Reliability and Heat Transfer Performance of a Miniature High-Temperature Thermosyphon-Based Thermal Valve

Jeffrey Alleman, Gregory Glatzmaier, Philip Parilla, David Ginley, Eric Toberer, Christopher Oshman, Jonathan Rea, Corey Hardin, Nathan Siegel, Michele Olsen

Research output: Contribution to journalArticlepeer-review

7 Scopus Citations


Latent heat thermal energy storage systems have the advantages of near isothermal heat release and high energy density compared to sensible heat, generally resulting in higher power block efficiencies. Until now, there has been no highly effective and reliable method to passively extract that stored latent energy. Most modern attempts rely on external power supplied to a pump to move viscous heat transfer fluids from the phase change material (PCM) to the power block. In this work, the problem of latent heat dispatchability has been addressed with a redesigned thermosyphon geometry that can act as a “thermal valve” capable of passively and efficiently controlling the release of heat from a thermal reservoir. A bench-scale prototype with a stainless steel casing and sodium working fluid was designed and tested to be reliable for more than fifty “on/off” cycles at an operating temperature of 600 °C. The measured thermal resistances in the “on” and “off” states were 0.0395 K/W and 11.0 K/W respectively. This device demonstrated efficient, fast, reliable, and passive heat extraction from a PCM and may have application to other fields and industries using thermal processing.

Original languageAmerican English
Pages (from-to)1079-1086
Number of pages8
JournalInternational Journal of Heat and Mass Transfer
StatePublished - Oct 2018

Bibliographical note

Publisher Copyright:
© 2018 Elsevier Ltd

NREL Publication Number

  • NREL/JA-5H00-71737


  • CSP
  • Heat pipe
  • Latent heat
  • PCM
  • Thermal valve
  • Thermosyphon


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