Single pass high-efficiency condensing water heater

Abstract

A heating system for a water heating appliance includes a heater for generating heated process air, a blower for delivering the heated process air through an airflow path, a flue that defines an upstream section of the airflow path, a heat exchange structure disposed downstream of the flue and defining a medial section of the airflow path, and a condensing section that defines a downstream section of the airflow path and is disposed downstream of the heat exchange structure. The heat exchange structure includes a heat exchange portion having airflow obstructions that generate a turbulence and transfer heat from the heated process air to a media surrounding an outer surface of the heat exchange structure. The airflow path within the heat exchange portion extends outward and generally perpendicular to a direction of the airflow path within the flue.

What is claimed is: 
     
         1 . A heating system for a water heating appliance, the heating system comprising:
 a heater for generating heated process air;   a blower for delivering the heated process air through an airflow path;   a flue that defines an upstream section of the airflow path;   a heat exchange structure disposed downstream of the flue and defining a medial section of the airflow path, the heat exchange structure including a heat exchange portion having airflow obstructions that generate a turbulence and transfer heat from the heated process air to a media surrounding an outer surface of the heat exchange structure, wherein the airflow path within the heat exchange portion extends outward and generally perpendicular to a direction of the airflow path within the flue; and   a condensing section that defines a downstream section of the airflow path, the condensing section disposed downstream of the heat exchange structure.   
     
     
         2 . The heating system of  claim 1 , wherein the airflow obstructions include a plurality of fins, wherein each fin of the plurality of fins is positioned in an angular orientation with respect to adjacent fins of the plurality of fins. 
     
     
         3 . The heating system of  claim 1 , wherein the flue and the heat exchange structure define a sensible heat exchange area, and wherein the condensing section defines a latent heat exchange area that causes a condensation of humidity within the heated process air, wherein the heated process air transitions to cooled process air as the heated process air moves through the airflow path. 
     
     
         4 . The heating system of  claim 1 , wherein the heated process air moves through the flue along a central axis of the airflow path, wherein the condensing section includes a plurality of condensing tubes that are oriented parallel with the central axis, and wherein the heat exchange portion of the heat exchange structure directs the heated process air in a direction that is oblique to the central axis. 
     
     
         5 . The heating system of  claim 2 , wherein the heat exchange structure includes an outer wall that forms one of a conical shape and a dome shape, and wherein the plurality of fins are attached to an inner surface of the outer wall. 
     
     
         6 . The heating system of  claim 5 , wherein the heat exchange structure includes an inner wall that opposes the outer wall to define a portion of the airflow path therebetween, and wherein the plurality of fins are disposed between the outer wall and the inner wall. 
     
     
         7 . The heating system of  claim 2 , wherein the plurality of fins are positioned in concentric rings of fins, and wherein each ring of fins is disposed at an angle with respect to a corresponding concentric ring. 
     
     
         8 . The heating system of  claim 1 , wherein the condensing section includes an outlet, and wherein the flue, the heat exchange structure, and the condensing section cooperate to define a single pass condensing heat exchanger where the heated process air moves sequentially through the airflow path. 
     
     
         9 . A single pass condensing water heating appliance comprising:
 an outer housing that defines a fluid reservoir therein;   a heater for heating process air to define heated process air;   a blower coupled to the outer housing that delivers the heated process air through an airflow path that extends through, and is in thermal communication with, the fluid reservoir;   a flue disposed within the outer housing and defining an upstream section of the airflow path;   a heat exchange structure having a transition that is positioned proximate an end of the flue, the heat exchange structure defining a medial section of the airflow path, the heat exchange structure including an interior chamber having a plurality of airflow obstructions that generate a turbulence within the heated process air that increases a residency of the heated process air within the heat exchange structure, wherein the plurality of airflow obstructions transfers heat from the heated process air to a media within the fluid reservoir; and   a condensing section attached to the heat exchange structure and defining a downstream section of the airflow path.   
     
     
         10 . The single pass condensing water heating appliance of  claim 9 , wherein the transition of the heat exchange structure directs the heated process air toward the airflow obstructions, and wherein the transition of the heat exchange structure includes a heat-resistive material. 
     
     
         11 . The single pass condensing water heating appliance of  claim 9 , wherein the flue defines a central axis, and wherein the heated process air moves through the flue along the central axis, and wherein the transition redirects the heated process air to travel in a direction that is one of perpendicular to the central axis and oblique to the central axis. 
     
     
         12 . The single pass condensing water heating appliance of  claim 11 , wherein the condensing section includes a plurality of condensing tubes that are oriented parallel with the central axis, and wherein the plurality of condensing tubes direct the heated process air from the heat exchange structure to an outlet. 
     
     
         13 . The single pass condensing water heating appliance of  claim 9 , wherein the flue and the heat exchange structure define a sensible heat exchange area, and wherein the condensing section defines a latent heat exchange area that causes a condensation of humidity within the heated process air. 
     
     
         14 . The single pass condensing water heating appliance of  claim 9 , wherein the airflow obstructions include a plurality of heat exchange fins, wherein each fin of the plurality of fins is positioned in an angular orientation with respect to adjacent fins of the plurality of fins. 
     
     
         15 . The single pass condensing water heating appliance of  claim 14 , wherein the plurality of fins are positioned in concentric rings of fins. 
     
     
         16 . The single pass condensing water heating appliance of  claim 9 , wherein the flue and the heat exchange structure define a sensible heat exchange area, and wherein the condensing section defines a latent heat exchange area that causes a condensation of humidity within the process air. 
     
     
         17 . The single pass condensing water heating appliance of  claim 9 , wherein the heat exchange structure includes an outer wall that forms one of a conical shape and a dome shape, and wherein the plurality of airflow obstructions are attached to an inner surface of the outer wall. 
     
     
         18 . A heating system for a water heating appliance, the heating system comprising:
 a flue that defines an upstream section of an airflow path that directs heated process air along a central axis;   an air delivery system that delivers the heated process air into the airflow path via the flue;   a heat exchange structure attached to an end of the flue opposite the air delivery system, the heat exchange structure defining a medial section of the airflow path, the heat exchange structure having a heat exchange portion that directs the heated process air outward from the end of the flue and in a direction generally perpendicular to the central axis within the flue, wherein the heat exchange structure includes airflow obstructions that transfer heat from the heated process air, through a wall of the heat exchange structure and to a media surrounding an outer surface of the wall of the heat exchange structure; and   a condensing section that is attached to the heat exchange structure and defines a downstream section of the airflow path.   
     
     
         19 . The heating system of  claim 18 , wherein the flue and the heat exchange structure define a sensible heat exchange area, and wherein the condensing section defines a latent heat exchange area that causes a condensation of humidity within the heated process air. 
     
     
         20 . The heating system of  claim 18 , wherein the airflow obstructions include a plurality of fins, wherein each fin of the plurality of fins is positioned in concentric circles and positioned in an angular orientation with respect to adjacent fins of the plurality of fins.