Patent Publication Number: US-2022211072-A1

Title: Control of frozen beverage dispenser

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims the benefit of U.S. Provisional Application Ser. No. 62/845,972 filed May 10, 2019 and U.S. Provisional Application Ser. No. 62/802,082 filed Feb. 6, 2019, the disclosures of which are expressly incorporated herein by reference. 
    
    
     BACKGROUND 
     Frozen beverages are produced via devices that freeze a mixture of ingredients including syrup, water, and optionally, carbon dioxide in a mixing chamber. The mixture freezes on the inner surface of the mixing chamber, which is surrounded by a helical coil through which a refrigerant passes. A rotating shaft is disposed inside the chamber, which has a plurality of outwardly projecting blades that scrape the frozen mixture off the inside wall of the mixing chamber. Once the beverage is in the desired frozen state, the product is dispensed from the chamber through a product valve. 
     Current frozen beverage products are generally limited to full-calorie frozen beverages. Caloric products contain common sugars, such as sucrose or high fructose corn syrup (“HFCS”), which are used as sweeteners. These sugars play an important part in the freezing point depression of frozen beverages. Under normal operating conditions of frozen beverage machines, the addition of caloric sweeteners depresses the freezing point of the product, making them dispensable in a slush-like state. By contrast, a diet beverage—or non-caloric beverage—contains no common sugars such as sucrose or corn syrup, and thus lacks a freezing point depressant. Without this modified freezing point, diet syrup freezes into blocks of ice in a conventional frozen beverage machine. 
     Brix value is generally defined as the percent of soluble solids made up of sugars. A solution having a standard brix value, for example, greater than 10 degrees Brix, generally tends to be sweeter and may be difficult to freeze. On the other hand, a beverage having a low brix value, for example, less than 10 degrees Brix, may more readily freeze harder and faster than a standard brix solution. Since the brix value of diet or low-calorie beverages typically ranges from about 3.5 to about 5.0, commercial success for dispensing diet or low-calorie frozen beverages has been minimal. 
     In some conventional frozen beverage machines for diet, low-calorie, and reduced-calorie beverages, the freezing point of the syrup is depressed by the addition of freezing point suppression ingredients, such as erythritol, sodium, potassium chloride, or any other food grade freezing point suppressant. A frozen beverage machine capable of producing a diet or low-calorie frozen beverage, which has a brix value of less than about 10, while having the consistency of a full-calorie frozen beverage (i.e., without large pieces of ice) has been elusive. 
     SUMMARY 
     In a first aspect of the disclosure, a frozen product dispenser comprises a product barrel configured to receive a product solution. The frozen product dispenser comprises a refrigeration system coupled to the product barrel and configured to cool the product solution within the product barrel. The frozen product dispenser comprises a temperature sensor configured to measure a temperature of the product solution within the product barrel. The frozen product dispenser comprises a drive motor configured to rotate a scrapper blade within the product barrel. The frozen product dispenser comprises a torque sensor configured to measure a torque applied by the drive motor. The frozen product dispenser comprises a control unit configured to control operation of the refrigeration system based on the measured temperature and the measured torque. 
     In some implementations of the first aspect of the disclosure, the control unit is configured to limit a rate of change of the measured torque to a configured rate of change in torque. 
     In some implementations of the first aspect of the disclosure, the control unit is configured to limit a rate of change of freezing the product solution within the product barrel to a configured rate of change of freezing. 
     In some implementations of the first aspect of the disclosure, the torque sensor is a current sensor configured to measure an amount of current drawn by the drive motor. 
     In some implementations of the first aspect of the disclosure, the control unit is configured to control operation of a compressor of the refrigeration system. The control unit is configured to turn off the compressor when a determined rate of change in the measured torque exceeds a configured rate of change. The control unit is further configured to wait for a configured delay period after turning off the compressor. 
     In some implementations of the first aspect of the disclosure, the product solution has a Brix value less than 10. 
     In some implementations of the first aspect of the disclosure, the refrigeration system comprises a hot gas bypass configured to supply gas output from the compressor to an input of an evaporator line. The hot gas bypass comprises a shut-off valve configurable between an open and closed position, wherein the control unit is configured to instruct the shut-off valve to open or close based on the measured torque. 
     In some implementations of the first aspect of the disclosure, the refrigeration system further comprises a temperature sensor on the evaporator line, wherein the control unit is configured to instruct the shut-off valve to close upon a determination that a temperature measured by the temperature sensor on the evaporator line exceeds a threshold temperature. 
     In a second aspect of the disclosure, a method of controlling a frozen product dispenser comprises operating a refrigeration system to cool a product solution in a product barrel. The method comprises operating a drive motor to rotate a scrapper blade within the product barrel. The method comprises measuring, by a temperature sensor, a temperature of the product solution within the product barrel. The method comprises measuring, by a torque sensor, a torque applied by the drive motor. The method comprises controlling, by a control unit of the frozen product dispenser, operation of the refrigeration system based on the measured temperature and the measured torque. 
     In some implementations of the second aspect of the disclosure, the control unit is configured to limit a rate of change of the measured torque to a configured rate of change in torque. 
     In some implementations of the second aspect of the disclosure, the control unit is configured to limit a rate of change of freezing the product solution within the product barrel to a configured rate of change of freezing. 
     In some implementations of the second aspect of the disclosure, the torque sensor is a current sensor configured to measure an amount of current drawn by the drive motor. 
     In some implementations of the second aspect of the disclosure, controlling operation of the refrigeration system comprises controlling operation of a compressor of the refrigeration system. 
     In some implementations of the second aspect of the disclosure, controlling operation of the refrigeration system comprises turning off the compressor when a determined rate of change in the measured torque exceeds a configured rate of change. 
     In some implementations of the second aspect of the disclosure, controlling operation of the refrigeration system comprises waiting for a configured delay period after turning off the compressor. 
     In some implementations of the second aspect of the disclosure, the product solution has a Brix value less than 10. 
     In some implementations of the second aspect of the disclosure, controlling operation of the refrigeration system comprises controlling operation of a hot gas bypass to supply gas output from the compressor to an input of an evaporator line. 
     In some implementations of the second aspect of the disclosure, controlling operation of the hot gas bypass comprises instructing a shut-off valve to open based on the measured torque. 
     In some implementations of the second aspect of the disclosure, controlling operation of the hot gas bypass further comprises instructing the shut-off valve to close based on a measured temperature of the evaporator line exceeding a threshold temperature. 
     In a third aspect of the disclosure, a frozen product dispenser comprises, a product barrel configured to receive a product solution, the product barrel comprising a heat transfer surface configured to directly contact the product solution. A heat transfer chamber is coupled to the heat transfer surface and comprises a heat transfer medium. A refrigeration system is coupled to the heat transfer chamber and configured to cool the heat transfer medium within the heat transfer chamber. A first temperature sensor is configured to measure a temperature of the product solution within the product barrel. A second temperature sensor is configured to measure a temperature of the heat transfer medium. A drive motor configured to rotate a scrapper blade within the product barrel. A control unit is configured to control operation of the refrigeration system based on the measured temperature of the product and the measured temperature of the heat transfer medium. 
     In some implementations of the third aspect of the disclosure, the heat transfer medium is a fluid with a freezing point lower than an operating temperature of the refrigeration system. 
     In some implementations of the third aspect of the disclosure, a freezing point of the product is higher than the freezing point of the heat transfer fluid. 
     In some implementations of the third aspect of the disclosure, the control unit is configured to control operation of the refrigeration system to maintain the heat transfer medium at a cooling temperature. 
     In some implementations of the third aspect of the disclosure, the cooling temperature is a function of time or temperature of the product. 
     In some implementations of the third aspect of the disclosure, the control unit is configured to turn on a compressor of the refrigeration system based on the temperature of the product and configured to turn off the compressor based on the temperature of the heat transfer medium. 
     In some implementations of the third aspect of the disclosure, the control unit is further configured to wait for a configured delay period after turning off the compressor. 
     In a fourth aspect of the disclosure, a method of controlling a frozen product dispenser comprises operating a refrigeration system to cool a heat transfer medium surrounding a product barrel. The product barrel comprising a heat transfer surface in direct contact with a product solution in the product barrel. The method comprises operating a drive motor to rotate a scrapper blade within the product barrel. The method comprises measuring, by a first temperature sensor, a temperature of the product solution within the product barrel. The method comprises measuring, by a second temperature sensor, a temperature of the heat transfer medium. The method comprises controlling, by a control unit of the frozen product dispenser, operation of the refrigeration system based on the measured first temperature and the measured second temperature. 
     In some implementations of the fourth aspect of the disclosure, the heat transfer medium is a fluid with a freezing point lower than an operating temperature of the refrigeration system. 
     In some implementations of the fourth aspect of the disclosure, a freezing point of the product is higher than the freezing point of the heat transfer fluid. 
     In some implementations of the fourth aspect of the disclosure, controlling operation of the refrigeration system comprises maintaining the heat transfer medium at a cooling temperature. 
     In some implementations of the fourth aspect of the disclosure, the cooling temperature is a function of time or temperature of the product. 
     In some implementations of the fourth aspect of the disclosure, controlling operation of the refrigeration system comprises turning on a compressor of the refrigeration system based on the temperature of the product. Controlling operation of the refrigeration system further comprises turning off the compressor based on the temperature of the heat transfer medium. 
     In some implementations of the fourth aspect of the disclosure, the method further comprises waiting for a configured delay period after turning off the compressor. 
     These and other features will be more clearly understood from the following detailed description taken in conjunction with the accompanying drawings and claims. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       For a more complete understanding of the present disclosure, reference is now made to the following brief description, taken in connection with the accompanying drawings and detailed description, wherein like reference numerals represent like parts. 
         FIG. 1  is a system block diagram of an exemplary frozen product dispenser according to several aspects of the disclosure. 
         FIG. 2  is a flow diagram of the control algorithm for the frozen product dispenser of  FIG. 1 . 
         FIG. 3  shows graphs of experimental results comparing the torque of a frozen product dispenser with no defrost over time for a standard and low Brix solution. 
         FIG. 4  shows graphs of experimental results comparing the torque of a frozen product dispenser with defrost over time for a standard and low Brix solution. 
         FIG. 5  is a system block diagram of an exemplary frozen product dispenser with a hot gas bypass according to several aspects of the disclosure. 
         FIG. 6  is a flow diagram of the control algorithm for the frozen product dispenser of  FIG. 5 . 
         FIG. 7  is a system block diagram of an exemplary frozen product dispenser with a thermal conduction barrier according to several aspects of the disclosure. 
         FIG. 8  is a flow diagram of the control algorithm for the frozen product dispenser of  FIG. 7 . 
         FIG. 9  illustrates an exemplary computer system suitable for implementing the several embodiments of the disclosure. 
     
    
    
     DETAILED DESCRIPTION 
     It should be understood at the outset that although illustrative implementations of one or more embodiments are illustrated below, the disclosed systems and methods may be implemented using any number of techniques, whether currently known or in existence. The disclosure should in no way be limited to the illustrative implementations, drawings, and techniques illustrated below, but may be modified within the scope of the appended claims along with their full scope of equivalents. Use of the phrase “and/or” indicates that any one or any combination of a list of options can be used. For example, “A, B, and/or C” means “A”, or “B”, or “C”, or “A and B”, or “A and C”, or “B and C”, or “A and B and C”. 
     Low Brix frozen beverage products (e.g., products with less than 10 degrees Brix) freeze harder and faster in a frozen product dispenser than standard Brix products (e.g., products with greater than 10 degrees Brix). Therefore, a viscosity of low Brix products in the frozen product dispenser may rapidly change and the scrapper blade of the dispenser may slip while trying to scrape ice off a product barrel of the frozen beverage dispenser. 
     Accordingly, the frozen product dispenser of the pending disclosure provides a controller adapted to control the rate of freezing in addition to the temperature range of the product. The controller is configured to monitor the temperature of the product as well as the torque applied to the scrapper blade. For example, the torque may be measured based on monitoring a current draw of a scrapper motor. Each measurement of the torque may be time stamped so as to track the torque over time and determine a rate of change in the torque. The rate of freezing may be controlled by setting a maximum rate of increase in the torque. Upon determining that the rate of increase in the monitored torque exceeds the maximum rate, a compressor for the frozen product dispenser may be turned off for a predetermined period of time. 
     In some implementations, rather than turning off the compressor upon determining that the rate of increase in the monitored torque exceeds the maximum rate, a hot gas bypass may be opened between the compressor and an evaporator. The relatively hot gas from the compressor increases the temperature of the evaporator and thereby reduces the rate of freezing of the product. Following the opening of the hot gas bypass, the compressor may additionally be turned off for a period of time. 
     In some implementations, rather than controlling the rage of freezing by tightly controlling the heat transfer rate through direct thermal contact between the evaporator and the product, an intermediary heat transfer fluid may be used. For example, the evaporator may be positioned within a heat transfer chamber filled with a glycol solution or other heat transfer fluid that is not susceptible to freezing at the evaporator operating temperatures. In this way, the evaporator may be controlled to cool the heat transfer fluid to a cooling temperature, which in turn cools the product in the frozen product dispenser. By decoupling direct thermal contact between the evaporator and the product in the frozen product dispenser, tight control of the temperature of the evaporator may not be required. The frozen product dispenser with the heat transfer fluid may additionally control the rate of freezing based on the torque measurements and/or using a hot gas bypass, as described above. 
     Referring now to the drawings,  FIG. 1  is a system block diagram of an exemplary frozen product dispenser according to several aspects of the disclosure. Although the frozen product dispenser  100  as described herein is used in the context of a noncarbonated frozen product, it is understood that the invention is equally applicable to any type of frozen or partially frozen dispensable product or confection such as carbonated beverages, ice creams, yogurts, coffee drinks, and the like. 
     The product dispenser  100  may include a product supply  102  with a liquid product stored therein. For example, the product supply  102  may include product concentrate. The product supply  102  may provide a particular flavor, or brand of a product or a beverage flavoring, i.e., a cherry flavoring or the like. As described above, the product supply  102  may be carbonated or noncarbonated. The product supply  102  may be housed in any type of conventional storage structure such as a syrup tank, a bag-in-box, a figal, or similar types of containers. A pump  104  is fluidically coupled to the product supply  102  and configured to draw the product from the product supply  102 . The pump  104  is generally positioned adjacent to the product supply  102  and may be of conventional design, such as a diaphragm pump, piston pump, gear pump, or any other suitable pump. The pump  104  and the product supply  102  may be positioned outside of a frame of the product dispenser  100  itself. 
     The product dispenser  100  also may include a water source  106  and optionally include a gas source  108 . The water source  106  may be any type of potable water source, such as a water tank or municipal water supply. The gas source  108  may provide carbon dioxide gas or any type of compressed gas for carbonated beverages. The gas source  108  may be housed in any type of pressurized gas container. The gas source  108  may have a regulator (not shown) thereon so as to meter the flow of the gas. The gas source  108  and the regulator may be positioned outside of the frame of the product dispenser  100 . 
     The product supply  102  and the water source  106  may be connected to a flow control device  110  positioned within the product dispenser  100 . The flow control device  110  may contain a number of metering valves, such as volumetric valves or the like, to meter the appropriate amount of concentrate flow from the product supply  102  and the appropriate amount of water flow from the water source  106  so as to mix the desired product. 
     The flow control device  110  in turn may be connected to a product barrel  112 . For carbonated beverages, an expansion chamber  114  may be positioned between the flow control device  110  and the product barrel  112 . A fluid line between the flow control device  110  and the product barrel  112  may merge with a gas line in communication with the gas source  108  so as to introduce carbon dioxide or other types of gas into the fluid flow. The fluid and the carbon dioxide gas mix so as to form a carbonated beverage. The expansion chambers  114  then serves to reduce or balance the amount of pressure that may be in the fluid flow without the loss of the carbonation. The expansion chambers  114  may be of conventional design. Alternatively, a conventional carbonator tank may be used to mix the fluid flow with the gas flow as is known in the art. 
     In the example provided above, a product concentrate is provided by the product supply  102 . In some implementations, a pre-mixed product may be provided by the product supply  102  and pumped with the pump  104  directly to the product barrel  112  or poured directly into the product barrel  112  from the product supply  102 . Other variations are contemplated by this disclosure for accommodating other known configurations of frozen product dispensers. 
     The product barrel  112  may hold the product therein as is known by those skilled in the art. For example, for carbonated products, the incoming fluid is generally pressurized and the product barrel  112  will hold this pressure. The product barrel  112  also may be unpressurized depending upon the product used therein. The product barrel  112  may be a metal, plastic, or other rigid structure and may be at least partially enclosed with foam or other insulation. As described in more detail below, the product barrel  112  may be encircled by an evaporator line  116  so as to at least partially freeze the product therein. 
     Positioned within the product barrel  112  may be a scraper blade  118 . The scrapper blade  118  rotates so as to prevent the product therein from freezing completely. The scraper blade  118  also may scrape the partially frozen product off of the interior surface of the barrel  112 . In the example shown in  FIG. 1 , the scrapper blade  118  comprises a plurality of offset blade segments connected to a central shaft  120 . Other scraper blade configurations and orientations are contemplated by this disclosure, such as an auger, screw, or the like. The scraper blade  118  is driven by a drive motor  122  for rotating within the product barrel  112  about the central shaft  120 . 
     The product barrel  112  is in communication with a nozzle  124  such that the frozen product may be dispensed from the nozzle  124 . For example, upon a consumer actuating a dispense button or lever (not shown), frozen product may be dispensed from the nozzle  124  of the product dispenser  110 . 
     The product dispenser  100  also includes a refrigeration system  126  so as to at least partially freeze the product within the product barrel  112 . The refrigeration system  126  may include a compressor  128  in fluid communication with a condenser  130 . A fan  132  or another type of an air-moving device may cool the condenser  130  as is known in the art. In turn, the condenser  130  may be in fluid communication with an expansion valve  134 . For example, the expansion valve  134  may be a capillary tube of a predetermined length. 
     The expansion valve  134  may be in fluid communication with the evaporator  116 , which is positioned around the product barrel  112 . In some implementations, the evaporator  116  may be shrink-fitted on to the outer surface of the product barrels  112 . Each of the components of the refrigeration system  126  may be connected by a series of fluid lines. 
     A control unit  136  may control the operation of the product dispenser  100 . The control unit  136  may include a microprocessor so as to control the refrigeration system  126  and other elements of the product dispenser  100  as a whole. The control unit  136  is programmed so as to accommodate moderating the rate of freezing of a product in the product barrel  112 . 
     Specifically, the control unit  136  is configured to monitor the temperature of the product in the product barrel  112 . The control unit  136  is also configured to monitor the rate of freezing of a product in the product barrel  112  by measuring a torque applied by the drive motor  122 . For example, a temperature sensor  138 , such as a thermistor or thermocouple, may be in thermal communication with the product in the product barrel  112  and configured to provide a measurement of the temperature to the control unit  136 . 
     As the product in the product barrel  112  begins to freeze, the viscosity of the product increases. Accordingly, an amount of current drawn by the drive motor  122  to turn the scrapper blade  118  likewise increases. The control unit  136  is therefore configured to measure a torque applied by the drive motor  122  by measuring a current drawn by the drive motor via an ammeter  140 . Other sensors for measuring a torque applied by the drive motor  122  are contemplated by this disclosure. The measured current provided by the ammeter  140  may be supplied to the control unit  136  as an analog or digital signal. In some implementations, the ammeter  140  may transform a measured current to a torque value provided by the drive motor  122  and supply the determined torque value to the control unit  136 . A described in detail with reference to  FIG. 2 , using the measurements from the temperature sensor  138  and the ammeter  140 , the control unit  136  turns the compressor  128  of the refrigeration system  126  on or off as needed to prevent a product from freezing. 
     The control unit  136  may be configured with a desired product temperature range, such as a lowest temperature and a highest temperature for the product to be dispensed from the product dispenser  100 . In some implementations, the lowest temperature may be set depending on the product to be within a predetermined range of the freezing point of the product. The lowest temperature may be set to prevent complete freezing of the product within the product barrel  112 . For low Brix products, the predetermined range will be closer to the freezing point of the product than for standard Brix products. For example, the lowest temperature for a low Brix product may be set to be within 1° C. of the freezing point of the product. In contrast, the lowest temperature for a standard Brix product may be set to be within 3° C. of the freezing point of the product. Other temperature ranges are contemplated by this disclosure. 
     The control unit  136  may be configured with a desired rate of freezing for a product. For example, the change in current draw as measured by the ammeter  140  over time may be set for a product. For a low Brix product the rate of freezing may be configured to be less than the rate of freezing used for a standard Brix product. 
     The control unit  136  may be configured to set the desired product temperature and the desired rate of freezing through a user interface (not show) on the product dispenser  100  or through programming the control unit  136  via an external programming device, such as a mobile phone or a dedicated service interface device carried by a service technician. 
     In use, syrup or other types of concentrate or product from the product supply  102  may be pumped via the pump  104  to the flow control device  110 . Likewise, water from the water source  106  is provided to the flow control device  110 . For carbonated products, the ingredients are mixed therein and then flow towards the expansion chamber  114 . In the process, the fluid is mixed with carbon dioxide or other type of compressed gas from the gas source  108 . The product then flows from the expansion chamber  114  to the barrel  112 . For noncarbonated products, the mixed ingredients flow directly to the product barrel  112 . The product is then partially frozen therein by the refrigeration system  126  while being mixed and rotated via the scraper blade  118 . The frozen product is then served via the nozzle  124 . 
       FIG. 2  is a flow diagram of the control algorithm  200  for the control unit  136  of the frozen product dispenser  100  of  FIG. 1 . At  202 , the control unit  136  is configured to set the product temperature range. For example, the control unit  136  is configured to set a lowest temperature (T Low ) and a highest temperature (T High ) for the product to be dispensed from the product dispenser  100 . 
     At  204 , the control unit  136  is configured to set the freezing rate of the product. For example, the control unit  136  is configured to set a maximum rate of increase in torque provided by the drive motor  122 . As noted above, as the product freezes in the product barrel  112 , the viscosity increases, thereby leading to an increased torque applied by the drive motor  122  to turn the scrapper blade  118 . In some implementations, the maximum rate of increase in torque is set as: 
       τ= rt+τ   0   Equation (1),
 
     where τ is the maximum torque at a given time, r is the configured rate of increase in torque, t is time, and τ 0  is an initial torque applied by the drive motor  122 . The values of r and τ 0  may be configured at  204  depending on the product to be dispensed. 
     At  206 , the control unit  136  senses a temperature (T P ) of the product in the product barrel  112  via the temperature sensor  138 . At  208 , the control unit  136  determines whether the sensed temperature of the product is greater than the highest temperature. If so, at  210 , the control unit  136  instructs the compressor  128  to turn on. 
     Otherwise, at  212 , the control unit  136  determines whether the sensed temperature of the product is less than the lowest temperature. If so, at  214 , the control unit  136  instructs the compressor  128  to turn off and continues operation at  206 , as described above. In some implementations, the control unit  136  may wait for a delay period after turning off the compressor  128  before proceeding to operation  206  so as to prevent short-cycling the compressor  128 . 
     At  216 , the control unit  136  senses the torque applied by the drive motor  122  via the ammeter  140 . The control unit  136  may maintain a database of torque readings, each stored with a corresponding time stamp so as to track the change in torque over time. At  218 , the control unit  136  determines whether the change in torque over time exceeds the configured rate of change for the torque. For example, the control unit  136  may determine a difference in two successive torque readings over a given period of time and determine whether the difference is greater than the configured rate of change in torque as normalized of the given period of time. Alternatively, the control unit  136  may solve Equation 1 for a given time and determine whether the sensed torque is greater than the torque calculated by Equation 1. Other variations in determining the rate of change for the torque are contemplated by this disclosure. 
     If the control unit  136  determines at  218  that the change in torque over time exceeds the configured rate of change for the torque, at  220 , the control unit  136  instructs the compressor  128  to turn off  220 . At  222 , the control unit  136  waits for a configured delay period before proceeding back to  206 . For example, the delay period may be set between 30 seconds to 2 minutes. Other delay periods are contemplated by this disclosure to limit the rate of change in freezing a product. In some implementations, the control unit  136  may instruct the compressor  128  to turn back on after  222 . 
     Otherwise, if the control unit  136  determines at  218  that the change in torque over time does not exceed the configured rate of change for the torque, the control unit  136  proceeds back to  206 . 
       FIG. 3  shows graphs of experimental results comparing the torque of a frozen product dispenser with no defrost over time for standard and low Brix products. For example, the graph  310  shows the torque over time for a standard Brix product and the graph  320  shows the torque over time for a low Brix product.  FIG. 4  shows graphs of experimental results comparing the torque of a frozen product dispenser with defrost over time for standard and low Brix products. For example, the graph  410  shows the torque over time for a standard Brix product and the graph  420  shows the torque over time for a low Brix product. In the examples provided in  FIGS. 3 &amp; 4 , the standard Brix product has a Brix value of 10.9 and the low Brix product has a Brix value of 7.3. 
     As shown, the rate of freezing the low Brix solution is lower than the rate of freezing the standard Brix product. In some implementations, the rate of freezing the low Brix solution is between 70-80% the rate of freezing of the standard Brix solution. By limiting the rate of freezing of the low Brix solution, the frozen product dispenser is able to dispense a frozen slush product and prevent low- or no-calorie products from freezing into blocks of ice. 
       FIG. 5  is a system block diagram of an exemplary frozen product dispenser  500  with a hot gas bypass  142  according to several aspects of the disclosure. The frozen product dispenser  500  is substantially similar to the frozen product dispenser  100  described above, with like numerals representing like parts. The frozen product dispenser  500  additionally includes a hot gas bypass  142  that is configured to selectively supply hot gas to the evaporator line  116  to increase the temperature of the evaporator line  116  and thereby reduce the rate of freezing of the product in the product barrel  112 . 
     The hot gas bypass  142  comprises a shut-off valve  144  and an expansion valve  146 . The shut-off valve  144  is configured to be selectively controlled by the control unit  136  to be in an open position or a closed position. In the closed position, the shut-off valve  144  prevents compressed refrigerant from the compressor  128  from passing through the shut-off valve  144 . Instead, when the shut-off valve is in the closed position, refrigerant from the compressor  128  flows through the condenser  130  as described above. In the open position, the shut-off valve  144  allows compressed refrigerant from the compressor  128  to pass through the shut-off valve  144  and the expansion valve  146  to supply hot gas directly to the evaporator line  116  without first being cooled through the condenser  130 . In other words, the hot gas bypass  142  bypasses the condenser  130 . The expansion valve  146  may be a capillary tube or other expansion valve configured to reduce the pressure of the hot gas. In various implementations, the expansion valve  146  may provide more, less, or an equal amount of pressure drop as the expansion valve  134 . 
     By increasing the temperature of the evaporator line  116 , the hot gas bypass  142  operates to selectively inject heat into the product in the product barrel  112 , thereby reducing the rate of freezing of the product. A temperature sensor  148 , such as a thermistor or thermocouple, is positioned on at an outlet of the evaporator line  116  and configured to measure a temperature at the outlet of the evaporator line  116 . The temperature sensor  148  is configured to supply a signal to the control unit  136  indicative of the temperature of the outlet of the evaporator line  116 . Upon the temperature of the outlet of the evaporator line  116  exceeding a threshold evaporator temperature, the control unit  136  is configured to turn off the hot gas bypass  142  by instructing the shut-off valve  144  to be in the closed position. For example, the threshold evaporator temperature may be within 1-3° C. above or below the freezing point temperature of the product. Other threshold evaporator temperatures may be used. In some implementations, the compressor  128  may additionally be turned off upon the temperature of the outlet of the evaporator line  116  exceeding the threshold evaporator temperature. 
       FIG. 6  is a flow diagram of the control algorithm  600  for the control unit  136  of the frozen product dispenser  500  of  FIG. 5 . At  602 - 618 , the control unit  136  operates substantially the same as in  202 - 218 , described above. 
     If the control unit  136  determines at  618  that the change in torque over time exceeds the configured rate of change for the torque, at  620 , the control unit  136  turns on the hot gas bypass  142  by instructing the shut-off valve  144  to open. Accordingly, hot compressed gas output from the compressor  128  is supplied through the shut-off valve  144  and expansion valve  146  to the evaporator line  116 , thereby increasing the temperature of the evaporator line  116 . 
     At  622 , the control unit  136  receives a signal from the temperature sensor  148  indicative of a temperature of the outlet of the evaporator line  116 . The control unit  136  determines whether the temperature of the outlet of the evaporator line  116  exceeds the threshold evaporator temperature. If not, the shut-off valve  144  remains open to continue to supply hot gas to the evaporator line  116 . Otherwise, upon the temperature of the outlet of the evaporator line  116  exceeding the threshold evaporator temperature, the control unit  136  turns off the hot gas bypass  142  at  624  by instructing the shut-off valve  144  to close. In some implementations, the control unit  136  may additionally instruct the compressor  128  to turn off for a predetermined period of time. 
     Otherwise, if the control unit  136  determines at  618  that the change in torque over time does not exceed the configured rate of change for the torque, the control unit  136  proceeds back to  606 . 
       FIG. 7  is a system block diagram of an exemplary frozen product dispenser  700  with a thermal conduction barrier according to several aspects of the disclosure. The frozen product dispenser  700  is substantially similar to the frozen product dispenser  100  described above, with like numerals representing like parts. The frozen product dispenser  700  additionally includes a heat transfer chamber  150  with a heat transfer fluid  152  positioned therein. In the example shown, the evaporator line  116  is shown to pass through the heat transfer chamber  150  without making direct thermal contact with a heat transfer surface  156  of the product barrel  112 . Instead, heat is indirectly transferred between the heat transfer surface  156  and the evaporator line  116  via the intervening heat transfer fluid  152 . In use, the heat transfer surface  156  of the product barrel  112  is in intimate contact with a product provided in the product barrel  112  and configured to cool the product therein. In some implementations, the evaporator line  116  may be positioned outside of the heat transfer chamber  150 . 
     The heat transfer fluid  152  acts as an intermediary heat transfer medium between the evaporator line  116  and the heat transfer surface  156 . The heat transfer fluid  152  may be a glycol solution or other heat transfer fluid that is not susceptible to freezing at the evaporator line  116  operating temperatures. For example, the evaporator line  116  may have a temperature of −10° C. or lower, well below a freezing point of a product in the product barrel  112 . The heat transfer fluid  152  has a freezing temperature below the operating temperature of the evaporator line  116 . In some implementations, the heat transfer fluid  152  may be a gel or solid material, such as an aluminum block. 
     A temperature sensor  154 , such as a thermistor or thermocouple, is positioned to measure a temperature of the heat transfer fluid  152 . The temperature sensor  154  is configured to supply a signal to the control unit  136  indicative of the temperature of the heat transfer fluid  152 . 
     The control unit  136  is configured to control the refrigeration system  126  in order to maintain the heat transfer fluid  152  at a predetermined cooling temperature. The cooling temperature is a temperature that the product in the product barrel  112  is exposed to via the heat transfer surface  156 . For example, the control unit  136  is configured to cycle operation of the compressor  128  so as to maintain the heat transfer fluid  152  at the cooling temperature. Upon the temperature sensor  154  measuring a temperature of the heat transfer fluid  152  to be above the cooling temperature, the control unit  136  controls the refrigeration system  126  to turn on to cool the heat transfer fluid  152 . Upon the temperature sensor  154  measuring a temperature of the heat transfer fluid  152  to be below the cooling temperature, the control unit  136  controls the refrigeration system  126  to turn off to maintain the heat transfer fluid  152  at the cooling temperature. Upon turning off the refrigeration system  126 , the control unit  136  may wait for a predetermined period of time before turning the refrigeration system  126  back on so as to avoid short-cycling the compressor  128 . The cooling temperature may be a function of time or product temperature. 
     For example, the control unit  136  may operate to maintain the heat transfer fluid  152  at a minimum temperature for a first period of time when the product is first introduced into the product barrel  112 . For example, the minimum temperature may be the operating temperature of the evaporator line  116 . Providing the minimum temperature for the first period of time minimizes the pull-down time when new product is loaded into the product barrel  112 . After the first period of time, the cooling temperature may be raised as a function of time over a second period of time to limit the freezing rate of the product. For example, over the second period of time, the cooling temperature may be raised on a linear basis, a non-linear basis, or some other basis with time. At the end of the second period of time, the cooling temperature will be at a maximum temperature. For example, the maximum temperature may be at the freezing point of the product or within a threshold temperature of the freezing point of the product (e.g., 1-3° C.). The cooling temperature may be maintained at the maximum temperature so as to keep the product in the product barrel  112  at a desired freezing temperature to be maintained as a slush or frozen slurry. For example, the maximum temperature may be the set point temperature for the product. 
     In another example, the control unit  136  may operate to maintain the heat transfer fluid  152  at the minimum temperature until the product temperature sensor  138  measures that the product has reached a first threshold temperature. Upon reaching the first threshold temperature, the cooling temperature may be raised as a function of the product temperature as measured by the temperature sensor  138  to limit the freezing rate of the product. For example, the cooling temperature may be raised on a linear basis, a non-linear basis, or some other basis with the temperature measured by the temperature sensor  138  until reaching the maximum temperature. Upon reaching the maximum temperature, the control unit may operate to maintain the heat transfer fluid at the maximum temperature. 
     By decoupling direct thermal contact between the evaporator and the product in the frozen product dispenser, tight control of the temperature of the evaporator line  116  may not be required. Therefore, the frozen product dispenser  700  is more resilient to maintenance conditions of the refrigeration system  126 , such as a dirty condenser  130 , which may otherwise impact the temperature of the evaporator line  116 . 
     Other variations for controlling the cooling temperature may be used. For example, the cooling temperature may simply be maintained at the maximum temperature at all times so as to limit the freezing rate of the product. Other variations to the frozen product dispenser  700  are contemplated, such as to additionally control the rate of freezing based on the torque measurements and/or using a hot gas bypass, as described above. 
       FIG. 8  is a flow diagram of the control algorithm  800  for the frozen product dispenser of  FIG. 7 . At  802  and  806 - 814 , the control unit  136  operates substantially the same as in  202  and  206 - 214 , described above. At  804 , the control unit  136  is configured to set the cooling temperature for the product. For example, the control unit  136  is configured to set the cooling temperature as a function of time or temperature of the product. 
     At  818 , the control unit  136  senses the temperature of the heat transfer fluid  152 , such as a glycol solution, via the temperature sensor  154 . At  820 , the control unit  136  determines whether the temperature of the heat transfer fluid  152  is less than the cooling temperature configured at  804 . If the control unit  136  determines that the temperature of the heat transfer fluid  152  is less than the cooling temperature, the control unit  136  instructs the compressor to turn off at  814 . After waiting for a predetermined delay period at  816 , the control algorithm progresses back to  806 . Otherwise, if the control unit  136  determines that the temperature of the heat transfer fluid  152  is not less than the cooling temperature, the control algorithm progresses back to  806 . Other variations of the control algorithm  800  are contemplated by this disclosure. For example, instead of or in addition to turning off the compressor  814 , a hot gas bypass may be turned on to raise the temperature of the evaporator line  116  so as to maintain the temperature of the heat transfer fluid  152  at the cooling temperature. 
     It should be appreciated that the logical operations described herein with respect to the various figures may be implemented (1) as a sequence of computer implemented acts or program modules (i.e., software) running on a computing device (e.g., the computing device described in  FIG. 9 ), (2) as interconnected machine logic circuits or circuit modules (i.e., hardware) within the computing device and/or (3) a combination of software and hardware of the computing device. Thus, the logical operations discussed herein are not limited to any specific combination of hardware and software. The implementation is a matter of choice dependent on the performance and other requirements of the computing device. Accordingly, the logical operations described herein are referred to variously as operations, structural devices, acts, or modules. These operations, structural devices, acts and modules may be implemented in software, in firmware, in special purpose digital logic, and any combination thereof. It should also be appreciated that more or fewer operations may be performed than shown in the figures and described herein. These operations may also be performed in a different order than those described herein. 
     Referring to  FIG. 9 , an example computing device  900  upon which embodiments of the invention may be implemented is illustrated. For example, the control unit  136  may be implemented as a computing device, such as computing device  900  programmed to implement any of the control algorithms shown and describe with reference to  FIGS. 2, 6, and 8 . It should be understood that the example computing device  900  is only one example of a suitable computing environment upon which embodiments of the invention may be implemented. Optionally, the computing device  900  can be a well-known computing system including, but not limited to, personal computers, servers, handheld or laptop devices, multiprocessor systems, microprocessor-based systems, network personal computers (PCs), minicomputers, mainframe computers, embedded systems, and/or distributed computing environments including a plurality of any of the above systems or devices. Distributed computing environments enable remote computing devices, which are connected to a communication network or other data transmission medium, to perform various tasks. In the distributed computing environment, the program modules, applications, and other data may be stored on local and/or remote computer storage media. 
     In an embodiment, the computing device  900  may comprise two or more computers in communication with each other that collaborate to perform a task. For example, but not by way of limitation, an application may be partitioned in such a way as to permit concurrent and/or parallel processing of the instructions of the application. Alternatively, the data processed by the application may be partitioned in such a way as to permit concurrent and/or parallel processing of different portions of a data set by the two or more computers. In an embodiment, virtualization software may be employed by the computing device  900  to provide the functionality of a number of servers that is not directly bound to the number of computers in the computing device  900 . For example, virtualization software may provide twenty virtual servers on four physical computers. In an embodiment, the functionality disclosed above may be provided by executing the application and/or applications in a cloud computing environment. Cloud computing may comprise providing computing services via a network connection using dynamically scalable computing resources. Cloud computing may be supported, at least in part, by virtualization software. A cloud computing environment may be established by an enterprise and/or may be hired on an as-needed basis from a third party provider. Some cloud computing environments may comprise cloud computing resources owned and operated by the enterprise as well as cloud computing resources hired and/or leased from a third party provider. 
     In its most basic configuration, computing device  900  typically includes at least one processing unit  920  and system memory  930 . Depending on the exact configuration and type of computing device, system memory  930  may be volatile (such as random access memory (RAM)), non-volatile (such as read-only memory (ROM), flash memory, etc.), or some combination of the two. This most basic configuration is illustrated in  FIG. 9  by dashed line  910 . The processing unit  920  may be a standard programmable processor that performs arithmetic and logic operations necessary for operation of the computing device  900 . While only one processing unit  920  is shown, multiple processors may be present. Thus, while instructions may be discussed as executed by a processor, the instructions may be executed simultaneously, serially, or otherwise executed by one or multiple processors. The computing device  900  may also include a bus or other communication mechanism for communicating information among various components of the computing device  900 . 
     Computing device  900  may have additional features/functionality. For example, computing device  900  may include additional storage such as removable storage  940  and non-removable storage  950  including, but not limited to, magnetic or optical disks or tapes. Computing device  900  may also contain network connection(s)  980  that allow the device to communicate with other devices such as over the communication pathways described herein. The network connection(s)  980  may take the form of modems, modem banks, Ethernet cards, universal serial bus (USB) interface cards, serial interfaces, token ring cards, fiber distributed data interface (FDDI) cards, wireless local area network (WLAN) cards, radio transceiver cards such as code division multiple access (CDMA), global system for mobile communications (GSM), long-term evolution (LTE), worldwide interoperability for microwave access (WiMAX), and/or other air interface protocol radio transceiver cards, and other well-known network devices. Computing device  900  may also have input device(s)  970  such as a keyboards, keypads, switches, dials, mice, track balls, touch screens, voice recognizers, card readers, paper tape readers, or other well-known input devices. Output device(s)  960  such as a printers, video monitors, liquid crystal displays (LCDs), touch screen displays, displays, speakers, etc. may also be included. The additional devices may be connected to the bus in order to facilitate communication of data among the components of the computing device  900 . All these devices are well known in the art and need not be discussed at length here. 
     The processing unit  920  may be configured to execute program code encoded in tangible, computer-readable media. Tangible, computer-readable media refers to any media that is capable of providing data that causes the computing device  900  (i.e., a machine) to operate in a particular fashion. Various computer-readable media may be utilized to provide instructions to the processing unit  920  for execution. Example tangible, computer-readable media may include, but is not limited to, volatile media, non-volatile media, removable media and non-removable media implemented in any method or technology for storage of information such as computer readable instructions, data structures, program modules or other data. System memory  930 , removable storage  940 , and non-removable storage  950  are all examples of tangible, computer storage media. Example tangible, computer-readable recording media include, but are not limited to, an integrated circuit (e.g., field-programmable gate array or application-specific IC), a hard disk, an optical disk, a magneto-optical disk, a floppy disk, a magnetic tape, a holographic storage medium, a solid-state device, RAM, ROM, electrically erasable program read-only memory (EEPROM), flash memory or other memory technology, CD-ROM, digital versatile disks (DVD) or other optical storage, magnetic cassettes, magnetic tape, magnetic disk storage or other magnetic storage devices. 
     It is fundamental to the electrical engineering and software engineering arts that functionality that can be implemented by loading executable software into a computer can be converted to a hardware implementation by well-known design rules. Decisions between implementing a concept in software versus hardware typically hinge on considerations of stability of the design and numbers of units to be produced rather than any issues involved in translating from the software domain to the hardware domain. Generally, a design that is still subject to frequent change may be preferred to be implemented in software, because re-spinning a hardware implementation is more expensive than re-spinning a software design. Generally, a design that is stable that will be produced in large volume may be preferred to be implemented in hardware, for example in an application specific integrated circuit (ASIC), because for large production runs the hardware implementation may be less expensive than the software implementation. Often a design may be developed and tested in a software form and later transformed, by well-known design rules, to an equivalent hardware implementation in an application specific integrated circuit that hardwires the instructions of the software. In the same manner as a machine controlled by a new ASIC is a particular machine or apparatus, likewise a computer that has been programmed and/or loaded with executable instructions may be viewed as a particular machine or apparatus. 
     In an example implementation, the processing unit  920  may execute program code stored in the system memory  930 . For example, the bus may carry data to the system memory  930 , from which the processing unit  920  receives and executes instructions. The data received by the system memory  930  may optionally be stored on the removable storage  940  or the non-removable storage  950  before or after execution by the processing unit  920 . 
     It should be understood that the various techniques described herein may be implemented in connection with hardware or software or, where appropriate, with a combination thereof. Thus, the methods and apparatuses of the presently disclosed subject matter, or certain aspects or portions thereof, may take the form of program code (i.e., instructions) embodied in tangible media, such as floppy diskettes, CD-ROMs, hard drives, or any other machine-readable storage medium wherein, when the program code is loaded into and executed by a machine, such as a computing device, the machine becomes an apparatus for practicing the presently disclosed subject matter. In the case of program code execution on programmable computers, the computing device generally includes a processor, a storage medium readable by the processor (including volatile and non-volatile memory and/or storage elements), at least one input device, and at least one output device. One or more programs may implement or utilize the processes described in connection with the presently disclosed subject matter, e.g., through the use of an application programming interface (API), reusable controls, or the like. Such programs may be implemented in a high level procedural or object-oriented programming language to communicate with a computer system. However, the program(s) can be implemented in assembly or machine language, if desired. In any case, the language may be a compiled or interpreted language and it may be combined with hardware implementations. 
     Embodiments of the methods and systems may be described herein with reference to block diagrams and flowchart illustrations of methods, systems, apparatuses and computer program products. It will be understood that each block of the block diagrams and flowchart illustrations, and combinations of blocks in the block diagrams and flowchart illustrations, respectively, can be implemented by computer program instructions. These computer program instructions may be loaded onto a general purpose computer, special purpose computer, or other programmable data processing apparatus to produce a machine, such that the instructions which execute on the computer or other programmable data processing apparatus create a means for implementing the functions specified in the flowchart block or blocks. 
     These computer program instructions may also be stored in a computer-readable memory that can direct a computer or other programmable data processing apparatus to function in a particular manner, such that the instructions stored in the computer-readable memory produce an article of manufacture including computer-readable instructions for implementing the function specified in the flowchart block or blocks. The computer program instructions may also be loaded onto a computer or other programmable data processing apparatus to cause a series of operational steps to be performed on the computer or other programmable apparatus to produce a computer-implemented process such that the instructions that execute on the computer or other programmable apparatus provide steps for implementing the functions specified in the flowchart block or blocks. 
     Accordingly, blocks of the block diagrams and flowchart illustrations support combinations of means for performing the specified functions, combinations of steps for performing the specified functions and program instruction means for performing the specified functions. It will also be understood that each block of the block diagrams and flowchart illustrations, and combinations of blocks in the block diagrams and flowchart illustrations, can be implemented by special purpose hardware-based computer systems that perform the specified functions or steps, or combinations of special purpose hardware and computer instructions. 
     While several embodiments have been provided in the present disclosure, it should be understood that the disclosed systems and methods may be embodied in many other specific forms without departing from the spirit or scope of the present disclosure. The present examples are to be considered as illustrative and not restrictive, and the intention is not to be limited to the details given herein. For example, the various elements or components may be combined or integrated in another system or certain features may be omitted or not implemented. 
     Also, techniques, systems, subsystems, and methods described and illustrated in the various embodiments as discrete or separate may be combined or integrated with other systems, modules, techniques, or methods without departing from the scope of the present disclosure. Other items shown or discussed as directly coupled or communicating with each other may be indirectly coupled or communicating through some interface, device, or intermediate component, whether electrically, mechanically, or otherwise. Other examples of changes, substitutions, and alterations are ascertainable by one skilled in the art and could be made without departing from the spirit and scope disclosed herein.