STUDY ON CONDENSATION HEAT TRANSFER OF MICRO STRUCTURED SURFACES

摘要

Condensation heat transfer experiments for steam were performed by using mirror-finished copper surfaces, mirror-finished silicon surfaces and silicon surfaces with micro grooves or micro pins on it. The micro-grooves and the micro-pins were created by the MEMS technology. The film- and also the drop-wise condensation were observe don the copper surface. The film-wise condensation heat flux was in good agreement with the values of the Nusselt equation. It was approximately one-tenth of the drop-wise condensation heat flux. The condensation on the mirror-finished silicon surface was the drop-wise condensation. The heat flux was approximately one-tenth of the drop-wise condensation heat flux on the copper surface. The condensation on the micro-grooved and the micro-pin silicon surfaces was film-wise. The condensation heat fluxes were approximately one-tenth of the copper surface film-wise condensation heat flux. When the contact angle was smaller than 70 degree, the condensation was film-wise and when larger than the value, drop-wise. It seemed that the hollow parts of the micro-grooved or the micro-pin surface were filled with condensate first after the condensation was initiated. It made the surface hydrophilic and the condensation film-wise.