Abstract: A thermal engine is disclosed which is operable as a heat pump, refrigerator, or air conditioner. Vaporized working fluid from a first evaporator, which extracts heat from elements desired to be cooled, is fed to a first region of an osmotic pump which also has a second region containing a solution of the working fluid and a preselected solute, the second region being separated from the first region by a membrane permeable to the vaporized working fluid but not to the solute. A second evaporator, which may be driven by waste heat, is operatively coupled to the second region of the osmotic pump by means of a counterflow heat exchanger having a first path for conveying relatively dilute solution from the second region of the osmotic pump to the second evaporator and a second path for conveying relatively concentrated solution from the second evaporator to the second region of the osmotic pump.

Abstract: A unidirectional heat pipe (22) acting as a thermal diode or a heat switch, enables heat to be removed from electronic equipment (14) when temperatures outside of a missile envelope (12) are lower than those of the electronic equipment. When the temperature exterior to the missile envelope is greater than that of the electronic equipment, the heat therefrom is conducted to a package (16) containing phase change material which absorbs the heat from the electronic equipment, at which time the heat pipe acts as a thermal insulator. Heat is also removed from the PCM package by the heat pipe when exterior temperatures are lower than interior temperatures.

Abstract: A heat pipe has a large area vapor tube for radiant heat loss and has connected thereto a subcooled liquid return tube for a return of the condensed liquid to the evaporator portion of the vapor tube. Wicking material plugs return the liquid and provide equilibrium along the length of the system. The separate return of the liquid through liquid tube permits a long heat pipe which may have several thermal connections.

Abstract: A heat pipe cooling module assembly (20) for cooling electronic components (28) includes a plurality of heat pipe modules (22) comprising condenser and evaporator sections (24, 26) and working fluid therein. In a preferred embodiment, each evaporator section comprises a sandwich construction of a pair of flat outer plates (34), a pair of wick pads (36) and a separator plate (38) comprising channels extending from the evaporator section into the condenser section.

Abstract: A heat pipe (10) includes an evaporator (18) to which a heat generating device is coupled. A heat dissipating condenser 14 is coupled to the evaporator by a thermally insulating tube 46. A capillary is on the interior surfaces of the evaporator, the condenser and the thermally insulating tube. Both working fluid and inert gas are placed therein. Reservoirs (16) for receiving the inert gas are joined to the condenser. Both the condenser and the gas reservoirs are thermally secured to a heat sink (28); however there is a path of higher thermal conductivity between the reservoir and the heat sink than between the condenser and the heat sink.

Abstract: Input and output tubes in an osmotically pumped heat pipe (10) are utilized to improve solvent-solute mixing and sweeping across a solvent-permeable membrane (46, 146, 246), to enable its operation in 0-g, 1-g and negative-g applications. Lean mixture solution flows through a path (16) of low pressure to an evaporator (14) where the solvent evaporates. Rich mixture solution from the evaporator then returns to the solvent-permeable membrane through a path (18) of higher pressure than the low pressure path to enable sweeping of the membrane and consequent increased mixing with the incoming condensed solvent.

Abstract: An arrangement for reducing non-symmetrical, thermally induced strains in a gun tube (12) comprising a heat pipe jacket (18) in thermal engagement with the gun tube to provide both high radial and circumferential thermal conductance from the tube.

Abstract: For controlling passage of energy through a variable transmittance window, an enclosure (12) is positioned in the path of the energy. A reservoir (22), saturated with working fluid, is coupled by a conduit (20) to the enclosure. The working fluid is selected to have a property which is capable of affecting passage of the energy through or into the enclosure. By applying or withdrawing heat from the reservoir, working fluid is respectively supplied to, or withdrawn from, the space within enclosure 12. Depending upon the properties of the working fluid, enclosure 12 will operate as an absorber, reflector or transmitter of light or thermal or other energy.

Abstract: A high concentration gradient across a solvent permeable membrane (20), separating the solution and solvent reservoirs (12, 16) or an osmotic pumped heat pipe (10), is effected by inducing convection currents across the membrane material on its solution reservoir side (34). The induced convection current is created by the difference in densities of rich and lean solute-solvent mixtures which are caused respectively to traverse separate paths (40, 42). These convection currents sweep and mix with the solvent which has been freshly pumped through the membrane from the solution reservoir side (34).

Abstract: An osmotically pumped environmental control system (10) comprises a closed circuit heat pipe (12) including an osmotic pump (13) with solvent and solution reservoirs (18, 14) separated from one another by a solvent permeable membrane (20). Heat is inserted into the closed path at an evaporator (22) from high temperature sources and heat is wihdrawn from the system by first and second stage cooling modules (38, 40) to withdraw heat therefrom. A further heat input (30) from low temperature sources slightly warms the condensate for return to a solvent reservoir (18).

Abstract: A selected number of heat pipes, located in the front rows of a plurality of otherwise operable heat pipes which are disposed between intake and exhaust ducts, have liquid-trap sections extending into a switching section. During normal operation, reservoirs in the switching section are dry and the plurality of heat pipes operate in a conventional manner. However, if some of the heat pipes in the exhaust dust become frosted over or otherwise too greatly cooled due to excessive cold in the intake duct, thermostatically or command-controlled valves or louvres cause the fluid stream in the exhaust duct to warm up or defrost the excessively cooled heat pipes therein. Prevention of excessive cooling is used to avoid frost build-up in air conditioning equipment, or solidification of solids and condensation of corrosive liquids.

Abstract: A plunger placed through an opening in a heat pipe enclosure is heated to a temperature above the saturation temperature of the working fluid in the heat pipe to prevent the fluid from condensing across the gap between the plunger and the opening and to allow non-condensible gases to escape. Thereafter, the plunger is melted to seal the heat pipe. The plunger and at least that part of the heat pipe with the opening therethrough are made from the same materials.

Abstract: A heat pipe extends into the path of flow of a viscous fluid, e.g., polymer, for transferring heat from or to the flowing fluid and thereby for solidifying and stopping flow of the fluid or, conversely, for melting the solidified matter for resumed flow thereof. Control may simply increase or decrease the fluid viscosity for varying the rate of flow.

Abstract: A heat pipe has its evaporator at its upper end and its condenser at its lower end and an adiabatic section separating the two so that capillary wicks or grooves do not extend through the heat pipe. A central liquid return tube extends between the evaporator and condenser. A vapor bubble generator is placed at the condenser section in the reservoir where the liquid state of the working fluid collects. When the vapor bubble generator is operated, bubbles form which, because of their buoyancy, will rise to the top of the central tube. As they rise, small amounts of working fluid in its liquid state will be carried with the bubbles and spill over the top of the tube and onto the evaporator wick. As a consequence, the heat pipe is insensitive to its vertical height and can operate against gravitational forces.

Abstract: A system wherein a plurality of thermoelectric modules are thermally connected by heat pipes forming a cascaded structure that is capable of operating effectively and reliably with large temperature gradients, the heat pipes providing relatively low temperature gradient interfaces between the thermoelectric modules and thereby act as stress isolation structures.

Abstract: The heat pipe assembly is formed into an H-shape or a Y-shape. The H-shaped configuration comprises two heat pipes, each having condenser and evaporator sections with wicking therein coupled by a tube with wick at their evaporator sections. The Y-shaped configuration utilizes a common evaporator section in place of the two evaporator sections of the H-shaped configuration. In both configurations, the connection between the vapor spaces of the two heat pipes equalizes vapor pressure within the heat pipes. Although both heat pipes have wicks, they have sufficient fluid only to saturate a single pipe. If heat is applied to the condenser section of one of the pipes, this heat pipe becomes inoperative since all the fluid is transferred to the second pipe which can operate with a lower thermal load.

Abstract: A vapor chamber cooking device is disclosed wherein a capillary wick is disposed along the bottom surface of a sealed vapor chamber, the top wall of which provides a cooking surface. A plurality of internal structural support members having vapor pressure equilization holes are disposed between the wick and the upper surface of the chamber and secured to the upper chamber surface. A quantity of volatile working fluid is disposed in the chamber sufficient to saturate the wick when in a liquid state. An arrangement is provided for heating the chamber to vaporize working fluid contained therein, and a feedback control arrangement responsive to the vapor pressure within the chamber controls the heating arrangement to maintain the chamber vapor pressure within a predetermined range. Additional arrangements may be provided to respond to predetermined conditions of overpressure within the chamber to relieve the overpressure conditions.