A duplex heat exchanger comprises unit heat exchangers which have a plurality of tubes arranged parallel with each other and comprise fins each interposed between two adjacent ones of such tubes, opposite ends of each tube being connected to a pair of headers in fluid connection therewith. The unit heat exchangers are closely juxtaposed to each other fore and aft in a direction of air flow. Coolant circuits of said unit heat exchangers are connected either in series or in parallel with each other.

An improved air-cooled vacuum steam condenser in a steam turbine cycle comprising a turbine for generating mechanical power, a boiler for generating steam, a conduit arrangement coupling the boiler to the turbine and then another conduit arrangement coupling the turbine exhaust back to the boiler through steam condensing mechanism. The steam condensing mechanisms include a plurality of finned tubes through which the expanded exhaust steam may flow counter to its condensate and be condensed; a plurality of front headers at the lower ends of the condensing tubes for conveying the exhaust steam from the turbine and receiving the condensate from the finned tubes; a plurality of rear headers at the upper ends of the condensing tubes for receiving the non-condensible gasses; and means in the rear headers to remove non-condensible gasses from the rear headers.

A heat recovery system includes an upstream superheater section and a duct burner arranged to provide improved performance. The upstream superheater section and duct burner are arranged to reduce the negative effects of heat extraction by the upstream superheater section on the duct burner operation. The arrangement provides a downstream flow from the upstream SH section that is temperature stratified and positions the duct burner elements in the areas of maximum temperature. The tubes of the upstream superheater section and the duct burner elements are arranged in a variety of ways to provide temperature stratification, for example, in the horizontal or vertical directions.

An auxiliary outside air refrigeration mechanism for a refrigerated storage room comprises an air-to-air heat exchanger wherein the two air supplies are sealed from each other by a physical seal and by a positive pressure air differential between the air supplies. An inlet and outlet for one air supply is connected to receive and return storage room air and an inlet and outlet for the other air supply is connected to receive and circulate outside air. A control mechanism automatically renders the auxiliary refrigerating mechanism operational when the outside temperature is a predetermined temperature below the upper temperature limit in the storage room. The control mechanism actuates the auxiliary refrigerating mechanism at a temperature below the temperature at which the conventional mechanical refrigerating unit is actuated, thus supplementing the conventional refrigerating unit when the outside temperature is cold. The control mechanism automatically switches off the outside air circulation when condensate in the heat exchanger freezes, and the unit self defrosts and drains the water through an inclined opening. The heat exchanger employs a special tube bundle formed of thin-walled thermoplastic tubes heat welded in openings in thermoplastic traverse mounting plates at opposite ends of the tube bundle.

A high pressure washer of this invention comprises a heat exchanger for heating a cleaning fluid, and a dispenser for dispensing heated cleaning fluid under pressure onto a surface to clean it. The heat exchanger comprises a tubular casing and a generally coaxial tubular heat shield inside the casing defining a combustion chamber. A burner is mounted adjacent a first end wall of the casing for discharging flames and hot combustion gases into the combustion chamber. A heating coil inside the casing extends longitudinally with respect to the casing for containing cleaning fluid to be heated. The heating coil comprises a length of unfinned tubing disposed in a gap between the heat shield and a second end wall of the casing, and a length of finned tubing in the annular space between the heat shield and the casing. The burner is operable to emit flame and hot gases of combustion into said combustion chamber in a direction toward the second end wall of the casing. The heat shield serves to protect the finned tubing by directing the hot gases of combustion for contact first with said unfinned tubing, resulting in cooling of the gases, followed by contact with the finned tubing in said annular space, thereby enhancing the heat transfer between the gases and the fluid contained within the heating coil.