Contact

Dr. Wei Ding
Dr. -Ing.
Experimental Thermal Fluid Dynamics
w.dingAthzdr.de
Phone: +49 351 260 - 2170

Dr. Eckhard Krepper
Computational Fluid Dynamics
e.krepperAthzdr.de
Phone: +49 351 260 - 2067
Fax: +49 351 260 - 12067

Dr. Dirk Lucas
Head Computational Fluid Dynamics
d.lucasAthzdr.de
Phone: +49 351 260 - 2047
Fax: +49 351 260 - 12047

Wall boiling Model

Time averaged Eulerian multiphase approaches and the heat flux partitioning method is popular to be applied in the computational fluid dynamic simulations of wall boiling especially in the forced convective boiling. In such CFD simulations, many submodels for the bubble dynamics and the implementation of the bubble dynamics into the global models are particularly important. In order to get accurate bubble dynamics, a single bubble model for nucleate boiling based on the known microlayer theory was developed. The single bubble model considers the dynamic bubble geometry, contact angle and bubble inclination angle in flow boiling at different time periods. The model is able to show the dependency of bubble departure diameter (lift off diameter) and frequency on the different physical quantities such as heat flux, liquid properties, sub-cooling temperature, design of channel (diameter, length), mass flow rate and so on. The implementation of this developed single bubble model requires an update of the conventional nucleation site activation and heat partitioning models in time averaged Eulerian multiphase approaches. The new activation approach considers a distribution of cavity sizes and their influence on the activation temperature. The dynamics of the bubbles generated from different size cavities at the same position differ from each other. The updated heat partitioning model assumes the heat flux at the evaporative area always as constant and equal to the known feed heat flux when the boiling system is in the steady state.



With the help of the multiple size group (MUSIG) model and a breakup and coalesce model, the time averaged Eulerian approach could simulate the bubble size distribution in a heated pipe. With the necessary calibration of the nucleation site density the comparisons between the calculation results of the DEBORA and the Bartolomej’s experiments demonstrate the accuracy of this approach.



Reference

  • W. Ding, E. Krepper, U. Hampel
    A Mechanistic model to predict the bubble departure in pool and forced convection boiling considering the sublayer.
    ISACC, Shenzhen, China (2015)
  • W. Ding, E. Krepper, U. Hampel
    Prediction of the bubble departure in pool and forced convection boiling considering the sublayer: a sub model of CFD approaches.
    ICMF, Italia (2016)
  • E. Krepper and W. Ding
    Review of Subcooled Boiling Flow Models
    Handbook of Multiphase Flow Science and Technology, Yeoh G.H. (Ed.), Springer Singapore (2017), DOI: 10.1007/978-981-4585-86-6
  • D. Sarker, R. Franz, W. Ding, U. Hampel
    Single bubble dynamics during subcooled nucleate boiling on a vertical heater surface: An experimental analysis of the effects of surface characteristics.
    International Journal of Heat and Mass Transfer 109:907-921, (2017) DOI: 10.1016/j.ijheatmasstransfer.2017.02.017

Contact

Dr. Wei Ding
Dr. -Ing.
Experimental Thermal Fluid Dynamics
w.dingAthzdr.de
Phone: +49 351 260 - 2170

Dr. Eckhard Krepper
Computational Fluid Dynamics
e.krepperAthzdr.de
Phone: +49 351 260 - 2067
Fax: +49 351 260 - 12067

Dr. Dirk Lucas
Head Computational Fluid Dynamics
d.lucasAthzdr.de
Phone: +49 351 260 - 2047
Fax: +49 351 260 - 12047