| 摘要 |
A combustion furnace is provided which is convertible in the field for upflow or downflow operation. The furnace includes a cabinet in which a burner, heat exchanger, air blower and combustion gas blower are located. The burner, heat exchanger and combustion gas blower are mounted on a vestibule panel, which is removably mountable at opposed first and second mounting positions within the cabinet, whereby the burner, heat exchanger and combustion gas blower are reversibly positionable with respect to the air blower. The combustion gas blower is coupled to an elongated flue for exhausting combustion gases from the cabinet and is positionable with respect to the air blower to allow the flue to clear the compartment in which the air blower is located when the apparatus is configured for downflow operation. The vestibule panel includes an extruded portion extending into the air flowing across the heat exchanger. The extruded portion has an opening adapted to receive a temperature sensor, whereby the sensor is retained at a predetermined position in the air flow for sensing the temperature thereof. The heat exchanger preferably includes a plurality of serpentine tubes of generally circular cross-section, through which the combustion gases are drawn by the combustion gas blower. The tubes are crimped at selected locations therealong to define corresponding regions of generally oblong cross-section. The oblong cross-sections slow down the flow of combustion gases through the heat exchanger tubes, thereby enhancing heat transfer from the combustion gases to the air flowing across the outer surfaces of the tubes.
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