Patent Publication Number: US-2021188046-A1

Title: Isolated evaporator piping pod

Description:
BACKGROUND 
     The following description relates to evaporators and, more specifically, to an isolated evaporator piping pod for certain refrigerants, such as A2L refrigerants. 
     Regulations in various regions around the world are requiring that refrigerant suppliers reduce distributions of high global warming potential (GWP) refrigerants. This presents an issue, however, in that new blends of low GWP refrigerants, such as A2L refrigerants, are often characterized as being mildly flammable. Thus, if an A2L refrigerant, for example, leaks into a cargo container interior through evaporator tubing, the leaked A2L refrigerant can create a mildly flammable environment that could ignite if a sufficient energy source exists. 
     While the potential ignition of leaked, mildly flammable refrigerant can be addressed by various options, such as the provision of safety systems, doing so is costly and time consuming. 
     BRIEF DESCRIPTION 
     According to an aspect of the disclosure, a transport refrigeration unit (TRU) is provided and includes a wall defining an inlet and an outlet and a pod attachable to the wall to define, with a portion of the wall, an interior configured to accommodate a heat exchange portion of a heat exchanger, a fan that drives air flow from the inlet and to the outlet through the heat exchange portion and the air flow. The pod is configured to isolate coolant flow control elements of the heat exchanger from the interior. 
     In accordance with additional or alternative embodiments, the heat exchange portion includes evaporator tubes having first and second opposite ends and the coolant flow control elements include return bend elements that respectively connect corresponding ends of two or more evaporator tubes at one of the first and second opposite ends. 
     In accordance with additional or alternative embodiments, the pod defines a first aperture through which the first end of each of the evaporator tubes extends and a second aperture through which the second end of each of the evaporator tubes extends. 
     In accordance with additional or alternative embodiments, the pod defines first apertures through which the return bend elements associated with the first end extend and second apertures through which the return bend elements associated with the second end extend. 
     According to another aspect of the disclosure, a pod is provided for an evaporator including evaporator tubes and return bend elements connecting corresponding evaporator tube ends. The pod includes peripheral flanges which are attachable to a wall of a cargo area, a convex portion formed to define, with a portion of the wall, an interior to accommodate the evaporator tubes and a fan, the interior being fluidly communicative with the cargo area through an inlet and an outlet defined in the wall and the fan drives air flow from the inlet to the outlet and through the evaporator tubes and plate sections respectively secured to opposite end sections of the evaporator tubes and respective local portions of the peripheral flanges and the convex portion to isolate the return bend elements from the interior. 
     In accordance with additional or alternative embodiments, the return bend elements include return bends and brazed joints that connect the return bends to the corresponding ends of the two or more evaporator tubes. 
     In accordance with additional or alternative embodiments, the peripheral flanges form a polygonal profile and the convex portion includes rounded edges. 
     In accordance with additional or alternative embodiments, the interior includes a lower section defined between the inlet and the evaporator tubes, an upper section defined between the fan and the outlet and a central section defined between evaporator tubes and the fan. 
     In accordance with additional or alternative embodiments, respective outer planes of the plate sections are coplanar with respective outermost planes of the opposite end sections of the evaporator tubes or the plate sections are respectively formed to define apertures through which the return bend elements are connectable with the corresponding evaporator tube ends. 
     In accordance with additional or alternative embodiments, the plate sections respectively define, with respective distal portions of the peripheral flanges and the convex portion, distal interiors isolated from the interior and the distal portions of the convex portion define apertures through which the distal interiors are communicative with an exterior of the cargo area. 
     In accordance with additional or alternative embodiments, the convex portion includes removable panels. 
     According to another aspect of the disclosure, a transport refrigeration unit (TRU) is provided and includes a wall defining an inlet and an outlet between a cargo area and an exterior, an evaporator and a pod. The pod includes peripheral flanges attachable to the wall, a convex portion defining, with a portion of the wall, an interior communicative with the cargo area through the inlet and the outlet and configured to accommodate the evaporator and a fan that drives air flow from the inlet and to the outlet through the evaporator and plate sections respectively secured to opposite end sections of evaporator tubes of the evaporator and respective local portions of the peripheral flanges and the convex portion to divide the interior into a first interior configured to accommodate the evaporator tubes and the fan and second interiors isolated from the first interior and configured to accommodate return bend elements of the evaporator. 
     In accordance with additional or alternative embodiments, the return bend elements include return bends and brazed joints that connect the return bends to corresponding ends of the two or more evaporator tubes. 
     In accordance with additional or alternative embodiments, the peripheral flanges form a polygonal profile and the convex portion comprises rounded edges. 
     In accordance with additional or alternative embodiments, a width of the first interior is equal to or slightly less than a width of the evaporator tubes. 
     In accordance with additional or alternative embodiments, the first interior includes a lower section defined between the inlet and the evaporator tubes, an upper section defined between the fan and the outlet and a central section defined between evaporator tubes and the fan. 
     In accordance with additional or alternative embodiments, respective outer planes of the plate sections are coplanar with respective outermost planes of the opposite end sections of the evaporator tubes. 
     In accordance with additional or alternative embodiments, the plate sections are respectively formed to define apertures through which the return bend elements are connectable with the corresponding evaporator tubes. 
     In accordance with additional or alternative embodiments, the distal portions of the convex portion define apertures through which the second interiors are communicative with an exterior of the cargo area. 
     In accordance with additional or alternative embodiments, the convex portion includes removable panels. 
     These and other advantages and features will become more apparent from the following description taken in conjunction with the drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The subject matter, which is regarded as the disclosure, is particularly pointed out and distinctly claimed in the claims at the conclusion of the specification. The foregoing and other features and advantages of the disclosure are apparent from the following detailed description taken in conjunction with the accompanying drawings in which: 
         FIG. 1  is a trailer with a transport refrigeration unit (TRU) in accordance with embodiments; 
         FIG. 2  is a graphical depiction of flammability vs. charge loss for various refrigerants; 
         FIG. 3  is a perspective view of a conventional pod for an evaporator of a TRU; 
         FIG. 4  is a side view of the conventional pod of  FIG. 3 ; 
         FIG. 5  is a side view of a pod with isolation plates in an operational condition in accordance with embodiments; 
         FIG. 6  is a front view of the pod including the isolation plates of  FIG. 5  in accordance with embodiments; 
         FIG. 7  is a cutaway front view of the pod including the isolation plates of  FIG. 5  in accordance with embodiments; 
         FIG. 8  is a side view of plates of the pod of  FIGS. 5 and 6  in accordance with embodiments; 
         FIG. 9  is a side view of plates of the pod of  FIGS. 5 and 6  in accordance with embodiments; 
         FIG. 10  is a side view of a removable panel in accordance with embodiments; 
         FIG. 11  is a front view of a pod in accordance with alternative embodiments; 
         FIG. 12  is a side view of the pod of  FIG. 11  in accordance with further alternative embodiments; and 
         FIG. 13  is a side view of the pod of  FIG. 11  in accordance with further alternative embodiments. 
     
    
    
     These and other advantages and features will become more apparent from the following description taken in conjunction with the drawings. 
     DETAILED DESCRIPTION 
     As will be described below, a pod is provided to isolate piping, valves, return bends and other brazed joints from exposure to the outdoor ambient section of a transport refrigeration unit. The pod includes an enclosure with covers so that if a leak occurs, the leaked fluid cannot be pulled into the air stream by the evaporator fan. A refrigerant and condensate drain would allow leaked fluid to flow out of the enclosed area to the outside of the cargo storage area. 
     With reference to  FIG. 1 , a trailer  10  is provided and is attachable to a truck for transportation of various goods. The trailer  10  includes a body  11  that defines an interior or a cargo area  12  in which the various goods can be stowed during transportation. To an extent that these goods need to be kept in an air conditioned environment, such as where the goods include perishable items, the trailer  10  may further include a transport refrigeration unit (TRU)  13 . The TRU  13  is attachable a portion of the body  11 , such as a front of the body  11 , and is configured to draw heated air in from the cargo area  12 , to cool the heated air and to exhaust cooled air back into the cargo area  12 . Within the TRU  13 , the cooling is accomplished by flowing the heated air over and across evaporator tubing of an evaporator. The evaporator tubing is charged with refrigerant at a lower temperature than the heated air such that, as the heated air flows over and across the evaporator tubing, the refrigerant removes heat from the heated air. 
     While several different types of refrigerant can be used, some refrigerants tend to have relatively high GWP whereas others tend to have relatively low GWP and, as regulations change, the use of the relatively low GWP refrigerants is becoming increasingly required. This being the case, with reference to  FIG. 2 , it is seen that the relatively low GWP refrigerants tend to be more flammable than the relatively high GWP refrigerants. Therefore, where the relatively low GWP refrigerants are used in TRU applications, it is typically necessary to prevent leakage of the relatively low GWP refrigerants into the flows moving through the TRU  13  and/or into the cargo area  12 . 
     With continued reference to  FIG. 1  and with additional reference to  FIGS. 3 and 4 , a conventional pod  301  can be provided for use with the TRU  13  to constrain and control flows of heated air from the cargo area  12  through the TRU  13  (see  FIG. 1 ). The conventional pod  301  is attachable along its periphery to a wall of the cargo area  12  and has a convex portion that forms interior regions  302  and  303  that can respectively accommodate an evaporator of the TRU  13  and a fan that drives airflow from the cargo area  12 , through an inlet defined in the wall, through the evaporator and back into the cargo area  12  through an outlet defined in the wall. As shown in  FIG. 3 , the interior region  302  in particular has sufficient room to accommodate an entirety of the evaporator, including the evaporator tubing and the return bend elements. The evaporator tubing is generally provided as substantially straight tubes that run across a substantial length of the evaporator. The return bend elements include return bends that connect corresponding ends of two or more evaporator tubes to one another and braze joints by which the return bends actually connect to the corresponding ends of the two or more evaporator tubes as well as additional piping and valves. 
     Refrigerant leaks from the evaporator tubing are uncommon, but refrigerant leaks from the return bend elements are a present issue. Thus, since the interior region  302  of the conventional pod  301  accommodates the return bend elements, leaks of refrigerant (i.e., mildly flammable, low GWP refrigerants) can occur and result in leaked refrigerant entering into the flows of air through the TRU  13  or into the cargo area  12  directly. 
     With reference to  FIGS. 5-7 , a transport refrigeration unit (TRU)  501  is provided and includes a cargo area wall  510  (i.e., for the cargo area  12  of  FIG. 1 ), an evaporator  520  and a pod  530 . The cargo area wall  510  is formed to define an inlet  511  and an outlet  512  that are each fluidly communicative with the cargo area  12 . The evaporator  520  includes evaporator tubes  521  (see  FIG. 7 ) and return bend elements  522 . The evaporator tubes  521  are substantially straight and extend along a substantial length of the evaporator  520 . The return bend elements  522  are provided at opposite end sections  5211  and  5212  of the evaporator tubes  521  and include return bends that fluidly connect corresponding ends of two or more evaporator tubes  521 , brazed joints that actually connect the return bends to the evaporator tubes  521 , feeder piping and valves. 
     The pod  530  includes peripheral flanges  531  that are attachable to the cargo area wall  510 , a convex portion  532  and plate sections  533 . The convex portion  532  is attached to the peripheral flanges  531  and is formed to define, with a corresponding portion  513  of the cargo area wall  510 , an interior  540  (see  FIG. 7 ). The interior  540  is communicative with the cargo area  12  through the inlet  511  and the outlet  512  and is configured and sized to accommodate the evaporator  520  and a fan  550 . The fan  550  is operable to drive air flow from the inlet  511  and to the outlet  512  through the evaporator  520 . The plate sections  533  are respectively secured to the opposite end sections  5211  and  5212  of the evaporator tubes  521  and to respective local portions of the peripheral flanges  531  and the convex portion  532 . The plate sections  533  thus divide the interior  540  into a first interior  541  and second interiors  542 . 
     The first interior  541  is configured and sized to accommodate the evaporator tubes  521  and the fan  550 . Each of the second interiors  542  is isolated from a corresponding side of the first interior  541  and each of the second interiors  542  is sized and configured to accommodate the corresponding return bend elements  522  as well as the valves and other required piping to connect the evaporator  520  to the refrigeration system. 
     The plate sections  533  therefore effectively isolate the return bend elements  522  from the first interior  541 . As such, leakage of refrigerant from the return bend elements  522  is prevented from flowing into the first interior  541  and from flowing into the cargo area  12  directly or indirectly. 
     In accordance with embodiments, the peripheral flanges  531  form a form a polygonal profile  5310  with a relatively wide, lower section that is configured and sized to surround the evaporator  520  and a relatively narrow, upper section that is configured and sized to surround the fan  550 . As shown in  FIG. 5 , the convex portion  532  includes a forward body  5321 , sidewalls  5322  extending from the peripheral flanges  531  to the forward body  5321 , rounded edges  5323  at the peripheral flanges  531  and rounded edges  5324  at the forward body  5321 . The sidewalls  5322  may be sized such that a width of the first interior  541  is equal to or slightly less than a width of the evaporator tubes  521 . 
     As shown in  FIG. 5 , the first interior  541  includes a lower section  5410 , an upper section  5411  and a central section  5412 . The lower section  5410  is defined between the inlet  511  and the evaporator tubes  521 . The upper section  5411  is defined between the fan  550  and the outlet  512 . The central section  5412  is defined between the evaporator tubes  521  and the fan  550  and is fluidly interposed between the lower section  5410  and the upper section  5411 . 
     As shown in  FIG. 7  and with additional reference to  FIGS. 8 and 9 , respective outer planes  5330  of the plate sections  533  may be substantially coplanar with respective outermost planes of the opposite end sections  5211  and  5212  of the evaporator tubes  521 . Thus, substantial entireties of the return bend elements  522  can be isolated from the first interior  541 . In accordance with further embodiments, the plate sections  533  can be provided as sheet metal or plastic with a single aperture  801  (see  FIG. 8 ) or with multiple apertures  901  (see  FIG. 9 ). The single aperture  801  can be provided to sealably surround the evaporator tubes  521  to an extent the evaporator tubes  521  are provided in a unitary body. On the other hand, the multiple apertures  901  can be provided to sealably surround each individual evaporator tube  521  in an event the evaporator tubes  521  have interstitial spaces between them. 
     As shown in  FIG. 5 , distal portions of the convex portion  532  (i.e., the portions of the convex portion  532  that surround the second interiors  542 ) may be formed to define drain apertures  560 . Leaked refrigerant flowing out of the return bend elements  522 , which is isolated from the first interior  541  within each of the second interior  542  can flow out of the second interiors  542  and toward an exterior via the drain apertures  560 . 
     With reference to  FIG. 10 , the convex portion  532  may include removable panels  1001  at various locations including locations at which the removable panels  1001  would provide access to the first interior  541  and locations at which the removable panels  1001  would provide access to the second interiors  542  and the return bend elements  522  (see  FIG. 10 ). 
     With reference to  FIGS. 11-13 , alternative embodiments of the pod  530  are provided in which the pod  530  itself is configured to isolate at least the return bend elements  522  from the interior  540 . As shown in  FIG. 11 , the pod  530  is generally formed as described above to define, with the corresponding portion  513  (see  FIG. 5 ) of the cargo area wall  510 , the interior  540 . The interior  540  is configured to accommodate the evaporator  520 , the fan  550  and the air flow generated by the fan  550  through the evaporator  520 . The opposite sides  1101 ,  1102  of the pod  530  are tapered around the opposite end sections  5211  and  5212  of the evaporator tubes  521  such that pod  530  itself is configured to isolate the return bend elements  522  from the interior  540 . 
     In accordance with embodiments and, as shown in  FIG. 12 , the pod  530  is formed to define a first aperture  1201  and a second aperture  1202  (see  FIG. 8  and the accompanying text for similar configurations). The end sections  5211  of the evaporator tubes  521  extend through the first aperture  1201  such that the return bend elements  522  associated with the end sections  5211  are isolated as a whole from the interior  540 . The end sections  5212  of the evaporator tubes  521  extend through the second aperture  1202  such that the return bend elements  522  associated with the end sections  5212  are isolated as a whole from the interior  540 . 
     In accordance with embodiments and, as shown in  FIG. 13 , the pod  530  is formed to define first apertures  1301  and second apertures  1302  (see  FIG. 9  and the accompanying text for similar configurations). The return bend elements  522  associated with the end sections  5211  respectively extend through corresponding ones of the first apertures  1301  and are thus isolated on an individual basis from the interior  540 . The return bend elements  522  associated with the end sections  5212  respectively extend through corresponding ones of the second apertures  1302  and are thus isolated on an individual basis from the interior  540 . 
     Technical effects and benefits of the present disclosure are an elimination of a need for expensive ventilation and circulation systems that might otherwise be effectively required by regulations relating to mildly flammable, low GWP refrigerants. The pod described herein is designed such that no leak points are exposed inside a cargo box and may reduce potential false alarms, system shutdowns and loss of cargo events. 
     While the disclosure is provided in detail in connection with only a limited number of embodiments, it should be readily understood that the disclosure is not limited to such disclosed embodiments. Rather, the disclosure can be modified to incorporate any number of variations, alterations, substitutions or equivalent arrangements not heretofore described, but which are commensurate with the spirit and scope of the disclosure. Additionally, while various embodiments of the disclosure have been described, it is to be understood that the exemplary embodiment(s) may include only some of the described exemplary aspects. Accordingly, the disclosure is not to be seen as limited by the foregoing description, but is only limited by the scope of the appended claims.