A gas-fired atmospheric pressure steam humidifier having high efficiency and ultra-low NOx(3) emissions is disclosed. In some examples, the gas-fired humidifier can have an efficiency of greater than 90 percent and a NOx(3) output of less than 20 parts per million (ppm). In one aspect, the humidifier includes a secondary heat exchanger having a first heat exchange section for pre-heating combustion air and a separate second heat exchange section for pre-heating make-up water, wherein the first and second heat exchange sections are in heat transfer communication with exhaust gases generated by the gas-fired burner and combustion blower assembly. In some examples, the first heat exchange section includes orifices for enabling flue gas recirculation.

A gas-fired atmospheric pressure steam humidifier having high efficiency and ultra-low NOx(3) emissions is disclosed. In some examples, the gas-fired humidifier can have an efficiency of greater than 90 percent and a NOx(3) output of less than 20 parts per million (ppm). In one aspect, the humidifier includes a secondary heat exchanger having a first heat exchange section for pre-heating combustion air and a separate second heat exchange section for pre-heating make-up water, wherein the first and second heat exchange sections are in heat transfer communication with exhaust gases generated by the gas-fired burner and combustion blower assembly. In some examples, the first heat exchange section includes orifices for enabling flue gas recirculation.

An evaporator with integrated heat recovery incorporates a vapor tube in a combustion chamber surrounded by a water jacket. The water jacket is in fluid communication with an exhaust gas heat exchanger. Coolant circulates through the exhaust gas heat exchanger to recover heat from exhaust gasses leaving the combustion chamber and then circulates through the water jacket surrounding the combustion chamber to recover heat not delivered to the operating fluid. The evaporator may incorporate a condenser within the housing and in fluid communication with the exhaust gas heat exchanger and water jacket. Coolant may enter the evaporator housing at the condenser before circulating through the exhaust gas heat exchanger and water jacket.

A damper assembly for minimizing heat loss through an exhaust includes a housing mounted within the stack and a bladder received within the housing. The bladder is selectively movable between a first position in which the bladder is deflated and received within the housing, and second position in which the bladder is positioned outside the housing and inflated such that a peripheral surface of the bladder contacts an interior sidewall of the stack to create a gas seal.

A damper assembly for minimizing heat loss through an exhaust includes a housing mounted within the stack and a bladder received within the housing. The bladder is selectively movable between a first position in which the bladder is deflated and received within the housing, and second position in which the bladder is positioned outside the housing and inflated such that a peripheral surface of the bladder contacts an interior sidewall of the stack to create a gas seal.

A damper assembly for minimizing heat loss through an exhaust stack includes a housing mountable within the stack and an umbrella received within the housing. The umbrella is selectively movable between a first position in which the umbrella is received within the housing, and second position in which the umbrella is extended from the housing such that a peripheral edge of the umbrella is in close association with an interior sidewall of the exhaust stack to minimize a flow of fluid past the umbrella and out of the stack.

A damper assembly for minimizing heat loss through an exhaust stack includes a housing mountable within the stack and an umbrella received within the housing. The umbrella is selectively movable between a first position in which the umbrella is received within the housing, and second position in which the umbrella is extended from the housing such that a peripheral edge of the umbrella is in close association with an interior sidewall of the exhaust stack to minimize a flow of fluid past the umbrella and out of the stack.

A flame tube having a tubular body with an inner side surface, extending around an axis (A), an inlet section and an outlet section, a plurality of fins leaning out, substantially in the radial direction (R), from the inner side surface towards the axis (A) is provided. The fins have an extended surface whose tangent (T), in a point (C) normal to the radial direction (R), is skew with respect to the axis (A), a first and a second fin forming an interspace between the respective extended surfaces facing one another and whose ideal extension (P) in the direction of the tangent (T) encounters a third fin.

A flame tube having a tubular body with an inner side surface, extending around an axis (A), an inlet section and an outlet section, a plurality of fins leaning out, substantially in the radial direction (R), from the inner side surface towards the axis (A) is provided. The fins have an extended surface whose tangent (T), in a point (C) normal to the radial direction (R), is skew with respect to the axis (A), a first and a second fin forming an interspace between the respective extended surfaces facing one another and whose ideal extension (P) in the direction of the tangent (T) encounters a third fin.

A heat exchanger pipe in a flow duct for gases. The pipe first section has a second section with an inner pipe for transferring heat transfer medium; an outer pipe that radially encloses a part of the inner pipe; and a medium layer between the outer pipe and the part of the inner pipe. The second section of the heat exchanger pipe bends less than 90 degrees. Furthermore, the first section is insulated in its entirety, or non-insulated in the vicinity of other heat recovery surfaces only. In the device the temperature of the heat transfer medium flowing in the inner pipe is at least 500? C., the temperature of the outer surface of the outer pipe is higher than 600? C., or an auxiliary agent is fed to the thermal device.