BX-15 Boiling Outside Low-finned Tubes
This report reviews recent HTRI flow boiling data from an ideal inline bundle of low-finned tubes, as well as some literature data. By comparing data for plain and low-finned tube bundles, we demonstrate applications and limitations of using low-finned tubes to enhance total heat transfer rates. After reviewing the current boiling method in HTRI Xchanger Suite 7, we propose a much simpler asymptotic model of two mechanisms, discuss a new correlation for the nucleate boiling surface correction factor, and present a new convective boiling method. The proposed flow boiling method, applicable to both hydrocarbons and refrigerants, greatly improves the prediction of the experimental data from low-finned tubes. Overall, this two-mechanism model predicts boiling heat transfer coefficients about 3 percent higher and with less than half the standard deviation compared to the current four-mechanism model.