Abstract: Heat exchanger tubes and heat pipes are simultaneously radially expanded into engagement with heat transfer fins and provided with internal spiral grooving by a generally spherical shaped tool disposed on the end of an elongated mandrel. The tool comprises a spherical segment having helical teeth formed on the exterior thereof and the tool is mounted for free rotation on the end of the mandrel. In forming a finned tube type heat exchanger a series of platelike fins are disposed in alignment with each other with tube receiving openings formed slightly oversize with respect to the outside diameter of the tube prior to expansion. The tube is supported by the fins and is secured at one end by a suitable device such as an expanding jaw collet connected to a hydraulic cylinder for extending the mandrel through the tube.

Abstract: Relatively small diameter heat pipes having generally horizontally arranged evaporator sections and inclined or vertically oriented condenser sections are provided with a flow separator for conducting working fluid vapor from the evaporator section to the condenser section and liquid working fluid is returned to the evaporator section in the flow passage formed between an outer cylindrical tubular member and an inner cylindrical member forming the flow separator. The flow separator may be formed as a cylindrical tube positioned within the outer tubular envelope such that the ends of the flow separator are open and are spaced from the end closures of the outer tube by a small distance. The hydraulic radius of the inner tube flow path is equal to or greater than the hydraulic radius of the annular passage formed between the tubes.

Abstract: A system for recovering waste heat from a stream of heated gas is disclosed. The system includes a convection heat transfer chamber, a boiler tank, and a plurality of heat pipes thermally interconnecting the convection heat transfer chamber with the boiler tank. Each of the heat pipes includes an evaporator section which is disposed in heat transfer relation with a stream of heated gas flowing through the convection heat transfer chamber, and a condenser section disposed in heat transfer relation with a volume of water disposed within the boiler tank. The evaporator sections and condenser sections are totally enclosed within the convection heat transfer chamber and boiler tank, respectively, and are connected in closed cycle fluid communication with each other.

Abstract: A system for recovering waste heat from a stream of heated gas is disclosed. The system includes a convection heat transfer chamber, a boiler tank, and a plurality of heat pipes thermally interconnecting the convection heat transfer chamber with the boiler tank. Each of the heat pipes includes an evaporator section which is disposed in heat transfer relation with a stream of heated gas flowing through the convection heat transfer chamber, and a condenser section disposed in heat transfer relation with a volume of water contained within the boiler tank. The boiler tank is provided with a header plate having an array of heat pipe openings through which the heat pipes project. A heat support sleeve is received in each heat pipe opening in sealed engagement with the header plate, with the heat pipes projecting through the support sleeves and thermally interconnecting the convection heat transfer chamber with the boiler tank.

Abstract: A system for recovering waste heat from a stream of heated gas is disclosed. The system includes a convection heat transfer chamber, a boiler tank, and a plurality of heat pipes thermally interconnecting the convection heat transfer chamber with the boiler tank. Each of the heat pipes includes an evaporator section which is disposed in heat transfer relation with a stream of heated gas flowing through the convection heat transfer chamber, and a condenser section disposed in heat transfer relation with a volume of water contained within the boiler tank. The boiler tank is provided with a header plate having an array of heat pipe openings through which the heat pipes project. A heat pipe support sleeve is received in each heat pipe opening in sealed engagement with the header plate, with the heat pipes projecting through the support sleeves and thermally interconnecting the convection heat transfer chamber with the boiler tank.

Abstract: A system for recovering waste heat from a stream of heated gas is disclosed. The system includes a convection heat transfer chamber, a boiler tank, and a plurality of heat pipes thermally interconnecting the convection heat transfer chamber with the boiler tank. Each of the heat pipes includes an evaporator section which is disposed in heat transfer relation with a stream of heated gas flowing through the convection heat transfer chamber, and a condenser section disposed in heat transfer relation with a volume of water contained within the boiler tank. The boiler tank is provided with a header plate having an array of heat pipe openings through which the heat pipes project. A heat pipe support sleeve is received in each heat pipe opening in sealed engagement with the header plate, with the heat pipes projecting through the support sleeves and thermally interconnecting the convection heat transfer chamber with the boiler tank.

Abstract: A unit for recovering thermal energy which utilizes a plurality of unique heat pipes, and the method and apparatus for fabricating the heat pipes is disclosed. The heat pipes are disposed horizontally and are filled with a volume of working fluid sufficient to cause the liquid phase to travel in either direction by gravity. Circumferential capillary grooves in the side walls of the heat pipes transport the liquid phase vertically above the liquid level to increase the area of the liquid-vapor interface. Additionally, the solid metal strips which form the grooves provide a low impedance thermal path from the walls of the heat pipe to the liquid-vapor interface where evaporation and condensation occur. These two factors significantly increase the efficiency of the system. A divider plate having an X-shaped cross section separates the liquid phase from the high velocity vapor phase to prevent slugging under high energy transfer conditions.

Abstract: A system for recovering waste heat from a stream of heated gas is disclosed. The system includes a convection heat transfer chamber, a boiler tank, and a plurality of heat pipes thermally interconnecting the convection heat transfer chamber with the boiler tank. Each of the heat pipes includes an evaporator section which is disposed in heat transfer relation with a stream of heated gas flowing through the convection heat transfer chamber, and a condenser section disposed in heat transfer relation with a volume of water contained within the boiler tank. The boiler tank is provided with a header plate having an array of heat pipe openings through which the heat pipes project. A heat pipe support sleeve is received in each heat pipe opening in sealed engagement with the header plate, with the heat pipes projecting through the support sleeves and thermally interconnecting the convection heat transfer chamber with the boiler tank.

Abstract: A laundry drying system and method in which fresh air flows through a low temperature duct of a preheater, then through a primary heater before entering a laundry drying chamber is described. The air enters into contact with laundry in the chamber, then is exhausted, flowing through a high temperature duct of the preheater. In the preheater, heat pipes transfer heat from the exhaust air in the high temperature duct to the fresh air in the low temperature duct. Thus, heat which would otherwise be discarded in the exhaust air stream is recovered for use in the drying process. The preheater preferably uses heat pipes having a liquid return tube and set in a plate fin heat exchanger. To provide for a cool down cycle, there is a bypass which defeats the operation of the preheater. Lint exhausted by the drying chamber is partly collected by a dry type lint remover between the chamber exhaust and the preheater.

Abstract: A home laundry dryer in which both the fresh air entering a laundry drum and the air exhausted from the drum pass through a thermal recovery unit in the dryer. The unit has a high temperature passage through which the exhaust air flows and a low temperature passage through which the entering air flows. Heat from the exhausted air is transferred by means of heat pipes from the high temperature passage to the entering air in the low temperature passage. This heat transfer lowers the energy required to raise the entering air to a selected drying temperature. The dryer, including the thermal recovery unit, fits in a housing of substantially standard size for home dryers.

Abstract: A thermal transfer system comprising a closed, generally horizontally disposed tubular envelope having heat transfer fins mounted at axially spaced points along its outer surface is disclosed. The interior surface of the tubular envelope has a large number of small circumferentially extending capillary grooves characterized by a restricted opening relative to the base of the grooves. A liquid phase/vapor phase working fluid is contained within the envelope with the liquid phase normally comprising about 50 to about 75 percent of the volume of the envelope at normal operating temperatures. A liquid phase return tube rests on the bottom of the envelope and is open at both ends. The liquid phase return tube has an inside diameter of about 30 to about 40 percent of the inside diameter of the tubular envelope and has a length of between about 65 percent and about 85 percent of the length of the envelope.