Patent Publication Number: US-2021164720-A1

Title: Push-through conditioned air vestibule and controller

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application cross-references and claims the benefit of priority of U.S. Provisional Patent Application No. 62/067,346, filed 22 Oct. 2014, entitled PUSH-THROUGH CONDITIONED AIR VESTIBULE AND CONTROLLER, the disclosure of which is incorporated, in its entirety, by this reference. 
    
    
     TECHNICAL FIELD 
     The present invention relates to a conditioned air vestibule for a cold storage doorway. More particularly, the present invention relates to an air curtain arrangement and control system that controls temperature of the air discharged across a doorway and a method of controlling the airflow temperature to prevent formation of frost, water, and fog. 
     BACKGROUND 
     In the field of cold storage freezers and similar devices, various systems such as solid doors, strip curtains, and air curtains, may be used to separate the cold storage room from an adjacent relatively warm anteroom. It is desirable to allow traffic from people and equipment through a doorway between the cold storage room and the adjacent warm room safely and with a minimum transfer of relatively cool and warm air between the cold room and the warm room. 
     The use of air curtains is one method of allowing a doorway to remain open to traffic while also preventing substantial energy loss between the cold and warm sides of the vestibule. Air curtains generally direct air across the doorway to counter infiltration of warm to the cold room and exfiltration of cold air from the cold room. By way of example, air curtains may direct air horizontally or vertically across the doorway from or toward an upper portion of the air curtain. 
     As a safety precaution, it is desirable to prevent the formation of fog, ice, and water in the doorway. Ice may form from the mixing of air from the cold and warm sides of the vestibule. The formation of ice at an air curtain depends on the temperature and relative humidity of the cold and warm rooms, and may be characterized by a psychrometric saturation curve. The mixing of air from the relatively warm and cold sides may be characterized by a straight line between points representing the warm side temperature and humidity and the cold side temperature and humidity, which may be plotted on a psychrometric saturation chart along with the curve. Generally, ice may form whenever the temperature is below 32 degrees Fahrenheit and the mixing line is to the left of, and above, the psychrometric saturation curve, as it is typically plotted. 
     The formation of ice may be prevented by heating the air discharged from the air curtain. By way of example, the discharged air may be heated to a temperature at a point on the psychrometric saturation chart such that lines to such point from both the cold side and warm side temperature/humidity points remain to the right of, and below, the psychrometric saturation curve, as it is typically plotted. 
     While avoiding the formation of ice, water, and fog, it is also desirable to operate the air curtain as efficiently as possible, by adding the minimum amount of heat necessary to avoid such problems. With respect to the psychrometric saturation chart, this means keeping the point representing the airstream with the added heat as close to the saturation curve as possible, without causing mixing lines from this point to the cold side and warm side temperature/humidity points to contact or cross the saturation curve. 
     Because temperature and humidity conditions in the cold and warm side rooms may change, it is desirable in some applications to dynamically condition the discharged air in response to changing conditions. Conventional systems have various shortcomings. Some systems permit operation of the air curtain at points directly on the saturation curve. In changing environments, this permits the formation of ice, water, and fog because the system may not respond as quickly as the conditions change and because the sensors may not be sufficiently accurate for all positions in the vestibule. This is particularly a problem for systems that rely upon mathematical approximations of the psychrometric saturation curve. 
     SUMMARY 
     An aspect of the present disclosure relates to a push through conditioned air vestibule unit that may comprise an air vestibule having a top side, a first lateral side, and a second lateral side that may form a passage through the unit. A plurality of movable barrier members may be configured to reduce external air flow through the passage. First and second lateral side supply or return air ducts may be configured to supply air to or return air from the top side from the first and second lateral sides. An air moving device may be configured to circulate, receive, or supply air from the first and second lateral side return air ducts and to move air into the passage. The unit may also have a temperature conditioning device configured to adjust the temperature of air moved into the passage, an external thermal sensor configured to measure a temperature external to the passage, an internal thermal sensor configured to measure a temperature within the passage, an external humidity sensor configured to measure a humidity external to the passage, and an internal humidity sensor configured to measure a humidity internal to the passage. A system controller may be in communication with the external and internal thermal sensors and the external and internal humidity sensors and may be configured to increase the temperature of air moved into the passage using the temperature conditioning device if the partial pressure of moisture vapor internal to the passage is not greater than or equal to the partial pressure of moisture vapor external to the passage. 
     The movable barrier members of the unit may comprise flexible strips hanging from the top side of the unit and may be impact-type doors. A distance through the passage may be about 6 inches or greater. The first and second lateral return air ducts may comprise return air openings at bottom ends of the first and second lateral sides. 
     The system controller may be configured to maintain a partial pressure of moisture in the passage equal to or higher than a partial pressure of moisture external to the passage, such as, for example by being configured to cycle the temperature conditioning device on and off. 
     The air vestibule may be positioned between a first room and a second room, the first room having a warmer temperature than the second room. The external thermal sensor and the external humidity sensor may measure temperature and humidity, respectively, of the first room. 
     In another aspect, a method of controlling air condition in a conditioned air vestibule unit is provided. The method may comprise providing a conditioned air vestibule having a heat source, a plurality of thermal sensors, a plurality of humidity sensors, and an air moving device, measuring an external temperature and a vestibule temperature using the plurality of thermal sensors, measuring an external humidity and a vestibule humidity using the plurality of humidity sensors, calculating an external partial pressure of moisture vapor external to the vestibule, calculating a vestibule partial pressure of moisture vapor within the vestibule, and enabling the heat source to heat air provided to the air moving device if the vestibule partial pressure is greater than or equal to the external partial pressure. 
     The vestibule temperature and vestibule humidity may be measured within a passage through the conditioned air vestibule. The external temperature and external humidity may be measured from an external area warmer than a passage through the conditioned air vestibule. 
     In performing the method, the heat source may be cycled on and off. The method may further comprise circulating air in the conditioned air vestibule unit by drawing air from a bottom of the conditioned air vestibule into the air moving device and expelling air from the air moving device into the conditioned air vestibule after being heated by the heat source. 
     Air may also be moved into the conditioned air vestibule using the air moving device. The air moved into the vestibule may remove or prevent formation of ice and/or frost in the conditioned air vestibule. 
     Some embodiments may comprise a non-transitory computer-readable medium having instructions encoded thereon that, when executed by a processor of a computer, cause the computer to perform steps comprising: measuring an external temperature and a vestibule temperature of a conditioned air vestibule having a heat source, a plurality of thermal sensors, a plurality of humidity sensors, and an air moving device, the external and vestibule temperatures being measured using the plurality of thermal sensors; measuring an external humidity and a vestibule humidity using the plurality of humidity sensors; calculating an external partial pressure of moisture vapor external to the vestibule; calculating a vestibule partial pressure of moisture vapor within the vestibule; and enabling the heat source to heat air provided to the air moving device if the vestibule partial pressure is greater than or equal to the external partial pressure. 
     The above summary of the present invention is not intended to describe each embodiment or every implementation of the present invention. The Figures and the detailed description that follow more particularly exemplify a preferred embodiment. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The accompanying drawings and figures illustrate a number of exemplary embodiments and are part of the specification. Together with the present description, these drawings demonstrate and explain various principles of this disclosure. A further understanding of the nature and advantages of the present invention may be realized by reference to the following drawings. In the appended figures, similar components or features may have the same reference label. 
         FIG. 1  is a perspective view of an example of a push-through conditioned air vestibule of the present disclosure. 
         FIG. 2  is a block diagram of modules implemented by a system controller of a push-through conditioned air vestibule of the present disclosure. 
         FIG. 3  is a flowchart illustrating an example process by which a heat source may be controlled in a push-through conditioned air vestibule. 
         FIG. 4  is a block diagram of a computer system that may be used to implement embodiments of the present disclosure. 
     
    
    
     While the embodiments described herein are susceptible to various modifications and alternative forms, specific embodiments have been shown by way of example in the drawings and will be described in detail herein. However, the exemplary embodiments described herein are not intended to be limited to the particular forms disclosed. Rather, the instant disclosure covers all modifications, equivalents, and alternatives falling within the scope of the appended claims. 
     DETAILED DESCRIPTION 
     Aspects of the present disclosure may improve the effectiveness of conditioned air vestibules such as those used to link freezers to warmer areas. These systems may reduce refrigeration load while preventing frost, ice, and wetness at the entryway to the vestibule. An example embodiment of the vestibule may comprise two pairs of impact-type doors, or fixed strips, and an electrically or hot-gas heated anti-frost air-conditioning (AFC) section with temperature reset control. In some cases, the vestibule may be about 6 inches in depth in the direction of travel through the vestibule. These benefits may reduce refrigeration losses, increase warehouse (or other commercial or industrial location) productivity, reduce coil defrosting burdens, and improve refrigeration cycle efficiency. 
       FIG. 1  shows an example of a push-through conditioned air vestibule  100  according to an embodiment of the present disclosure. The vestibule  100  comprises a top side  102 , a first lateral side  104 , and a second lateral side  106  through which a passage  108  is formed. The passage  108  may be lined with movable barrier members  110  on each end of the passage  108 . The first lateral side  104  may comprise a first air return duct  112 , and the second lateral side  106  may comprise a second air return duct  114 . These ducts  112 ,  114  may be configured to bring air to the top side  102  from their respective lateral sides  104 ,  106 . An air moving device  116  may be positioned in the top side  102  and configured to receive air from the return air ducts  112 ,  114  and then move air into the passage  108 , such as through vents exposed into the passage  108  at the top side  102  of the vestibule  100 . The top side  102  may also comprise a temperature conditioning device  118  that receives airflow and adjusts the temperature of air moved into the passage  108 . 
     An external thermal sensor  120  may be configured to measure a temperature of external air, such as the temperature of a warm room outside the passage  108 , and an internal thermal sensor  122  may be configured to measure the temperature of air in the passage  108 . An external humidity sensor  124  and internal humidity sensor  126  may also be configured to measure humidity of their respective areas relative to the passage  108 . 
     The vestibule  100  may also include a system controller  128  configured to control the temperature conditioning device  118  and air moving device  116  while receiving data from the sensors (e.g., sensors  120 ,  122 ,  124 ,  126 ). 
     In some embodiments the vestibule  100  may comprise more than one unit, such as multiple vestibules  100  having aligned passages in a series. The vestibule  100  may be positioned such that it separates a cooler area from a warmer area. A common application would be use of the vestibule  100  as an air curtain between a freezer and a warm room of a warehouse, for example. In a single vestibule  100 , more than one air curtain may be implemented, such as a first air curtain directing air primarily toward the first lateral side  104  and a second air curtain directing air primarily toward the second lateral side  106  adjacent to the first air curtain. 
     The top side  102  may include a conduit system connecting the lateral side return air ducts  112 ,  114  to the air moving device  116  and the temperature conditioning device  118 . Positioning the air moving device  116  and temperature conditioning device  118  in the top side  102  may be beneficial because the top side  102  is central to each of the lateral sides  104 ,  106 , so only one air moving device  116  and/or temperature conditioning device  118  may be required to receive and control air flow for both lateral sides  104 ,  106 . Additionally, positioning these components  116 ,  118  in the top side  102  may reduce the lateral profile of the vestibule  100 , thereby either allowing the vestibule  100  to fit within narrower openings or to maximize the width of the passage  108 . 
     The top side  102  in  FIG. 1  is shown having the controller  128  housed therein, but the controller  128  may alternatively be stored in another area of the vestibule  100 . For example, the controller  128  may be positioned in one of the lateral sides  104 ,  106  to be more accessible from the ground level. 
     The first lateral side  104  and second lateral side  106 , along with the return air ducts  112 ,  114 , may extend from a ground level to the top side  102  of the vestibule  100 . The return air ducts  112 ,  114  may each have a return air vent  130  positioned near the ground level. At the ground level, the return air vents  130  may receive cooler air that is moved up through the return air ducts  112 ,  114  by the air moving device  116  to the top side  102  where its temperature may be adjusted by the temperature conditioning device  118 . In an alternative embodiment, the air discharge openings may be situated near or in the floor of the air curtain and the return vents may be situated in or near the upper portion of the air curtain, such that the air is discharged across the opening in a generally upward direction. 
     The passage  108  may extend between the first and second lateral sides  104 ,  106  and may be used as a doorway between rooms on each side of the vestibule  100 . In an example embodiment, the passage  108  may be about 6 inches across (i.e., between the movable barrier members  110  at each end of the passage  108 ). The passage  108  may allow push-through access, meaning personnel, carts, vehicles, and equipment may push or move through the passage  108  unimpeded. 
     The movable barrier members  110  may comprise strips of flexible material, such as, for example, vinyl strips that hang from the top side  102  to the ground level. The movable barrier members  110  may be connected by clips, fasteners, or joints to the top side  102 . In some embodiments the movable barrier members  110  may be referred to as impact-type doors. The movable barrier members  110  may provide insulation and airflow isolation to the passage  108  by acting as a barrier to airflow while hanging vertically, yet may not hinder the passage of equipment and personnel through the passage  108 . Thus, the movable barrier members  110  may help maintain the temperature and humidity of air within the passage  108  due to preventing the outflow or inflow of external air while they close off the ends of the passage  108 . 
     The air moving device  116  may comprise a device that, when active, pushes or pulls air through the ducts of the vestibule  100  and through the passage  108 . One example air moving device  116  may comprise a fan or plurality of fans that may be driven by an electric motor. The motor may be controlled by the system controller  128  so that the speed and direction of motion of the fan may be controlled by the controller  128 . 
     The temperature conditioning device  118  may comprise a heating or cooling system capable of changing the temperature of air flowing through the ducts of the vestibule  100 . For example, a temperature conditioning device  118  may comprise a heater comprising electric coils or heated pipes that warm the air in the ducts as it passes by the coils or pipes. In some arrangements the temperature conditioning device  118  may be controllable to output a desired amount of heat based on commands received from the system controller  128 . In one application, the temperature conditioning device  118  may beneficially be a heater so that air provided to the passage  108  may be warmer than air in a cold side of the vestibule  100 . 
     The heat provided by the temperature conditioning device  118  may also affect the humidity of the air in the ducts and passage  108 , so in some configurations the vestibule  100  may further comprise a humidity conditioning device configured to increase or decrease the relative humidity of air in the passage  108 . In some embodiments, the humidity conditioning device may expel water or mist into the air at or near the temperature conditioning device  118 . 
     The external thermal sensor  120  and internal thermal sensor  122  may comprise thermocouples configured to measure temperature external or internal to the passage  108 . Other types of thermal sensors may also be used. The external humidity sensor  124  and internal humidity sensor  126  may comprise electronic hygrometers. The external thermal sensor  120  and external humidity sensor  124  may be positioned to measure temperature and humidity of a warm room to the front or rear of the vestibule  100 . The internal thermal and humidity sensors  122 ,  126  may measure the temperature and humidity of air in the passage  108 . 
     The system controller  128  may be a computing device such as, for example, a computer or integrated control circuit. A computer system suitable for implementing the system controller  128  is described in further detail in connection with  FIG. 4 . The system controller  128  may comprise a plurality of modules for executing its functions. As shown in  FIG. 2 , a system controller  128  may comprise a vestibule control module  200 - a . The vestibule control module  200 - a  may comprise a plurality of modules executable by the system controller  128 . 
     The vestibule control module  200 - a  may comprise a temperature measurement module  205  and a humidity measurement module  210 . The temperature measurement module  205  may be configured to receive signals from the thermal sensors  120 ,  122  and convert the signals into signals readable by a partial pressure calculation module  215 . Likewise, the humidity measurement module  210  may receive signals from the humidity sensors  124 ,  126  and convert the signals into a form readable by the partial pressure calculation module  215 . 
     A partial pressure calculation module  215  may receive the signals from the temperature and humidity measurement modules  205 ,  210  and may implement psychrometric equations to calculate the partial pressures of moisture vapor in the air of the vestibule and external to the vestibule. The temperature and relative humidity of the external area and of the vestibule may be used as inputs to these equations. In one example embodiment, the following equations may be implemented: 
         L   o   =C   8   /T   o   +C   9   +C   10   T   o   +C   11   T   o   2   +C   12   T   o   3   +C   13   /nT   o   [Equation 1],
 
         L   i   =C   8   /T   i   +C   9   +C   10   T   i   +C   11   T   i   2   +C   12   T   i   3   +C   13   /nT   i   [Equation 2],
 
         P   wso   =e   Lo   [Equation 3],
 
         P   wsi   =e   Li   [Equation 4],
 
         P   wo =Φ o ( P   wso )  [Equation 5], and
 
         P   wi =Φ i ( P   wsi )  [Equation 6],
 
     wherein: 
     T o  is the temperature of air in the external area, T i  is the temperature of air in the vestibule, P wo  is the partial pressure of vapor in the external area, P w1  is the partial pressure of vapor in the vestibule, Φ o  is the relative humidity of the external area, Φ i  is the relative humidity of the vestibule, P wso  is the saturation pressure of the external area, P ws1  is the saturation pressure of the vestibule, L o  is the natural log of saturation pressure of the external area, L i  is the natural log of saturation pressure of the vestibule, C 8 =−1.0440397×10 4 , C 9 =−11.294650, C 10 =−2.7022355×10 −2 , C 11 =1.2890360×10 −5 , C 12 =−2.4780681×10 −9 , and C 13 =6.5459673. Thus, the partial pressure calculation module  215  may determine P wo  and P wi  and provide these values to the comparator module  220 . The comparator module  220  may receive partial pressure calculations from the partial pressure calculation module  215 , compare the partial pressure values, and send a result to a thermal control module  225 . 
     The thermal control module  225  may receive the results of the comparator module  220  and, via an interface with the air moving device  116  and the temperature conditioning device  118 , may control the temperature and humidity of air provided to the passage  108  of the vestibule  100 . 
       FIG. 3  illustrates an embodiment of a process  300  that may be executed by the modules of the system controller  128 . The process  300  may include blocks  305  and  310 , wherein the temperature of the air of the external area and the vestibule air are measured. These temperatures may be measured by the internal and external thermal sensors  122 ,  120 , respectively. In blocks  315  and  320 , the humidity of the air of the external area and the vestibule air may be measured, such as by the external and internal humidity sensors  124 ,  126 . At blocks  325  and  330 , the system controller  128  may calculate the partial pressure of moisture vapor in the external area and in the vestibule. At block  335 , the system controller  128  may compare the partial pressures calculated in blocks  325  and  330  and determine whether the partial pressure of moisture vapor in the vestibule (i.e., PvV) is greater than or equal to the partial pressure of moisture vapor in the external area (i.e., PvW). If PvV is less than PvW, the system controller  128  may execute block  340  to enable a heat source. The heat source may be part of the temperature conditioning device  118 . Enabling the heat source may comprise turning a heat source in the temperature conditioning device  118  on and off. If PvV is greater than or equal to PvW, the process  300  may restart and continue to monitor conditions in the vestibule and external area. 
       FIG. 4  depicts a block diagram of a computer system  400  suitable for implementing the present systems and methods. Computer system  400  includes a bus  405  which interconnects major subsystems of computer system  400 , such as a central processor  410 , a system memory  415  (typically RAM, but which may also include ROM, flash RAM, or the like), an input/output controller  420 , an external audio device, such as a speaker system  425  via an audio output interface  430 , an external device, such as a display screen  435  via display adapter  440 , an input device  445  (e.g., a keyboard, touchscreen, etc.) (interfaced with an input controller  450 ), a sensor  455  (interfaced with a sensor controller  460 ), one or more universal serial bus (USB) device  465  (interfaced with a USB controller  470 ), and a storage interface  480  linking to a fixed disk  475 . A network interface  485  is also included and coupled directly to bus  405 . 
     Bus  405  allows data communication between central processor  410  and system memory  415 , which may include read-only memory (ROM) or flash memory (neither shown), and random access memory (RAM) (not shown), as previously noted. The RAM is generally the main memory into which the operating system and application programs are loaded. The ROM or flash memory can contain, among other code, the Basic Input-Output system (BIOS) which controls basic hardware operation such as the interaction with peripheral components or devices. For example, a vestibule control module  200 - b  which may implement the present systems and methods may be stored within the system memory  415 . Applications resident with computer system  400  are generally stored on and accessed via a non-transitory computer readable medium, such as a hard disk drive (e.g., fixed disk  475 ), an optical drive (e.g., an optical drive that is part of a USB device  465  or that connects to storage interface  480 ), or other storage medium. Additionally, applications can be in the form of electronic signals modulated in accordance with the application and data communication technology when accessed via network interface  485 . 
     Storage interface  480 , as with the other storage interfaces of computer system  400 , can connect to a standard computer readable medium for storage and/or retrieval of information, such as a fixed disk drive  475 . Fixed disk drive  475  may be a part of computer system  400  or may be separate and accessed through other interface systems. A modem connected to the network interface  485  may provide a direct connection to a remote server via a telephone link or to the Internet via an internet service provider (ISP). Network interface  485  may provide a direct connection to a remote server via a direct network link to the Internet via a POP (point of presence). Network interface  485  may provide such connection using wireless techniques, including digital cellular telephone connection, Cellular Digital Packet Data (CDPD) connection, digital satellite data connection or the like. 
     Many other devices or subsystems (not shown) may be connected in a similar manner (e.g., document scanners, digital cameras and so on). Conversely, all of the devices shown in  FIG. 4  need not be present to practice the present systems and methods. The devices and subsystems can be interconnected in different ways from that shown in  FIG. 4 . The operation of a computer system such as that shown in  FIG. 4  is readily known in the art and is not discussed in detail in this application. Code to implement the present disclosure can be stored in a non-transitory computer-readable medium such as one or more of system memory  415 , or fixed disk  475 . The operating system provided on computer system  400  may be MS-DOS®, MS-WINDOWS®, OS/2®, UNIX®, Linux®, or another known operating system. 
     Moreover, regarding the signals and network communications described herein, those skilled in the art will recognize that a signal can be directly transmitted from a first block to a second block, or a signal can be modified (e.g., amplified, attenuated, delayed, latched, buffered, inverted, filtered, or otherwise modified) between the blocks. Although the signals of the above described embodiments are characterized as transmitted from one block to the next, other embodiments of the present systems and methods may include modified signals in place of such directly transmitted signals as long as the informational and/or functional aspect of the signal is transmitted between blocks. To some extent, a signal input at a second block can be conceptualized as a second signal derived from a first signal output from a first block due to physical limitations of the circuitry involved (e.g., there will inevitably be some attenuation and delay). Therefore, as used herein, a second signal derived from a first signal includes the first signal or any modifications to the first signal, whether due to circuit limitations or due to passage through other circuit elements which do not change the informational and/or final functional aspect of the first signal. 
     The present description provides examples, and is not limiting of the scope, applicability, or configuration set forth in the claims. Thus, it will be understood that changes may be made in the function and arrangement of elements discussed without departing from the spirit and scope of the disclosure, and various embodiments may omit, substitute, or add other procedures or components as appropriate. For instance, the methods described may be performed in an order different from that described, and various steps may be added, omitted, or combined. Also, features described with respect to certain embodiments may be combined in other embodiments. 
     Various inventions have been described herein with reference to certain specific embodiments and examples. However, they will be recognized by those skilled in the art that many variations are possible without departing from the scope and spirit of the inventions disclosed herein, in that those inventions set forth in the claims below are intended to cover all variations and modifications of the inventions disclosed without departing from the spirit of the inventions. The terms “including” and “having” come as used in the specification and claims shall have the same meaning as the term “comprising.”