Simulation of Taylor flow evaporation for bubble-pump applications.
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| Název: | Simulation of Taylor flow evaporation for bubble-pump applications. |
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| Autoři: | Rattner, Alexander S.1, Garimella, Srinivas2 sgarimella@gatech.edu |
| Zdroj: | International Journal of Heat & Mass Transfer. Jan2018, Vol. 116, p231-247. 17p. |
| Témata: | *HEATS of vaporization, *BUBBLE dynamics, *FLUID dynamics, *HEAT transfer, *PUMPING machinery |
| Abstrakt: | Single-pressure absorption systems incorporate bubble-pump generators (BPGs) for refrigerant separation and passive fluid circulation. In conventional spot-heated BPGs, heat is transferred over a small area, requiring high source temperatures. Distributed-heated BPGs receive thermal input over most of the component surface, enabling low temperature operation. In this investigation, a Volume-of-Fluid phase-change simulation formulation is developed and validated. This approach is applied to the evaporating Taylor flow pattern in distributed-heated BPGs. A 2-D axisymmetric simulation is performed, which yields detailed information about the developing heat transfer and two-phase flow phenomena. Results are used to assess predicted trends and sub-models from a 1-D segmented BPG model. Close agreement is obtained between segmented model and simulation results for bubble rise velocity (5–7% deviation), bubble and slug lengths, void fraction (3%), and hydrodynamic pressure drop (18%). Specifying average Taylor bubble lengths from the simulation as an input to the segmented model reduces hydrodynamic pressure drop deviation to 6%. Simulated flow-evaporation heat transfer coefficients are significantly higher than those predicted using analytic models from the literature. A new flow evaporation heat transfer correlation that accounts for developing slug flow effects is proposed, and yields close agreement with simulation results for heat transfer coefficient (AAD = 11%) and overall heat transfer rate (2%). Overall, this investigation provides validation for a distributed-heated BPG modeling approach, which can enable passive refrigeration for diverse applications. [ABSTRACT FROM AUTHOR] |
| Databáze: | Academic Search Index |
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