Provided is a gas furnace. The gas furnace includes: a manifold with an exhaust port for discharging fuel gas; a nozzle attached to the exhaust port; a burner for burning a mixture of air and fuel gas ejected from the nozzle; a primary heat exchanger that provides a first flow path and allows a combustion gas produced by the combustion of the mixture to move through the first flow path; and a secondary heat exchanger located adjacent to the primary heat exchanger, that provides a second flow path and allows the combustion gas discharged from the primary heat exchanger to move through the second flow path, wherein the secondary heat exchanger includes: at least one tube forming the second flow path; and a baffle inserted into the at least one tube, the baffle including: a plate longitudinally extending in a lengthwise direction and twisted in the shape of a screw; and a plurality of holes formed to penetrate the plate.

A sound level reducing apparatus and method for reducing the outdoor sound level produced by a high efficiency gas furnace. The apparatus comprising a muffler having an internal length determined by an identified target pure tone frequency producing an undesirable sound level. The internal length may be optimized to reduce the sound level across a range of operational frequencies.

A gravity-style furnace subunit for a gas-induced draft furnace. A heat conduction tube configured to be located inside of a gas-induced draft furnace cabinet, the heat conduction tube being separated from a row of draft-induced heat conduction tubes inside the cabinet. A burner assembly having a burner tube located within the heat conduction tube through an inlet opening of the heat conduction tube. The burner assembly permits air flow through the inlet opening into the heat conduction tube. A pilot assembly located within the heat conduction tube and adjacent to the burner tube. A thermopile module having located adjacent to a flame outlet of the pilot assembly within the heat conduction tube. A gas valve configured to control gas flow to the burner assembly, the gas valve electrically coupled to the thermopile module and to actuate gas flow there-through when the thermopile module generates a predefined voltage difference.

A reverse combustion type combustion apparatus (1) includes a combustion section (2) that combusts fuel in a downward direction, heat exchangers (4, 5) disposed under the combustion section (2), and an exhaust box (6) disposed under the heat exchangers (4, 5). The exhaust box (6) is a molded product made from a synthetic resin material; the exhaust box (6) includes an opening portion (30) for introduction of combustion exhaust gases generated by an upper portion, a fixing portion (33) for fixing the heat exchanger (5), and an inclined bottom portion (35) that collects condensed water generated by the heat exchanger (5); and, at the lower end portion of the exhaust box (6), at least three legs (40) are integrally formed and make the exhaust box (6) stand up by itself.

An air heater is used for a drying tower, wherein the air heater includes a combustion chamber, a burner, an air heating chamber, a process air access, a process air exit and/or a flue gas exit. During operation of the air heater, a process air is supplied to the air heating chamber by way of the process air access, a fuel is burned by means of the burner, a heat thus generated in the combustion chamber is transferred to the process air in the air heating chamber and the heated process air is discharged out of the air heater by way of the process air exit, and the air heater comprises an expendable combustion chamber, wherein the expendable combustion chamber is disposed within the combustion chamber. Further, a drying tower is used for drying a product to be dried with an air heater.

A gas furnace includes: a combustion part in which a fuel gas is burnt to generate a combustion gas; a heat exchanger having a gas flow path through which the combustion gas flows; a blower configured to blow air around the heat exchanger; and an inducer configured to discharge the combustion gas from the heat exchanger, wherein the heat exchanger includes: at least one single path in which a single gas flow path is formed; a single-multiple return bend configured to communicate with the single path and convert a flow direction of the combustion gas; and at least one multiple path having a plurality of paths that communicate with the single-multiple return bend and form multiple gas flow paths.

A heat exchanger includes a lamellar structure of a plurality of parallel heat exchange elements with an intermediate air gap between each pair of adjacent heat exchange elements. Along a longitudinal direction of the lamellar structure the heat exchange elements is interconnected in a top portion of the lamellar structure that forms an inlet channel through the heat exchange elements and in a bottom portion of the lamellar structure that forms an outlet channel through the heat exchange elements. The heat exchange elements form parallel channels between the inlet and the outlet channels. In the outlet channel, the heat exchanger includes a filler body, that is filling up a lower level of the outlet channel and forms a floor along the longitudinal direction of the lamellar structure.

A control module for preventing acoustic resonance noise generation from a heat exchanger of a heating furnace, comprising a control signal generated by the control module. The control signal is configured to operate an induction fan of the heating furnace at more than one speed for a given heat demand mode of the heating furnace.

A sound level reducing apparatus and method for reducing the outdoor sound level produced by a high efficiency gas furnace. The apparatus comprising a muffler having an internal length determined by an identified target pure tone frequency producing an undesirable sound level. The internal length may be optimized to reduce the sound level across a range of operational frequencies.

The present disclosure provides a production system and a production method of potassium manganate, belonging to the technical field of production of potassium manganate. The production system of potassium manganate comprises a hot air generating device, a production device and a circulating air pipeline. The hot air generating device is configured provide hot air in a manner of burning fuel gas. The production device is configured to absorb heat in the hot air generated by the hot air generating device. The circulating air pipeline is configured to introduce the hot air passing through the production device into the hot air generating device to adjust temperature of the hot air.