1. Field of the Invention
The present invention relates generally to heat exchangers and, more specifically, to heat exchangers using an oscillating flow through heat exchange outputs.
2. Description of the Related Art
In a classical "heat pipe", heat is transported by a phase change from liquid to gas at the heated end of the pipe, a transport of the heated vapor down the pipe to cooler regions, a phase change from gas to liquid releasing the heat to the cooled walls, and a capillary pumping of the condensed liquid which returns it to the heated end of the pipe.
The capability of cooling structures to survive extremely large heat fluxes has become increasingly important, particularly with aerospace applications. As an example, the cowl lip of a scramjet engine may be subjected to shock interference heating which can produce heat fluxes with values on the order of 100,000 BTU per square foot per second. Thus, a need exists for an active cooling concept that is capable of handling this extreme heat flux requirement.
A wide variety of heat transfer devices are currently known and used. U.S. Pat. No. 2,581,760, issued to Harpoothian et al., discloses a aircraft deicing system which employs a heated fluid circulating at high velocity close to the external skin of the aircraft.
German Patent 1,033,223 discloses a press to fabricate matrices and printing plates from plastics. In the process, heating and cooling are required to make the plates. In one aspect of the disclosure, the liquid within ducts is either transferable in an oscillatory fashion or can be pumped in one direction. However, the structure described as having a possible oscillatory flow is not a heat exchanger in which heat transfer is enhanced. Instead, the fluid is used to better distribute the heat input from electric heaters embedded inside the fluid passages. The oscillatory movement is described to be slow so that the plate is heated on the bottom and then the heated fluid is transferred to top plate by a pump to be used to heat the top plate while the bottom plate starts a cooling cycle using a separate cool fluid.
U.S. Pat. No. 2,941,759 discloses an aeronautical heat exchanger which cools leading edges of airfoils or other surfaces heated by air friction by transpiring a coolant such as water through a course outer wall.
U.S. Pat. No. 4,257,556, issued to Skala, discloses a heat transfer system which can supply heat by liquid convection from a hot reservoir to a number of intermittent users. A thermally degradable fluid is typically used in portions of the system and the time at temperatures which cause degradation is minimized. A liquid metal may be pumped by an electromagnetic pump, although the pumping does not create an oscillating flow.
U.S. Pat. No. 3,265,122 generally discloses an oscillating fluid in a heat exchanger.
U.S. Pat. No. 4,488,592, issued to Mittal et al., discloses an oscillating pump which circulates coolant through a large scale integrated circuit. The volume of chambers of the pump are sufficient to move a volume of coolant fluid sequentially through one of two heat exchangers and the large scale integrated circuit. Thus, the pump merely represents a "reverse flow" system in which fluid circulates back and forth through a structure to be cooled. U.S. Pat. No. 4,590,993, issued to Kurzwig, describes a heat transfer device which attempts to transport large heat flux without net mass transfer. An oscillating flow is described to occur between one reservoir and another. Basically, heat is transported from a hot reservoir to a cool one with no net flow of heat through the side walls.