A Simple Method for Increasing the Boiling Critical Heat Flux

The article considers a study of the possibility to increase the boiling critical heat flux q_cr through the use of surfaces consisting of areas with different heat conductivity. The results of experiments on studying pool boiling heat transfer for saturated dielectric fluid methoxynonafluorobutane (Novec 7100) on bimetallic surfaces are presented. The studies were carried out for bimetallic samples and also for samples made of copper and grade 08Kh18N10T stainless steel in the pressure range 0.1–0.4 MPa. A description of the experimental setup and the procedures used is given. The boiling curves for each sample in the entire presented range of fluid pressures with a step of 0.1 MPa are obtained, and the tables of critical heat-flux values are given. The effect that the liquid pressure has on the relative increase of q_cr for bimetallic samples is shown. The values of q_cr obtained on all samples are compared with one another, and the increase of q_cr on bimetallic surfaces by up to 20% is shown. The previously performed studies are briefly reviewed, and the experimental data obtained by other researchers on boiling heat transfer on surfaces with modulated heat conductivity and for boiling of Novec 7100 fluid are presented, including that on samples with a modified heat-transfer surface. The obtained results are compared with rather few data of other researchers. The temperature field in a bimetallic sample is numerically simulated, and the temperature distribution over the heat-transfer surface is presented. The growth of q_cr is due to nonisothermal properties of the heat-transfer surface, which causes the boiling to become regularized.