Patent Application
20170138610
The present invention relates generally to the field of waste heat recovery. More particularly, the present invention relates to a method and system for extracting heat from flue gas that is exiting from a cooking appliance, such as for instance a commercial deep fryer or gas oven.
This application claims priority to Canadian Patent Application No. 2911796, filed Nov. 12, 2015, the entire contents of which are incorporated herein by reference.
In the restaurant industry, and in other settings in which commercial cooking appliances are used, it is required to vent waste heat to the outside via an exhaust hood that is positioned above the cooking appliance. Unfortunately, this practice results in a very inefficient use of energy in the kitchen. For instance, the flue gas from a commercial deep fryer may be exhausted at a temperature in the range 700-1100° F. At the same time, additional energy is consumed for space heating and to heat water for other applications in the kitchen, such as dish washing, hand cleaning, etc.
Various attempts have been made to partially recover the waste heat that is produced by commercial cooking appliances, to be used for other purposes such as space heating and/or production of hot water. In one approach a heat exchanger is located within the exhaust hood above the appliance for extracting heat from the air as it is being vented to the outside. This approach is not entirely satisfactory because grease and other particulates tend to build up rather quickly on the heat-exchanger surfaces, thereby insulating the surfaces and reducing the efficiency of the system over time. Further, the temperature of the air that enters the exhaust hood is much lower than the temperature of the air immediately after it exits the flue of the cooking appliance, and as such less heat is available to be extracted. In another approach a heat exchanger is introduced directly into the flue of the cooking appliance. This approach is also not entirely satisfactory because the heat exchanger is subjected to extremely high temperatures, which necessitates a very robust design and may cause solder joints etc. to fail relatively quickly. Additionally, modifying the cooking appliance to accept the heat exchanger within the flue may violate safety code regulations and/or void manufacturer warranties.
In accordance with an aspect of at least one embodiment, there is provided a system for extracting heat from a flue gas exiting from a cooking appliance, the system comprising: a flue extension having an open first end and an open second end opposite the first end, the first end aligned with but spaced apart from a flue of the cooking appliance for receiving a flue gas at a first temperature as it exits via the flue of the cooking appliance, and the second end facing but spaced apart from an exhaust hood for discharging the flue gas at a second temperature to the exhaust hood, the second temperature being lower than the first temperature; a mount for supporting the flue extension within a space between the flue of the cooking appliance and the exhaust hood, the mount being other than secured to either the cooking appliance or the exhaust hood; and a heat exchanger assembly disposed within the flue extension and comprising a heat exchanger tube for circulating a volume of a thermal fluid, the heat exchanger tube comprising a plurality of substantially straight tube sections that are arranged substantially normal to a flow direction of the flue gas through the flue extension.
In accordance with an aspect of at least one embodiment, there is provided a system for extracting heat from a flue gas exiting from a cooking appliance, comprising: a flue extension having an open first end, an open second end that is opposite the first end, and a central passageway extending between the first and second ends; a first heat exchanger assembly disposed within the central passageway of the flue extension; a mount for supporting the flue extension and the first heat exchanger within a space between a flue of the cooking appliance and an exhaust hood disposed above the cooking appliance, the mount being operable between: a first configuration in which the first end of the flue extension is aligned with but spaced apart from the flue of the cooking appliance by a first distance, and a second configuration in which the first end of the flue extension is spaced apart from the flue of the cooking appliance by a second distance that is greater than the first distance; a storage tank for containing a medium to be heated; a second heat exchanger disposed within the storage tank, the second heat exchanger being in fluid communication with the first heat exchanger; and a pump for circulating a thermal fluid within a closed circuit that includes the first heat exchanger and the second heat exchanger.
In accordance with an aspect of at least one embodiment, there is provided a method for extracting heat from a flue gas exiting a cooking appliance, comprising: using a mount, supporting a flue extension between a flue of the cooking apparatus and an exhaust hood disposed above the cooking apparatus, such that an open first end of the flue extension is aligned with but spaced apart from the flue of the cooking apparatus by a first distance, and wherein the mount is other than secured to either the cooking appliance or the exhaust hood; providing a heat exchanger assembly within the flue extension, the heat exchanger assembly including a heat exchanger coil; receiving the flue gas via the open first end of the heat exchanger, the flue gas being constrained by the flue extension to flow around the heat exchanger coil and out through an open second end of the flue extension along a direction generally toward the exhaust hood; and while the flue gas is being constrained to flow around the heat exchanger coil, circulating a heat transfer fluid within the heat exchanger coil, whereby heat is transferred from the flue gas to the thermal fluid.
The instant invention will now be described by way of example only, and with reference to the attached drawings, wherein similar reference numerals denote similar elements throughout the several views, and in which:
The following description is presented to enable a person skilled in the art to make and use the invention, and is provided in the context of a particular application and its requirements. Various modifications to the disclosed embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be applied to other embodiments and applications without departing from the scope of the invention. Thus, the present invention is not intended to be limited to the embodiments disclosed, but is to be accorded the widest scope consistent with the principles and features disclosed herein. Also, it is to be understood that the phraseology and terminology used herein is for the purpose of description and should not be regarded as limiting. The use of “including,” “comprising,” or “having” and variations thereof herein is meant to encompass the items listed thereafter and equivalents thereof as well as additional items. The phrase “heat exchanger assembly” is used interchangeably with the term “coil” throughout the description and in the claims.
Referring now to
Of course, the material that is used to fabricate the flue extension 104 and the mount 400 must meet hygienic kitchen standards, must not corrode, and must be able to withstand the operating temperature of the cooking appliance 108. By way of a specific and non-limiting example, “403 stainless steel” is used.
Referring now to
In general, maximizing the outside diameter of the heat exchanger tube 900 and maximizing the number of turns of the coil, while also minimizing the wall thickness of the heat exchanger tubes 900, results in greater heat transfer to the thermal fluid and accordingly produces a higher thermal fluid outlet temperature. The spacing between adjacent turns of the coil is limited by the maximum allowable flue gas flow rate reduction. That is to say, packing the turns of the double helical coil too closely together causes a flow restriction, and the flue gas venting may become inadequate. In the heat exchanger assembly 102 that is shown in
Alternatively, a heat exchanger assembly having a different shape and/or a different configuration may be used in the system 100. For instance a common “trombone-shaped” coil 1100, as shown in
During operation the flue extension 104 is aligned above the flue 702 of the cooking appliance 108, as is shown in
When maintenance or cleaning is required, a user simply grasps the handle 910 and pivots the flue extension 104 (including the optional gasket 704) upward and away from the flue 702 of cooking appliance 108. The flue 702 and/or surrounding surfaces etc., may then be cleaned, moved and/or maintained.
Providing a flue extension 104 in alignment with the flue 702 of the cooking appliance 108, and disposing the heat exchanger assembly 102 within the flue extension 104, avoids the need modify either the flue 702 or the exhaust hood 110. Further, the volume and pressure of the flue gas flow through the flue 702 and exhaust hood is substantially unaffected by the presence of the heat exchanger assembly 102 within the flue extension 104. Further still, the heat exchanger assembly 102 and flue extension 104 can be rapidly moved out of the way to provide access to the flue 702 when required, including in emergency situations. The flue extension 104 channels the flue gas upward and toward the exhaust hood, limiting the amount of heat that escapes into the environment around the cooking appliance. Additionally, the heat exchanger assembly 102 removes some of the heat from the flue gas, thereby lowering the temperature of the flue gas and further limiting the amount of heat that escapes into the environment around the cooking appliance.
Optionally, a different type of mount is used, such as for instance a “drawer-slider” type mount that support horizontal movement of the flue extension and heat exchanger assembly. Such a mount is appropriate when the vertical dimension of the space 106 between the cooking appliance 108 and exhaust hood 110 is limited. Alternatively, the mount is stationary and the flue extension 104 is secured to the mount using quick-release fasteners, or the flue extension 104 simply “snaps” into place on the mount, such that the flue extension 104 and heat exchanger assembly 102 may be removed from the mount for cleaning/maintenance purposes. Further alternatively, the flue extension 104 and heat exchanger assembly 102 may be suspended from the ceiling or from another support surface above the cooking appliance, such as for instance using cables or chains.
While several inventive embodiments have been described and illustrated herein, those of ordinary skill in the art will readily envision a variety of other means and/or structures for performing the function and/or obtaining the results and/or one or more of the advantages described herein, and each of such variations and/or modifications is deemed to be within the scope of the invent of embodiments described herein. More generally, those skilled in the art will readily appreciate that all parameters, dimensions, materials, and configurations described herein are meant to be exemplary and that the actual parameters, dimensions, materials, and/or configurations will depend upon the specific application or applications for which the inventive teachings is/are used. Those skilled in the art will recognize, or be able to ascertain using no more than routine experimentation, many equivalents to the specific inventive embodiments described herein. It is, therefore, to be understood that the foregoing embodiments are presented by way of example only and that, within the scope of the appended claims and equivalents thereto, inventive embodiments may be practiced otherwise than as specifically described and claimed. Inventive embodiments of the present disclosure are directed to each individual feature, system, article, material, kit, and/or method described herein. In addition, any combination of two or more such features, systems, articles, materials, kits, and/or methods, if such features, systems, articles, materials, kits, and/or methods are not mutually inconsistent, is included within the inventive scope of the present disclosure.
All definitions, as defined and used herein, should be understood to control over dictionary definitions, and/or ordinary meanings of the defined terms. The indefinite articles “a” and “an,” as used herein in the specification and in the claims, unless clearly indicated to the contrary, should be understood to mean “at least one.” The phrase “and/or,” as used herein in the specification and in the claims, should be understood to mean “either or both” of the elements so conjoined, i.e., elements that are conjunctively present in some cases and disjunctively present in other cases.
Multiple elements listed with “and/or” should be construed in the same fashion, i.e., “one or more” of the elements so conjoined. Other elements may optionally be present other than the elements specifically identified by the “and/or” clause, whether related or unrelated to those elements specifically identified. Thus, as a non-limiting example, a reference to “A and/or B”, when used in conjunction with open-ended language such as “comprising” can refer, in one embodiment, to A only (optionally including elements other than B); in another embodiment, to B only (optionally including elements other than A); in yet another embodiment, to both A and B (optionally including other elements); etc.
As used herein in the specification and in the claims, “or” should be understood to have the same meaning as “and/or” as defined above. For example, when separating items in a list, “or” or “and/or” shall be interpreted as being inclusive, i.e., the inclusion of at least one, but also including more than one, of a number or list of elements, and, optionally, additional unlisted items. Only terms clearly indicated to the contrary, such as “only one of” or “exactly one of,” or, when used in the claims, “consisting of,” will refer to the inclusion of exactly one element of a number or list of elements. In general, the term “or” as used herein shall only be interpreted as indicating exclusive alternatives (i.e. “one or the other but not both”) when preceded by terms of exclusivity, such as “either,” “one of,” “only one of,” or “exactly one of” “Consisting essentially of,” when used in the claims, shall have its ordinary meaning as used in the field of patent law.
As used herein in the specification and in the claims, the phrase “at least one,” in reference to a list of one or more elements, should be understood to mean at least one element selected from any one or more of the elements in the list of elements, but not necessarily including at least one of each and every element specifically listed within the list of elements and not excluding any combinations of elements in the list of elements. This definition also allows that elements may optionally be present other than the elements specifically identified within the list of elements to which the phrase “at least one” refers, whether related or unrelated to those elements specifically identified. Thus, as a non-limiting example, “at least one of A and B” (or, equivalently, “at least one of A or B,” or, equivalently “at least one of A and/or B”) can refer, in one embodiment, to at least one, optionally including more than one, A, with no B present (and optionally including elements other than B); in another embodiment, to at least one, optionally including more than one, B, with no A present (and optionally including elements other than A); in yet another embodiment, to at least one, optionally including more than one, A, and at least one, optionally including more than one, B (and optionally including other elements); etc.
It should also be understood that, unless clearly indicated to the contrary, in any methods claimed herein that include more than one step or act, the order of the steps or acts of the method is not necessarily limited to the order in which the steps or acts of the method are recited.
Numerical ranges include the end-point values that define the ranges. For instance, “between X and Y” includes both X and Y, as well as all temperature values between X and Y.
In the claims, as well as in the specification above, all transitional phrases such as “comprising,” “including,” “carrying,” “having,” “containing,” “involving,” “holding,” “composed of,” and the like are to be understood to be open-ended, i.e., to mean including but not limited to. Only the transitional phrases “consisting of” and “consisting essentially of” shall be closed or semi-closed transitional phrases, respectively.
The foregoing description of methods and embodiments of the invention has been presented for purposes of illustration. It is not intended to be exhaustive or to limit the invention to the precise steps and/or forms disclosed, and obviously many modifications and variations are possible in light of the above teaching. It is intended that the scope of the invention and all equivalents be defined by the claims appended hereto.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2911796 | Nov 2015 | CA | national |
