A typical gas furnace includes a flame or burner for heating flue gases, a primary heat exchanger for transferring heat from the heated gases to the circulate air, and a blower for circulating the circulate air through a home (or any surrounding area). The gas furnace often also includes an inducer for drawing out or otherwise venting the heated flue gases from the primary heat exchanger.
With respect to the primary heat exchanger in particular, it serves to transfer heat from the heated flue gases to the circulate air, while ensuring that the heated flue gases are never in contact with the circulate air. In order to obtain optimum efficiencies of operation of the gas furnace, it is generally necessary to maximize the heat transfer that occurs between the heated flue gases within the primary heat exchanger and the circulate air passing over the outer surfaces of the primary heat exchanger. However, several requirements and constraints must be taken into account when designing such a primary heat exchanger for achieving optimum performances.
One such consideration, for instance, pertains to reducing the height and/or overall size of the primary heat exchanger panels. By virtue of reducing the height of the primary heat exchanger, the overall height of the gas furnace can be reduced such that it can be placed in smaller (or compact) spaces, such as in attics, crawl spaces, closets, and the like. This further reduces the materials, as well the costs required to manufacture and build the primary heat exchangers, as well as the overall gas furnace cabinet.
Another consideration pertains to the aggregate pressure drop within the gas furnace. More specifically, the internal pressure drop within the primary heat exchanger panels must be maintained at acceptable levels so as to minimize the load, as well as the power consumed by the inducer, which in turn minimizes any added utility expenses to the consumer. Furthermore, minimizing the load on the inducer promotes the longevity of the inducer and the associated gas furnace.
Yet another consideration is the durability/longevity of the primary heat exchanger, which in turn can extend the life of the associated gas furnace. To promote longevity of the primary heat exchanger (and the associated gas furnace), the primary heat exchanger must be free of any excessive surface temperatures, or hotspots, and any thermal stresses must be minimized. This can generally be achieved by utilizing a high temperature material in the construction of the primary heat exchanger. However, such materials are typically expensive and can lead to higher manufacturing and other related costs.
Accordingly, there is a need for a primary heat exchanger for gas furnaces that is compact in size, costs less to manufacture, and promotes longer furnace life while optimizing performance. Moreover, there is a need for a compact primary heat exchanger that optimizes the overall length and surface area for providing more efficient transfer of heat. There is also need for a primary heat exchanger that would minimize the aggregate pressure drop through the primary heat exchanger and the coupling box so as to reduce the load on the inducer of the gas furnace.