Experimental and analytical study of a loop heat pipe at a positive elevation using neutron radiography
An experimental and analytical study has been conducted of a loop heat pipe's steady state operating conditions at a positive elevation, which refers to when the condenser is higher than the evaporator. A unique trend of the steady state operating temperature as a function of evaporator heat lo...
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Published in | International journal of thermal sciences Vol. 77; no. 77; pp. 84 - 95 |
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Main Authors | , , |
Format | Journal Article |
Language | English |
Published |
Kidlington
Elsevier Masson SAS
01.03.2014
Elsevier |
Subjects | |
Online Access | Get full text |
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Summary: | An experimental and analytical study has been conducted of a loop heat pipe's steady state operating conditions at a positive elevation, which refers to when the condenser is higher than the evaporator. A unique trend of the steady state operating temperature as a function of evaporator heat load at a positive elevation was observed in the experimental data. A gravity-assisted operating theory was proposed and explained in detail. In addition, the proposed hypothesis was validated by neutron radiography, a non-destructive visualization tool. When the LHP is operated at a positive elevation, it can operate in the capillary-controlled mode, which means the system is driven by pressure gain from both surface tension and liquid head, or in the gravity-controlled mode, which means the system is driven only by the pressure gain from the liquid head. A pressure–temperature diagram illustrating the thermodynamic states of the circulating fluid was presented when the system is operating in a gravity-controlled mode. Experimental temperature data were presented for a loop heat pipe operating at 25.4, 76.2, and 127.0 mm positive elevations. Lastly, predicting results from an analytical model with the newly added features at a positive elevation were compared with the experimental results obtained at a 76.2 mm positive elevation. The model prediction and the experimental data agree well, which means the operating mechanisms were understood and captured in the model. This is the first study of a loop heat pipe focusing on a positive elevation, which unveils the unique temperature trend at low heat load operating conditions.
•A loop heat pipe was studied experimentally using neutron radiography.•A gravity-controlled operating mode at a positive elevation was presented.•An analytical model was formulated to predict steady state performance.•Analytical model and experimental data showed agreement at a positive elevation.•The mechanism explains the unique steady state trend at a positive elevation. |
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Bibliography: | ObjectType-Article-2 SourceType-Scholarly Journals-1 ObjectType-Feature-1 content type line 23 |
ISSN: | 1290-0729 1778-4166 |
DOI: | 10.1016/j.ijthermalsci.2013.10.010 |