128 and 129. As with conductor member 107 in the embodiment of FIG. 2, each individual conductor provides a flow path of minimal length if it has a small cross-sectional area, or a longer flow path if of larger cross-sectional area. Conductors 125-129 may be spot welds, solder joints, wires positioned between condenser 102 and bin 18, or any other configuration providing a heat flow path of selected dimensions. As with the condenser in the embodiment of FIG. 2, a connected circuit of parallel or series condenser tubes may be employed to constitute the complete condenser 102. 
     FIG. 7 illustrates another embodiment of the invention functioning to maintain a sufficiently high condensing temperature by employing an undersized ice-melting condenser in direct contact with the bottom of bin 18. The undersized condenser 130 is in direct thermal contact with the bottom of bin 18 and forms an alternative condenser as part of the system illustrated in FIG. 1. The total area of condensing surface on which refrigerant vapor can condense within undersized condenser 130 is substantially smaller than the condensing surface area of the non-melting condenser 71 (in FIG. 1). Condenser 71 operates at normal refrigeration condensing temperatures (typically 80° F., or higher) and has at least one and one-half times the condensing surface area of condenser 130. This arrangement permits a normal high condensing temperature to be maintained in condenser 130 while the heat rejection temperature is quite low (approximately 32° F.). Liquid line 75 carries off condensed liquid, and hot gas line 73 delivers compressed vapor to condenser 130. 
     As described in my aforementioned U.S. Pat. No. 4,897,099, the system of the present invention is operated selectively in the ice-making, non-melting mode, or in the ice-making, melting mode, by causing the changeover solenoid valves 69, 70 (FIG. 1) to direct compressed vapor to either non-melting condenser 71 (FIG. 1) or to melting condensers 102 (FIGS. 1-3 and 6) or 109 (FIG. 4) or 130 (FIG. 7). However, when switching from one condenser to another, it is possible for an indeterminate quantity of refrigerant liquid to be trapped in the condenser from which flow is being switched This may cause some variation in the refrigerant charge in the operational condenser. A conventional receiver 101 (FIG. 1) may be employed to provide a reservoir of refrigerant liquid to compensate for these variations. 
     Another method for achieving normal high condensing temperature utilizes a condenser flooding technique. Referring specifically FIG. 8 in the accompanying drawings, a melting condenser 135 is in direct contact with the bottom of collection bin 18. Condenser 135 has a condensing surface area similar to the non-melting condenser 71, but the system is overcharged with refrigerant so that, when in the ice-melting mode, condenser 135 functions in a partially flooded condition. Flooding causes the effective condensing surface area to be reduced and the condensing temperature to be increased to a suitable level in a manner often employed with low ambient refrigeration systems. When the system is switched to the non-melting mode, condenser 71 is operative but, under some off-cycle conditions, migration of some of the refrigerant overcharge may tend to flood condenser 71. However, any such excess refrigerant is absorbed in receiver 136, thereby maintaining condenser 71 free of flooding. When the system is switched back to the ice-melting mode, any liquid in receiver 136 tends to remain trapped by back pressure on check valve 72, thus preventing the desired flooding of condenser 135. To correct this problem, a heater 137 is activated to build up the temperature and pressure in receiver 136, thus forcing the trapped refrigerant liquid through check valve 72 and into the active refrigeration cycle. Activation of heater 137 can be terminated after an appropriate time interval by timer 138. As a result of this forced removal of refrigerant fluid l from condenser 71 and receiver 136 in the melting mode, condenser 71 tends to be dry of refrigerant when the system is switched back to the non-melting mode. However, receiver 101 is full at such time and some of the refrigerant therein is absorbed into the active cycle to provide a suitable operating charge. 
     In the embodiment of the invention shown in FIG. 7, condenser tube 130 can be attached by metal to metal direct contact to the bottom of bin 18. An alternative arrangement is to have this tube surrounded by a bath of low temperature liquid such as ethelene glycol, whereby the liquid makes contact with the bin bottom. FIG. 9 illustrates such an arrangement wherein liquid trough 140 contains the liquid and tube 130 is submerged in the liquid. Tubes 130a, 130b, 130c are continuations of tube 130 and are formed to provide a condenser circuit. The liquid contained in trough 140 is at a level sufficiently high to contact the bottom 142 of bin 18. Heat from the condenser tubes travels through the liquid by conduction and convection to bin bottom 142. By this method, heat from the condenser tubes is evenly distributed over the bottom 142 of bin 18. Condenser tube 135, in the embodiment illustrated in FIG. 8, can similarly be arranged in this manner. 
     Throughout the preceding discussion the term &#34;tube&#34; is sometimes used as a convenient designation for condenser passages. It is to be noted, however, that condenser passages can be constructed in other ways and are not to be limited to actual tubing. 
     Reference has been made herein to the use of heating means at the bottom of an ice collection bin to achieve melting of ice in the bin. The preferred embodiment of the invention employs a metal bin having heating means located outside the bin so that heat can flow through the metal bin bottom to melt the ice. However, the ice bin may alternatively be made of non-metallic material, and the ice-melting device may be placed inside the bin. It would be necessary, however, for such ice-melting device to include a flat metal plate of the same dimensions as the bin bottom so that heat from the heating unit is distributed evenly throughout the area of the bin bottom. This plate on which the ice melts effectively comprises the actual bin bottom, and any references hereinabove to the bin bottom would include such plate. 
     From the foregoing description it will be appreciated that the invention makes available a novel method and apparatus for efficiently melting ice collected in a bin as part of an ice-forming process in which the ice is formed as purified ice pieces from an unpurified source of water, and wherein the purified ice is melted to provide a supply of purified water. 
     Having described preferred embodiments of a new and improved ice maker and water purifier with controlled condensing temperature in accordance with the present invention, it is believed that other modifications, variations and changes will be suggested to those skilled in the art in view of the teachings set forth herein. It is therefore to be understood that all such variations, modifications and changes are believed to fall within the scope of the present invention as defined by the appended claims.