Abstract:
An apparatus for recovering energy from freezer exhaust includes a heat exchanger disposed for coaction with a freezer in a first atmosphere, the heat exchanger having a first heat transfer surface in communication with the freezer exhaust and the first atmosphere, and a second heat transfer surface in communication with the freezer exhaust and the first atmosphere; a discharge conduit in communication with the first and second heat transfer surfaces, and extending to a second atmosphere remote from the first atmosphere; a first valve assembly disposed for coaction with the first and second heat transfer surfaces, the first valve assembly movable to direct a flow of the freezer exhaust to a select one of the first and second heat transfer surfaces or optionally to direct the flow to both the first and second heat transfer surfaces; and a first blower to move a flow of the first atmosphere to a select one or both of the first and second heat transfer surfaces for heat transfer with the flow of the freezer exhaust.

Description:
BACKGROUND 
     The present invention relates to use of cryogen exhaust from freezing and chilling applications and systems. 
     Use of cryogen gas for freezing or chilling applications is known. Unfortunately, much of the gas which is not used is merely exhausted, wherein the heat exchange energy available from the exhausted gas is wasted, instead of being recovered for subsequent heat transfer use for the freezing system, the freezer plant or other applications. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       For a more complete understanding of the present embodiments, reference may be had to the following drawing figures taken in conjunction with the description of the embodiments, of which: 
         FIGS. 1 and 2  show front and side schematic views partially in cross-section, respectively, of an energy recovery system embodiment of the present invention. 
         FIG. 3  shows a side schematic view partially in cross-section of another energy recovery system embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Referring to  FIGS. 1 and 2  there is shown a freezer  10 , such as a spiral, emersion or tunnel freezer, which is disposed on a floor  12  of a plant or factory. The freezer  10  is used to freeze, chill or cool products such as for example food products. The freezer  10  includes a product outlet  14  and an exhaust  16  from the freezer  10 . The exhaust  16  removes unused cryogen from the freezer  10 . 
     The exhaust  16  is bifurcated or branched at a diverter duct  17  into exhaust conduits  18 , 20  for which a switch valve  22  is associated therewith to control the flow of cryogen exhaust from the freezer  10  to each of the conduits  18 , 20 . For example, cryogen exhaust  24  can be directed to either of conduit  18 , 20  depending upon the disposition of the switch  22 . In  FIG. 1  for example, the switch  22  is disposed such that the cryogen exhaust  24  is directed through conduit  20 . It is also possible for the switch  22  to be positioned to permit the cryogen exhaust  24  to flow through both conduits  18 , 20  simultaneously. 
     Heat exchangers  26 , 28  are disposed in communication with the conduits  18 , 20 , respectively. Therefore, the cryogen exhaust flow  24  directed through the conduit  20  will enter into the heat exchanger  28 , after which upper conduit  20 ′ in communication with the heat exchanger  28  continues to direct the exhaust through an upper exhaust conduit  30 . The upper exhaust conduit  30  extends through a roof  32  of the plant. A blower  34  disposed on the roof  32  draws the cryogen exhaust  24  through the conduit  30 . An upper conduit  18 ′ extends from the heat exchanger  26  to the upper exhaust conduit  30  as well. Cryogen exhaust  24  can be directed through the conduit  18 ′ if the switch  22  closes off the conduit  20 . 
     Referring also to  FIG. 2 , conduits  36 , 38  are in communication with and connected to the heat exchangers  26 , 28 , respectively. The conduits  36 , 38  intersect at another diverter duct  37  where a switch valve  40  is disposed for controlling flow of warmer plant air from the channels  36 , 38 . The channels  36 , 38  are brought together to a single conduit  42  which is in communication with a blower  44  or fan. 
     Each one of the heat exchangers  26 , 28  provides for exhaust emissions shown generally by arrows  46 , 48 , respectively. 
     This embodiment of the present invention is shown at components  16 - 48 , collectively referred to as the energy recovery system embodiment “A”. 
     The embodiment A operates as follows. Referring to  FIGS. 1 and 2 , by way of example the switch  22  has closed off conduit  18 , such that the conduit  20  is open and clear, while the switch  40  has closed off the conduit  36  such that the conduit  38  is open and clear. The exhaust  24  travels up the exhaust pipe  16  along the conduit  20  into the heat exchanger  28  for heat exchange with warmer plant air  52 . Concurrent therewith, the blower  44  pulls the warmer plant air  52 , i.e. the ambient temperature of the plant atmosphere, and directs same as indicated by the arrow  52  through the conduit  38  to the heat exchanger  28 . The warmer plant air  52  contacts the heat exchange member (coils, fins, etc., not shown) of the heat exchanger  28  in which the cooler cryogen exhaust  24  is present, heat transfer thereby occurs, after which the chilled ambient air  48  from the heat exchanger  28  is emitted back into the atmosphere of the plant to reduce the overall temperature of the plant. This is desirable for purposes of the plant operation maintaining the ambient temperature at a cooler or lesser temperature than would normally be the case in order to substantially reduce if not eliminate contaminates and contagens in the plant atmosphere. Unused cryogen shown at the arrow  31  is moved through the conduit  30  by the blower  34  and exhausted to the atmosphere external to the factory or used in a subsequent application. 
     At a certain point, the heat transfer by the heat exchanger  28  of the cryogen exhaust will cause freeze-up and require “de-riming” of the heat exchanger  28 . Therefore, the valves  22 , 40  are switched to the opposite position to thereby open the conduits  18 , 36  for heat exchange in a similar manner with heat exchanger  26 . As that is occurring, the heat exchanger  28  is permitted to de-ice and be cleaned so that it is ready for operation when the heat exchanger  26  must be shut-down for de-icing, etc. That is, the warm atmosphere drawn in by the blower  44  through the conduit  36  contacts heat transfer coils of the heat exchanger  26  in which the colder cryogen exhaust  16  is provided to effect heat transfer. This provides for the plant air to be cooled with the cooled air  46  emitted back into the plant atmosphere. 
     The heat exchanger  26  will eventually, as had occurred with the heat exchanger  28 , freeze up and will require de-riming and at such time the valves  22 , 40  are again switched to alter the pathway of the cryogen exhaust  24  to provide heat transfer effect at the heat exchanger  28 . 
     The arrangement of the embodiment permits for easy maintenance and repair of the heat exchangers  26 , 28 , while still permitting at least one of the heat exchangers to continue operating. 
     It is possible to provide for switching of the conduits between the heat exchangers  26 , 28  based upon an amount of time that elapses or when a temperature of the plant air reaches a desired temperature. The present embodiments provide for reuse of sterile plant air inside the plant and thereby reduce the necessity for additional external or internal air-conditioning systems. Being able to switch between a plurality of the heat exchangers  26 , 28  eliminates the chance of ice plugging or blocking of the exhaust  46 , 48  and the conduits  18 , 20 ,  18 ′, 20 ′ and  36 , 38 . The heat exchangers  26 , 28  can be of the stainless steel type for easy cleaning and sanitation. 
     After the heat transfer effect to provide for the exhaust  46 , 48  into the plant atmosphere, the remaining cryogen exhaust is directed along the conduits  18 ′, 20 ′ which converge into and communicate with the upper exhaust conduit  30 , which is in communication with the roof exhaust blower  34 . 
     Another embodiment is shown in  FIG. 3 , where there is shown a freezer  60  such as for example an immersion freezer, a tunnel freezer or a spiral freezer, having a freezing chamber  62  therein which is in communication with an exhaust duct  64  for venting any unused cryogen gas from the freezer chamber  62 . The exhaust duct  64  may be insulated to prevent heat loss from same. The freezer  60  is disposed in a processing room  66  of a plant or facility having a roof  68 . 
     The exhaust duct  64  extends in this embodiment up through the roof  68  of the plant where it is in communication with a heat exchanger  70 . An exhaust blower  72  is interposed in the exhaust duct  64  for withdrawing unused cryogen gas  73  from the freezer  60  into the heat exchanger  70 . 
     The heat exchanger is provided with an inlet  74  which is in communication with the exhaust blower  72 . A differential pressure (D/P) switch  76  is in communication with the exhaust duct  64  proximate the inlet  74 . The D/P switch measures the pressure difference between and across the duct  64 . The heat exchanger  70  is also provided with an outlet  78 . A temperature sensor  80  measures the cryogen vapor temperature in the heat exchanger  70  to aid in controlling the speed of the exhaust blower  72 . 
     A fresh air intake  82  includes a particulate filter  84  disposed therein, the air intake  82  connected to a duct  86 , which may also be insulated. The duct  86  is in communication with another inlet  88  of the heat exchanger  70 . An air blower  90  is interposed in the duct  86  for communication therewith to draw fresh outside air through the intake  82  into the duct  86  and through to the inlet  88  of the heat exchanger. The intake  82  is disposed upstream of the blower  90  as shown in  FIG. 3 . The warmer outside air shown generally at arrow  83 , is cooled upon exposure to the cryogen exhaust  73  transiting the heat exchanger  70  between the inlet  74  and the outlet  78 . 
     Thereafter, the warm outside air  83  which has been cooled in the heat exchanger  70 , exits the heat exchanger at an outlet  92  of the heat exchanger  70  to another duct  94 . A temperature sensor  96  senses the chilled air prior to it being introduced into a filter unit  98 . The filter  98  may also include an ultraviolet (UV) sterilizer. The filter  98  is interposed in the duct  94 , the duct  94  passing through the roof  68  back into the processing room  66  providing a chilled sterile air flow  95  into said room. 
     A differential pressure (D/P) switch  89  is also provided in communication with the duct  86  proximate the inlet  88  of the heat exchanger  70 . The D/P switch  89  measures the pressure difference across the duct  86 . An O 2  sensor  100  is in communication with the duct  94  to monitor oxygen content of the air flow  95  prior to same being introduced into the processing room  66 . 
     The present embodiment of  FIG. 3  allows for maintaining the air in the processing room  66  at a lower temperature to thereby reduce the necessity of installed HVAC systems to be operated to cool the processing room  66  air. Maintaining the air in the processing room  66  at a reduced temperature inhibits bacteria and other contaminates and also puts less of a strain on a refrigeration system for the processing room  66 . 
     The exhaust duct  64  is also provided with a vent spill valve  102  which actuates a valve door  104  built into the duct  64  proximate the inlet  74  of the heat exchanger  70 . Should the switch  76  indicate pressure is at an unacceptable level at the inlet  74 , this may indicate that there is plugging or fouling of the duct  64  and accordingly, the valve door  104  can be opened as indicated by the arrow  106  to clear the heat exchanger  70  of flow inhibiting material. The switch  76  can also be activated by the oxygen sensor  100  in the event levels of oxygen are too low in the air flow  95  returning to the processing room  66 . 
     The outlet  78  of the heat exchanger  70  provides for the warmed cryogen exhaust indicated generally by arrow  79  to be vented to the atmosphere or used in subsequent applications. 
     This embodiment of the present invention is shown in components  64 - 106 , collectively referred to as the energy recovery system embodiment “B”. By monitoring temperature of the system with the sensors  80 , 96 ; and pressure at the ducts  64 , 86  with the D/P switches  76 , 89 , freezing and ice fouling at the ducts is prevented by varying the speed of the cold exhaust air blower  72  and the warmer air blower  90 . Time switching, instead of D/P (differential pressure) switching, can be used for the heat exchangers. 
     The heat exchangers  26 ,  28 ,  70  can be those distributed by Munters AB, Stockholm, Sweden, with offices in the United States. 
     It will be understood that the embodiments described herein are merely exemplary, and that one skilled in the art may make variations and modifications without departing from the spirit and scope of the invention. All such variations and modifications are intended to be included within the scope of the invention as described and claimed herein. Further, all embodiments disclosed are not necessarily in the alternative, as various embodiments of the invention may be combined to provide the desired result.