A model for evaluation of the heat transfer enhancement by spontaneous vapor bubble behaviors

A new method was proposed for the boiling heat transfer enhancement by taking advantage of the unique movement of vapor bubbles along a heated wall. This spontaneous behavior of bubbles was caused by setting a porous plate parallel to a horizontal heated surface with a narrow gap. Experimental data showed the improvement of the heat transfer performance in small heat flux cases by this behavior, which should be due to the following two effects.: (I)A thin evaporative liquid film was made on the heated wall by the trapped and flattened vapor bubbles. (2)The superheated liquid close to the heated wall was swept out by the vapor bubble movement. An analytical model was proposed based on the mass conservation. In this model taken into account were the liquid inflow through the porous plate and the drainage of liquid from the exit of the narrow gap conduit caused by the vapor flow. The comparison between the experimental and calculated results showed a good agreement.