Details

Autor(en) / Beteiligte

• Ding, Wei
• Zhang, Jinming
• Sarker, Debasish
• Hampel, Uwe

Titel

The role of microlayer for bubble sliding in nucleate boiling: A new viewpoint for heat transfer enhancement via surface engineering

Ist Teil von

• International journal of heat and mass transfer, 2020-03, Vol.149, p.119239, Article 119239

Ort / Verlag

Oxford: Elsevier Ltd

Erscheinungsjahr

2020

Link zum Volltext

Quelle

ScienceDirect Journals (5 years ago - present)

Beschreibungen/Notizen

• •Theoretical explanation and experimental verification of the microlayer presenting beneath the bubble during the sliding.•Confirmation that both bubble expansion and motion will extend the microlayer during nucleation and sliding.•Confirmation that the bubble may have a comparable or even more residence time and sliding area that on originating cavity with a suitable surface treatment.•Bubble sliding on a microlayer completely or partially will enhance the heat transfer. In an experimental study with a stainless steel heater (surface with maximum roughness Rt = 0.82 µm and contact angle hysteresis θhys = 53°), we investigated the bubble growth and motion during nucleation and departure. Complementary to that we analysed the formation of microlayer during the bubble growth and motion with computational fluid dynamics (CFD) simulation. From the simulations we found that the bubble motion leads to an expansion of the microlayer. From the experiments we obtained the drag coefficient on the bubble during bubble growth with an assumption of the absence of the wall surface tension force. From the comparison of this drag coefficient and the proposed values from the literature, we conclude that the vapor bubble does not directly contact the solid wall during the sliding. Using well-known mechanistic bubble growth models for further analysis of available microlayer area with the experimental data we conclude that a microlayer exists and the bubble must slide completely on this microlayer after leaving its originating cavity. From the change of microlayer size we can also explain the bubble regrowth after departure.