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Pressure profiles in a loop heat pipe under gravity influence
| Content Provider | NASA Technical Reports Server (NTRS) |
|---|---|
| Author | Ku, Jentung |
| Copyright Year | 2015 |
| Description | During the operation of a loop heat pipe (LHP), the viscous flow induces pressure drops in various elements of the loop. The total pressure drop is equal to the sum of pressure drops in vapor grooves, vapor line, condenser, liquid line and primary wick, and is sustained by menisci at liquid and vapor interfaces on the outer surface of the primary wick in the evaporator. The menisci will curve naturally so that the resulting capillary pressure matches the total pressure drop. In ground testing, an additional gravitational pressure head may be present and must be included in the total pressure drop when LHP components are placed in a non-planar configuration. Under gravity-neutral and anti-gravity conditions, the fluid circulation in the LHP is driven solely by the capillary force. With gravity assist, however, the flow circulation can be driven by the combination of capillary and gravitational forces, or by the gravitational force alone. For a gravity-assist LHP at a given elevation between the horizontal condenser and evaporator, there exists a threshold heat load below which the LHP operation is gravity driven and above which the LHP operation is capillary force and gravity co-driven. The gravitational pressure head can have profound effects on the LHP operation, and such effects depend on the elevation, evaporator heat load, and condenser sink temperature. This paper presents a theoretical study on LHP operations under gravity neutral, anti-gravity, and gravity-assist modes using pressure diagrams to help understand the underlying physical processes. Effects of the condenser configuration on the gravitational pressure head and LHP operation are also discussed. |
| File Size | 281231 |
| Page Count | 12 |
| File Format | |
| Alternate Webpage(s) | http://archive.org/details/NASA_NTRS_Archive_20150011463 |
| Archival Resource Key | ark:/13960/t5p898z2c |
| Language | English |
| Publisher Date | 2015-07-12 |
| Access Restriction | Open |
| Subject Keyword | Thermal Control Systems Loop Heat Pipes Gravitation Evaporators Pipe Flow Pressure Heads Vapors Pressure Distribution Gravitational Fields Liquid-vapor Interfaces Condensers Heat Pipes Liquid Flow Antigravity Heat Sinks Menisci Loads Forces Viscous Flow Ntrs Nasa Technical Reports Server (ntrs) Nasa Technical Reports Server Aerodynamics Aircraft Aerospace Engineering Aerospace Aeronautic Space Science |
| Content Type | Text |
| Resource Type | Article |
