Experimental and LBM simulation study on the effect of bubbles merging on flow boiling

• Published in: International journal of heat and mass transfer Vol. 132; pp. 1053 - 1061
• Main Authors: Wang, Jue, Cheng, Yi, Li, Xiao-Bin, Li, Feng-Chen
• Format: Journal Article
• Language: English
• Published: Oxford Elsevier Ltd 01.04.2019; Elsevier BV
• Subjects: Additives; Bubbles; Bubbles merging; Computational fluid dynamics; Computer simulation; Experiment; Flow boiling; Flow-density-speed relationships; Heat flux; Heat transfer; High speed cameras; LBM; Nucleation; Nucleation site; Simulation; Surfactants; Flow boiling; Bubbles merging; Nucleation site; Experiment; LBM
• ISSN: 0017-9310; 1879-2189
• DOI: 10.1016/j.ijheatmasstransfer.2018.11.140

•Surfactant addition enhances water flow boiling heat transfer and increases CHF.•More nucleation sites and smaller bubble sizes exist in surfactant solution flow boiling.•Bubbles merging makes the middle nucleation sites neighbored by others lose its effectiveness.•Prevention of bubbles merging is one factor of boiling heat transfer enhancement. Surfactant additives can prevent bubbles merging and change the flow mode in flow boiling. This work presented the effect of bubbles merging on flow boiling heat transfer performance of water. Flow boiling experiment and lattice Boltzmann method (LBM) were carried out in a rectangular channel. With a high speed camera, the flow boiling process has been recorded. D2Q9 model and the Peng-Robinson (P-R) equation of two phase state (EOS) were used to simulate flow boiling process. The present experimental results showed that surfactant addition could enhance the flow boiling heat transfer and increased the critical heat flux (CHF). And there were more nucleation sites, larger bubbles density and smaller bubble size in surfactant solution. The present simulation results showed that the flow boiling without bubbles merging has higher and more stable average Nu number. The bubbles merging made the middle nucleation sites lose effectiveness. It implies that preventing bubbles merging is another factor of surfactant addition enhancing boiling heat transfer.