Abstract:
A cooling system for a beverage comprises an enclosure for housing a beverage container, a cold plate through which the beverage flows, and a refrigeration system that controllably cools the enclosure and the cold plate in a differential manner. In preferred embodiments, preference is given during normal operation to cooling the cold plate, and only cooling the enclosure when the cold plate is determined to be at or below a desired temperature. In some embodiments a special defrost cycle warms the cold plate while continuing to cool the enclosure. Controls can be mechanical, electronic or any combination of the two, and preferably utilizes information from both pressure and temperature sensors.

Description:
This application is a continuation-in-part application of U.S. application Ser. No. 14/988,609 filed Jan. 5, 2016, which is incorporated by reference herein in its entirety. 
    
    
     FIELD OF THE INVENTION 
     The present invention relates to methods and systems for preferentially cooling a cold plate and a supply container of the beverage cooling system. 
     BACKGROUND 
     The following description includes information that may be useful in understanding the present invention. It is not an admission that any of the information provided herein is prior art or relevant to the presently claimed invention, or that any publication specifically or implicitly referenced is prior art. 
     There are many cooling systems for beer or other beverages. Typically, most of the components of the refrigeration system are local to, and directly cool the keg or other beverage supply container. In other instances there are two refrigeration systems, one to cool the supply container, and another refrigeration system to cool a cold plate through which the beverage is passed just prior to dispensing. 
     For example, U.S. Pat. No. RE43,458E to Cleland (“Cleland”) discloses a beverage chilling apparatus having a refrigerant cooling system. In Cleland, the cold plate is chilled by refrigerants that is compressed by a compressor and chilled by a condenser. However, Cleland fails to teach that the same compressor and condenser can also be used to chill the supply container. 
     Using two different refrigeration systems is inefficient, but to our knowledge, no one has ever undertaken the difficult task to cool both the supply container and a cold plate using a single refrigeration system. 
     All publications herein are incorporated by reference to the same extent as if each individual publication or patent application were specifically and individually indicated to be incorporated by reference. Where a definition or use of a term in an incorporated reference is inconsistent or contrary to the definition of that term provided herein, the definition of that term provided herein applies and the definition of that term in the reference does not apply. 
     Thus, there is still a need for improved refrigeration system, in which a given compressor can be used to cool both the supply container and a cold plate, simultaneously or otherwise. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic of the cooling system configured to cool both (a) an enclosure cavity for a supply container and (b) a cold plate. 
         FIG. 2  is a schematic of one embodiment of the cooling system configured to cool both (a) an enclosure cavity for a supply container and (b) two cold plates. 
         FIG. 3  is a schematic of another embodiment of the cooling system configured to cool both (a) an enclosure cavity for a supply container and (b) two cold plates. 
         FIG. 4  is a schematic of electronic controls for the cooling system. 
         FIG. 5  is a schematic of mechanical controls for the cooling system. 
         FIG. 6  is a schematic of one embodiment of the cooling system with two cold plates. 
     
    
    
     DETAILED DESCRIPTION 
     The following discussion provides many example embodiments of the inventive subject matter. Although each embodiment represents a single combination of inventive elements, the inventive subject matter is considered to include all possible combinations of the disclosed elements. Thus if one embodiment comprises elements A, B, and C, and a second embodiment comprises elements B and D, then the inventive subject matter is also considered to include other remaining combinations of A, B, C, or D, even if not explicitly disclosed. 
     In some embodiments, the numbers expressing quantities of properties such as dimensions used to describe and claim certain embodiments of the invention are to be understood as being modified in some instances by the term “about.” Accordingly, in some embodiments, the numerical parameters set forth in the written description and attached claims are approximations that can vary depending upon the desired properties sought to be obtained by a particular embodiment. In some embodiments, the numerical parameters should be construed in light of the number of reported significant digits and by applying ordinary rounding techniques. Notwithstanding that the numerical ranges and parameters setting forth the broad scope of some embodiments of the invention are approximations, the numerical values set forth in the specific examples are reported as precisely as practicable. The numerical values presented in some embodiments of the invention may contain certain errors necessarily resulting from the standard deviation found in their respective testing measurements. 
     Unless the context dictates the contrary, all ranges set forth herein should be interpreted as being inclusive of their endpoints and open-ended ranges should be interpreted to include only commercially practical values. Similarly, all lists of values should be considered as inclusive of intermediate values unless the context indicates the contrary. 
     As used in the description herein and throughout the claims that follow, the meaning of “a,” “an,” and “the” includes plural reference unless the context clearly dictates otherwise. Also, as used in the description herein, the meaning of “in” includes “in” and “on” unless the context clearly dictates otherwise. 
     The recitation of ranges of values herein is merely intended to serve as a shorthand method of referring individually to each separate value falling within the range. Unless otherwise indicated herein, each individual value is incorporated into the specification as if it were individually recited herein. All methods described herein can be performed in any suitable order unless otherwise indicated herein or otherwise clearly contradicted by context. The use of any and all examples, or exemplary language (e.g. “such as”) provided with respect to certain embodiments herein is intended merely to better illuminate the invention and does not pose a limitation on the scope of the invention otherwise claimed. No language in the specification should be construed as indicating any non-claimed element essential to the practice of the invention. 
     Groupings of alternative elements or embodiments of the invention disclosed herein are not to be construed as limitations. Each group member can be referred to and claimed individually or in any combination with other members of the group or other elements found herein. One or more members of a group can be included in, or deleted from, a group for reasons of convenience and/or patentability. When any such inclusion or deletion occurs, the specification is herein deemed to contain the group as modified thus fulfilling the written description of all Markush groups used in the appended claims. 
     As used herein, and unless the context dictates otherwise, the term “coupled to” is intended to include both direct coupling (in which two elements that are coupled to each other contact each other) and indirect coupling (in which at least one additional element is located between the two elements). Therefore, the terms “coupled to” and “coupled with” are used synonymously. 
     The present invention provides apparatus, systems, and methods in which a cooling system comprises an enclosure having a cavity sized and dimension to house a beverage or other material to be cooled, a cold plate for further cooling the material, and a refrigeration system fluidly coupled to each of the cavity and the cold plate. 
     It is contemplated that the cavity can be in any size to house a beverage or other material to be cooled. Preferably, the size of the cavity can be at least 0.03 m 3 . In some embodiments, where the smaller size of the cavity is preferred, the size of the cavity can be 0.02 m 3  or less. In these embodiments, the size of the cavity is preferably between 0.01 m 3  and 0.02 m 3 , inclusive. 
     In one aspect of preferred embodiments, the cooling system includes one or more circuits that collectively control operation of the refrigeration system, including alteration of when and how much the cold plate is cooled relative to the cavity. For example, the cold plate could be cooled preferentially relative to the cavity. In another example, or at other times, the cold plate could be cooled simultaneously with cooling of the cavity. 
     In another aspect of preferred embodiments, the circuit(s) are configured to operate the refrigeration system in multiple different modes, including (a) a box mode in which the refrigeration system operates to cool the cavity, (b) a cold plate mode in which the refrigeration system operates to cool the cold plate, and (c) a cold plate defrost mode, in which the refrigeration system operates to defrost the cold plate. Some embodiments can also include (d) a box defrost mode, in which the refrigeration system operates to defrost the cavity. 
     In some embodiments, the cold plate defrost mode can utilize a valve that shunts hot refrigerant or other hot gas to the cold plate. The hot gas can advantageously be generated by turning off or otherwise lowering the speed of a condenser fan so that the refrigerant temperature increases, preferably to at least 50° C.). In some preferred embodiments, the cold plate defrost mode can utilize a circuit that cooperates with one or more temperature or pressure sensors to operate the valve. Alternatively or additionally, the cold plate defrost mode can be operated using a timer, and a resistance heater to provide heat to the cold plate. 
     The cooling system can be installed in any suitable structure, including for example in a wheel mounted cart, or as an under counter installation. Depending on the installation, the cold plate can be physically coupled to the enclosure by bolts, screws or other coupling. In other embodiments, the cold plate can be physically distal to the enclosure, such that the cold plate is coupled to the enclosure only by one or more fluid lines. In these embodiments, the cold plate would typically be spaced apart from the enclosure by at least 0.1 meter, and most likely between 0.1 meter and 5 meters. 
     The enclosure is preferably insulated, with at least one wall having an insulation R-value of at least 1, more preferably at least 2, and most preferably at least 3. As used herein, R-value is defined as square-meter Kelvin per watt (m 2 ·K/W). See http://sizes.com/units/rvalue.htm. The currently preferred materials for insulation include urea-formaldehyde or urethane foam. 
     In another aspect of preferred embodiments, the enclosure includes a door and a door switch, and the cooling system includes a circuit that cooperates with the door switch. For example, when the door of the enclosure opens, the circuit preferentially turns off refrigeration to the cavity, but not to the cold plate. Yet, in some embodiments, the circuit can turn off refrigeration to the cavity and the cold plate at the same time for at least some period of time (e.g., at least 1 second, at least 3 seconds, at least 5 seconds, etc.) 
       FIG. 1  is a schematic of the cooling system  100 , which is configured to cool both (a) an enclosure cavity  101  for a supply container and (b) a cold plate  170 . The cooling system  100  includes a receiver tank  130 , which acts as the reservoir for the refrigerant. The receiver tank  130  fluidly communicates with the cold plate  170  via refrigerant line. The cooling system  100  also includes an enclosure cavity  101  having an evaporator  105  and a temperature sensor  180 , a compressor  160 , a condenser  155 , an accumulator  140 , expansion valves  120 ,  175  and a drier  150 . The cooling system  100  further includes four solenoid valves  125 ,  126 ,  127 ,  128 , and three pressure transducers  135 ,  165 ,  192 . In a preferred embodiment, the cooling system  100  further includes a sight-glass  145 . Also, in some embodiments, the cooling system  100  also includes a fan motor  190  coupled with the condenser  155 . 
     In some embodiments, the cold plate  170  comprises 40 pounds of cast aluminum, which is a standard cold plate known to those skilled in the art. In these embodiments, it is contemplated that the beverage and refrigerant lines may be wound or located within the cold plate  170  to increase the length of the lines positioned within the cold plate  170 . 
     The cooling system  100  is configured to operate in a plurality of modes: cold plate cooling mode, box cooling mode, and cold plate defrost mode. In the cold plate cooling mode, the refrigerant enters the compressor  160  as a low pressure gas and is discharged from the compressor  160  as a high pressure gas. Then, the refrigerant passes through the Transducer C  192  and enters the condenser  155 . The refrigerant is cooled in the condenser  155 , exiting it as a high pressure liquid, and passes through a drier  150 , which retains unwanted scale, dirt and moisture, and then through the sight-glass  145 , where bubbles will be observed if the cooling system  100  is low on refrigerant. 
     Then, the refrigerant, which is still in a high pressure liquid state, enters the receiver tank  130 , which serves as a storage or surge tank for the refrigerant. The refrigerant, then exits the receiver tank  130 , and encounters the solenoid valve A  125  and then the first thermal expansion valve TXV  175 . A pressure differential is provided across the thermal expansion valve  175 . The thermal expansion valve  175  includes a sensor bulb that measures the degree (or lack) of superheat of the suction gas exiting the cold plate  170  and expands or contracts to allow the flow of refrigerant to be varied according to need. The refrigerant leaving the thermal expansion valve  175  will be in a low pressure liquid or liquid/vapor state when it enters the cold plate  170 . The thermal expansion valve  175  is used instead of a capillary tube in order to provide improved response to the cooling needs of the cold plate  170 . 
     In some embodiments, the thermal expansion valve  175  is coupled with a small equalizer tube connected to the downstream of the cold plate  170 . In these embodiments, the equalizer tube helps to equalize the pressure between upstream and downstream side of the cold plate  170 . 
     After passing through the thermal expansion valve  175 , the refrigerant enters the cold plate  170 . As the liquid or liquid/vapor refrigerant enters the cold plate  170 , it is subjected to a much lower pressure due to the suction created by the compressor  160  and the pressure drop across the thermal expansion valve  175 . It will also be adjacent warmer beverage lines. Thus, the refrigerant tends to expand and evaporate. In doing so, the liquid refrigerant absorbs energy (heat) from beverage lines within the cold plate  170 . 
     In a preferred embodiment, a transducer A  165  is a pressure sensor, which is coupled with the refrigerant line just downstream of the cold plate  170 , and measures pressure of the refrigerant coming out of the cold plate  170 . In other embodiments, the transducer A  165  can be a temperature sensor, which measures the temperature of the refrigerant coming out of the cold plate  170 . The low pressure gas leaving the cold plate  170  encounters the Solenoid valve B  126 . From the Solenoid valve B  126 , the gas passes into accumulator  140 , which help prevent any slugs of liquid refrigerant from passing directly into the compressor  160 , and continues back to the compressor  160 . 
     The cold plate cooling mode begins by closing the solenoid valve A  125  and solenoid valve B  126  for a short time (e.g., less than 0.1 second, less than 0.2 second, less than 1 second, etc.). While the solenoid valve A  125  and solenoid valve B  126  is closed, either an electronic circuit (see  FIG. 2 ) or a mechanical control mechanism (see  FIG. 3 ) compares the refrigerant pressure derived from Transducer A  165  against a first set point pressure. The first set point pressure can vary based on the setting for the desired temperature. For example, if the desired temperature of the cold plate is about 29° F., then the first set point pressure is 67 psi. In other example, if the desired temperature of the cold plate is about 35° F., then the first set point pressure is 77 psi. However, the set point pressures can vary depending on the type of refrigerants. 
     If the refrigerant pressure derived from transducer A  165  is above the first set point pressure, then the electronic circuit or the mechanical control mechanism operates the cooling system  100  to open the solenoid valve A  125  and solenoid valve B  126  so that the refrigerant can flow through the cold plate  170 . In some embodiments, the refrigerant pressures at the transducer A  165  are measured periodically (e.g., every 1 second, every 5 seconds, every 10 seconds, etc.) until the refrigerant pressures reaches to the first set point pressure. For each measurement, the solenoid valve A  125  and solenoid valve B  126  is closed, and then the refrigerant pressure derived from transducer A  125  is compared against a first set point pressure. Once the refrigerant pressure derived from transducer A  165  reaches to the first set point pressure, then the cooling system  100  is operated to switch the cold plate cooling mode to the box cooling mode. 
     In the box cooling mode, the refrigerant enters the compressor  160  as a low pressure gas and is discharged from the compressor  160  as a high pressure gas. The refrigerant passes through the Transducer C  192  and enters the condenser  155 . The refrigerant is cooled in the condenser  155 , exiting it as a high pressure liquid, and passes through a drier  150 , which retains unwanted scale, dirt and moisture, and the through the sight-glass  145 , where bubbles will be observed if the cooling system  100  is low on refrigerant. 
     Then, the refrigerant, which is still in a high pressure liquid state, enters the receiver tank  130 , which serves as a storage or surge tank for the refrigerant. The refrigerant, then exits the receiver tank  130 , and encounters the solenoid valve C  127  and then the thermal expansion valve TXV  120 , while other solenoid valves  125 ,  126  are closed. The refrigerant leaving the thermal expansion valve  120  will be in a low pressure liquid or liquid/vapor state when it enters the enclosure cavity  101  having the evaporator  105  and the temperature sensor  180 . At the evaporator  105 , the refrigerant tends to expand and evaporate, which provides cooling capacity to the enclosure cavity  101 . 
     The low pressure gas leaving the air evaporator  105  passes through the accumulator  140 , which helps prevent any slugs of liquid refrigerant from passing directly into the compressor  160 , then through the transducer B  135 . The refrigerant continues back to the compressor  160 . 
     In a preferred embodiment, the transducer B  135  is a pressure sensor, which is coupled with the refrigerant line just downstream of the cold plate  170 , and measures pressure of the refrigerant coming out of the evaporators  105 . In other embodiments, the transducer B  135  can be a temperature sensor, which measures the temperature of the refrigerant coming out of the evaporators  105 . 
     In the box cooling mode, the enclosure cavity  101  is cooled while measuring the pressure between Solenoid A  125  and Solenoid B  126  to determine if it needs to go back to Cold Plate Cooling mode, which is the prioritized mode. The enclosure cavity  101  also includes the air thermometer  180 , which is readable by the control board. The box cooling mode begins by opening the solenoid C valve  127  (corresponding to solenoid C valve  223  in  FIG. 2 , and solenoid C valve  323  in  FIG. 3 ), and while solenoid A  125  (corresponding to solenoid C valve  225  in  FIG. 2 , and solenoid C valve  325  in  FIG. 3 ) and B  126  (corresponding to solenoid C valve  226  in  FIG. 2 , and solenoid C valve  326  in  FIG. 3 ) are closed, it checks pressure between solenoid A  125  and B  126 . 
     If the pressure is above the set point between solenoid A  125  and B  126  while in box cooling mode, then it goes back to the cold plate cooling mode. If the box thermometer  180  hits its set point while in box cooling mode, then solenoid C  127  closes (solenoid A  125  and B  126  are already closed) and the control board reads pressure at pressure transducer B  135 . Once the board sees pressures, which is read at pressure transducer B  135 , reaches the set point, the compressor  160  turns off and goes into an idle mode. 
     In some embodiments, the cooling system  100  is configured to continue monitoring the pressure (or temperature) at the transducer A  165 . For example, during the idle mode, the system  100  constantly reads pressure transducer  165  (corresponding to pressure transducer  265  in  FIG. 2 , or pressure transducer  365  in  FIG. 3 ) and box thermometer (temperature sensor)  180  (corresponding to box thermometer  280  in  FIG. 2 ) while the compressor is off. If the pressure transducer  165  (corresponding to pressure transducer  265  in  FIG. 2  and pressure transducer  365  in  FIG. 3 ) sees its above set point, it goes to cold plate mode. If the box thermometer (temperature sensor)  180  (corresponding to box thermometer  280  in  FIG. 2 )(or pressure transducer  336  in  FIG. 3 ) sees its above set point, it goes into the box cooling mode. If the pressure (or temperature) of refrigerant between Solenoid A  125  and B  126  (corresponding to Solenoid A  225  and B  226  in  FIG. 2 , Solenoid A  325  and B  326  in  FIG. 3 ) and is above the first set point during the box cooling mode, the cooling system  100  is configured to turn off solenoid C valve  127  (corresponding to Solenoid C  223  in  FIG. 2 , and Solenoid C  323 ,  329  in  FIG. 3 ) and begins the cold plate cooling mode. Thus, the cooling system  100  preferentially allocates the cooling capacity to the cold plate over the box evaporators. 
     In some embodiments, the cooling system further includes another solenoid between the pressure transducer  336  (as shown in cooling system  300  in  FIG. 3 ) and the suction accumulator  140  (corresponding to suction accumulator  240  in  FIG. 2  or suction accumulator  340  in  FIG. 3 ) to measure the pressure of the cavity of the cooling system  100 . In these embodiments, the enclosure cavity  101  is cooled the same way as the cold plate mode described above. The difference is instead of closing Solenoid A  125  and B  126 , it closes C  127  (corresponding to Solenoid C  223  in  FIG. 2 , and Solenoid C  323 ,  329  in  FIG. 3 ) (and Solenoid E  329  in  FIG. 3 ). 
     During the cold plate defrost mode, the Condenser Fan  190  is off, Solenoid B  126  and C  127  are opened and Solenoid A  125  and D  128  are closed. This configuration allows refrigerant to leave the cold plate and build up high pressure hot gas for set time (e.g., at least 10 seconds, at least 30 seconds, at least 1 minute, at least 5 minutes, etc.). Then, the pressure at the transducer  192  is monitored until it reaches its high pressure set point (e.g., 250 psi). Once the pressure hits its high pressure set point, Solenoid D  128  opens for a few seconds to let high pressure hot gas into the cold plate  170 . Once the high pressure hot gas is introduced, then, Solenoid B  126  and D  128  is closed and a pressure at the transducer  165  is checked to see if the cold plate  170  warmed up to a predetermined temperature. If the temperature at the cold plate  170  does not reach the set point, then the cold plate defrost mode is repeated until the cold plate  170  warmed up to the set point. If it hit its set point, then the system  100  goes back to idle mode. In some embodiments, the cold plate defrost mode begins automatically by detecting the temperature of the cold plate  170 . In other embodiments, the cold plate defrost mode begins only when a user initiate the cold plate defrost mode (e.g., by clicking a button, etc.) 
     In some embodiments, the cooling system is configured to run a box defrost mode upon the user&#39;s choice of mode. For example, when the user of the system  100  clicks the button to use Defrost mode, defrost mode becomes priority. In other embodiments, the box defrost mode is operated by a timer without a user&#39;s intervention. In the box defrost mode, all valves are closed and the compressor  160  is turned off for a set time (e.g., at least 1 minute, at least 5 minutes, at least 10 minutes, etc.), so that the enclosure cavity  101  can be defrosted under the temperature substantially close to the room temperature. However, the machine may still go into cold plate mode or cold plate defrost mode if needed during box defrost mode. 
       FIG. 2  shows a schematic of one embodiment of an alternative cooling system  200  configured to cool both (a) an enclosure cavity  201  for a supply container and (b) two cold plates  270 ,  271 . In this cooling each of two cold plates  270 ,  271  are coupled with a pressure transducer  265  or  266 , and a solenoid valve  226  or  227 , in its downstream, and a TXV valve  275  or  221 , and a solenoid valve  225  or  224 , in its upstream, respectively. For a defrost mode, the cooling system  200  further includes a solenoid  229 , which plays a similar role to the cold plate  271  with a solenoid  228  to the cold plate  270  (corresponding to Solenoid D  128  in  FIG. 1 ). 
       FIG. 3  shows a schematic of another embodiment of an alternative cooling system  300  configured to cool both (a) an enclosure cavity  301  for a supply container and (b) two cold plates  370 ,  371 . In this cooling each of two cold plates  370 ,  371  are coupled with a pressure transducer  365  or  366 , and a solenoid valve  326  or  327 , in its downstream, and a TXV valve  375  or  321 , and a solenoid valve  325  or  324 , in its upstream, respectively. For a defrost mode, the cooling system  300  further includes a solenoid  329 , which plays a similar role to the cold plate  371  with a solenoid  328  to the cold plate  370  (corresponding to Solenoid D  128  in  FIG. 1 ). In this embodiment, the cooling system  300  does not include a temperature sensor  180 ,  280  in the enclosure cavity  101 ,  201  as shown in  FIGS. 1 and 2 . Instead, the system  300  is operated by measuring pressures in the pressure transducers only. 
     The cooling system  300  further includes another solenoid  329  and pressure transducer  336  in  FIG. 3  between the evaporator  305  and the suction accumulator  330  to measure the pressure of the evaporator  305  of the cooling system  300 . In this embodiment, when the pressure transducer  336  sees its above set point during box cooling more, the cooling system  300  is configured to turn off solenoid C valve  323  and solenoid  329  and begin the idle mode. 
     Similar to the cooling system  100  of  FIG. 1 , the cooling systems  200 ,  300  are configured to operate in a plurality of modes: cold plate cooling mode, box cooling mode, and cold plate defrost mode. The mechanisms of operating of the plurality of modes of the cooling systems  200 ,  300  are substantially same with cooling system  100  as described above. 
       FIG. 6  shows a schematic of another embodiment of an alternative cooling system  600  having two cold plates  670 ,  671 , without showing an air evaporator (or enclosure cavity encompassing the air evaporator). Similar to the cooling system  300  depicted in  FIG. 3 , each of two cold plates  670 ,  671  are coupled with a pressure transducer  665  or  666 , and a solenoid valve  626  or  627 , in its downstream, and a TXV valve  675  or  621 , and a solenoid valve  625  or  624 , in its upstream, respectively. For a defrost mode, the cooling system  600  further includes a solenoid  629 , which plays a similar role to the cold plate  671  with a solenoid  628  to the cold plate  670  (corresponding to Solenoid D  128  in  FIG. 1 ). In this embodiment, the cooling system  600  does not include a temperature sensor  180 ,  280  in the enclosure cavity  101 ,  201  as shown in  FIGS. 1 and 2 . Instead, the system  600  is operated by measuring pressures in the pressure transducers only. 
     Also similar to the cooling system  100  of  FIG. 1 , the cooling systems  600  are configured to operate in a plurality of modes: cold plate cooling mode, box cooling mode, and cold plate defrost mode. The mechanisms of operating of the plurality of modes of the cooling systems  600  are substantially same with cooling system  100  as described above. 
     While  FIGS. 2, 3, and 6  illustrate the cooling system  200 ,  300 ,  600  having two cold plates, it is contemplated that the cooling system can include more than two cold plates (e.g., three cold plates, four cold plates, etc.). In such embodiment, each of the cold plate can be coupled with either pressure transducer or a temperature sensor. 
     In some embodiments, the two or more cold plates (as shown in  FIGS. 2, 3, and 6 ) are controlled to maintain the same temperature with each other (e.g., both at 29° F., both at 34° F., etc.). In these embodiments, two or more cold plates can be used to cool multiple types of beverages without having a large size single cold plate. In other embodiments, two or more cold plates are controlled to maintain different temperature from each other. Preferably, at least one of the two or more cold plates can be maintained at a temperature below 32° F., more preferably below 29° F. For example, the cold plate  270  is maintained at below 29° F., while the cold plate  271  is maintained at about 34° F. Thus, in these embodiments, two or more cold plates can be used to cool multiple types of beverages that have different optimal temperature to serve without having two separate cooling systems. 
       FIG. 4  is a schematic of exemplary digital control box for the cooling system of  FIG. 1 . It is generally preferred that one digital control box comprises a plurality of circuit boards, each of which is coupled with at least one transducer, sensor motor, heater, solenoid or door and communicate with those. For example, each of a defrost circuit, a pumpdown circuit, and beer evaporator circuit is coupled with a defrost solenoid, airbox solenoid, and gas line solenoid, respectively, and controls open and close of the solenoid. For another example, temperature sensor circuit is coupled with a temperature sensor, and receives temperature sensor data. In this embodiment, it is preferred that the digital control box further comprises a main control board, which is configured to communicate with a plurality of circuits in the box and store the pre-set values for temperature or pressure to enable automatic controlling based on pre-programmed command. 
       FIG. 5  is a schematic of exemplary analog control mechanisms to operate the cooling system of  FIG. 1 . In a preferred embodiment, the analog control mechanisms include two time delay control boxes that are coupled with each other. Each time delay control box is coupled with at least one or more switches or solenoids via one or more sections to control its opening and closing. In some embodiments, the time delay control boxes comprises at least one transistor and capacitor, a delay time per section can either be controlled by an external voltage or locked to an external reference frequency by means of a control system which features a large capture range. 
     It should be apparent to those skilled in the art that many more modifications besides those already described are possible without departing from the inventive concepts herein. The inventive subject matter, therefore, is not to be restricted except in the spirit of the appended claims. Moreover, in interpreting both the specification and the claims, all terms should be interpreted in the broadest possible manner consistent with the context. In particular, the terms “comprises” and “comprising” should be interpreted as referring to elements, components, or steps in a non-exclusive manner, indicating that the referenced elements, components, or steps may be present, or utilized, or combined with other elements, components, or steps that are not expressly referenced. Where the specification claims refers to at least one of something selected from the group consisting of A, B, C . . . and N, the text should be interpreted as requiring only one element from the group, not A plus N, or B plus N, etc.