ABSTRACT

A predictive method to correlate the local boiling heat transfer data deduced from Feldman’s [1, 2] tests on flow boiling of CFC114 in an electrically heated, small perforated fin passage is proposed. Those tests were performed by Feldman [1, 2] over a wide range of vapour quality, with mass fluxes up to 49 kg/(m²s), heat fluxes up to 3540 W/m² and a pressure of 0.3 MPa corresponding to a reduced pressure of p_red=0.094. These low mass and heat fluxes reflect the industrial process application of the compact plate fin heat exchangers. We decided to ameliorate the method of determination of the heat transfer coefficients as compared with this previously used by Feldman [1, 2], by taking the fins efficiency into account. This correction contributed to obtain heat transfer coefficients values 17 to 31% higher than Feldman’s [1, 2] previous ones. The analysis of the heat transfer mechanisms in Feldman’s [1, 2] study showed that the nucleate and convective boiling regions were quite distinct. It allowed in the present study the individual identification of the data points which are purely nucleate and these which are purely convective and justified the use of an asymptotic model to predict the data. In order to establish a correlation, the trends of the corrected Feldman experimental heat transfer data in the nucleate boiling region on the one hand, in the convective boiling region on the other hand were compared to literature correlations. By basing on the latter, a semi-empirical correlation is proposed. The nucleate boiling component is expressed as a function of mean heat flux, fins dimensions and fluid thermodynamic properties and the forced convective component was found to be well represented by F and Martinelli parameters.