Pool boiling performance enhancement using orthogonally intersecting U-grooved micro-channelled structured surfaces

Abstract

The bubble dynamics of microchannels have a direct impact on pool boiling heat transfer. The present investigation of heat transfer performance during pool boiling on three micro-channelled surfaces developed through the wire electric discharge machining process. All these developed surfaces have orthogonally intersecting U-grooved microchannels with depths of 100 μm (A1), 200 μm (A2), and 300 μm (A3). Heat transfer rates were compared to those of a bare reference surface in order to evaluate the enhancement achieved with these developed. All the experiments were performed with deionised water at saturation temperature under atmospheric pressure to get steady-state heat transfer characteristics. A hypothesis model was used to explain the observed bubble dynamics. The results showed remarkable improvements in heat transfer for all microchannel configurations as compared to the bare surface. Among them, the A2 configuration exhibited the highest performance, achieving a 171 % increase in the maximum heat transfer coefficient and a 76 % rise in the critical heat flux compared to the bare surface. The A1 and A3 surfaces demonstrated enhancements of 28 % and 76 % in HTC and 23 % and 37 % in CHF, respectively, relative to the bare surface. Furthermore, the performance of the A2 surface was found to be better compared to the data from the published literature. The superior heat transfer rates of the A2 surface can be attributed to a larger heat exchange area, increased bubble nucleation sites, enhanced macro-convection from bubble movement, and an efficient rewetting mechanism.