Experimental and analytical study of a loop heat pipe at a positive elevation using neutron radiography

Po Ya Abel Chuang, John Michael Cimbala, Jack S. Brenizer

Research output: Contribution to journalArticle

7 Citations (Scopus)

Abstract

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.

Original languageEnglish (US)
Pages (from-to)84-95
Number of pages12
JournalInternational Journal of Thermal Sciences
Volume77
DOIs
StatePublished - Mar 1 2014

Fingerprint

Neutron radiography
neutron radiography
heat pipes
Heat pipes
Gravitation
Evaporators
Thermal load
evaporators
Temperature
gravitation
Liquids
Surface tension
Analytical models
Visualization
trends
heat
Thermodynamics
condensers
Fluids
liquids

All Science Journal Classification (ASJC) codes

  • Condensed Matter Physics
  • Engineering(all)

Cite this

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abstract = "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.",
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Experimental and analytical study of a loop heat pipe at a positive elevation using neutron radiography. / Chuang, Po Ya Abel; Cimbala, John Michael; Brenizer, Jack S.

In: International Journal of Thermal Sciences, Vol. 77, 01.03.2014, p. 84-95.

Research output: Contribution to journalArticle

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