A Novel Furnace Design Utilizing a Low Temperature Plastic Condensing Heat Exchanger
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Date
1982-03
Authors
Wright, John L.
Sullivan, Harry F.
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Abstract
The initial phase of a research and development program for the Consumers' Gas Co. and the Federal Department of Energy, Mines and Resources to design a condensing heat exchanger/gas fired residential air furnace has been completed. Progress to date has resulted in a novel design utilizing a relatively low temperature plastic material for the last stage heat exchanger. To utilize this low temperature plastic, a method of reducing the temperature of the flue gas entering the final heat exchanger was devised using a unique flue gas recirculation process.
Heat transfer calculations and pressure drop prediction methods have indicated that the design is sound and can easily be accommodated in a residential furnace with only moderate increase in cost and space requirements. The existing design is also well suited to incorporation as
a retrofit package and this is also being pursued.
Based on the calculated performance, a condensing heat exchanger was sized, fabricated and installed on a conventional 80,000 BTU/hr input gas fired residential furnace. The initial experimental tests have given very encouraging results. Based on a final flue gas exit temperature of 85F with an excess air condition of 25%, these initial tests yielded a furnace efficiency of approximately 97%. Although combustion air preheat has not been employed in these initial tests, this feature is planned
as part of the prototype design.
Description
Keywords
Furnaces, Heat exchangers, Materials testing, Performance testing, Closed-cycle systems, Cooling