Experiment Investigation Of Pool Boiling Heat Transfer From Enhanced Porous Surface Tubes With Heat Flux Homogenized And Varied Along The Tube Axial

One of the ideal goals of reactor design is to maintain the temperature as a constant. To develop reactor tube with high efficient heat exchange capacity that could remove reaction heat efficiently and reduce axial temperature difference of the tube, an experiment research had been conducted to investigate the boiling characteristics of two enhanced surface tubes:the sintered porous coated tube(High Flux) and mechanically fabricated porous surface tube(GEWA-T). In present work, the tested sections were designed in two categories:the heat flux homogenized and varied along the axis of the tested tube. The incipient boiling superheat, heat transfer coefficient and temperature distribution along the axis of tubes were analyzed. The results indicate that the enhanced surface tubes can lower the incipient boiling superheat and enhance nucleate boiling heat transfer coefficient compared with plain tube. The incipient boiling superheats from enhanced tubes is48%-60%those of the plain tubes. The nucleate boiling coefficient of High Flux and GEWA-T were as much as4.5and2.2times those from plain tubes. Furthermore, the enhanced surface tubes can lower temperature difference along the axial direction of the heating tube and improve the thermal stability compared with plain tube. In addition, the influences of the orientation(vertical and horizontal) and diameter(20,25and32mm) of the heating tube and the sintered coating particle size(between30and105μ m) on the nucleate pool boiling were also investigated. It is found that, at high heat flux, the horizontal tube has better boiling performance than the vertical tube due to decrease in bubble slug formation on the tube surface and easy liquid access to the surface. And the influence of tube orientation on boiling performance is smaller for enhanced tube than for smooth tube. The heat transfer coefficient on smooth tubes as well as enhanced tubes decreased with increase in the tube diameter. The data for different sintered porous coatings suggest that particle size has slight effect on boiling heat transfer and greater enhancement is found with larger particle size.