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Hea-P

Hea-P in a nutshell
 
In collaboration with Euro Heat Pipes (EHP), Cenaero is continuously improving a thermohydraulic model able to predict the heat transport capacity of grooved heat pipes for microgravity applications. A Java user-friendly interface of the code is available and developed by Cenaero in order to ease the heat pipe design, to perform optimisation and robust design analysis and to cope with thermal issues involving the heat pipes technology.
 
Hydraulic modeling for your grooved heat pipes design and optimisation
 
Hea-P includes a one-dimensional hydraulic model able to predict the maximum heat transport capacity of grooved heat pipes. The code relies on the equilibrium between the friction losses induced by the liquid and the vapor motions and the capillary pressure developed in the grooves. The convergence criterion imposed to calculate the maximum heat transport capacity assumes the maximum capillary pressure is reached at the end of the evaporator section. 
 
Moreover, the friction loss estimated inside of the heat pipe has been improved. Most of the one-dimensional heat pipe models use correlation formula established in the literature for circular closed channels. Nevertheless, it can be demonstrated this leads to important errors that we can not neglect. Recently, the Shah method which allows for an accurate description of the friction losses for any kind of duct shapes, opened or not, has been implemented. It was applied in the liquid phase for all kinds of grooves and for all liquid filling rates inside of them. It was also implemented in the vapor core in laminar regime. By using CFD, it has been demonstrated that the relative difference between the Shah method and a three-dimensional CFD calculation is lower than few percent, which witnesses the great efficiency of the method. Moreover it is characterised by a fast execution in comparison with the CFD run.
 
Thermo-hydraulic modeling suite for your involving heat pipe applications
 
A multi-scale thermal model is also available in Hea-P. It includes a 3D-nodal thermal network model and specific effort was achieved to investigate the localised thermal exchanges inside the groove, especially the phase changes in the condenser and the evaporator. As these strongly depend on the heat pipe hydraulic characteristics, especially the liquid level inside of the groove along the pipe axis, a staggered coupling between the hydraulic and the thermal models is available.
 

Hea-T module for the microscopic heat transfer coefficients in condensation and evaporation

 

Based on the work of Stephan and Busse, the Hea-Tv1 module investigates the heat exchanges across the contact lines in the grooves in both evaporation and condensation zones.

It is coupled to Hea-P which provides the thermo-hydraulic characterization at the macroscopic scale needed to perform an accurate and coherent estimation of the heat exchanges across the contact lines. It is currently available for Ammonia/Aluminium grooved heat pipes. This completes the developments of Hea-P which is now consistent in terms of coupled thermal and hydraulic characterization, on both macroscopic and microscopic scales. Hea-P becomes therefore completely independent of the experiments even if a reverse analysis is still possible for the user through the graphical user interface.

 
Hea-P validation
 
Hea-Pv5 was experimentally validated by EHP on a rotative bench that mimics the microgravity conditions for low foilling rate and by the TEPLO mission supported by ESA. Both hydraulic and thermal data's were correlated. More details are coming soon.
 
Robust design and optimisation of the manufactured heat pipes
 
Its acccuracy and its short CPU time makes of Hea-P an ideal tool for performing optimization. It is successfully coupled with our Minamo optimisation platform to achieve constrained multi-objective optimization taking into account the large variety of design variables. Moreover it has been used several times to perform a robust design analysis of the heat pipes manufactured by extrusion.

Hea-P latest release
 

The Hea-P one-dimensional code and its interface appear as a suitable and accurate design tool for the industry. In March 2010, a new version of Hea-P has been released (Hea-Pv6). This new Hea-P version has been developed to allow the coupling between the macroscopic thermo-hydraulic characterization provided by the former Hea-Pv5 and the microscopic heat exchange estimate provided by the Hea-T module. Hea-Pv6 and its Hea-Tv1 module will become the standard version for microgravity calculations.

Since five years, it is extensively used by EHP for their heat pipe design and thermal issues involving heat pipes.


Hea-P perspectives
 

We plan to extend the developments of the Hea-T module to other fluids and investigate advanced effects such as the influence of the wall roughness or the flow near the contact lines on the microscopic heat exchanges. We also continuously improve the developments of suitable models for gravity-assisted applications. Please contact us for the current status of the code on that issue.