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AssigneeThe United States of America as represented by the Administrator of the National Aeronautics and Space Administration
InventorsDavid F. Chao, Nengli Zhang
Estimating the term…
The performance of a heat pipe system is greatly improved by the use of a dilute aqueous solution of about 0.0005 and about 0.005 moles per liter of a long chain alcohol as the working fluid. The surface tension-temperature gradient of the long-chain alcohol solutions turns positive as the temperature exceeds a certain value, for example about 40° C. for n-heptanol solutions. Consequently, the Marangoni effect does not impede, but rather aids in bubble departure from the heating surface. Thus, the bubble size at departure is substantially reduced at higher frequencies and, therefore, increases the boiling limit of heat pipes. This feature is useful in microgravity conditions. In addition to microgravity applications, the heat pipe system may be used for commercial, residential and vehicular air conditioning systems, micro heat pipes for electronic devices, refrigeration and heat exchangers, and chemistry and cryogenics.
A heat pipe system comprising a closed evaporating-condensing cycle and including a working fluid having a positive gradient of surface tension with temperature at operating temperature range of the system.
A working fluid for a heat pipe system wherein the fluid exhibits a positive gradient of surface tension at its operating temperature range of the system.
A method of achieving heat exchange under conditions of microgravity comprising the use of a working fluid in a heat exchanger wherein the fluid comprises an aqueous solution and an effective amount of a long-chain alcohol to provide the fluid with a positive gradient of surface tension with temperatures above about 40° C. at atmospheric pressure.
A method of increasing the heat transfer rate of an aqueous working fluid in a heat pipe comprising adding an effective amount of an alcohol to the working fluid to provide a solution having a positive gradient of surface tension with temperature in the range of operating temperatures of the fluid in the heat pipe.
Dependencies are inferred from the claim text.