Method and system for extracting heat from a flue gas

Abstract

A system is provided for extracting heat from a flue gas after it is expelled from a cooking appliance, such as a commercial deep fryer. A flue extension is provided between the flue of the cooking appliance and an exhaust hood positioned above the cooking appliance. Within the flue extension is disposed a heat exchanger assembly, which includes a coil that forms part of a closed fluid loop including a second heat exchanger that is disposed within a fluid medium that is to be heated, such as water. A mount supports the flue extension, and allows movement of the flue extension between an operating configuration and a stowed configuration. The flue extension is positioned closer to the flue of the cooking appliance when in the operating configuration compared to the stowed configuration. Mounting the flue extension is achieved without modifying the cooking appliance or the exhaust hood.

What is claimed is: 
     
         1 . 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 secured to a surface that is proximate the cooking appliance and that is other than a surface of 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.   
     
     
         2 . The system of  claim 1 , wherein the mount supports a movement of the flue extension between an operating configuration in which the first end of the flue extension is spaced apart from the flue of the cooking appliance by a first distance and a stowed 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. 
     
     
         3 . The system of  claim 2 , wherein the mount comprises a single link pivoting assembly. 
     
     
         4 . The system of  claim 1 , wherein the heat exchanger tube has an inlet end for receiving the volume of the thermal fluid into the heat exchanger tube and an outlet end for providing the volume of the thermal fluid out of the heat exchanger tube. 
     
     
         5 . The system of  claim 4 , further comprising a storage tank for containing a fluid medium that is to be heated and further comprising a second heat exchanger assembly disposed within the storage tank, an inlet end of the second heat exchanger assembly being in fluid communication with the outlet end of the heat exchanger tube and an outlet end of the second heat exchanger assembly being in fluid communication with the inlet end of the heat exchanger tube. 
     
     
         6 . The system of  claim 5 , further comprising a pump for circulating the thermal fluid within a closed circuit that includes the heat exchanger assembly and the second heat exchanger assembly. 
     
     
         7 . The system of  claim 1 , wherein the heat exchanger tube comprises a plurality of external fins for increasing a total area of thermal contact with the flue gas. 
     
     
         8 . 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:
 i) 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 
 ii) 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.   
     
     
         9 . The system of  claim 8 , further comprising at least one temperature sensor and at least one flow meter for measuring a temperature and a flow rate, respectively, of the thermal fluid. 
     
     
         10 . The system of  claim 9 , further comprising a controller that is responsive to data signals provided from the at least one temperature sensor and from the at least one flow meter for controlling the circulating of the thermal fluid within the closed circuit. 
     
     
         11 . The system of  claim 8 , wherein the first heat exchanger assembly comprises a heat exchanger tube for circulating a volume of the 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. 
     
     
         12 . The system of  claim 11 , wherein the heat exchanger tube has an inlet end for receiving the volume of the thermal fluid into the heat exchanger tube and an outlet end for providing the volume of the thermal fluid out of the heat exchanger tube. 
     
     
         13 . The system of  claim 11 , wherein the heat exchanger tube comprises a plurality of external fins for increasing a total area of thermal contact with the flue gas. 
     
     
         14 . The system of  claim 8 , wherein the mount comprises a single link pivoting assembly. 
     
     
         15 . The system of  claim 8 , further comprising a gasket that extends between the first end of the flue extension and the flue of the cooking appliance when the mount is in the first configuration, the gasket for guiding a flow of the flue gas into the central passageway of the flue extension. 
     
     
         16 . 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 secured to a surface that is proximate the cooking appliance and that is other than a surface of 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 flue extension, 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 thermal fluid within the heat exchanger coil, whereby heat is transferred from the flue gas to the thermal fluid.   
     
     
         17 . The method of  claim 16 , further comprising circulating the thermal fluid from the heat exchanger assembly to a second heat exchanger assembly disposed within a storage tank containing a medium that is to be heated. 
     
     
         18 . The method of  claim 16 , further comprising actuating the mount into a stowed 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. 
     
     
         19 . The method of  claim 16 , wherein the thermal fluid is water. 
     
     
         20 . The method of  claim 16 , comprising sensing a temperature and a flow rate of the thermal fluid, and in response to the sensed temperature and sensed flow rate controlling the circulating of the thermal fluid.