烧结电镀强浸润管壁结构强化R245fa流动沸腾特性的实验研究

R245fa Flow Boiling Performance in Enhanced Heat Transfer Tube With Sintering and Electroplating Superhydrophilic Composite Coats

实验研究了有机工质R245fa在内径为10 mm的不锈钢光管和烧结电镀多尺度镀层强化管内的流动沸腾传热特性。实验工况为:饱和压力0.6 MPa,质量流速189.3~708.14 kg·s^(-1)·m^(-2),热流密度4.94~44.74 k W·m^(-2),干度0.01~0.9。实验结果表明:实验条件下观测到分层流与环状流两种流型,发现管内多尺度强浸润镀层能够促进环状流的转变提前。与光管相比,烧结电镀多尺度镀层强化管具有明显的强化沸腾换热的效果,其传热强化因子平均为1.87,最大强化效果为3.15。随着热流密度以及干度的增大,传热强化因子先增加后降低。流型可视化对比发现,强化管壁面的强润湿性促进上壁面液相吸附以及快速再浸润,对流动沸腾换热具有积极作用。

R245fa flow boiling performance in a bare stainless-steel tube(BT)and a sintering and electroplating multiscale reinforced tube(SET)with the same inner diameter of 10 mm were investigated experimentally.Experimental conditions were as follows:saturation pressure 0.6 MPa,mass flow 189.3~708.14 kg·s−1·m−2,heat flux 4.94~44.74 kW·m−2,and vapor quality 0.01 to 0.9.Two flow patterns were observed under the experimental conditions,which are stratified flow and annular flow.The multiscale superhydrophilic coats of SET could promote the earlier transition of annular flow.The experimental result indicated that the SET can effectively enhance the heat transfer.The average and maximum values of the heat transfer enhancement ratio(EF)were 1.87 and 3.15,respectively.The EF increased and then decreased with the rising heat flux and vapor quality.The visualization shown that the strong wettability of SET could accelerate the diffusion of R245fa liquid on the tube wall surface,which has a positive effect on flow boiling heat transfer.