Convection oven with linear counter-flow heat exchanger

Abstract

A convection oven includes a cooking chamber for cooking a food product, an air circulator that circulates process air in a first direction through the cooking chamber and along a circulation path in a circulation passage. A heat exchanger includes one or more heat transfer ducts longitudinally arranged along the circulation path. One or more heating elements heat a fluid that is circulated in a second direction through the one or more heat transfer ducts which is opposite to the first direction. The process air absorbs heat from the heated fluid as the process air travels along the circulation path back to the cooking chamber. A partition wall may separate first and second parallel portions of the one or more heat transfer ducts. A heat exchanger may preheat fluid entering the one or more heat transfer ducts using heated fluid leaving the heat transfer ducts.

1 . A convection oven comprising:
 a cooking chamber having a process air entrance and a process air exit;   a circulation passage connecting the process air entrance and the process air exit;   an air circulator configured to move process air along a circulation path through the circulation passage in a first direction from the process air exit to the process air entrance, and configured to circulate process air through the cooking chamber; and   a heat exchanger including a plurality of heat transfer ducts longitudinally arranged in the circulation passage along the circulation path, each of the plurality of heat transfer ducts being separately sealed from the cooking chamber and the circulation passage, one or more heating elements configured to heat a fluid provided to a duct input end portion of each of the plurality of heat transfer ducts, the heat exchanger configured to move the heated fluid through the plurality of heat transfer ducts in a second direction opposite to the first direction, each of the plurality of heat transfer ducts including a duct output end portion terminating at a duct outlet from which the heated fluid is removed from the heat transfer duct, the duct output end portion being positioned downstream in the first direction of the duct input end portion in the circulation path.   
     
     
         2 . The convection oven of  claim 1 , wherein each of the plurality of heat transfer ducts is spaced apart from each of the others of the plurality of heat transfer ducts. 
     
     
         3 . The convection oven of  claim 1 , wherein each of the plurality of heat transfer ducts includes a bent portion disposed between and connecting a first duct portion of the heat transfer duct and a second duct portion of the heat transfer duct, the second duct portion being closer to the process air exit along the circulation path than the first duct portion. 
     
     
         4 . The convection oven of  claim 1 , wherein each of the plurality of heat transfer ducts includes a linear first duct portion comprising at least a majority of the overall length of the heat transfer duct. 
     
     
         5 . The convection oven of  claim 1 , wherein each of the plurality of heat transfer ducts includes a linear first duct portion positioned to receive the heated fluid from the duct input end portion, a linear second duct portion positioned to provide the heated fluid to the duct output end portion, and a bent portion connecting together the linear first duct portion and the linear second duct portion for communication of the heated fluid from the linear first duct portion to the linear second duct portion. 
     
     
         6 . The convection oven of  claim 5 , wherein the linear first duct portion extends in parallel with the linear first duct portion of each of the others of the plurality of heat transfer ducts, and the linear second duct portion extends in parallel with the linear second duct portion of each of the others of the plurality of heat transfer ducts, the linear second duct portion being positioned upstream of the linear first duct portion in the first direction along the circulation path. 
     
     
         7 . The convection oven of  claim 5 , wherein the bent portion is connected to a lower end portion of the linear first duct portion and to a lower end portion of the linear second duct portion. 
     
     
         8 . The convection oven of  claim 7 , wherein the one or more heating elements are positioned at the duct input end portion and at least partially above the linear first duct portion. 
     
     
         9 . The convection oven of  claim 1 , wherein the one or more heating elements includes a different heating element for heating the fluid provided to each of the plurality of heat transfer ducts. 
     
     
         10 . A convection oven comprising:
 a cooking chamber having a process air entrance and a process air exit;   a circulation passage connecting the process air entrance and the process air exit;   an air circulator configured to move process air along a circulation path through the circulation passage in a first direction from the process air exit to the process air entrance, and configured to circulate process air through the cooking chamber; and   a heat exchanger including a plurality of heat transfer ducts longitudinally arranged in the circulation passage along the circulation path, each of the plurality of heat transfer ducts being spaced apart from the others of the plurality of heat transfer ducts, one or more heating elements configured to heat a fluid provided to each of the plurality of heat transfer ducts, the heat exchanger configured to move the heated fluid through the plurality of heat transfer ducts in a second direction opposite to the first direction.   
     
     
         11 . The convection oven of  claim 10 , wherein each of the plurality of heat transfer ducts includes a linear first duct portion, a linear second duct portion and a bent portion connecting together the linear first duct portion and the linear second duct portion for communication of the heated fluid from the linear first duct portion to the linear second duct portion. 
     
     
         12 . The convection oven of  claim 11 , wherein the linear first duct portion is positioned to receive the heated fluid heated by the one or more heating elements, the linear first duct portion extends in parallel with the linear first duct portion of each of the others of the plurality of heat transfer ducts, and the linear second duct portion extends in parallel with the linear second duct portion of each of the others of the plurality of heat transfer ducts, the linear second duct portion being positioned upstream of the linear first duct portion in the first direction along the circulation path. 
     
     
         13 . The convection over of  claim 12 , wherein the linear first duct portion is arranged parallel to and spaced apart from the linear second duct portion. 
     
     
         14 . The convection oven of  claim 11 , wherein the bent portion is connected to a lower end portion of the linear first duct portion and to a lower end portion of the linear second duct portion. 
     
     
         15 . The convection oven of  claim 14 , wherein the one or more heating elements are positioned at least partially above the linear first duct portion. 
     
     
         16 . The convection oven of  claim 10 , wherein each of the plurality of heat transfer ducts includes a third duct portion extending from the second duct portion and terminating at a duct outlet from which the heated fluid is removed from the heat transfer duct. 
     
     
         17 . The convection oven of  claim 16 , wherein the third duct portion is positioned downstream in the first direction of the first duct portion in the circulation path. 
     
     
         18 . The convection oven of  claim 10 , wherein the one or more heating elements includes a different heating element for heating the fluid provided to each of the plurality of heat transfer ducts. 
     
     
         19 . The convection oven of  claim 10 , wherein each of the plurality of heat transfer ducts includes a first duct portion and a second duct portion, the first duct portion being positioned to receive the heated fluid heated by the one or more heating elements, the first duct portion extending in parallel with the first duct portion of each of the others of the plurality of heat transfer ducts and extending along the circulation path, and the second duct portion extending in parallel with the second duct portion of each of the others of the plurality of heat transfer ducts and extending along the circulation path, the second duct portion being positioned upstream of the first duct portion in the first direction along the circulation path, and the second duct portion being spaced apart from the first duct portion. 
     
     
         20 . The convection oven of  claim 19 , wherein the first duct portion of each of the plurality of heat transfer ducts has a duct inlet to receive the fluid heated by the one or more heating elements. 
     
     
         21 . The convection oven of  claim 19 , wherein the second duct portion is located closer to the process air exit along the circulation path than the first duct portion. 
     
     
         22 . The convection oven of  claim 21 , wherein the second duct portion is positioned adjacent to the process air exit in the circulation passage. 
     
     
         23 . The convection oven of  claim 19 , wherein the first duct portion is closer to the process air entrance along the circulation path than the second duct portion. 
     
     
         24 . The convection oven of  claim 10 , wherein each of the plurality of heat transfer ducts has a duct inlet to receive the heated fluid heated by a different corresponding one of the one or more heating elements. 
     
     
         25 . The convection oven of  claim 24 , wherein each heating element of the plurality of heating elements is arranged adjacent to another of the heating elements of the plurality of heating elements such that ignition of one heating element ignites an adjacent one of the heating elements. 
     
     
         26 . The convection oven of  claim 10 , wherein each of the plurality of heat transfer ducts has a duct outlet from which the heated fluid is removed, and further comprises a fluid circulator configured to circulate the heated fluid through the plurality of heat transfer ducts, the fluid circulator being connected at the duct outlets of the plurality of heat transfer ducts. 
     
     
         27 . The convection oven of  claim 10 , wherein each of the plurality of heat transfer ducts has a duct inlet to receive the heated fluid heated by the one or more heating elements, and further comprises a fluid circulator configured to circulate the heated fluid through the plurality of heat transfer ducts, the fluid circulator being connected at the duct inlets of the plurality of heat transfer ducts. 
     
     
         28 . The convection oven of  claim 10 , wherein each of the plurality of heat transfer ducts terminates at an exhaust duct outlet from which the heated fluid is exhausted from the heat transfer duct, the exhaust duct outlet being positioned downstream in the first direction in the circulation path, and the heat exchanger further includes a fluid intake chamber arranged to receive the fluid to be heated by the one or more heating elements and a collection chamber arranged to receive and collect the exhausted heated fluid, the collection chamber being positioned to transfer heat from the heated fluid therein to the fluid in the fluid intake chamber to preheat the fluid received in the fluid intake chamber before being heated by the one or more heating elements heat. 
     
     
         29 . The convection oven of  claim 28 , wherein the collection chamber and the fluid intake chamber having a heat conductive common wall that radiates heat from the heated fluid in the collection chamber to heat the fluid in the fluid intake chamber. 
     
     
         30 . A convection oven comprising:
 a cooking chamber having a process air entrance and a process air exit;   a circulation passage connecting the process air entrance and the process air exit;   an air circulator configured to move process air along a circulation path through the circulation passage in a first direction from the process air exit to the process air entrance, and configured to circulate process air through the cooking chamber; and   a heat exchanger including a plurality of heat transfer ducts longitudinally arranged in the circulation passage along the circulation path, each of the plurality of heat transfer ducts being spaced apart from the others of the plurality of heat transfer ducts, one or more heating elements configured to heat a fluid provided to each of the plurality of heat transfer ducts, the heat exchanger configured to move the heated fluid through the plurality of heat transfer ducts in a second direction opposite to the first direction, each of the plurality of heat transfer ducts including a linear first duct portion, a linear second duct portion and a bent duct portion in fluid communication with both the linear first duct portion and the linear second duct portion.   
     
     
         31 . The convection oven of  claim 30 , wherein the linear first duct portion is positioned to receive the heated fluid heated by the one or more heating elements, the linear first duct portion extends in parallel with the linear first duct portion of each other of the plurality of heat transfer ducts, and the linear second duct portion extends in parallel with the linear second duct portion of each other of the plurality of heat transfer ducts. 
     
     
         32 . The convection over of  claim 31 , wherein the linear first duct portion is arranged parallel to and spaced apart from the linear second duct portion. 
     
     
         33 . The convection oven of  claim 30 , wherein the linear first duct portion has first and second end portions, the linear second duct portion has first and second end portions, and the bent duct portion has first and second end portions, the first end portion of the linear first duct portion being positioned to receive the heated fluid heated by the one or more heating elements, the second end portion of the linear first duct portion being connected to the first end portion of the bent portion, the first end portion of the linear second duct portion being positioned to exhaust the heated fluid, and the second end portion of the linear second duct portion being connected to the second end portion of the bent portion. 
     
     
         34 . The convection oven of  claim 33 , wherein the first end portion of the linear first duct portion is positioned above the second end portion of the linear first duct portion, and the first end portion of the linear second duct portion is positioned above the second end portion of the linear second duct portion. 
     
     
         35 . The convection oven of  claim 30 , wherein the one or more heating elements are positioned above the linear first duct portion and in fluid communication with the first linear duct portion, and the bent portion connects together lower end portions of the first and second linear duct portions. 
     
     
         36 . The convection oven of  claim 35 , further including one or more duct outlets configured to receive the heated fluid from the plurality of heat transfer ducts, and wherein the one or more duct outlets are positioned above the second linear duct portion and in fluid communication with the second linear duct portion. 
     
     
         37 . The convection oven of  claim 30 , further including one or more duct outlets configured to receive the heated fluid from the heat transfer ducts, and wherein the one or more heating elements are positioned above the linear first duct portion and in fluid communication with the linear first duct portion, the one or more duct outlets are positioned above the linear second duct portion and in fluid communication with the linear second duct portion, and the bent portion is positioned below the one or more duct outlets and the one or more heating elements and is in fluid communication with lower end portions of the linear first and second duct portions to pass the heated fluid from the linear first duct portion to the linear second duct portion. 
     
     
         38 . The convection oven of  claim 30 , further comprising a partition wall in the circulation passage, wherein the linear first duct portion is separated from the linear second duct portion by the partition wall, and the bent duct portion is positioned at a lower end of the partition wall. 
     
     
         39 . The convection oven of  claim 38 , wherein the linear first duct portions of the plurality of heat transfer ducts are positioned adjacent to a first side of the partition wall at spaced apart positions therealong, and the linear second duct portions of the plurality of heat transfer ducts are positioned adjacent to an opposite second side of the partition wall at spaced apart positions therealong. 
     
     
         40 . The convection oven of  claim 39 , wherein the linear first duct portions have an upright orientation and the linear second duct portions have an upright orientation. 
     
     
         41 . The convection oven of  claim 40 , wherein the linear first duct portions are in parallel arrangement and the linear second duct portions are in parallel arrangement. 
     
     
         42 . A convection oven comprising:
 a cooking chamber having a process air entrance and a process air exit;   a circulation passage connecting the process air entrance and the process air exit, the circulation passage having a partition wall disposed therein which terminates at a distal end to define a first passage portion and a second passage portion, the first passage portion having a first end portion and a second end portion, the second passage portion having a first end portion and a second end portion, the process air exit being in fluid communication with the first end portion of the first passage portion, the second end portion of the first passage portion being in fluid communication with the first end portion of the second passage portion, and the second end portion of the second passage portion being in fluid communication with the process air entrance, the second end portion of the first passage portion and the first end portion of the second passage portion being located at the distal end of the partition wall;   an air circulator configured to move process air along a circulation path through the circulation passage in a first direction from the process air exit to the process air entrance, and configured to circulate process air through the cooking chamber, the first direction of process air from the process air exit along the circulation path being from the first end portion of the first passage portion to the second end portion of the first passage portion, then from the second end portion of the first passage portion to the first end portion of the second passage portion, and then from the first end portion of the second passage portion to the second end portion of the second passage portion before moving to the process air entrance; and   a heat exchanger including one or more heat transfer ducts longitudinally arranged in the circulation passage along the circulation path, each of the one or more heat transfer ducts being separately sealed from the cooking chamber and the circulation passage, each of the one or more heat transfer ducts includes a first duct portion positioned within the second passage portion and a second duct portion positioned within the first passage portion, with the partition wall positioned between the first and second duct portions, one or more heating elements configured to heat a fluid provided to a duct inlet of the first duct portion of each of the one or more heat transfer ducts, the heat exchanger configured to move the heated fluid through both the first duct portion in the second passage portion and the second duct portion in the first passage portion of the one or more heat transfer ducts in a second direction opposite to the first direction.   
     
     
         43 . The convection oven of  claim 42 , wherein the first duct portion extends substantially in parallel with and along the second passage portion of the circulation path, and the second duct portion extends substantially in parallel with and along the first passage portion of the circulation path, the second duct portion being positioned upstream of the first duct portion relative to the first direction along the circulation path, and the second duct portion being spaced apart from the first duct portion. 
     
     
         44 . The convection oven of  claim 42 , wherein the heat exchanger includes a plurality of heating elements, and the heat exchanger includes a plurality of heat transfer ducts, each heat transfer duct having a duct inlet into which the heated fluid enters from a corresponding one of the plurality of heating elements. 
     
     
         45 . The convection oven of  claim 44 , wherein each heating element of the plurality of heating elements is arranged adjacent to another of the heating elements of the plurality of heating elements such that ignition of one heating element ignites an adjacent one of the heating elements. 
     
     
         46 . The convection oven of  claim 42 , wherein each of the one or more heat transfer ducts further comprises a duct outlet from which the heated fluid is removed, the duct outlet being positioned downstream relative to the first direction along the circulation path from the duct inlet. 
     
     
         47 . The convection oven of  claim 42 , further comprising a thermal mass adjacent to the one or more heat transfer ducts in the circulation passage along the circulation path, the thermal mass being configured to absorb heat from the process air in the circulation passage. 
     
     
         48 . The convection oven of  claim 47 , further comprising a liquid sprayer configured to spray liquid onto the thermal mass to generate steam when the thermal mass absorbs heat from the process air. 
     
     
         49 . The convection oven of  claim 42 , wherein the heat exchanger further includes an outlet port from which at least some of the heated fluid is removed from the heat exchanger, a collection chamber arranged between a duct outlet of the one or more heat transfer ducts and the outlet port and configured to collect the heated fluid removed from the one or more heat transfer ducts, and a fluid inlet that receives the fluid to be heated by the one or more heating elements, wherein the collection chamber is positioned near the fluid inlet and configured to preheat the fluid received in the fluid inlet before the one or more heating elements heat the fluid. 
     
     
         50 . The convection oven of  claim 49 , wherein the collection chamber includes a chamber wall that contacts the fluid received in the fluid inlet and radiates heat from the collected heated fluid to heat the fluid received in the fluid inlet. 
     
     
         51 . The convection oven of  claim 42 , wherein each of the one or more heat transfer ducts includes a bent duct portion disposed between and connecting the first duct portion and the second duct portion, the bent duct portion bending around the distal end of the partition wall. 
     
     
         52 . The convection oven of  claim 51 , wherein the first and second duct portions of each of the one or more heat transfer ducts have an upright orientation, with the bent duct portion being positioned below the first and second duct portions. 
     
     
         53 . The convection oven of  claim 42 , wherein the first direction of movement of the process air along the circulation path in the first passage portion is downward and the first direction of movement of the process air along the circulation path in the second passage portion is upward, and wherein the heated fluid in the second duct portion in the first passage portion moves upward and the heated fluid in the first duct portion in the second passage portion moves downward. 
     
     
         54 . The convection oven of  claim 42 , wherein the first end portion of the first passage portion is positioned adjacent to the second end portion of the second passage portion. 
     
     
         55 . The convection oven of  claim 42 , wherein each of the one or more heat transfer ducts includes a third duct portion extending from the second duct portion and terminating at a duct outlet from which the heated fluid is removed from the heat transfer duct, the third duct portion being positioned downstream in the first direction of the first duct portion in the circulation path. 
     
     
         56 . The convection oven of  claim 55 , wherein the third duct portion is transversely arranged across the circulation passage. 
     
     
         57 . The convection oven of  claim 42 , further comprising:
 a fluid circulation element configured to move the heated fluid from the first duct portion to the second duct portion of the one or more heat transfer ducts in the second direction opposite to the first direction.