Loop Heat Pipes (LHP)

Modeling Loop Heat Pipes and other Capillary Devices

TadSat4 Loop Heat PipeThe methods for modeling LHPs and capillary pumped loops (CPLs) are very different than modeling heat pipes. Unlike a heat pipe, these devices require full thermohydraulic modeling of the fluid and containment system. In addition to supporting the modeling of single phased pumped loops, SINDA/FLUINT and FloCAD® have several features which make it uniquely capable of modeling two-phase pumped loops and capillary pumped pumps. Using SINDA/FLUINT and FloCAD, the analyst can capture everything from the system level effects of the LHP all the way down to detailed thermodynamic and hydrodynamic transient events such as LHP start-up, reservoir quenching, partially primed wicks, and pressure oscillations.

When it comes to modeling two-phase loops, SINDA/FLUINT has the unique advantage over other fluid flow codes in that a portion of the software development team (engineers by training) were actively involved in the development of CPL's and LHP's during the late 1980s and early 1990s, while they were also working on the development of SINDA/FLUINT. Consequently, when obstacles were encountered in the process of modeling these two-phase loops, new features were added to the software to overcome previous modeling limitations. Such features include Interface elements for modeling compensation chambers and reservoirs along with the liquid/vapor interface in the wick, a capillary evaporator pump, and a capillary device to model wicks, grooves, tubules, etc. During this time period, the ability to model the dissolution and evolution of noncondensible gases was added to the code.

Unique features relevant for analyzing LHPs and CPLs

  • Complete thermodynamics: phases appear and disappear as conditions warrant
  • Capillary modeling tools for static or vaporizing wicks
    • Vapor trapping (up to the bubble point) in capillary devices
    • Capillary flow regulators (constant back-pressure devices)
    • From top-level steady-state evaporator-pump modeling to detailed tracking of unsteady liquid/vapor interfaces within wicks
    • Full phasic nonequilibrium two-fluid modeling for unsteady hydrodynamics in heat pipes, LHP compensation chambers, etc.
  • Two-phase heat transfer correlations built-in or user-defined
  • Two-phase pressure drop correlations built-in or user-defined
  • Automatic flow regime mapping
  • Homogeneous and slip flow modeling, including countercurrent flow in the presence of gravity and other accelerations
  • Conservation of total charge mass for accurate pressure predictions in transients or parametric studies
  • Complex liquid/gas mixtures including optional dissolution of any gaseous solute into liquids
  • Fast and easy geometric model generation of condensers (serpentine, manifolded, etc.), including bonding or contact to thermal surfaces and solids, using FloCAD

LHP with Serpentine Condenser Line, postprocessed FloCAD model shown on the right

Resources

Please visit our support forum for a sample of how to model an LHP, or for an advanced example.

Publications

 

FloCAD online training

Class times: May 2 & 4 from 10am to 2pm MT

Cost: $425

This online class will provide an introduction to fluid modeling components within FloCAD. The class will be held over a 2-day period, with daily sessions running approximately 4 hours each. The class uses a mixture of lecture, demonstrations, and self-paced tutorials to allow attendees to practice building fluid system models and interpreting results. The presentations will comprise 2 - 3 hours of each session, and the instructor will be available during the remainder of the time for questions during tutorials. Attendees must have basic working knowledge of SINDA and Thermal Desktop as these topics will not be covered but their usage is required for FloCAD.

Register here

Thermal Desktop, RadCAD, and TD Direct in-class training

Date: April 25-28, 2017, 8:00 a.m. to 5:00 p.m., daily
Location: Lakewood, CO

CRTech will be hosting introductory training for Thermal Desktop, RadCAD and TD Direct. Lecture and hands-on tutorials introduce attendees to basic Thermal Desktop and RadCAD usage and allow practice building models and interpreting results. The class will also introduce students to SpaceClaim direct modeling CAD interface and advanced meshing tools in TD Direct.

Daily Schedule

Day 1 and 2: Introduction to SINDA and Thermal Desktop
Day 3: Introduction to RadCAD
Day 4: Introduction to TD Direct
 

To learn more about this class and to register, visit our Training Page.

Anode and cathode of a flow battery

Using Sinaps? It is not too soon to get started with TD/FloCAD!

This webinar describes the process for converting from Sinaps to Thermal Desktop (TD) and FloCAD. This process includes using an exporter which works with Version 6.0 of the CRTech tool suite (expected to be released in May of 2017).

Come learn about the basics of TD/FloCAD, including many compelling features not available in Sinaps. The webinar will also cover how to manage the transition period, during which you may be using both programs simultaneously. This is also a chance to ask questions. 

If you missed this webinar, please contact us for the presentation material and recording.